Preconstruction groundwater assessment for the Jollyville transmission main WTP4

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Preconstruction groundwater assessment for the Jollyville transmission main WTP4

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Preconstruction groundwater assessment for the Jollyville transmission main WTP4
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City of Austin
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Geology ( local )
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"The City of Austin (City) requested that a preconstruction groundwater assessment be completed to address potential impacts of the construction of the Jollyville Transmission Main tunnel project. This assessment evaluated the groundwater conditions in the project area and assessed the potential impacts of tunnel and shaft construction on groundwater flow in the project area, in particular, on springs that are found on hillsides and on flow in Bull Creek. Springs and seeps in the project area provide habitat for the Jollyville Plateau Salamander, a candidate species for listing under the Endangered Species Act that occupies habitat along Bull Creek. The base flow in Bull Creek is seasonally supplied by discharge from springs along the creek, which originate as groundwater discharge from the hillsides. The City is taking actions to avoid or mitigate potential groundwater impacts from construction and operation of the four access shafts and the tunnel that comprise the Jollyville Transmission Main (JTM) project. Adverse impacts on spring flows in the vicinity of project facilities would be considered a significant environmental issue for the project." -- Authors
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Description
"The City of Austin (City) requested that a
preconstruction groundwater assessment be completed to
address potential impacts of the construction of the
Jollyville Transmission Main tunnel project. This assessment
evaluated the groundwater conditions in the project area and
assessed the potential impacts of tunnel and shaft
construction on groundwater flow in the project area, in
particular, on springs that are found on hillsides and on
flow in Bull Creek. Springs and seeps in the project area
provide habitat for the Jollyville Plateau Salamander, a
candidate species for listing under the Endangered Species
Act that occupies habitat along Bull Creek. The base flow in
Bull Creek is seasonally supplied by discharge from springs
along the creek, which originate as groundwater discharge
from the hillsides. The City is taking actions to avoid or
mitigate potential groundwater impacts from construction and
operation of the four access shafts and the tunnel that
comprise the Jollyville Transmission Main (JTM) project.
Adverse impacts on spring flows in the vicinity of project
facilities would be considered a significant environmental
issue for the project." --
Authors



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PRECONTRUCTION GROUNDWATER ASSESSMENT FOR THE JOLLYVILLE TRANSMISSION MAIN WTP4 FDU 3960 2207 7240 SUBPROJECT ID NO. 6935.016 Documents Prepared for the Department of Public Works and Austin Water Utility By Daniel B. S tephens & Associates, Inc. December 2010 This document is released for purpose of interim review under the authority of Andrew C. A. Donnelly, P.G., in December, 2010. It is not to be used for permitting, final planning decisions, bidding or construction.

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JOLLYVILLE TRANSMISSION MAIN TABLE OF CONTENTS TABLE OF CONTENTS...........................................................................................................I List of Figures..............................................................................................................ii List of Tables..............................................................................................................iii Acronyms and Abbreviations......................................................................................iv EXECUTIVE SUMMARY........................................................................................................1 1.0 INTRODUCTION.........................................................................................................1 1.1 BACKGROUND AND PURPOSE....................................................................2 1.2 PREVIOUS INVESTIGATIONS.......................................................................2 1.3 GROUNDWATER ASSESSMENT..................................................................3 1.3.1 Approach.............................................................................................3 1.3.2 Rationale..............................................................................................4 2.0 GEOLOGY AND HYDROGEOLOGY..........................................................................6 2.1 STUDY AREA..................................................................................................6 2.2 GEOLOGY.......................................................................................................6 2.2.1 Stratigraphy.........................................................................................7 2.2.2 Structural Geology.............................................................................10 2.3 GROUNDWATER..........................................................................................11 2.3.1 Occurrence and Movement...............................................................12 2.3.2 Recharge...........................................................................................16 2.3.3 Discharge...........................................................................................17 2.3.4 Hydraulic Characteristics...................................................................18 2.3.5 Groundwater Levels...........................................................................20 2.4 SURFACE WATER.......................................................................................22 2.4.1 Springs...............................................................................................22 2.4.2 Bull Creek..........................................................................................23 2.5 WATER QUALITY.........................................................................................26 3.0 POTENTIAL GROUNDWATER IMPACTS...............................................................28 3.1 SHAFT EXCAVATION / CONSTRUCTION IMPACTS..................................28 3.1.1 Water Treatment Plant 4 Shaft Site...................................................29 3.1.2 Four Points Shaft Site........................................................................33 3.1.3 Parks and Recreation Department Site.............................................36 3.1.4 Jollyville Reservoir Shaft Site............................................................39 3.2 TUNNEL EXCAVATION / CONSTRUCTION IMPACTS...............................42 3.2.1 Reach 1: WTP4 to Four Points..........................................................42 3.2.2 Reach 2: Four Points to Parks and Recreation Department..............44 3.2.3 Reach 3: Parks and Recreation Department to Jollyville Reservoir..46 3.3 FOREST RIDGE TRANSMISSION MAIN SHAFT........................................47 4.0 DESIGN MITIGATION MEASURES.........................................................................51 4.1 BEST MANAGEMENT PRACTICES.............................................................51 4.2 SURFACE AND GROUNDWATER MONITORING......................................55 4.3 BASELINE ENVIRONMENTAL CONDITIONS.............................................56 DECEMBER 2010 i Preconstruction Groundwater Assessment

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 ii Preconstruction Groundwater Assessment 4.4 CONTINGENCY MEASURES.......................................................................56 4.5 CONSTRUCTION MONITORING AND INSPECTIONS...............................57 4.6 SHAFT AND TUNNEL INFLOW ASSESSMENT..........................................57 5.0 SUMMARY AND CONCLUSIONS............................................................................60 6.0 REFERENCES..........................................................................................................65 LIST OF FIGURES 1-1 Jollyville Alignment and Shaft Locations 2-1 Study Area Location 2-2 Physiographic Provinces 2-3 Study Area with Surface Geology 2-4 Study Area Topography 2-5 Generalized Stratigraphic Section 2-6 Boring Locations 2-7 Stratigraphic Section along Alignment 2-8 TWDB Wells within 2 Miles of Alignment 2-9 Detailed Surface Geology and Monitoring Locations at Former WTP4 Site 2-10 Dye Tracing Results 2-11 Cross Section View of Dye Tracing Results 2-12 Nested Piezometer Locations 2-13 Nested Piezometers B-5 and B-8A 2-14 Nested Piezometers B-8, B-9, and B-10 2-15 Cross Section along Alignment 2-16 Overall Distribution of Hydraulic Conductivity in Glen Rose Formation 2-17 Distribution of High Hydraulic Conductivity Values for the Glen Rose Formation 2-18 Distribution of Hydraulic Conductivity for Walnut Formation 2-19 Water Levels in the Edwards/Walnut Groundwater Flow System 2-20 Water Levels in the Upper Glen Rose Groundwater Flow System 2-21 Approximate Four Points Surface and Groundwater Divides 2-22 Surface Watersheds 2-23 Springs and Seeps 2-24 Bull Creek Low Flow Study Measurement Locations 2-25 Streamflow vs. Precipitation in upper Bull Creek 2-26 Bull Creek Streamflows vs. Drainage Area 2-27 Bull Creek Gain-Loss Study Results 2-28 Profile of Streamflow in Bull Creek 2-29 Piper Diagram of Bull Creek Samples 2-30 Piper Diagram of Glen Rose Samples 3-1 Locations of Alignment and Proposed Shafts 3-2 Proposed WTP4 Shaft Location 3-3 Potential Areas of Groundwater Discharge from Proposed WTP4 Shaft Location 3-4 Proposed Four Points Shaft Location

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 iii Preconstruction Groundwater Assessment 3-5 Estimated Potential Impact Area from Four Points Shaft Location 3-6 Proposed PARD Shaft Location 3-7 Proposed Jollyville Reservoir Shaft Location 3-8 Reach 1 3-9 Cross Section Along Reach 1 3-10 Distribution of Hydraulic Conductivities along Reach 1 3-11 Reach 2 3-12 Cross Section Along Reach 2 3-13 Distribution of Hydraulic Conductivities along Reach 2 3-14 Reach 3 3-15 Cross Section Along Reach 3 3-16 Distribution of Hydraulic Conductivities along Reach 3 3-17 Proposed Forest Ridge Shaft Location 3-18 Potential Area of Groundwater Discharge from Proposed Forest Ridge Shaft Location LIST OF TABLES 2-1 Groundwater Levels........................................................................................................2 1 2-2 Bull Creek Streamflow Measurements............................................................................24 2-3 Bull Creek Streamflow Measurements............................................................................26 3-1 Summary of Packer Tests near the Proposed WTP4 Shaft Location.............................31 3-2 Summary of Packer Tests near the Proposed Four Points Shaft Location.....................35 3-3 Summary of Packer Tests near the Proposed PARD Shaft Location.............................38 3-4 Summary of Packer Tests near the Proposed Jollyville Reservoir Shaft Location....................................................................................................................... ....41 3-5 Summary of Packer Tests near the Proposed Forest Ridge Shaft Location...................49 4-1 Tunnel Inflow Calculations..............................................................................................59

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 iv Preconstruction Groundwater Assessment ACRONYMS AND ABBREVIATIONS BCCP Balcones Canyonlands Conservation Preserve BCP Balcones Canyonlands Preserve BDR Basis of Design Report BMPs best management practices cm/s centimeters per second DO dissolved oxygen EC Environmental Commissioning ft bgs feet below ground surface ft msl feet above mean sea level GDM Geotechnical Design Memorandum GIS geographic information system gpm gallons per minute HDPE high-density polyethylene IPMP Integrated Pest Management Plan JTM Jollyville Transmission Main K hydraulic conductivity PARD Parks and Recreation Department psi pounds per square inch LAN Lockwood, Andrews, and Newman, Inc. TCEQ Texas Commission on Environmental Quality TDS total dissolved solids TPH total petroleum hydrocarbons TSS total suspended solids TWDB Texas Water Development Board USGS U.S. Geological Survey WIID Water Information Integration & Dissemination

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 v Preconstruction Groundwater Assessment WTP4 Water Treatment Plant No. 4

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 ES-1 Preconstruction Groundwater Assessment EXECUTIVE SUMMARY The City of Austin (City) requested that a preconstruction groundwater assessment be completed to address potential impacts of the construction of the Jollyville Transmission Main tunnel project. This assessment evaluated the groundwater conditions in the project area and assessed the potential impacts of tunnel and shaft construction on groundwater flow in the project area, in particular, on springs that are found on hillsides and on flow in Bull Creek. Springs and seeps in the project area provide habitat for the Jollyville Plateau Salamander, a candidate species for listing under the Endangered Species Act that occupies habitat along Bull Creek. The base flow in Bull Creek is seasonally supplied by discharge from spri ngs along the creek, which originate as groundwater discharge from the hillsides. The City is taking actions to avoid or mitigate potential groundwater impacts from constructi on and operation of the four access shafts and the tunnel that comprise the Jollyville Transmission Main (JTM) project. Adverse impacts on spring flows in the vicinity of project facilities would be considered a significant environmental issue for the project. The study area is located in northwest Austin. The rocks present in the study area include the Edwards, Comanche Peak, Walnut, and upper Glen Rose formations. The Edwards Formation, consisting primarily of dolomite, dolomitic limestone, and limestone, is a more resistant unit typically found at the higher elevations on hilltops in the area. Karst features such as caves, sinkholes, and solution cavities are common within the Edwards. The Comanche Peak Formation is a limestone unit between the Edwards and Walnut formations, but which is interfingered within the Edwards Formation in the study area and is found only at the eastern end of the tunnel alignment. The Walnut Formation, a limestone found beneath the Edwards Formation, is less permeable and typically yields little to no water to wells. However, in some areas the Walnut Formation can allow significant amounts of water to move through it, and it can yield ecologically significant volumes of water to springs. The upper Glen Rose Formation typically consists of alternating beds of marl, along with thin beds of limestone and dolomite, and appears to be fairly tight in the study area with very low estimated hydraulic conductivities. The JTM tunnel will be constructed entirely in the Glen Rose Formation. Two different groundwater flow regimes are described in the area of interest: a flow system that occurs primarily in the Edwards and Walnut formations, and a deeper flow system present in the upper Glen Rose Formation. Precipitation enters the Edwards as recharge where it crops out and moves downward through the Edwards until encountering a less permeable layer. It then moves laterally, primarily discharging as springs and seeps along the hillsides found in the area. The

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 ES-2 Preconstruction Groundwater Assessment Edwards Formation is the source for about 40% of the known springs that discharge to creeks within one mile of the proposed transmission line (i.e. tunnel) alignment. The Comanche Peak, Walnut Formation, and upper Glen Rose Formation contain about 5%, 38%, and 18% of the known springs, respectively. Very few wells and very little groundwater pumpage occurs in the study area. Groundwater flow in the Edward/Walnut flow system is primarily away from t he topographic highs in the area. Based on dye tracing conducted by the City of Austin in the area near the old WTP4 site, groundwater flow velocities were estimated to be on the order of tens of feet per day, indicating that flow in this flow system is ty pical of flow in a karst regime. The second groundwater flow regime described is found within the upper Glen Rose Formation. A strong downward hydraulic gradient is observed within the Glen Rose Formation and estimated hydraulic conductivities in the Glen Rose are generally much lower than in the Edwards. The upper 50 feet of the Glen Rose appears to be more permeable, but below this zone the Glen Rose is consistently very tight, often yielding estimated hydraulic conductivities too low to be measured during field tests. For the purposes of this assessment, the Jollyville Transmission Main project can be divided into five components: the main transmission line tunnel and four shafts associated with it, including shafts at Water Treatment Plant 4 (WTP4), Four Points, the Parks and Recreation Department (PARD) site (parkland off of Spicewood Springs Road), and the Jollyville Reservoir site. Three of these shafts (WTP4, Four Points, and Jollyville Reservoir) will be completed through the Edwards Formation, and because of the karstic nature of the Edwards Formation at these shaft locations, the specific impact of each of the individual shaft constructions cannot be definitively quantified and it cannot be determined whether springs in this area will necessarily be impacted by each proposed shaft. The fourth shaft (PARD) will be completed through only the upper Glen Rose Formation and is not expected to impact any springs in the area. The transmission main tunnel will be completed in the deeper portions of the upper Glen Rose Formation, which tends to have low permeability or hydraulic conductivities. Because of this completion depth, and because hydraulic gradients in the Glen Rose Formation are strongly downward, no significant impacts on springs and seeps in the Edwards/Walnut flow system are expected from the tunnel excavation. Due to the presence of sensitive Jollyville Plateau Salamander habitat, additional mitigation and contingency measures are designed and will be implemented as necessary to prevent or otherwise minimize groundwater flow into and impact on the shafts and tunnels during and after project construction. These techniques were

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 ES-3 Preconstruction Groundwater Assessment developed through a collaborative effort between the environmental and engineering project teams. An assessment of the proposed Forest Ridge Transmission Main shaft location is also included in this assessment and yielded similar conclusions. The Forest Ridge tunnel was not assessed in this report.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 1 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 1.0 INTRODUCTION The City of Austin is undertaking the design and construction of two tunnels for the purpose of conveying treated water from Water Treatment Plant No. 4 (WTP4) to the Jollyville Reservoir and the existing Forest Ridge transmission main for distribution to the City of Austin. The current proposed route of the Jollyville Transmission Main (JTM) is shown in Figure 1-1. The project will move water from WTP4, currently under construction near the southwest corner of the intersection of RR 620 and Bullick Hollow Road/FM 2222 at the western end of the tunnel alignment, through a tunnel to the Jollyville Reservoir, located near the intersection of McNeil Road and Highway 183 at the eastern end of the tunnel alignment. The project will include four shafts, also shown in Figure 1-1, for construction access and/or retrieval of material removed during tunneling. Details of the preliminary design of the tunnel and shafts are presented in the Basis of Design Report (BDR) (Black & Veatch, 2010a) and appended technical memoranda (Black & Veatch, 2009, 2010b). Although the final design has not yet been completed, it is evident that any of the existing alternatives will involve tunneling beneath the Balcones Canyonlands Preserve (BCP). The BCP contains known habitat locations of the Jollyville Plateau Salamander, a candidate species for listing under the Endangered Species Act. The species listing has been determined by the U.S. Fish and Wildlife Service to be warranted but precluded. The Jollyville Plateau Salamander uses habitat along Bull Creek, which originates as surface runoff and groundwater discharge from the hillsides and whose base flow is seasonally supplied by discharge from springs along the creek. Geographic information system (GIS) analysis of known Jollyville Plateau Salamander sites indicates that 52 sites where the salamander has been sighted are within one mile of the proposed JTM alignment and eleven sites are within 300 feet. Of the eleven sites, five are within the Glen Rose Formation and six are in the Edwards or Walnut formations. This groundwater assessment is intended to evaluate and address what impact, if any, the tunneling project may have on groundwater conditions in the local groundwater regime that would potentially affect the salamanders habitat. This report documents the purpose, methods, and work products associated with the groundwater assessment for the JTM tunneling project.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 2 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 1.1 BACKGROUND AND PURPOSE The City of Austin (City) requested that a groundwater assessment be completed to address potential impacts of the construction of the JTM tunnel project. This preconstruction groundwater assessment evaluated the groundwater conditions in the project area and assessed the potential impacts of the tunnel and shaft construction on groundwater flow in the project area, in particular impacts on springs that are found on hillsides in the area and on flow in Bull Creek. Springs and seeps in the project area provide habitat for the Jollyville Plateau Salamander, which occupies habitat along Bull Creek, a creek whose base flow is seasonally supplied by discharge from springs along the creek that originate as groundwater discharge from the hillsides. It was determined that the best approach in evaluating the potential impact to Jollyville Plateau Salamander habitat was a full conceptual model of groundwater flow in the study area, which is essentially a detailed description of the current understanding of the nature of groundwater flow in the study area and how this flow might be impacted by the installation of shafts and a tunnel as part of the proposed project. This document presents the groundwater assessment methodology and results to date, as well as design mitigation measures to minimize potential impacts. Goals of the groundwater assessment include: Review and summarize existing information on the hydrogeologic system so that potential impacts of the transmission main shafts and tunnels on the groundwater flow system, and therefore to the Jollyville Plateau Salamander, may be appropriately evaluated. Assess what effect, if any, the tunnel construction may have on spring flows along Bull Creek and flow within Bull Creek and its tributaries both within and outside the BCP. Assess what effect shaft construction in the Edwards Formation may have if the shaft intercepts a karst flow conduit and/or causes local dewatering of the Edwards Formation. This report also includes information about design mitigation measures that are intended to prevent or otherwise minimize the effects of construction of the project facilities. 1.2 PREVIOUS INVESTIGATIONS Studies and field work for the JTM project have been conducted since the midto late 1980s. A number of different engineering firms have provided services to the City over this period of time, including Woodward-Clyde, Fugro, Black & Veatch, and Lockwood,

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 3 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Andrews, and Newman, Inc. (LAN). Presently, both Black & Veatch and LAN are supporting the City on separate contracts involving different tunnel projects. Numerous geotechnical boring logs, packer tests, and piezometer installations have been performed that are local to the project area. Most, if not all of these efforts focused on geotechnical, engineering, and environmental aspects of the project. Reports on these results include Black and Veatch (2010a, 2010b), City of Austin (2001), Fugro Consultants (2008, 2009), Holt Engineering (2009), HVJ Associates (2007, 2009), Hicks and Company (2010a, 2010b), and Woodward Clyde Consultants (1986a, 1986b, 1986c). This groundwater assessment compiles and evaluates available data from these reports as they pertain to the goals of the assessment, including hydrogeologic characterization of the groundwater systems present beneath the project site. Several regional assessments of geology and hydrogeology in Travis County have been conducted previously. These include (among others) Hauwert (2009), Klemt and others (1975), Duffin and Musick (1991), Brune and Duffin (1983), Baker and others (1986), Garner and Young (1976), Small and others (1996), and Woodruff and others (1985). 1.3 GROUNDWATER ASSESSMENT 1.3.1 Approach The followin g methods were used to conduct the groundwater assessment associated with the JTM tunnel project in Travis County. Review and evaluate publicly availa ble hydrogeologic data and proprietary geotechnical and hydrogeologic data developed by the City of Austin over the duration of the project. Conduct field investigations to support the development of new primary hydraulic data with respect to local groundwater systems and conduct streamflow studies along the tunnel route. The general components of field work that were conducted to support the goals of the groundwater assessment included field reconnaissance, monitoring well and piezometer installation and monitoring, and a Bull Creek low flow study. Details of each component of field work are described below. Field Reconnaissance : A field reconnaissance of the study area was conducted to identify and locate existing wells, springs, and caves along the course of Bull Creek. Core Boring, Monitoring Well, and Piezometer Installation : The tunnel project exploration program included aerial photograph interpretation and geologic field

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 4 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 mapping followed by a subsurface boring program. The boring program was advanced in phases with an initial phase that included five borings and a followon phase that included 19 borings (including two angled borings). Monitoring wells or piezometers were completed in 13 borings, in either the Edwards or Glen Rose formations. Replacement piezometer s were installed at some locations after finding out that the original piezometer installation was not done by a licensed water well installer; groundwater level measurements from the original piezometers are not being used. After installation, water levels in the piezometers were periodically monitored. These data were used to evaluate water levels to help describe groundwater flow characteristics in the study area in support of this groundwater assessment. Additional borings and piezometers are being installed as the preconstruction groundwater assessment report is completed, and the results will be amended periodically. Bull Creek Low Flow Study: The relationship between groundwater and surface water was an important part of the groundwater assessment. A U.S. Geological Survey (USGS) stream gage located on Bull Creek at Loop 360 near Austin (USGS Gage 08154700) has a period of record from 1978 to the present. However, the gage is located outside the JTM tunnel alignment, and therefore, a low-flow study was conducted along Bull Creek from the headwaters to the USGS stream gage. This study consist ed of measuring stream discharge at a series of locations along the stream longitudinal profile. The purpose of this work was to provide data to understand stream gains and losses along Bull Creek closest to the tunnel alignment in the BCP. 1.3.2 Rationale The initial scope for the groundwater assessment included a numerical modeling task. However, after considerable discussions with the Environmental Commissioning (EC) team and project hydrogeologists, it was determined that a numeric groundwater flow model would not be the most appropriate method to assess and determine potential impacts of project facilities. Due to the lack of historical and current data on local groundwater use and wells, groundwater elevations, flow and recharge regimes, and necessary calibration information within the BCP and project footprint, as well as the limited and questionable ability of commonly used equivalent porous media groundwater flow models to accurately depict groundwater fl ow within karst flow regimes, a numerical model was not recommended or used for this assessment.. The complex and karstic nature of several of the formations being evaluated, in particular the Edwards and associated limestone found in the upper portions of the study

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 5 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 area, are best characterized using a conceptual assessment based on the data currently available, including spring and creek flows, dye tracing tests, field observations, and the supplemental information gathered through geologic and hydrogeologic investigations such as boring logs, piezometers, and monitoring wells. A numeric groundwater flow model may be appropriate at a later time when sufficient data are available to both characterize the flow system and determine what type of flow model is most appropriate for the groundwater flow that occurs in the study area. Although some researchers (Scanlon and others, 2003a) have concluded that an equivalent porous media model such as MODFLOW can be successfully used to model regional groundwater flow in a karst formation, this conclusion may not be applicable to this study area because the karstic units in the project area are not part of a regional aquifer system. In addition, an equivalent porous media model may not be an appropriate tool to evaluate the very localized impacts to specific springs that are of particular interest in the study area. An equivalent porous media model of the San Antonio segment of the Edwards Aquifer has recently been developed using MODFLOW (Lindgren and others, 2004). This model was moderately successful in simulating water levels in the deeper, confined, regional portion of that aquifer. However, this model was completely unable to simulate water levels or groundwater flow in the recharge areas of the Edwards Aquifer, which are more analogous to the Edwards Formation in the study area for this project. Additional research on the appropriateness of this type of model to the conditions in the study area is necessary before a numerical modeling effort is undertaken. In addition, it will be very difficult, if not impossible, to evaluate and address the type and extent of potential groundwater impacts for this project within the context of a regional or even a local numerical groundwater model. Assertions of flows of springs and groundwater flow movement through formations will likely be in the order of magnitude accuracy and definitely less than model sensitivity and calibration limits that can be attained using a numerical model.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 6 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 2.0 GEOLOGY AND HYDROGEOLOGY 2.1 STUDY AREA The study area is located in northwest Austin between FM 2222 and U.S. Highway 183 and Loop 360 and FM 620, as shown in Figure 2-1. The study area is located within the Edwards Plateau physiographic province, which is bounded on the east by the Rolling Prairie province and on the north by the Jollyville Plateau province, (Figure 2-2). The break between the Edwards Plateau and the Rolling Prairie provinces is defined by the Balcones Fault Zone. The rocks present in the study area include the Edwards, Comanche Peak, Walnut, and Glen Rose formations. Often the Comanche Peak Formation is included as a member of the Edwards and associated limestones. A surface geology map of the study area bas ed on the regional map of Garner and Young (1976) is shown in Figure 2-3. The topography in the study area is shown in Figure 2-4. Elevations in the study area range from approximately 700 to nearly 1,100 feet above sea level, with the highest point being near the southwest end of the tunnel alignment and the lowest point being within a tributary of Bull Creek. The topography in the study area is generally characterized by higher plateau areas and steeply incised stream valleys where the Colorado River and its tributaries have downcut through the more resistant formations. Slopes throughout this physiographic province generally average 5 to 15 percent, with steeper slopes adjacent to the Colorado River (Garner and Young, 1976). The climate is humid subtropical, characterized by hot summers and mild winters. Precipitation averages approximately 33 inches per year and tends to have a bimodal distribution, with the wettest months of the year typically being April through June, followed by September through October. However, precipitation trends can vary widely from year to year. Significant precipitation events of more than 10 inches per day can occur and in fact did occur during this investigation, in September 2010. 2.2 GEOLOGY The study area is located on the Edwards Plateau and is just west of the Balcones Fault Zone, which passes through the middle of Travis County. This fault system is approximately 6 to 8 miles wide and has resulted in a displacement of up to several hundred feet (Brune and Duffin, 1983). The area lies along the dissected edge of the Edwards Plateau physiographic province, which is bounded to the east by the Rolling Prairie and Blackland Prairie provinces and to the north by the Jollyville Plateau province

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 7 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 (Figure 2-2). The break between the Edwards Plateau and the Rolling Prairie/Blackland Prairie provinces is defined by the Balcones Escarpment. 2.2.1 Stratigraphy The general geology in the study area includes a thin veneer of soil overlying carbonate (limestone and dolomite) bedrock. Soils are generally comprised of clay and silty clay and commonly contain fragments of the underlying bedrock. The bedrock is comprised of Lower Cretaceous carbonate rock formations of the Comanche Series formed during the Trinity and Fredericksburg stages. In the study area, one formation from the Trinity stage is present: the upper Glen Rose Limestone. This is the oldest formation present at the surface within the study area. Three formations from the Fredericksburg stage are present. From bottom to top (or oldest to youngest) these formations are the Walnut, Comanche Peak, and Edwards. A generalized stratigraphic section, with a description of the individual units present, is shown in Figure 2-5. The following descriptions are based on Garner and Young (1976), Student Geology Society (1977), and Brune and Duffin (1983), as well as mapping and field work conducted by City of Austin staff. The Edwards Formation is the uppermost unit and is up to 200 feet thick in the study area. It is a more resistant unit and is typica lly found at the higher elevations on hilltops in the area. It is not laterally continuous over large distances because of the steeply incised valleys present in the study area (Figure 2-3). The Edwards includes cherty and rudistid-bearing dolomite, dolomitic limestone, limestone, grainstone, and mudstone. Rocks of the Edwards and associated limestones represent reef, lagoon, shoal, and supratidal depositional environments. Caverns and solution collapse features may occur within the Edwards Formation, and nodular chert is locally common. The formation has not been formally mapped or subdivided into finer hydrostratigraphic units north of the Colorado River. Based on hydrostratigraphic units described by Rose (1972), Small and others (1996), and Hauwert (2009), the Edwards limestone unit exposed within the project area is mainly the Dolomitic member. This member is a massively bedded, light gray crystalline limestone, mudstone to grainstone with Toucasia and Caprinid fossils present. The Dolomitic member can contain a variety of dissolution features, including honeycomb structures of varying size that provide a variety of preferential solution pathways through which groundwater flows. The member is very porous and has permeable zones formed by boxwork porosity in breccias or by burrowed zones (Small and others, 1996). Karst development is related to dissolution along fractures and bedding planes, and caves tend to form vertical shafts with bedding plane conduits. The Edwards generally thickens to the northeast in the vicinity of Balcones Fault Zone.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 8 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 However, this significant thickening is not observed in the project area or in cores collected along the JTM alignment. North of the Colorado River, the Texas Commission on Environmental Quality (TCEQ) defines the Edwards Aquifer to include only the Edwards Formation and Georgetown Formation, including the Comanche Peak Formation within the Edwards. The Walnut Formation is included as part of Northern Edwards Aquifer as defined by the TCEQ. In the study area, the Comanche Peak Formation is an approximately 20-foot-thick finegrained, nodular to marly limestone. It has generally been considered a separate formation from the Edwards, located between the Edwards and underlying Walnut Formation but is found within the Edwards Formation within the study area. According to Ikins (1941), the Comanche Peak Formation is restricted to the limestone unit between the Edwards and Walnut formations. South of the Travis/Williamson County line the Comanche Peak becomes interfingered within the Edwards. An approximately 20-foot-thick Comanche Peak interfingering is visible in the drainage along Springwood Springs Road near the intersection of Rustic Rock Drive, and it is also seen in the core collected during this investigation from boring JT-124 (Black and Veatch, 2010b). Where the Comanche Peak is underlain by the Walnut Formation and overlain by the Edwards, the thickness of Comanche Peak Formation is reported to be approximately 50 to 60 feet thick (in the Cedar Park area to the north of the alignment) and to feather out southward (Rogers, 1969). The Comanche Peak was observed in cores northeast of boring JT-124 and was not observed in any of the cores along the rest of the alignment. The contact between the Comanche Peak and Edwards formations is marked by a change from a fineto very fine-grained marl and nodular limestone that weathers white. The Walnut Formation is found beneath the Edwards Formation and can be up to 120 feet thick in northern Travis County. However, based on field work completed by City of Austin staff and from geotechnical borings completed along the JTM alignment reported by Black and Veatch (2009, 2010b), the Walnut appears to be thinner in the study area, ranging from 90 to 100 feet thick. C.H. Moore subdivided the Walnut into five formations: from the oldest to youngest, the Bull Creek, Bee Cave, Cedar Park, Keys Valley Marl, and Upper Marl members (Moore, 1964). However, in the study area, only the Cedar Park Member, the Bee Cave Member, and the Bull Creek Member are present. This formation is characterized by alternating nodular and marly limestone deposited in a lagoonal environment. Compared to the overlying Edwards Formation, the Walnut is less permeable and typically yields little to no water to wells. Groundwater movement occurs along joints and/or fractures or along horizontal bedding plane

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 9 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 contacts within the Walnut. Based on data from the City of Austin, numerous minor springs and seeps emanate from this formation. The upper Glen Rose Limestone is the oldest of the four formations of interest in the study area and is present only at land surface along Lake Travis and in the incised stream valleys along Bull Creek and its tributaries. The upper Glen Rose typically consists of beds of marl alternating with thin beds of limestone and dolomite. Rodda and others (1970) report that the upper Glen Rose is approximately 580 to 630 feet thick in northwest Austin. The exact thickness of the Glen Rose in the study area is unknown as the borings drilled for the project have not penetrated below the base of the formation. However, it is generally reported that in the vicinity of the Balcones Fault Zone, the entire Trinity Division (upper, middle, and lower) is approximately 1,000 feet thick. The upper Trinity, which includes the upper Glen Rose, lower Glen Rose, and Hensel Sand, is about 700 feet thick near the fault zone (Stricklen and others, 1971). Although the Glen Rose Limestone can be karstic in other areas of the state and can yield small to moderate amounts of water to wells, in the WTP4 study area it appears to be fairly tight, with only a limited number of enlarged joints and fractures observed in outcrops or cores collected from boreholes. Very low hydraulic conductivities were determined for the Glen Rose Formation based on packer testing that was part of the geotechnical investigation (Section 2.3.4) (Black and Veatch, 2009, 2010b). Coring and packer testing done during the geotechnical program did determine that the upper 50 feet of the Glen Rose Formation appear to be more permeable than the rest of this formation. Small springs and seeps have been obs erved to occur near or just below the Walnut/Glen Rose contact in a burrowed horizon, presumably from this more permeable zone. Numerous borings were completed as part of the geotechnical investigation for the tunnel project (Figure 2-6), and additional borings are proposed. The subsurface conditions encountered in the borings indicated thin soil or weathered rock overlying the Edwards, Comanche Peak, Walnut, and Glen Rose formations. The logs of the portions of the borings overlying the bedrock indica ted varying thicknesses of soil and weathered bedrock that was not cored. Surface soils encountered in the borings were typically thin, although some weathered rock areas extended to approximately 20 feet before rock coring began. The rock conditions encountered in the borings completed to date indicate that the Edwards Formation is less clayey than the Walnut or Glen Rose formations and, where present, generally ranges in thickness from 30 feet to more than 100 feet along the JTM alignment averaging 40 feet in the borings completed to date. The Walnut Formation

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 10 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 was observed in the borings where expected, generally ranging in thickness from 75 feet (eastern portion) to 95 feet (western portion), although thinner sections were encountered in some borings. No borings fully penetrated through the upper and lower Glen Rose formations past the Hensel Sand at the base of the lower Glen Rose, and therefore the total thickness of the Glen Rose along the alignment is not known. Details of the boring program are presented in the Geotechnical Design Memorandum (GDM) (Black and Veatch, 2010b). Surface casing was used to stabilize the thin soil horizon on top of the bedrock and the weakened weathered bedrock near the ground surface. Surface casing was also drilled into rock when water circulation was lost during the drilling process, which commonly occurred in the Edwards Formation. A summary of the borings, including logs and core photographs, is provided in the GDM. Information from the core boring program was used to construct a geotechnical profile through the study area along the tunnel alignment, shown in Figure 2-7. 2.2.2 Structural Geology The major structural feat ure in the Austin area is the Balcones Fault Zone, located approximately 3 miles to the southeast of the Jollyville Reservoir. This normal or tensional fault trends northeast-southwest (generally between N25E and N50E) through the Austin area. The fault zone is made up of a series of faults that extend along a belt up to 20 miles wide, from near Waxahachie to near Del Rio. The major individual faults, as well as the greater fault zone, dip between 55 and 75 to the east, with the maximum recorded displacement observed at approximately 600 feet along the largest fault strand (Mount Bonnell fault) (Garner and Young, 1976). Movement occurred during the Miocene age, about 15 to 20 million years ago; however, there has been no significant movement on the Balcones Fault Zone in recorded history, with the exception of a small tremor that occurred in 1902 about 9 miles south of Austin, near the town of Creedmore. The Balcones Fault Zone is not considered to be a seismic source. In the early 1960s a lineament study of the faults in northwest Travis County and western Williamson County was completed (Rogers, 1969). A total of 79 faults and lineaments were measured, and two dominant fault trends were found at 90 to each other, with average strikes of N26 E and N60 W. The N26 E-trending faults ranged from N20 E to N36 and the N60 W-trending faults ranged from N52 W to N68 W, all with dips that are nearly vertical (Rogers, 1969). The two major joint sets in the greater Austin area trend N40E and N45W, and two secondary joint sets trend N10W and N80E (both are orthogonal joint sets) (Rogers,

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 11 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 1969). All the joint sets are related to stresses developed on the Balcones Fault Zone. The Cretaceous formations in the Edwards Plateau regionally strike northeast and dip gently (less than 1) to the southeast. The exception to this regional trend is within and adjacent to the fault zone, where the orientation of strike is variable and dips can be nearly vertical near the major faults (Rogers, 1969). 2.3 GROUNDWATER Although the geologic units of interest in the study area are well known regionally as significant sources of groundwater (in particular the Edwards and associated limestones), they have not been extensively st udied within the study area except as part of the JTM investigation. Characteristics of these geologic units and groundwater flow within them have been extensively studied wi thin Travis County and central Texas, but the amount of information that can be directly used to help characterize the units in the study area is limited due to the differences in the nature of the systems in the study area compared to the rest of the region. The Edwards and associated limestones make up several significant aquifers in central Texas, including the Northern and Barton Springs segments of the Edwards Aquifer in the Austin area and the San Antonio segment of the Edwards Aquifer to the south. However, the Edwards Formation water bearing unit in the study area is much thinner and is broken up in to smaller, isolated sections, as described in Section 2.2.1. This results in small, topographically isolated sections of groundwater of limited thickness (less than 10 feet in the western portion of the study area) that discharges locally to springs and seeps in incised stream valleys, rather than being a part of a large regional aquifer system. As noted above, the study area has not historically been considered an area with the potential for significant groundwater production. Wells that are located within 2 miles of the tunnel alignment are shown in Figure 2-8. The wells that are present are typically open or screened over large intervals and only produce sufficient water for domestic and livestock purposes. Brune and Duffin (1983) classi fy the majority of the study area as less favorable for groundwater production with some moderately favorable zones at the eastern end of the study area. These favorability ratings relate only to the Trinity Aquifer and do not address the Edwards and associated limestones. This is presumably because the Edwards units in the study area are broken into small, isolated, somewhat topographically controlled sections of groundwater flow. Previous investigations in the region have stated that the Edwards in the study area should not be considered a true aquifer (HVJ, 2007). The small saturated thickness of the Edwards and the low permeability of the Walnut and Glen Rose generally preclude the ability for groundwater production in the study area.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 12 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Despite the low potential for the geologic units in the study area to produce significant quantities of groundwater for water supply, these units are an important source of water in the study area and are ecologically significant. Discharge from these units supports flow in Bull Creek, an important local stream and source of flow into Lake Austin. The springs and seeps also support habitat for a variety of flora and fauna, including the Jollyville Plateau Salamander, which requires discharge from these springs to survive. Of the 90 known salamander sites that were identified by City staff, 52 sites are within one mile of proposed JTM alignment and eleven sites are within 300 feet. 2.3.1 Occurrence and Movement For discussion purposes, the ground water flow system has been divided into two zones: (1) Edwards and Walnut formations, and (2) upper Glen Rose Formation, defined as the youngest two members (approximately upper 200 feet) of the Glen Rose Formation. About 184 spring and seeps have been identified to be within one mile of the proposed JTM route. Of the springs identified, 82% are above the Walnut/Glen Rose contact. The two flow systems for these are described in Sections 2.3.1.1 and 2.3.1.2. 2.3.1.1 Edwards and Walnut Groundwater Flow System The uppermost groundwater flow system in the study area occurs primarily within the Edwards, Comanche Peak, and W alnut formations. As noted in Section 2.2.1, the Edwards is commonly a karstic unit, with many solution openings of varying size and nature that can transmit water through the unit. Precipitation enters the overburden overlying the Edwards, then moves primarily downward through the unit in joints, fractures, vugs, conduits, or other preferential flow pathways until it encounters a less permeable layer. Some groundwater then moves laterally, discharging as springs and seeps along the steep incised canyons or hillsides found in the area. Less permeable layers that may cause the groundwater flow to move laterally may be another unit within the section, such as the much less permeable Walnut Formation, units within the Edwards such as the Comanche Peak, or simply bedding planes or less permeable horizons. In some cases, springs emanate from the Edwards/Walnut contact, the middle of the Walnut Formation at the Bee Cave Member/Bull Creek contact (which is a Cretaceous hard-ground contact), and at the base of the Walnut Formation at the Bull Creek Member/Glen Rose contact (which is a Cretaceous hard-ground contact), or even from the upper Glen Rose Formation. This may be where groundwater moving laterally encounters fractures in these formations that allow downward movement through an

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 13 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 otherwise tight formation. This groundwater still ultimately discharges on hillslopes or along creeks in the area, but from below the Edwards Formation. Although the Walnut is generally considered to be a fairly tight unit, burrow zones, fractures, and hard-ground bedding planes within this formation have been observed, and where present, they may allow some lateral and vertical water movement. In one boring drilled as part of the investigation on the proposed Forest Ridge shaft, 100% fluid loss was experienced while drilling within the Walnut (Holt, 2009). This indicates that while the Walnut Formation is generally described as a much less permeable unit than the Edwards, it definitely has the ability to allow significant amounts of water to move through fractures and joints within the formation. The Glen Rose Formation is also considered much tighter than the Edwards, but may also have some similar preferential flow pathways along bedding planes, joints, or fractures. Also, as noted above, the upper approximately 50 feet of the Glen Rose tends to be more permeable than the rest of the unit. Although some springs have been found in the upper portion of the Glen Rose discharging along or into Bull Creek, this discharge may be associated with groundwater that has originated in the Edwards-Walnut flow system and that is moving through the very upper portion of the Glen Rose. Dye tracing studies conducted by the City of Austin support this conceptual understanding of groundwater flow in the upper portions of the study area. Several studies were conducted in the former WPT4 site area where dye was injected into four boreholes and an old windmill well. Locations of the injection points and all of the monitoring points are shown in Figure 2-9. Existing recharge features would have been the preferred location for dye injection, as these would presumably be where established flow pathways already exist, but they were not used because of the fear of impact from the dye being used for the traces to biologic cave communities that exist in the recharge features. Therefore either existing wells or separate boreholes were drilled and used for dye injection. These borings accepted traced water as quickly as could be injected and so appeared to be adequate injection locations (David Johns, 2010, personal communication). A detailed geologic map of the WTP4 site, including springs mapped at the site, is also shown in Figure 2-9. Many of the mapped spri ng locations appear to be at or slightly above the Edwards/Walnut (Bull Creek and Bee Caves) contact. Although springs are present in the Edwards above the contact with the Walnut Formation, these appear to be in stream drainages where groundwater leaves the Edwards due to the topography in the immediate area. In addition, as discussed above, there may be spring discharge originating from within the Edwards Formation in places where groundwater encounters

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 14 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 a less permeable bedding plane or unit, or simply a bedding plane that allows groundwater to flow more easily. The results of the dye tracing studies are shown in Figure 2-10. Arrows show the general direction of dye movement from injection point to recovery point. These arrows are not meant to imply that the path is necessarily a straight line or occurs where the arrows on the figure are located, only the general direction that the groundwater moves from the injection location. The monitoring program found dye seeping out of hillsides at locations not originally anticipated by the investigators conducting the traces, and ultimately the dye was found at several spring locations, but not those initially expected (David Johns, 2010, personal communication). Dye from two injection points was not recovered at any of the monitored locations. However, these issues are not unexpected in a karst environment. One observation from the dye tracing study is the direction of movement of the dye away from the injection points located at topographic highs in the Edwards. In all cases where dye was recovered, it showed that the movement of groundwater was somewhat topographically controlled. Dye movement did not cross significant topographic divides (i.e., flow did not cross the hilltops), implying that springsheds in the dye tracing area were at least somewhat related to the local topography. Another dye tracing study conducted by the City of Austin in the Stillhouse Hollow Spring area on the eastern side of the Bull Creek watershed, which is also a flow system within the Edwards Formation, showed that groundwater can cross topographic/watershed divides to eventually discharge in springs (David Johns, personal communication, 2010). However, in the JTM study area, the incised streams with related springs are located very close to the hilltops where the dye injections occurred. Injected dye would be expected to move to the springs and seeps located very close to the injection points and seeps. Groundwater flow velocities based on the dye tracing studies are between 35 and 61 feet per day within the Edwards and Walnut formations (David Johns, personal communication, 2010). The velocities resulting from the study are on the order of 10s of feet per day, which along with the locations of dye discharge, support the conceptual model that the springs found in the area are associated with the groundwater flow system through the karstic Edwards Formation and the burrowed, nodular limestones that comprise the Walnut Formation, where flow velocities are high and flow directions are somewhat variable and cannot be anticipated. This flow system does not appear to be associated with a regional groundwater flow system. Figure 2-11 shows a crosssectional depiction of the results of t he dye tracing study and the groundwater flow directions determined by this study

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 15 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 In summary, groundwater flow directions are difficult to define in the study area. Here, groundwater flow in the Edwards and Walnut formations appears to be very local and primarily tied to the topography in the area and occurs primarily in preferential karst or fracture flow pathways such as conduits, bedding planes, fractures, joints, and burrows. Precipitation on the outcrop of the Edwards units in the topographically higher parts of the study area infiltrates into the subsurface and migrates to local springs and seeps in steeply incised stream valleys that dissect these topographically higher areas. Dye tracing studies conducted by the City of Austin appear to confirm that groundwater flow in these areas is controlled locally. The dye tracing studies conducted in the study area indicate that groundwater moves primarily radi ally away from the hilltops. However a dye tracing study conducted in another part of Austin in the Edwards Formation indicates that groundwater may move across significant topographic divides, even in the very shallow flow systems that commonly mimic topography. 2.3.1.2 Glen Rose Groundwater Flow System The second groundwater flow regime of interest in the study area is found within the upper Glen Rose Formation, located beneath the Edwards and Walnut formations. Groundwater within the upper Glen Rose Formation appears to be largely hydrologically disconnected from that within the Edwards Limestone due to the low-permeability characteristics of the Walnut and Glen Rose formations, as seen in packer tests, which indicated hydraulic conductivities that were generally much lower than in the Edwards. Several nested piezometers have been installed in the study area at two locations: (1) the old WTP4 site and (2) along the raw water transmission main route between Lake Travis and the raw water pump station (Figure 2-12). The nested piezometers consist of vibrating wire pressure transducers installed in sand-filled socks at selected depths in the boreholes, which were typically grouted above and below the sand sock depths and/or to the ground surface. The hydrographs for these piezometers are shown in Figures 2-13 and 2-14. These piezometers gener ally show a strong downward hydraulic gradient. The two piezometers near Lake Travis and the new WTP4 site, B-5 and B-8A (Figure 2-13), both have two monitored intervals, both of which are in the Glen Rose. In B-5, the monitored intervals are 160 feet apart (elevations of 492.7 and 652.7 feet), and in B-8A they are 125 feet apart (474.1 and 599.1 feet). These piezometers show differences in water levels of between 65 and 112 feet (B-5) and approximately 125 feet (B-8A). Three nested piezometers (B-8, B-9, and B-10) are located within about 200 feet of each other at the old WTP4 site (Figure 2-12), and hydrographs for these are shown in Figure 2-14. In each of these piezometer nests, the upper piezometer monitors a short

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 16 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 interval at the Edwards/Walnut formation contact, while the remaining two or three piezometers monitor short intervals in the Glen Rose. The shallowest interval monitored in the Glen Rose is about 137 feet below the Walnut/Glen Rose contact. In all cases the water levels in the Edwards/Walnut piezometers are much higher than in all of the Glen Rose piezometers. In B-8 and B-10, the two piezometers screened in the Glen Rose show a similar strong downward hydraulic gradient that was observed in B-5 and B-8A. One piezometer nest (B-9) shows an inconsistent gradient between the middle two sensors located at the 600and 662-foot elevations (they exhibit a similar water level). This could be a result of vertical communication along the grouted borehole interval between the two sensors. In general, there is a strong downward gradient (between 0.6 and 1.0 foot per foot) between the Edwards/Walnut and Glen Rose formations and between the middle and deeper portions of the Glen Rose Formation. The downward gradients shown by the nested piezometers in the Upper Glen Rose Formation make creating a "regional" picture of groundwater elevations very difficult. Some additional water levels are available for the formations in the area of interest, especially in the Glen Rose. The Texas Water Development Board (TWDB) Water Information Integration & Dissemination (WIID) database contains several dozen wells in the general area of the JTM; however, most of these have open-hole completions or are screened over large intervals, with an average listed open hole or screen length for Glen Rose/Upper Trinity wells in the TWDB database of more than 300 feet and a minimum screened length of 70 feet. Because of the strong vertical gradient within the Glen Rose based on the nested piezometer data, water level data from wells with long-screened or open-hole sections may be of little to no use in determining any type of regional lateral groundwater flow gradient. Therefore, the ability of these wells to be used to develop an understanding of groundwater flow in the study area is of limited or no value. 2.3.2 Recharge Recharge in the study area occurs in the Edwards and Walnut formations in the topographically higher parts and in the upper Glen Rose Formation in topographically lower areas, in the stream valleys where the Edwards and Walnut formations are not present. Recharge to the Edwards occurs from the infiltration of precipitation directly on the Edwards outcrop areas. Water then passes down through the karstic Edwards Limestone through conduits such as joints, shears, faults, bedding planes, sinkholes, vugs, and caves. In general, recharge rates are very difficult to quantify, as the process of precipitation becoming recharge is very complex and dependent on many factors, including current and previous climate conditions, soil conditions, geology, topography,

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 17 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 and the nature of the precipitation event. Historical estimates of recharge made by different researchers using different methodologies have varied widely for aquifers in Texas (Scanlon and others, 2003b). Recharge rates in central Texas, including the Edwards Aquifer, have typically been estimated as 11% of precipitation or less (Hauwert, 2009). However, recharge rates in karst aquifers have been estimated to be much higher than this, with an expectation of 20% to 60% of precipitation becoming recharge in karst areas worldwide (Hauwert, 2009). A recent study on the Barton Springs segment of the Edwards Aquifer estimates that 28 to 32% of precipitation becomes recharge in the Edwards, including a much higher than previously estimated amount from upland recharge (Hauwert, 2009). Recharge to the upper Glen Rose Formation occurs both from the infiltration of precipitation in stream valleys and the infiltration of water from Bull Creek and its tributaries. All flow within Bull Creek can sometimes be lost between Lanier and Pit springs in the study area, with flow reemerging near and at Pit Spring (Section 2.4.2). In addition, groundwater enters the Glen Rose from leakage from the overlying Edwards and Walnut formations in areas where they are present. Recharge (and/or discharge) may also occur from some of the local lakes (Lake Austin and Lake Travis). Brune and Duffin (1983) indicate that the Colorado River and the lakes along the Colorado (which include Lakes Austin and Travis) have a profound effect upon the ground water of the county, recharging some aquifers and receiving water from others. Based on the character of the Glen Rose in the study area, recharge rates to the Glen Rose Formation from precipitation are assumed to be signi ficantly lower than the rates described above for the Edwards and other karst formations. Rates for the Trinity Group as a whole, which includes the Glen Rose Formation, have been estimated in a majority of previous regional studies to be less than 8% of precipitation in the central Texas area (Scanlon and others, 2003b). 2.3.3 Discharge Discharge fr om the formations in the study area appears to mainly occur naturally. Very little pumpage takes place in the study area because the geologic formations (including the Edwards, which generally has a saturated thickness of less than 10 feet in the area between the WTP4 site and Bull Creek) yield very little water. A few wells do exist, but they likely produce only small quantities of water for domestic and/or livestock purposes. A search of the TWDB WIID database to determine groundwater usage in the study area found that approximately 50 wells are located within 2 miles of the tunnel alignment (Figure 2-8). Of these, nearly 40% are listed as unused and 45% are domestic wells. Approximately 80% of these wells produce from the Trinity (the Glen Rose Formation or

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 18 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 deeper); only nine wells at the eastern end of the tunnel alignment (Figure 2-8) produce from the Edwards Formation, and a majority of these are unused or abandoned. This well distribution supports the assumption that very little pumpage occurs in the study area, and only a small portion of what does occur is produced from the Edwards Formation. Most discharge from the formations in the study area occurs naturally to springs, seeps, and streams in the study area. These are described in detail in Section 2.4. 2.3.4 Hydraulic Characteristics The hydraulic characteristics o f the formations within the study area described in this section are based solely on the testing done during the JTM geotechnical investigation (Black and Veatch, 2009, 2010b). As noted in Section 2.3.3, very few wells exist in the study area. Although the Edwards and associated limestones are a significant aquifer in other parts of the Austin area, within the study area the Edwards is broken up by steeply incised stream valleys into small, isolated areas and is not part of the overall Edwards Aquifer system. In addition to the scarcity of Edwards Formation wells within the study area, pump tests conducted on other Edwards wells in the region, many of which were done on larger, high-capacity wells, are not comparable to the Edwards Formation within the study area. Wells in the study area are typically low-producing domestic and livestock wells, typically screened over large intervals and often over multiple formations, indicating very low capacity to transmit water to wells. Dye-tracing studies in the Edwards/Walnut flow system indicate very high groundwater flow velocities, on the order of tens of feet per day (David Johns, personal communication). This indicates that flow in this upper flow system is typical of flow in a karst or fractured rock system. Actual hydraulic characteristics in a local, shallow, karstic groundwater flow system such as the one in the study area will be very difficult to determine. Testing that was completed as part of the JTM project is described below. As part of the tunnel engineering design, packer testing was conducted on boreholes drilled in 2009 and 2010 to evaluate the in-situ hydraulic conductivity of the bedrock. These data are needed in order to estimate potential groundwater inflows during tunnel construction, but can also be used to generally describe the hydraulic characteristics of the formations being tested. Packer tests were generally performed in 10to 20-foot intervals through the Glen Rose and Walnut formations, though a few very long interval tests (up to 80 feet) were performed during a previous investigation in the study area. These packer tests allow for interpretation of fracture changes during testing, such as dilation, washout, or fracture filling, a nd thereby permit choosing a representative

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 19 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 hydraulic conductivity. Details of the packer testing can be found in the BDR. This section summarizes the testing. One indication of hydraulic conductivity is lost circulation during drilling. This occurs when water being injected to remove the drill cuttings is lost in the formation and no longer returns to the ground surface. This occurred repeatedly through the Edwards Formation, requiring casing to be drilled down into the Walnut Formation. Only one partial lost circulation zone was seen in the Walnut Formation during drilling for this investigation, but lost circulation zones occurred in several Glen Rose borings. The lost circulation zones in the Glen Rose correspond very closely to the higher hydraulic conductivity zones identified by packer testing. Due to the lack of data, quantitative conclusions cannot be made about the Edwards Formation, as only two tests were performed in this unit due to the casing being set through lost water circulation zones. However, the fact that circulation was repeatedly lost indicates the presence of zones of very high hydraulic conductivity, which is consistent with the karstic nature of this unit. Hydraulic conductivity values were calculated based on the results from each successful packer test. The calculated hydraulic conductivity for each test interval is included in a cross section shown in Figure 2-15. Of the 205 packer tests performed, 180 were in the Glen Rose, 23 in the Walnut, and 2 in the Edwards. The two tests that were able to be done in the Edwards Formation were in borings JT-100 and JT-104. One of the Edwards Formation tests showed an extremely low (less than 1.0 x 10 6 centimeters per second (cm/s)) hydraulic conductivity, and the second showed a very high hydraulic conductivity. Packer tests were not able to be performed on the remainder of the Edwards Formation in either of these borings, or on any of the Edwards Formation in any of the other borings on this project. Therefore, the two results from the Edwards Formation are not considered representative of the Edwards Formation in general, and the remainder of this discussion is limited to hydraulic conductivity in the Glen Rose and Walnut formations. In general, the Glen Rose has very low hydraulic conductivity, with the majority of the data (63%) having values of less than 1.0 x 10 6 cm/s (Figure 2-16). However, some zones within the Glen Rose Formation have higher hydraulic conductivity, especially in the very upper portions of this formation, within approximately 50 feet of the contact with the overlying Walnut Formation. The maximum calculated hydraulic conductivity value in the Glen Rose Formation was 3.0 x 10 3 cm/s. The majority of the high hydraulic conductivity measurements (>1 x 10 4 cm/s) were in vuggy zones primarily in dolomite, as shown in Figure 2-17.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 20 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Of the 23 packer tests performed in the Walnut Formation, 74% have a value of less than 1 x 10 6 cm/s (Figure 2-18). The maximum value was 2.5 x 10 3 cm/s, but this interval straddled the lower Walnut and the top of the Glen Rose and is possibly a result of Glen Rose hydraulic conductivity which, as noted above, tended to be higher immediately below the contact with the Walnut. The next highest value in the Walnut was 4 x 10 5 cm/s, reflecting a very low overall hy draulic conductivity in the Walnut Formation. However, during drilling for borehole B-02 that was done for the Forest Ridge assessment (Figure 2-6), several zones with up to 100% water loss were noted in the Walnut Formation; indeed, packer testing could not be conducted on the Walnut in this boring because of the amount of water loss (Holt Engineering, 2009). Therefore, areas with the potential to move larger amounts of water within the Walnut Formation are present in the study area. 2.3.5 Groundwater Levels Groundwate r elevations from piezometers and monitoring wells on November 30, 2010 are summarized in Table 2-1 and shown on Figures 2-19 and 20 for the Edwards/Walnut and upper Glen Rose groundwater flow systems, respectively. Groundwater elevations in the study area range in elevation from 720 to 979 feet above mean sea level (ft msl) and depths to groundwater vary from 15 to 75 feet below ground surface (ft bgs). Because a limited number of wells are screened or open only within shallower depths, Figure 2-19 includes the elevations of springs that discharge from the Edwards, Walnut, and Glen Rose formations to provide a more complete picture of the Edwards/Walnut groundwater system near the proposed tunnel alignment. Groundwater in the Edwards/Walnut flow system appears to follow topography, as commonly occurs in shallow, unconfined groundwater flow systems. As noted in Section 2.3.3, discharge occurs primarily at springs and seeps located in the incised stream valleys cutting down into and through the Edwards Formation. For this reason, it is assumed that topographic divides and/or surface watersheds also form groundwater divides, with groundwater flow on one side of the topographic divide generally tending to move toward springs and seeps located in stream valleys on the same side of the divide. Based on this assumption, it would appear that some groundwater divides occur in the Four Points area (Figure 2-21). Due to the scarcity of data, the exact locations of the divides in the area are not known. However, because field observations of the springs immediately adjacent to the WTP4 site indicate that discharge rates are relatively small compared to springs on the other side of the divide, it is assumed that the springsheds for these springs are also smaller and the groundwater divide in the area is therefore relatively close to the WTP4 site.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 21 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Table 2-1 Groundwater Levels Well Primary Formation Screened Approximate Screened Interval (ft bgs) Date Water Elevation (ft msl) JT-101A Edwards 63-83 11/30/10 978.5 JT-103A Glen Rose 130-150 11/30/10 827.8 JT-104A Glen Rose/Walnut 103-123 11/30/10 779.3 JT-109 Edwards 20-40 11/30/10 965.7 JT-110A Glen Rose 244-264 11/30/10 823.4 JT-112 Edwards 75-95 11/30/10 977.5 JT-113 Edwards 71-91 11/30/10 965.9 JT-114 Edwards 63-83 11/30/10 956.7 JT-118A Glen Rose 80-100 11/30/10 720.3 JT-120A Glen Rose 73-93 11/30/10 720.0 JT-124A Edwards 85-105 11/30/10 854.5 JT-125A Glen Rose 225-245 11/30/10 822.0 JT-126 Glen Rose 316-336 11/30/10 801.9 ft bgs = Feet below ground surface ft msl = Feet above mean sea level Also included on Figure 2-21 are water levels measured in four piezometers in the Edwards in the Four Points/WTP4 area. These water level data appear to confirm the presence of a groundwater divide, or divides, in the Four Points area. Water levels in two piezometers (JT-101A and JT-112) are higher than water levels on the western side of the WTP4 site (JT-109) and further to the east (JT-113 and JT-114), indicating the presence of a divide in the vicinity of JT-101A and JT-112. However, the general assumption that groundwater in the Edwards/Walnut flow system respects major watershed divides may not always hold true in a karst environment. Groundwater flow in a karst system, as described in Section 2.3.1, can be highly complex and difficult to define. Groundwater flow directions can vary significantly from

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 22 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 area to area, they can change at different water levels, and groundwater flow paths can cross major surface water divides. Dye tracing conducted by the City of Austin has shown that groundwater flow can cross topographic divides and discharge at springs that would not normally be expected to receive groundwater flow from a particular area (David Johns, personal communication, 2010). So while groundwater in the Edwards/Walnut flow system is expected to generally follow topography, there may be exceptions where groundwater moves in an unexpected direction. However, considering the limited saturated thickness of the Edwards in the Four Points area, the groundwater divide being relatively consistent with the surface divides would not be unexpected. Groundwater elevations associated within the Glen Rose groundwater flow system near the study area are shown in Figure 2-20. Glen Rose Formation groundwater levels in the study area range in elevation from 525 to 828 feet, with the depth to water ranging from less than 10 feet to more than 450 ft bgs. As discussed in Section 2.3.1.2 and shown in Figures 2-13 and 2-14, nested piezometers indicate that there is a strong downward gradient within the Glen Rose Formation. The contact between the Walnut and Glen Rose formations is at an elevation around 837 ft msl near nested piezometers B-8, B-9, and B-10; the water level elevation for the topmost Glen Rose piezometer for these locations is shown in Figure 2-20. Because of the strong downward gradient and the variability in depths where groundwater elevation data is available, attempting to relate lateral trends of water levels in the Glen Rose Formation based on the current data set would likely provide misleading results; therefore, while water levels are posted in Figure 2-20, no attempt has been made to contour them. 2.4 SURFACE WATER The study area is mostly contained within the Bull Creek watershed, although portions are also located within the Lake Travis, Panther Hollow, and Rattan Creek watersheds (Figure 2-22). Surface water flow within Bull Creek is supported by spring discharge from the Edwards/Walnut groundwater flow system found within the Edwards, Walnut, and upper Glen Rose formations. 2.4.1 Springs As describe d in Section 2.3.1.1, groundwater in the Edwards/Walnut flow system originates as precipitation that falls on the exposed Edwards Formation in the topographically higher parts of the study area. The water migrates downward until a more resistant horizon is encountered and then moves laterally until it emerges as spring discharge on the sides of the steeply incised stream valleys typically found in the area. This spring discharge supports flow in Bull Creek and its tributaries, provides important

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 23 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 habitat for a variety of species in the area including the Jollyville Plateau Salamander, and ultimately discharges into the Colorado River/Lake Austin. The locations of mapped springs and seeps in the study area are shown in Figure 2-23. It should be noted that the locations shown in Figure 2-23 are only those that have been currently mapped or are known to exist by City of Austin staff, and are thus only in those locations where field studies have been conducted to identify spring locations. City of Austin staff commonly find new springs when they are in the study area doing field work (Scott Hiers, personal communication, 2010). It is likely that more spring locations are present in the study area than those shown in Figure 2-23. 2.4.2 Bull Creek A detailed e valuation of low flow in Bull Creek was conducted as part of this groundwater assessment (Slade, 2010). Beginning in April 2009, monthly streamflow and water quality data and water levels in wells were collected in the upper Bull Creek basin, in the locations shown in Figure 2-24. The purpose of the study was to establish background baseflow and water quality conditions for Bull Creek to help assess any potential impact from the installation of the proposed tunneling project and to infer a relationship between the recorded flow data at the USGS stream gage located at Bull Creek and Loop 360 (outside the study area) and estimated flow within the study area. Climat ic conditions varied significantly during the course of the study, allowing the assessment of extremely diverse hydrologic conditions. During the first six months of the proj ect, the region was experiencing an extended drought (dry period baseflow), while the latter six months, following the drought, were extremely wet (wet period baseflow). The Bull Creek flow study provided a good baseline for conditions in Bull Creek. Streamflow within the creek consistently in creased from upstream of the former WTP4 to Spicewood Springs Crossing 7, although observations within the BCP property show that the creek typically goes dry for several hundred yards between Lanier Springs and Pit Spring (Figure 2-24). Measured flows from this study are summarized in Table 2-2. These flows were all measured after increased stormflow from any rainfall events had subsided. Streamflow in the study area varied widely during the dry period, with zero flow at all of the gaged locations in at least one month during the study period, while the wetter periods resulted in expectedly greater flow.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 24 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Table 2-2 Bull Creek Streamflow Measurements Location Wet/Dry? Discharge Range (cfs) Dry 0 0.22 Upstream Wet 0.16 Dry 0 0.83 Pit Spring Wet 1.25 3.13 Dry 0 1.97 Spicewood RC7 Wet 5.25 9 Dry 0 4.5 USGS Gage Wet 7.8 26 cfs = Cubic feet per second At the location designated Bull creek upstream old WTP4 in Figure 2-24, Figure 2-25 shows streamflows in upper Bull Creek compared to precipitation in the area. This figure demonstrates the variability that occurs in Bull Creek streamflow over time and the flashy nature of the flow. Very high-magni tude flows occur after several significant rainfall events, followed by a rapid return to base conditions, which then steadily decline until the next significant rainfall event. As shown in Figure 2-25, Bull Creek went dry during several periods in 2008 and 2009, although some of the apparently dry periods (such as at the beginning of 2008) may be due to data not being collected rather than to no flow in the creek. Because of this broad variability in magnitude, discharge at these sites cannot be used to give any meaningful indication of future unnatural changes in flow (Slade, 2010). However, a comparison with respect to runoff per square mile that was made between the most upstream site monitored (upstream of the old WTP4 site) and the most downstream site monitored (Spicewood Springs Road Crossing 7) indicates that this low-flow characteristic might be used as an indicator of unnatural changes in the flow regime in the future (Slade, 2010). Streamflow variation in the wet period was more related to surface drainage area size and the location of the monitoring station within the study area (more upstream or more downstream) (Slade, 2010). Expectedly, monitoring sites with both a larger surface drainage area and a further downstream location showed more variability in flow as well

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 25 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 as higher flow volumes. Flow at the upstream-most site (upstream of the old WTP4 site) had almost no variation during the wet period and was less than 1 cubic foot per second (cfs) during each monitoring event. Conversely, flow at the downstream-most site (Spicewood Springs Road Crossing 7) varied from slightly more than 5 cfs to 9 cfs during the wet period. It was concluded that any future variation in the upstream sites relatively constant discharge during this wet period might indicate changes in flow due to unnatural conditions (Slade, 2010). In addition, a statistical relationship was established between flow volumes at the other two monitored sites, and any departure from this relationship might also indicate disruption of the contributing flow regimes due to unnatural factors (Slade, 2010). The USGS gage is located approximately 5.5 miles downstream of the study area and has a surface drainage area of 22.3 square miles. Additionally, there are at least ten contributing drainages that intersect Bull Creek between the most downstream measuring point and the USGS station. Minimum, maximum, and mean stream flow rates at the USGS gage were acquired from the USGS website for the same dates that the low flow study was conducted. These data were then plotted alongside the low flow study data in an attempt to correlate the two (Figure 2-26). Expectedly, flow varied even more at the USGS gage during both dry and wet periods than at the low flow studys downstream-most station. During the dry period (low-flow conditions) flow varied from 0 cfs during two of those months to approximately 4.6 cfs. During the wet period (highflow conditions) flow varied from approximately 8 cfs to 26 cfs. Obviously, these higher flows are the result of a larger surface drainage area and more contributing drainages than were found in the upper Bull Creek study. While it is potentially feasible that unnatural disruption in the upper Bull Creek flow regime might result in quantifiable changes in flow downstream at the USGS gage, a meaningful relationship between recorded flow at the USGS stream gage and estimated flow in the area of the creek along the tunnel alignment cannot be drawn. A gain-loss flow study was conducted by the City of Austin on May 13, 2010. For this study 16 locations along Bull Creek from upstream of the former WTP4 site to Bull Creek at Lakewood/Loop 360 (Figure 2-27) were measured on the same day. Table 2-3 summarizes estimated streamflows based on field measurements, and Figure 2-28 shows a profile of Bull Creek streamflows through the entire length of Bull Creek that was measured. Both the table and the figure show the complete loss of water between Lanier and Pit Springs, and then the consistent gain in streamflow from Pit Spring to Bull Creek Crossing No. 6. Downstream of Crossing No. 6, streamflow increases slowly all the way to Lake Austin. One aberrant measurement at Bull Creek Crossing No. 4 is considered suspect. It should be noted that streamflow in the gain-loss study was

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 26 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 measured at approximately 3 cfs at the downstream gage, although the USGS gage reported a flow of 4.5 cfs on that date. Table 2-3 Bull Creek Streamflow Measurements Site No. Location Total Distance (feet) Streamflow (cfs) 101 Bull Creek upstream of WTP4 0 0.019 102 Bull Creek downstream of WTP4 (former gage) 4,400 0.42 104 Bull Creek downstream of Lanier Spring 7,650 0.423 105 Bull Creek 8,350 0.343 106 Bull Creek upstream of Pit Spring 9,750 0 107 Bull Creek downstream of Pit Spring 10,500 0.674 108 Bull Creek downstream of tub 5 13,100 1.424 109 Bull Creek Crossing No. 7 17,300 2.376 201 Bull Creek Crossing No. 6 19,100 2.735 202 Bull Creek Crossing No. 5 25,600 2.522 203 Bull Creek Crossing No. 4 28,500 3.641 204 Bull Creek Crossing No. 3 30,500 2.55 205 Bull Creek Crossing No. 2 33,250 2.665 206 Bull Creek Crossing No. 1 35,250 3.007 207 Bull Creek Crossing No. 11 39,150 2.749 208 Bull Creek @ Lakewood/Loop 360 46,900 2.935 cfs = Cubic feet per second 2.5 WATER QUALITY The water quality in Bull Creek is likely the result of a variety of sources, including the water quality of springs that support flow in the creek as well as the water quality of overland flow through surface features (Gi ng, 1995). In addition to runoff from developed areas, overland and subsurface water interacts with rocks from the Edwards, Comanche Peak, Walnut, and Glen Rose formations, all of which affect surface water quality in different ways. Water quality data from Bull Creek surface water samples and groundwater data from the TWDB database was compared in order to examine potential differences in water composition of Bull Creek and the underlying Walnut and Glen Rose formations. The TWDB database contained wells in the general area of the proposed transmission main

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 27 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 that are designated as being screened in the Glen Rose Formation. None of the study area wells in the database are designated as being screened in the Walnut Formation, and no wells in the study area with water quality data are screened in the Edwards Formation. Water samples from Bull Creek and the underlying upper Glen Rose Formation appear to contain different ratios of major cations and anions. In order to compare the distribution and differences of major cations and anions within each water sample, results were plotted on Piper diagrams. The tight grouping of samples from Bull Creek indicate a quite uniform composition (Figure 2-29), a predominantly calcium-bicarbonate water type with a trend toward chloride and sulfate enrichment. This result corresponds with the results from a previous study (Ging, 1995). Samples from the underlying Glen Rose Formation show a wider range of geochemical signatures (Figure 2-30), with higher concentrations of sulfate and magnesium in the water samples. The majority of samples from the Glen Rose appear to be geochemically distinct from the samples in Bull Creek. The TWDB samples from the lower Glen Rose Formation generally contain higher concentrations of dissolved ions than those from the upper Glen Rose Formation. As a general trend, the concentration of major ions in groundwater increases with depth within the study area. The results from Ging (1995) also indicate that the surface water flow system in Bull Creek is separate from the groundwater in the Glen Rose Formation as sampled from selected wells. Based on a review of the available data, there does not appear to be a distinct relationship between the underlying water in the Glen Rose Formation and surface water flow in Bull Creek. However, the available data are insufficient to make any definitive determination regarding connectivity. There are no water quality samples for the Edwards or Walnut formations in the study area. Further, most, if not all, of the data are dated. Gings data are from sampling events conducted in 1993. The groundwater data from the TWDB dates from as far back as 1934, and the other water samples from the upper branch of Bull Creek span a 30-year time frame from 1975 to 2005.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 28 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 3.0 POTENTIAL GROUNDWATER IMPACTS The transmission main and associated shafts being addressed by this assessment can generally be divided up into five individual components: the main transmission tunnel and four shaft locations associated with it (Figure 3-1). The geology and hydrogeology associated with these locations, including a discussion of the potential impact these locations have on groundwater flow in the area and spring discharge associated with that groundwater flow, are summarized in Sections 3.1 through 3.3. 3.1 SHAFT EXCAVATION / CONSTRUCTION IMPACTS Four shafts are required as part of the JTM project. Many of the questions regarding the proposed shafts are related to their potential impact on discharge to springs and seeps in the area and the subsequent impact on Jollyville Plateau Salamander habitat. Much of the discussion in this section is based on general trends observed in the study area and discussed in Section 2. Because of the nature of the groundwater flow systems in the study area, in particular the karstic nature of the formations underlying three of the proposed shaft locations, the specific impact of each individual shaft cannot be definitively quantified. Three of the four proposed shafts will be constructed through the Edwards Formation, and the potential impact of these shafts on discharge at individual springs in the vicinity of the shafts is unknown. A quantitative determination of the potential impact cannot be made, as individual conduit locations and flow directions at each shaft location are not known. However, some generalities can be made regarding the locations of the shafts and the springs they potentially impact. In general, groundwater in the Edwards/Walnut system on the topographic highs moves radially away from the hilltops to spri ngs and seeps along incised stream valleys dissecting the topography in the area. The closer a proposed shaft is to a drainage and the springs that discharge in that drainage, the more likely it is that subsurface flow at the shaft location will ultimately discharge in that drainage. In addition, the closer that a proposed shaft is to a particular spring, the more quickly any impact caused by the shaft will occur to the spring. The correlation between distance and likelihood and speed of impact is because the closer that a shaft location is to a spring or springs, the more likely that the shaft is located within the springshed of the spring(s). However, as discussed in Section 2, this is not a definitive rule in a karst environment, and groundwater flow in karst may behave in unexpected ways, moving in directions different or even opposite to

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 29 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 what would be expected, and even moving in different directions from the same location depending on water levels. An additional question that has been raised about the proposed shafts is the potential impact to springs in the event that the Edwards and Walnut formations undergo some local dewatering as a result of construction of the shaft. However, mitigation techniques will be used to minimize groundwater inflow to the shafts during construction and operation. Once the shafts are constructed, inflows into them are expected to be minimal. The proposed shaft locations include those at WTP4, Four Points, the Parks and Recreation Department (PARD) site, and the Jo llyville Reservoir site (Figure 3-1). These locations are described in Sections 3.1.1 through 3.1.4. 3.1.1 Water Treatment Plant 4 Shaft Site The WTP4 shaft is lo cated at the water treatment plant site near the intersection of RR 620 and Bullick Hollow Road at the western end of the alignment (Figure 3-1). A more detailed site map of this shaft location is shown in Figure 3-2. This shaft is a retrieval shaft and is anticipated to be approximately 20 to 30 feet in diameter and 205 feet deep. This shaft is located on a topographic high adjacent to several incised stream valleys that drain to Lake Travis. Several mapped seeps or springs are located near this proposed shaft location (Figure 3-2). The WTP4 shaft location will be constructed through the Edwards, Walnut, and Glen Rose formations. Numerous borings have been drilled in the site, one of which (JT-109) was specifically drilled at the location of the proposed shaft on May 25, 2010. The following is a description of the geology observed in this boring. The Edwards Formation is present at this location to a depth of 32.7 ft bgs. The Edwards is described as fineto coarse-grained limestone, vuggy, slightly weathered, weak, fossiliferous, with moderate hardness to a depth of 18 feet. The Edwards grades into massive, fine-grained limestone at 18 feet and persists until 32.7 feet. The Walnut Formation is observed in the boring starting at 32.7 ft bgs. The Walnut Formation is a fine-grained, slightly weathered, weak, moderately hard limestone with small scattered vugs. Some argillaceous laminations are present. A zone of argillaceous limestone extending from 66.5 to 79.4 ft bgs is classified as fresh, fine-grained, very weak, with moderate to low hardness. According to the boring log, the core from this section shows some erosion from the drilling fluid. At 79.4 ft bgs the argillaceous zone ends with the Walnut appearing as

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 30 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 massive, fine-grained, fresh, moderately hard limestone, which persists to the bottom of the formation. The Glen Rose Formation is observed in this boring at 111.6 ft bgs. Although initially limestone, the Glen Rose quickly becomes dolomite and is described as fine-grained, moderately weathered, weak, and moderately hard, becoming vuggy at approximately 117 ft bgs. The Glen Rose appears fresh at 120 feet with the scattered vuggy nature persisting through this transition from weathered to fresh. Beginning at 130.4 ft bgs, the Glen Rose alternates between zones of limestone and dolomite. The limestone sections are generally described as fresh, weak, and moderately hard, with bedding present in some zones but absent in others. The dolomite zones are similar to the limestone zones except that bedding is absent and they are described as vuggy, with some core sections shattered due to the extremely vuggy nature of the dolomite at that depth. The alternating pattern of limestone/dolomite appears to end at around 207 ft bgs, and the core for the remainder of the boring is described as fine-grained, fresh, weak, moderately hard limestone. The boring logs and core photographs from borings JT-100 and JT-110 were also reviewed for this assessment. JT-100 lie s approximately 380 feet south and 1 foot higher in elevation than JT-109. JT-110 lies approximately 1,360 feet southeast and 45 feet higher in elevation than JT-109. The original log descriptions for these two borings were done at separate times by different individuals, and many differences between the boring logs may be attributed to that. Lithology is generally similar to that found in JT-109, although the Edwards Formation is thicker in JT-110. Additionally, the Edwards Formation appears more weathered with more voids and vugs logged in JT-110 than in JT-100 or JT-109. Further, an approximately 17-foot-thick section of Edwards, from 18 to 35 ft bgs, is classified as dolomite in JT-110. Packer tests were conducted on these three borings and are tabulated for each tested interval in Table 3-1. The hydraulic conductivity (K) is an average of the step results for each interval. As noted in Section 2, very few packer tests were conducted in the Edwards Formation because of the inability to pressurize the boring within the Edwards. In fact, in many borings the Edwards had to be cased off because of lost circulation while drilling. This is indicative of a very hi gh hydraulic conductivity in this formation.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 31 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Table 3-1 Summary of Packer Tests near the Proposed WTP4 Shaft Location Boring No. Test Interval (feet) No. of steps Hydraulic Conductivity (cm/s) Geologic Formation JT-100 15 31.7 5 3.14 x 10 4 Edwards 35 51.7 3 < 10 7 Edwards/Walnut 55 71.7 5 < 10 7 Walnut 75 91.7 5 < 10 7 Walnut 95 111.7 3 < 10 7 Walnut 115 131.7 5 7.67 x 10 4 Glen Rose 135 151.7 5 9.57 x 10 4 Glen Rose 148 164.7 5 < 10 7 Glen Rose 163 179.7 5 < 10 7 Glen Rose 186.3 203 5 1.22 x 10 4 Glen Rose 203.2 220 4 < 10 7 Glen Rose JT-109 51.2 71.9 5 1.2 x 10 5 Walnut 71.2 91.9 5 3.7 x 10 5 Walnut 91.2 111.9 5 < 10 7 Walnut 111.2 131.9 5 2.2 x 10 3 Glen Rose 131.2 151.9 5 2.2 x 10 3 Glen Rose 151.2 171.9 5 3 x 10 6 Glen Rose 171.2 191.9 5 < 10 7 Glen Rose 191.2 207.2 5 6.3 x 10 7 Glen Rose 206.2 222.2 5 1.5 x 10 7 Glen Rose 221.2 233.7 5 < 10 7 Glen Rose JT-110 228.3 240.7 5 1.6 x 10 6 Glen Rose 238.3 250.7 5 4.6 x 10 7 Glen Rose 248.3 260.7 5 < 10 7 Glen Rose 258.3 270.7 5 1.1 x 10 6 Glen Rose 268.3 280.1 5 < 10 7 Glen Rose cm/s = Centimeters per second In general, the packer tests indicate that the Walnut Formation has a very low hydraulic conductivity, as would be expected. The Glen Rose had a variable hydraulic conductivity profile. In boring JT-109, the upper 40 feet of the Glen Rose had a significantly higher

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 32 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 estimated hydraulic conductivity from this testing than the remainder of the boring, which showed a very low hydraulic conductivity The upper 37 feet of boring JT-100 showed the same characteristic, although one interval near the bottom of this boring also showed a higher hydraulic conductivity. All tests in boring JT-110 were in the Glen Rose and resulted in very low estimates of hydraulic conductivity. The proposed WTP4 shaft is located at the WTP4 site, which is currently under construction. The location is on a topographic high and is surrounded by incised stream valleys on all sides except the southwest. The groundwater levels shown in Figure 2-21 and the local topography (and corresponding surface divides) suggest that groundwater flow is generally to the west or northwest across the WTP4 site, although insufficient data exists to fully define groundwater flow in this area. Based on our understanding of the Edwards/Walnut groundwater flow system which is the primary groundwater system that may be impacted by the proposed shaft, any of the springs in the area surrounding the shaft location could potentially be impacted by the shaft (Figure 3-3). However, the springs in this area will not necessarily be impacted by the proposed shaft. It is possible that: No individual conduits are intersected by the shaft, An individual conduit that supplies groundwater to a spring in the area is intersected, but the groundwater finds an alternate path to the same spring or springs after the installation of the shaft, An individual conduit that supplies groundwater to a spring in the area is intersected, but the groundwater flow is restored through mitigation measures employed during shaft construction, An individual conduit that supplies groundwater to a spring in the area is intersected and groundwater flow is not restored along the same path, but this conduit is not the sole source of water for a particular spring (dye tracing conducted by the City indicated that individual springs received dye from multiple sources injected during the tracing study), An individual conduit that supplies groundwater to a spring in the area is intersected, groundwater flow is not restored, and the springflow is reduced and/or may eventually go dry, or The spring may not be fed by conduits. No definitive conclusions can be reached as to which, if any, of these four scenarios will occur in the Edwards/Walnut groundwater flow system with the installation of the shaft. However, no adverse impact on the deep flow system in the Glen Rose Formation is anticipated during the construction of this shaft based on the downward hydraulic

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 33 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 gradient in this formation and the very low hydraulic conductivities seen in the boring drilled at the proposed shaft location. Section 4 presents design mitigation measures to control shallow groundwater flow into shafts. 3.1.2 Four Points Shaft Site The Four Points shaft is located in the Four Points (FM 2222/RR 620) area near the western end of the tunnel alignment (Figure 3-1). A more detailed site map of this shaft location is shown in Figure 3-4. This shaft is a working shaft and is anticipated to be 40 feet in diameter and 275 feet deep. This shaft is located on a topographic high adjacent to several incised stream valleys that are part of the Bull Creek and Panther Hollow watersheds (Figure 2-22). Three unnamed but mapped springs are located within 3,000 feet of the shaft, two a little over 2,000 feet to the north and northeast of the shaft, both located on a private preserve, and one located approximately 2,750 feet to the southeast of the proposed shaft location on 3M property (Figure 3-4). Additional springs are likely to be present in some steep canyons to the southwest of the proposed shaft location on the other side of FM 2222; however, this location has not been accessed by City of Austin staff and no springs or seeps have been mapped. Nevertheless, this is considered an unlikely direction for groundwater to move from the proposed Four Points shaft location because it is on the other side of surface and groundwater divides. Springs exist southeast of the shaft, but these are very unlikely to be impacted because they are located on the other side of surface and groundwater divides with the closest spring having a higher elevation than the water level in JT-112 at the shaft location. The Four Points shaft location will be constructed through the Edwards, Walnut, and Glen Rose formations. Boring JT-112 was drilled at the location of the proposed shaft on August 31, 2010 (Figure 3-4). Depth to water in a well installed at this location was estimated to be 80 ft bgs. The following is a description of the geology observed in this boring. The Edwards Formation is present in the boring to a depth of 84.6 ft bgs. The initial 10-foot section was drilled using an auger and is described as completely weathered, vuggy, and fractured, with clay and calcite. Hard rock coring began at a depth of 10 feet in Edwards Limestone described as fineto mediumgrained, vuggy, moderately hard, and moderately weathered with some fossils present. A claystone zone is present from approximately 31 feet to 35 feet deep and is described as very weak with low hardness and no vugs. From approximately 41 to 58 ft bgs the limestone becomes dolomitic, which is described as vuggy, weak, moderately hard, and slightly weathered. Notably, vugs are absent beginning at 52 feet, although the boring log notes some water

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 34 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 loss at approximately 56 feet. A 5-foot-thick bed of vuggy, very weak, slightly weathered dolomite is present from approximately 64 to 69 ft bgs. The boring log notes that 50% water loss occurred in this section and that there was no core recovery from 65 feet to 66.1 feet. For the remainder of the Edwards section the core is described as vuggy, fine-grained limestone with occasional fossils and moderately hard to hard, and the core retrieved from this interval was quite fractured. At a depth of approximately 70 feet, 100% water loss was reported. The Walnut Formation begins at a depth of 84.6 ft bgs and continues until the Glen Rose is encountered at 180 ft bgs. Initially, the Walnut is described as an argillaceous, fine-grained limestone that is slightly weathered, mottled, very weak, and has low to moderate hardness. At 108.5 feet, the rock character changes to massive, argillaceous, fine-grained, fresh, moderately hard, weak limestone with few vugs. The boring log notes that circulation was lost at 115 feet and subsequently regained at 135 ft bgs. A physical inspection of this core section shows the core as being quite solid throughout this 20-foot section, so the reason for the loss of circulation is unknown. The character changes at 177.3 ft bgs to a massive, fine-grained, slightly weathered limestone that is described as moderately strong, moderately hard, but no longer argillaceous in nature. The Glen Rose Formation was first observed in the boring at a depth of 180 feet and is described at fine-grained, argillaceous dolomite that is slightly weathered, moderately strong, and moderately hard with some calcite-filled vugs. An 18-foot-thick non-vuggy section runs from 187 feet to 205 feet, at which point vugs are again noted in the boring. The zone from 210.5 feet to 212.5 feet is described as vuggy and fossiliferous. Beginning at 212.5 ft bgs, the Glen Rose alternates between beds of limestone and beds of dolomite up to 9 feet thick. The limestone beds are generally fresh, hard, weak, fine-grained, and sometimes burrowed and/or mottled. Dolomite beds are fineto medium-grained, weak to moderately strong, hard, slightly to very vuggy, with fossils present in some beds. Packer tests were not run on JT-112 due to time restrictions on the right-of-entry to the boring location. However, packer tests were run on two nearby borings, JT-102 and JT-111. JT-102 is located approximately 800 feet to the east from the proposed shaft location, and JT-111 is located approximately 1,500 feet to the west of the proposed shaft location. Packer test summaries are tabulated for borings JT-102 and JT-111 in Table 3-2.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 35 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 In general, the packer tests indicate that the hydraulic conductivity in the Walnut in this area is very low, with five of the six Walnut intervals in JT-102 having no water loss during the testing. Hydraulic conductivities in the Glen Rose are somewhat variable: Table 3-2 Summary of Packer Tests near the Proposed Four Points Shaft Location Boring No. Test Interval (feet) No. of steps Hydraulic Conductivity (cm/s) Geologic Formation JT-102 88.2 103.6 3 < 10 7 Walnut 103.2 118.6 3 < 10 7 Walnut 118.2 133.6 3 < 10 7 Walnut 133.2 148.6 3 3.5 x 10 5 Walnut 148.2 163.6 3 < 10 7 Walnut 163.2 178.6 3 < 10 7 Walnut 178.2 193.6 5 1.03 x 10 4 Walnut/Glen Rose 193.2 208.6 5 1.01 x 10 4 Glen Rose 208.2 223.6 5 1.05 x 10 3 Glen Rose 223.2 240.4 5 2.7 x 10 4 Glen Rose 238.2 255 3 < 10 7 Glen Rose JT-111 192 208 5 2.8 x 10 6 Glen Rose 207 223 5 6.3 x 10 6 Glen Rose 222 248 5 3.0 x 10 6 Glen Rose 237 253 5 9.5 x 10 6 Glen Rose 252 268 5 8.3 x 10 6 Glen Rose 267 282 5 1.7 x 10 5 Glen Rose 282 299.5 5 < 10 7 Glen Rose cm/s = Centimeters per second In JT-111 the estimates of hydraulic conductivity are very low, with all intervals being approximately 10 5 cm/s or lower. This section of boring JT-111 includes the upper portion of the Glen Rose, which is commonly observed in the study area to be more permeable. In JT-102, higher permeability in the upper section of the Glen Rose is again observed, with the upper 50 feet of the formation having hydraulic conductivity estimates of approximately 10 4 cm/s.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 36 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 These two borings indicate the variability in characteristics of the formations of interest across even relatively small distances (in this case less than 2,500 feet). The proposed Four Points shaft location is on a topographic high and is surrounded by incised stream valleys to the north and southwest. Based on our understanding of the nature of flow in the Edwards/Walnut groundwater flow system (Section 2.3.1.1), the most likely area where groundwater from the proposed Four Points shaft location may flow is to the north and northeast of the proposed shaft location (Figure 3-5). This understanding is based on dye tracing studies conduc ted by the City of Austin at the old WTP4 site, which showed that in the Edwards/Walnut flow system groundwater moved radially from the top of the hilltops and discharged in springs and seeps in drainages. It is also possible that groundwater from the proposed shaft location may flow to springs located in the steep canyons to the southwest of the proposed shaft location, even though they are on the other side of a topographic divide and are in a different surface watershed than the shaft. As with the WTP4 shaft described in Section 3.1.1, the springs in this area will not necessarily be impac ted by the proposed shaft and no adverse impact on the deep flow system is anticipated by the construction of this shaft. Additional design mitigation measures to prevent shallow groundwater flow into the shafts are discussed in Section 4. 3.1.3 Parks and Recreation Department Site The PARD s haft is located near the intersection of Spicewood Springs Road and Old Lampasas Trail, to the northeast of the middle of the tunnel alignment (Figure 3-1). A more detailed site map of this shaft location is shown in Figure 3-6. This is a retrieval shaft and is anticipated to be approximately 20 to 30 feet in diameter and 1300 feet deep. This shaft is located on fill approximately 250 feet west of a tributary (Tributary 4) and north of an incised stream bottom near Bull Creek. Two mapped springs are located within half a mile of the location: Small Sylvia Spring, found approximately 2,300 feet to the northeast, and Texas Plume Spring, located approximately 2,600 feet to the northeast of the shaft location (Figure 3-6). Small Sylvia Spring is a confirmed Jollyville Plateau Salamander location. Recent field work has identified two seep horizons in Tributary 4 downstream of the PARD site and a small spring (Hicks and Company, 2010b). Additional small, unmapped seeps and springs have been observed in the vicinity of the PARD site. The PARD shaft location will be constructed entirely through the Glen Rose Formation and approximately 20 feet of construction fill located on top of the Glen Rose at the site. Boring JT-120 was drilled at the proposed shaft location on May 16, 2010 (at the same location as JT-120A shown on Figure 3-6). Because of the fill present at this location the

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 37 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 boring was not logged from surface to a depth of 21 feet. Below that depth, the Glen Rose Formation was the only formation present in this boring. The geology observed in the boring was as follows: Beginning at a depth of 21 ft bgs, the Glen Rose Formation alternates between beds of dolomite and limestone, with bed thicknesses of up to almost 10 feet thick. The dolomite beds can generally be described as vuggy, slightly weathered becoming fresh with depth, fineto coarse-grained, moderately hard, weak, and sometimes burrowed. The limestone beds can generally be described as fineto coarse-grained, fresh, weak, and moderately hard with some sections mottled and/or containing the occasional fossil. This alternating pattern continues to a depth of 96.5 feet. Beginning at a depth of 96.5 feet is a mottled, fine-grained, fresh limestone that is weak, fossiliferous, and moderately hard. Vugs appear to be rare or absent based both on review of lithologic logs and core photographs. The boring terminates at 154.5 feet. Packer test summaries are tabulated for boring JT-120 in Table 3-3. In general, the packer tests indicate that the upper 15 feet of the Glen Rose Formation has a higher hydraulic conductivity and the remainder of t he boring, very low hydraulic conductivities. In fact, most of the packer tests in this boring were unable to measure any water loss during the testing, and so the hydraulic conductivities are reported as zero. Both the Small Sylvia and Texas Plume springs are found hydrologically upgradient of the shaft location. In contrast to the proposed WTP4, Four Points, and Jollyville Reservoir shafts, which are all located topographically above the springs that they may impact and have the potential to directly intercept a discrete flow pathway that supplies groundwater to these springs, the PARD shaft is located topographically below (downgradient) of the springs in the area. Therefore, the only way the PARD shaft might influence discharge to these two springs is if the shaft indirectly diverted flow that would otherwise go to the spring orifices. Because this shaft is located more than 2,000 feet from both of these springs, is located in the low-hydraulic conductivity Glen Rose Formation and overlying fill, has mitigation measures in place to minimize inflow into the shaft while it is being constructed, and will not dewater the formation after completion, the potential that this shaft would divert springflow away from these springs is considered to be negligible.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 38 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Table 3-3 Summary of Packer Tests near the Proposed PARD Shaft Location Boring No. Test Interval (feet) No. of steps Hydraulic Conductivity (cm/s) Geologic Formation JT-120 22 37.7 5 6.3 x 10 4 Glen Rose 37 52.7 5 < 10 7 Glen Rose 52 67.7 5 4.7 x 10 5 Glen Rose 67 82.7 5 < 10 7 Glen Rose 82 97.7 5 < 10 7 Glen Rose 97 112.7 5 < 10 7 Glen Rose 112.7 127 5 < 10 7 Glen Rose 127 142.7 5 < 10 7 Glen Rose 142 154.5 5 < 10 7 Glen Rose cm/s = Centimeters per second The PARD shaft is also located approximately 600 feet from Bull Creek and 250 feet from an unnamed tributary to Bull Creek (Figure 3-6), and the potential for this shaft to draw water from either of these streams must thus be considered. One of the borings (JT-120A) drilled for the geotechnical investigation was completed at the PARD site. Water levels in this boring in October 2010 indicated that water was present in the well within the fill (13 ft bgs on November 30, 2010), which would mean that these water levels are higher than the streams adjacent to the site. This would indicate that groundwater at the PARD site is moving toward Bull Creek and its tributary. As with the potential impact of this shaft on the springs in the area, dewatering of Bull Creek would not occur because of direct interference of the shaft on flow to these creeks, but only if the shaft diverted flow within these creeks toward the shaft. However, as noted above, mitigation measures are in place to minimize groundwater inflow into the shaft during construction, and once complete, the shafts should not receive groundwater inflow. Because the potential for the shaft to reduce flow in Bull Creek at this location is not due to the interference of a specific flow path, the fact that the shaft design will prohibit water from entering during construction should eliminate the potential for impact on Bull Creek and its tributaries.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 39 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 3.1.4 Jollyville Reservoir Shaft Site The Jollyville Reservoir shaft is located near the intersection of U.S. Highway 183 and Spicewood Springs Road at the eastern end of the tunnel alignment (Figure 3-1). A more detailed site map of this shaft location is shown in Figure 3-7. This shaft is a working shaft and is anticipated to be 40 feet in diameter and 340 feet deep. The shaft location is in a more developed part of the project area, with a significant amount of light retail and residential development in the vicinity. The closest named spring to this shaft location is Tanglewood Spring, which is approximately 4,700 feet away from the site. Another unnamed but mapped spring/seep is located appr oximately 3,600 feet away from the proposed shaft location, near Tanglewood Spring (Figure 3-7). The proposed Jollyville Reservoir shaft location is on the opposite side of a topographic divide from Tanglewood Spring, in the Rattan Creek watershed. The Jollyville Reservoir shaft will be constructed through the Edwards, Comanche Peak, Walnut, and Glen Rose formations. A boring is planned at the site (JT-127). However, as of the date of this report, boring JT-127 has not been drilled. For this groundwater assessment, another boring was evaluated instead, boring JT-126, located approximately 2,400 feet to the southwest and 4 feet higher in elevation than the proposed JT-127. Boring JT-126 was drilled on May 26, 2010. The following is a description of the geology observed in boring JT-126. The Edwards Formation is present in the boring down to a depth of 139 feet and is described as alternating beds of limestone and dolomite. At the top of the core, the rock encountered is a fineto medium-grained, vuggy limestone that appears slightly to moderately weathered, weak, moderately hard, and massive with some indistinct bedding. This is followed by a vuggy, fine-grained dolomite with similar characteristics to the limestone above. This pattern of alternating beds of limestone and dolomite of varying thickness continues for the remainder of the Edwards portion of the section. From 50.4 feet to 52 ft bgs, the core was reported as broken due to large vugs in the dolomite. A review of the core photographs confirms the fractured nature of the core in this zone. From 84.3 feet to the Walnut contact at 139 ft bgs, the core is generally described as a fine-grained, fresh, weak limestone that is banded and mottled. The limestone becomes vuggy and fossiliferous at 96 ft bgs, and a large solution cavity is present in the core from 97 feet to 99 ft bgs. A dditionally, numerous bedding plane breaks are present in the core, and visible in the reviewed photographs, between 119.5 and 124.7 ft bgs.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 40 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 The Comanche Peak Formation is restricted to the limestone unit between the Edwards and Walnut formations. South of the Travis/Williamson County line the Comanche Peak becomes interfingered within the Edwards. An approximately 20-foot-thick Comanche Peak interfingering is visible in the drainage along Springwood Springs Road near the intersection of Rustic Rock Drive, and it is also seen in the core collected during this investigation from boring JT-124. Where the Comanche Peak is underlain by the Walnut Formation and overlain by the Edwards (in the Cedar Park area to the north of the alignment), the Comanche Peak Formation is reported to be approximately 50 to 60 feet thick and to feather out southward (Rogers, 1969). The Comanche Peak was observed in cores northeast of boring JT-124 but was not observed in any of the cores along the rest of the alignment. The contact between the Comanche Peak and Edwards formations is marked by a change from a fineto very fine-grained marl and nodular limestone that weathers white. The Walnut Formation is encountered at a depth of 139 feet. The Walnut at this contact is described as fine-grained, argillaceous limestone that is fresh, very weak, mottled, and fossiliferous, with low hardness and thin bedding that result in numerous fractures in the core. The limestone becomes more massive and less argillaceous with occasional burrows at 167 ft bgs. The core is described generally as alternating sections of more and less argillaceous limestone until grading into a calcareous claystone bed at a depth of 210.5 ft bgs. The claystone persists for approximately 6 feet, at which point limestone is again encountered. This limestone bed is approximately 38 feet thick and is described as fine-grained, fresh, and weak, with moderate hardness, and continues to the bottom of the Walnut Formation in this core. The Glen Rose Formation contact is at a depth of 254.6 ft bgs. The upper 30 feet of the Glen Rose is generally described as a vuggy, fine-grained dolomite that is fresh, weak, and moderately hard. Initially only slightly vuggy, the number of vugs increases with depth, but they are absent at approximately 263 feet and are again noted at a depth of approximately 270 feet. The log notes that circulation was lost at 256.3 ft bgs. The upper dolomite bed is interrupted by a 3-foot-thick bed of mottled, fine-grained, fresh, weak limestone from 272.6 feet to 275.7 ft bgs, at which depth the dolomite resumes. Beginning at 286.9 ft bgs, the Glen Rose alternates between beds of limestone and dolomite. The limestone is generally described as fineto medium-grained, fresh, weak, and moderately hard, with some sections being burrowed and/or mottled to massive. Vugs are rare to absent in the limestone beds. The dolomite in this depth interval is generally described as vuggy, fine-grai ned, fresh, and weak, with moderate

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 41 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 hardness. This alternating pattern persists until a depth of 320.1 feet when the core encounters a bed of argillaceous limestone. This bed is approximately 5 feet thick and is described as fine-grained, fresh, and very weak, with low hardness. At a depth of 324.7 feet, the rock grades back into limestone that is described as fine-grained, mottled, fresh, and weak, with moderate hardness. This character persists until the total depth is reached at 338.7 feet with a 1.4-foot-thick bed of vuggy dolomite interrupting the limestone from 332.8 feet to 334.2 ft bgs. Packer test summaries are tabulated for each tested interval in boring JT-126 in Table 3-4. The hydraulic conductivity is an average of the step results of each test. Only four intervals were tested in JT-126 due to time restrictions for access to the boring location. In general, the packer tests indicate moderate to low hydraulic conductivities for the Glen Rose in the JT-126 location. Hydraulic conductivities decreased from the upper tested zone to the lower tested zone. Table 3-4 Summary of Packer Tests near the Proposed Jollyville Reservoir Shaft Location Boring No. Test Interval (feet) No. of steps Hydraulic Conductivity (cm/s) Geologic Formation JT-126 271.5 287.5 5 9.6 x 10 5 Glen Rose 286.5 302.5 5 7 x 10 5 Glen Rose 301.5 338.8 5 1.5 x 10 5 Glen Rose 316.5 338.7 5 < 10 7 Glen Rose cm/s = Centimeters per second Shafts will have mitigation measures in place to minimize groundwater inflow. It is unknown whether any of the proposed shafts will directly intersect and alter flow in a preferential flow pathway (conduit) that will interrupt or change flow to a particular spring. Because of the distance between the proposed Jollyville Reservoir shaft location and the nearest spring, the fact that the shaft location is located within a separate watershed, nearly 2,500 feet on the other side of a topographic divide from the springs of interest, and the extent of development that has already occurred in the vicinity of the shaft location and between the location and the closest spring, the risk that the proposed shaft will impact discharge from Tanglewood Spring or any other springs in the study area is small.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 42 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 An additional boring will be drilled at the Jollyville Reservoir site, and data will be used to amend, as appropriate, the design and this groundwater assessment report. 3.2 TUNNEL EXCAVATION / CONSTRUCTION IMPACTS The main transmission tunnel alignment will be approximately 10 feet in excavated diameter and 34,600 feet in length. The tunnel depth will be variable, from more than 200 feet in the plateau portions at both the eastern and western ends of the alignment to 125 to 150 feet in the central portion of the alignment beneath the BCP. Originally planned to be much shallower, the tunnel depth has been increased in order to increase the distance below Bull Creek within the BCP and also to install the tunnel in the less permeable horizons of the Glen Rose Formation, below the higher-permeability zones that have been observed during packer testing in the upper 50 feet of the formation. The tunnel can be divided up into three reaches (Figure 3-1) that are separated by two intermediate proposed shafts at the Four Points and PARD sites. The geology and hydrogeology is somewhat different between these three reaches, and therefore these reaches, and their potential impact, are described separately in Sections 3.2.1 through 3.2.3. 3.2.1 Reach 1: WTP4 to Four Points Reach 1 of the main transmission tun nel is the western portion of the alignment, between the WTP4 shaft and the Four Points shaft (Figure 3-1). A more detailed view of Reach 1 is shown in Figure 3-8. This section of the alignment is the shortest of the three reaches, with a total length of approximately 4,500 feet. Nearly half of this length is within the WTP4 site footprint (Figure 3-8). This reach is located entirely on the topographically higher sections of the study area, with the entire length being overlain by the Edwards, Walnut, and Glen Rose formations. Given its location, the geology in this reach is largely the same as that of the proposed WTP4 and Four Points shaft locations (Sections 3.1.1 and 3.1.2). A cross section of this reach is shown in Figure 3-9, which includes the results from the packer tests. In general, an increase in the land surface elevation, and a corresponding increase in the thickness of the Edwards Formation is observed as one moves from west to east along the proposed tunnel alignment from the WTP4 site toward the Four Points Shaft site. Only limestone is present in the Edwards Formation at the WTP4 site. Moving east, beds of dolomite are observed in the cores beginning at boring JT-110. These beds of dolomite, which are up to 20 feet thick, are generally weaker, softer, and more vuggy than the limestone beds.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 43 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 The Walnut formation maintains a fairly consistent character and thickness between the proposed WTP4 and Four Points shaft locations. The Walnut consists of limestone and argillaceous limestone that is generally described as mottled and/or burrowed. Although the Walnut is not generally described as vuggy, vugs are present in some portions. The character of the Glen Rose Formation is also consistent between the two proposed shaft locations, consisting of alternati ng beds of limestone and dolomite. The two rock types share many similar characteristics with the dolomite sections, notably described as vuggy far more often than the limestone sections. The proposed tunnel alignment in this section is at a depth of between 220 and 270 feet (an elevation of approximately 780 ft msl), and the character of the Glen Rose at this depth is generally described as a fresh, fineto medium-grained mottled limestone, but with no vugs noted on the boring logs. The hydraulic characteristics of Reach 1 also reflect the hydraulic characteristics described for the proposed WTP4 and Four Points shaft locations (Sections 3.1.1 and 3.1.2). Packer testing of the Glen Rose at depth reveals extremely low hydraulic conductivity values that increase near the contact with the Walnut, a trend that has been observed across the study area. Figure 3-10 summarizes results of packer testing along Reach 1, and the lateral and vertical distribution of packer tests is included in the cross section in Figure 3-9. In several borings along Reach 1 the upper portion of the Glen Rose Formation has a higher hydraulic conductivity determined by packer testing (10 3 to 10 4 cm/s near WTP4), but much lower hydraulic conductivities (10 5 cm/s or lower) in the Glen Rose, where the tunnel will be located. Where performed, packer testing in the Walnut Formation showed low to moderately low hydraulic conductivities (10 5 cm/s or lower). Water levels in the Glen Rose appear to have a steep downward gradient, as described in Section 2.3.5. Some recharge to the Glen Rose appears to occur through the Walnut. The hydraulic conductivities are much lower in the deeper section of the Glen Rose, which is where the tunnel will be located. Because the deeper portions of the Glen Rose Formation, where the tunnel will be located, tend to be significantly less perm eable than the upper portions of this formation and of the overlying Edwards Formation, and because hydraulic gradients in the Glen Rose Formation already are strongly downward, significant impacts on springs and seeps in the Edwards/Walnut flow system are not expected during the boring and completion of the proposed tunnel. The strong downward gradient indicates that some degree of vertical groundwater seepage already exists, although the amount is limited by the low hydraulic conductivity of the deeper sections of the Glen Rose Formation.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 44 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 3.2.2 Reach 2: Four Points to Parks and Recreation Department Reach 2 of the main transmission tun nel is the central portion of the alignment, between the Four Points shaft and the PARD shaft (Figure 3-1). A more detailed view of Reach 2 is shown in Figure 3-11. This section of the alignment is the longest of the three reaches, with a total length of approximately 20,000 feet, and drops in elevation from approximately 780 ft msl at the proposed Four Points shaft site to approximately 650 ft msl at the proposed PARD shaft site. However, the depth of the tunnel may be modified to be deeper than is described here. This reach is different from Reaches 1 and 3 in that the majority of this alignment is located along Bull Creek and its tributaries, where most or all of the Edwards and Walnut formations have been eroded away. A cross section of this reach is shown in Figure 3-12, which includes the results from the packer tests. In general, the land surface elevation steadily decreases from the proposed Four Points shaft location to the PARD site, and the Edwards Formation thins from erosion until absent at an elevation of approximately 900 ft msl (at the original WTP4 site). Where the Edwards is present, it exhibits similar characteristics to those described for the proposed Four Points shaft location (Section 3.1.2). It is composed of both limestone and dolomite beds with the dolomite being generally more vuggy than the limestone. The Walnut Formation has been weathered away in this reach, at an elevation of approximately 830 ft msl. As described in Section 3.1.2, the Walnut is composed of beds of limestone and argillaceous limestone and continues to have occasional vugs or vuggy sections, although it isnt generally described as vuggy. The Glen Rose Formation continues to be present in this reach in alternating limestone and dolomite beds with occasionally argillaceous beds or lenses. While both rock types are often described as mottled and share many similar characteristics, the dolomite beds are again described as vuggy far more often than the limestone beds. The Glen Rose Formation at the proposed tunnel depth is generally a fine-grained, fresh, mottled limestone. There is a dolomite bed that ranges in thickness from approximately 1 to 3 feet around this depth that is also described as vuggy. Another bed of fresh, finegrained limestone is located beneath this thin dolomite bed. However, the majority of the section where the tunnel is proposed to be located in this reach is described as a finegrained, fresh limestone without vugs or other dissolution features. Field observation of the outcrop of the Glen Rose at the approximate horizon where the tunnel will be located also indicates a lack of vertical fractures. The hydraulic characteristics of Reach 2 reflect the same hydraulic characteristics described for the proposed Four Points and PARD shaft locations (Sections 3.1.2 and 3.1.3). Figure 3-13 summarizes results of packer testing along Reach 2, and the

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 45 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 lateral and vertical distributions of packer tests are shown in Figure 3-12. In a few borings, the upper portion of the Glen Rose Formation has a higher hydraulic conductivity determined by packer testing (10 3 to 10 4 cm/s), while much lower hydraulic conductivities (10 5 cm/s or lower) were found in the remainder of the Glen Rose, where the tunnel will be located. The Walnut and Edwards formations are not present in most of Reach 2 because they have been eroded away by Bull Creek and its tributaries. Based on several recent borings completed at the western end of Reach 2, the Edwards and Walnut formations are overlying the Gl en Rose, with similar characteristics as presented for the Four Points shaft (Section 3.1.2). As noted in Section 3.2.1, water levels in the Glen Rose appear to have a steep downward gradient. Some recharge to the Glen Rose appears to occur through the Walnut. The hydraulic conductivities are much lower in the deeper section of the Glen Rose, which is where the tunnel will be located. Much of Reach 2 is beneath the incised stream valleys of Bull Creek and its tributaries, and so little to no Walnut or Edwards is present. Because the deeper portions of the Glen Rose Formation, where the tunnel will be located, tend to be significantly less perm eable than the upper portions of this formation and of the overlying Edwards Formation, and because hydraulic gradients in the Glen Rose Formation already are strongly downward, significant impacts on springs and seeps in the Edwards/Walnut flow system and on streamflow in Bull Creek are not expected during the boring and completion of the proposed tunnel. The strong downward gradient indicates that some degree of vertical groundwater seepage already exists, although the amount is limited by the low hydraulic conductivity of the deeper sections of the Glen Rose Formation. Flow in Bull Creek is also not expected to be impacted by the boring and completion of the proposed tunnel. In general, the tunnel is located approximately 100 to 120 ft bgs where it parallels or crosses beneath Bull Creek along Reach 2. As noted in Sections 2.3.4 and 2.3.5, based on the available data, the Glen Rose in this area is fairly tight and generally already shows a strong downward gradient. Water level data appear to support this conclusion. Pit Spring has an elevation of 752 ft msl, and water levels in well NW-4 (Woodward-Clyde, 1986c), located immediately adjacent to Pit Spring and open in the Glen Rose Formation, are several feet below this. Despite this, flow in Bull Creek occurs. Flow is currently lost in Bull Creek in the reach between Lanier and Pit Springs within the BCP. However, it is assumed that it is lost in the gravels within the streambed, where it moves downward into the very upper portions of the Glen Rose and then moves laterally downstream as underflow, eventually reemerging around Pit Spring. The springs

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 46 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 emanating from the banks along Pit Spring are not believed to be part of this creek underflow, but rather are part of the Edwards/ Walnut flow system described in Section 2.3.1.1. Proposed dye tracing studies will investigate this issue. 3.2.3 Reach 3: Parks and Recreation Department to Jollyville Reservoir Reach 3 of the main transmission tun nel is the eastern portion of the alignment, between the PARD shaft and the Jollyville Reservoir shaft (Figure 3-1). A more detailed view of Reach 3 is shown in Figure 3-14. This section of the alignment is approximately 9,500 feet long and begins at the proposed PARD shaft location, which is at a relatively low elevation and on the outcrop of the Glen Rose Formation. As the tunnel alignment moves from the PARD location to the proposed Jollyville Reservoir location, the land surface elevation steadily increases, and ev entually the tunnel is overlain by the Edwards, Comanche Peak, Walnut, and Glen Rose formations. The Walnut Formation is again present at the approximately 760-ft-msl elevation along the proposed tunnel alignment, and the Edwards Formation returns at approximately the 840-foot elevation and thickens with increasing elevation. The geology in this reach is largely similar to that in the proposed PARD and Jollyville Reservoir shaft locations (Sections 3.1.3 and 3.1.4). A cross section of this reach is shown in Figure 3-15, which includes the results from the packer tests. The character of the Edwards Formation in this tunnel section is similar to the descriptions in Sections 3.1.3 and 3.1.4, being composed of beds of limestone and dolomite, although this section of the Edwards is generally described as being more vuggy and fossiliferous than previously encountered. The Walnut Formation remains composed of beds of limestone and argillaceous limestone, but is only occasionally described as vuggy. The Glen Rose Formation also maintains its character of alternating beds of dolomite and limestone of varying thickness. As described above, the dolomite beds are generally vuggy while the limestone beds are not. The proposed tunnel alignment through this section remains at an elevation of approximately 610 ft msl, although this is likely to be lowered across Reaches 2 and 3. Notably, the Glen Rose Formation at this elevation is composed of alternating beds of dolomite and limestone, differing from the previous reach, of which the majority of the section where the tunnel will be located is fine-grained limestone. Both limestone and dolomite beds around this elevation in Reach 3 are described as fine-grained, fresh, weak, and moderately hard, with the dolomite being notably vuggy while the limestone is not. The hydraulic characteristics of Reach 3 also reflect the hydraulic characteristics described for the proposed PARD and Jollyville Reservoir shaft locations (Sections 3.1.3

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 47 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 and 3.1.4). Figure 3-16 summarizes the results of packer testing along Reach 3, and the lateral and vertical distributions of packer tests are shown in Figure 3-15. In several borings, the upper portion of the Glen Rose Formation has a higher hydraulic conductivity determined by packer testing (10 4 to 10 5 cm/s near the PARD shaft site), but lower hydraulic conductivities (10 5 cm/s or lower) in the Glen Rose, where the tunnel will be located. Where performed, packer testing in the Walnut Formation showed very low hydraulic conductivities (less than 10 6 cm/s). Water levels in the Glen Rose appear to have a steep vertical downward gradient, as described above (e.g., Sections 3.2.1 and 3.2.2). Hydraulic conductivities are also much lower in the upper Glen Rose Formation where the tunnel will be located. Because the deeper portions of the Glen Rose Formation, where the tunnel will be located, tend to be significantly less perm eable than the upper portions of this formation and of the overlying Edwards Formation, and because hydraulic gradients in the Glen Rose Formation already are strongly downward, significant impacts on springs and seeps in the Edwards/Walnut flow system are not expected during the boring and completion of the proposed tunnel. The strong downward gradient indicates that some degree of vertical groundwater seepage already exists, although the amount is limited by the low hydraulic conductivity of the deeper sections of the Glen Rose Formation. 3.3 FOREST RIDGE TRANSMISSION MAIN SHAFT The Forest Ridge shaft is located directly east of the Four Points shaft at the eastern end of the proposed Forest Ridge Transmission Main tunnel alignment (Figure 3-17). Although not technically part of the JTM tunnel project, the potential impacts to groundwater and springs is similar to those of the shaft locations that are part of the JTM tunnel, and so this location is included in this groundwater assessment. As shown in Figure 3-17 (see also Figure 2-4), this shaft is located on a topographic high adjacent to several incised stream valleys that are within the BCP. Several mapped springs are present within 2,000 feet of the shaft, including Ribelin Spring #2 located 1,700 feet to the northwest of the proposed location, Ribelin Spring, located 1,900 feet to the north, and numerous unnamed springs to the southeast and south, including six within 1,000 feet of the proposed shaft location. Both Ribelin springs discharge from the Walnut Formation, and the unnamed springs discharge from both the Edwards and Walnut formations. Ribelin Spring 2 is one of the largest springs in the study area and a significant habitat location for the Jollyville Plateau Salamander (David Johns, personal communication, 2010).

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 48 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 The Forest Ridge shaft location will likely be constructed through the Edwards, Walnut, and Glen Rose formations. Several borings have been drilled at the site during a separate investigation conducted by Holt Engineering (2009), including boring B-02, which was specifically drilled at the location of the proposed shaft on September 21, 2009 (Figure 3-17). The following is a description of the geology observed in this boring. Alternating beds of limestone and dolomite of the Edwards Formation are present in the boring to a depth of 32.9 feet. The upper 10-foot section of the formation is a moderately weathered limestone with red clay and caliche in the fractures. A highly weathered zone is present from 3.5 feet to 4.5 feet. No core was recovered from 7.5 feet to 8 feet. The character of the Edwards changes at 11.7 feet to a slightly weathered, vuggy limestone with red clay filling the vugs, transitioning to calcite-filled vugs with depth. This persists until a depth of 26 feet, where a 3foot-thick bed of fine-grained dolomite is encountered. This dolomite bed continues down to a depth of 32.9 feet and is interrupted by a 1-foot-thick fine-grained, crystalline limestone bed present from 29 feet to 30 ft bgs. The Walnut Formation is found beginning at a depth of 32.9 feet and is described as a clayey, fossiliferous, bedded limestone that appears fresh in the 35to 40-foot interval, becoming vuggy at 38.3 feet. At a depth of 40 feet, the core is described as a friable, clayey limestone that is highly fossiliferous, vuggy, and slightly weathered. During the drilling of the boring 15 to 20% water loss was reported at a depth of 51 feet. The rock character transitions to a fine-grained, hard limestone at 60.6 feet, and 100% water loss was reported at a depth of 63.3 feet. Beginning at a depth of 65 feet, the core is described as clayey, fresh, fine-grained, fossiliferous limestone and maintains this character for approximately 59 feet until the contact with the Glen Rose at the 123.8-foot depth. During drilling 100% water loss was reported at depths of 71.4 feet and 115 feet, and 20% water loss was reported at a depth of 75 feet. The Glen Rose Formation contact is found at a depth of 123.8 feet. The Glen Rose is described as a fine-grained, fossiliferous limestone. Thin clay partings are present throughout. The initial 35-foot-thick limestone bed ends at a depth of 159 feet, where the boring encounters a 17foot-thick bed of dolomite with thin clay interbeds. Thin (less than 1 foot) vuggy sections are present in this dolomite bed. During drilling 100% water loss was reported at the 163to 165-foot interval. A bed of fineto medium-grained limestone with clay interbeds is present from 176 feet to 178.7 feet, followed by an almost 15-foot-thick bed of fine-grained dolomite that is described as mottled and vuggy in places. Beginning

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 49 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 at a depth of 193.6 feet, the Glen Rose alternates between beds of limestone and dolomite, with bed thicknesses of up to 9 feet. The limestone beds are generally described as fineto medium-grained, fresh, and occasionally fossiliferous with some clay lenses present in some beds. The dolomite beds are described as fineto medium-grained and fresh. Packer test summaries are tabulated for boring B-02 in Table 3-5. The hydraulic conductivity is an average of the step results of each test. Due to the large amount of water loss in the Walnut Formation in this boring, packer tests were restricted to the Glen Rose Formation. In general, the packer tests indicate that the Glen Rose Formation is quite variable in this location. No water loss was reported during the packer testing in the upper and bottom 20 feet, and tests in between indicated generally decreasing hydraulic conductivities with increasing depth. Table 3-5 Summary of Packer Tests near the Proposed Forest Ridge Shaft Location Boring No. Test Interval (feet) No. of steps Average K (cm/s) Geologic Formation B-02 129 139 3 < 10 6 Glen Rose 139 149 3 < 10 6 Glen Rose 149 159 5 2.8 x 10 4 Glen Rose 159 169 5 4.8 x 10 5 Glen Rose 169 179 3 1.3 x 10 6 Glen Rose 179 189 5 4.9 x 10 5 Glen Rose 189 229 5 7.5 x 10 6 Glen Rose 209 229 3 < 10 6 Glen Rose K= Hydraulic conductivity cm/s = Centimeters per second The proposed Forest Ridge shaft location is on a ridgeline within the boundaries of the BCP, and is surrounded by incised stream valleys on two sides (Figure 3-17). Based on our understanding of the nature of flow in the Edwards/Walnut groundwater flow system (Section 2.3.1.1), the most likely area where springs may receive groundwater from the proposed Forest Ridge shaft is to southeast of the proposed shaft location (Figure 3-18). This understanding is based on dye tracing studies conducted by the City of Austin at the old WTP4 site, which showed that in the Edwards/Walnut flow system groundwater moved radially from the tops of the hilltops and discharged in springs and seeps in drainages. While it may appear possible that springs to the northwest of the proposed

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 50 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 shaft location may be impacted, even though they are farther away from the shaft and across a minor topographic divide (Figure 3-18, data from wells installed at this proposed shaft location indicate that it is unlikely that these springs will be impacted by this proposed shaft. A well installed in the Edwards (B-02A) has been dry, and water levels in the well installed across the Glen Rose, Walnut, and Edwards formations (B-02) are approximately 855 feet (approximately the same elevation as Ribelin Springs), which is either below or within the Walnut Formation. These water levels are below the elevations of most of the springs to the east of the proposed shaft. Because specific design criteria were not available, the impact of the Forest Ridge Transmission Main tunnel is not included in this assessment.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 51 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 4.0 DESIGN MITIGATION MEASURES The environmental goals established for this project are based upon its location within a unique hydrogeologic system. Although this sy stem produces very small amounts of groundwater compared to the volumes that are important for human use, its springs support a unique Balcones Canyonlands ecosystem, including most of the entire habitat of the sensitive and vulnerable Jollyville Plateau Salamander. The project goals include: Preventing adverse impacts to water quality, Maintaining existing hydrologic regimes, Preventing discharge of pollutants from the sites, Meeting or exceeding the requirements of the Balcones Canyonlands Conservation Preserve (BCCP), Avoiding, minimizing, and mitigating impacts to threatened or endangered species, and species of concern, and Avoiding, minimizing, and mitigating impacts to the Jollyville Plateau Salamander. In furtherance of these overall goals, this section discusses general mitigation measures to be used during the JTM project. Many of the mitigation measures included here are discussed in greater detail in the Final EC Plan (Hicks and Company, 2010a) and in the BDR (Black and Veatch, 2010a), including several of the technical memoranda included with the BDR. To the maximum extent practicable, the JTM will be designed, constructed, and operated to prevent adverse impacts to downstream surface and subsurface water quality and quantity by providing no measurable increase in pollutant loading above the existing conditions. The karstic nature of the Edwards Limestone creates a sensitive area where the groundwater quality will quickly reflect inputs from the surface. There are a significant number of caves and recharge features within the study area that provide a potential conduit for water and contaminants to make their way directly into the groundwater. The EC Plan and BDR present techniques to avoid both karst conduits that convey groundwater to springs and cave passages that are hydrologically connected within the Edwards Formation. These techniques have been developed through a collaborative effort between the envir onmental and engineering project teams. 4.1 BEST MANAGEMENT PRACTICES Best management practices (BMPs) that apply to groundwater protection are incorporated into the JTM design and facilities construction to achieve the established

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 52 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 environmental goals. Habitat protection goals for the Jollyville Plateau Salamander are defined in terms of water quality, water quantity, and physical habitat. On-site planning, design, and operation of stormwater quality/quantity controls, spill/leak controls, and karst feature protection will meet the project goals to protect clean water, natural hydrology, and stable substrate in salamander habitat. The following measures are adapted for facilities design and will be incorporated into the contract documents: Develop a preconstruction groundwater assessment report. This report provides a groundwater assessment of the area of interest, focusing on groundwater hydrology as a basis for predicting potential impacts to area springs and evaluating the potential implications of the construction of the finished JTM tunnel and associated shafts to the Jollyville Plateau Salamander. Develop avoidance and minimization methods. Methods to avoid or minimize groundwater impacts will be developed based on the groundwater assessment. Monitor groundwater. Prior to construction, baseline conditions will be established for water quality indicator parameters including, but not limited to, total suspended solids (TSS), dissolved oxygen (DO), pH, total dissolved solids (TDS), total petroleum hydrocarbons (TPH), and fecal coliform. Develop contingency plan. A contingency plan will be developed to address unexpected groundwater, surface water, or spring flow impacts that might occur during construction in spite of the planned avoidance and minimization methods. Stage equipment for easy availability. All equipment and material necessary to conduct contingency plans and handle all known potential groundwater problems will be staged close to work sites. Monitor surface runoff and recharge characteristics. The naturally occurring drainage patterns to downstream tributaries will be maintained to the maximum extent practicable to preserve the quality of downstream habitat and to minimize channel erosion. Maintain existing groundwater flow paths during drilling, shaft construction, and tunneling activities. Particular attention will be given to quickly reconstructing any interrupted groundwater flow paths at shaft locations. Periodic stops, conduits, or other means to maintain natural flow characteristics will preserve existing groundwater flow patterns during the construction and operation phases of the shafts and transmission main. Existing, and if necessary additional new, groundwater monitor wells and piezometers will be used to monitor groundwater pressures and chemistry prior to and during construction.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 53 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Prevent tunnel from becoming a groundwater drain after construction Construct flow stops in critical reaches of the tunnel to prevent migration of water along any discontinuities between pipe and tunnel walls. Prevent sediment discharges from leaving the site. Increases in the naturally occurring sediment discharges from the sites would degrade the quality of downstream surface water and groundwater. Sediment might also physically block recharge features or degrade the seeps and springs that discharge groundwater into the streams. The JTM will be constructed and operated to minimize sediment discharges. Prevent impacts to groundwater from release of chemicals during pipeline disinfection or other maintenance A release of water treatment chemicals from chlorinated pipeline disinfection water or even discharge of treated water has the potential to cause environmental impacts to downstream areas. It is critical that chemical transport, storage, and use be accomplished in a manner that will minimize the possibility of an accidental discharge or release. Risk management plans and emergency response plans will be developed and implemented for the JTM. Prevent release of fertilizers and pesticides. If fertilizers and pesticides are used on the site for revegetation or to control pests they could be dissolved in stormwater and discharged from the site, and increases in nutrients from fertilizers or pesticides could negativ ely impact downstream waterways. Pesticides are known to be harmful to aquatic and benthic organisms and the food chain. Because these types of pollutants are difficult to remove through conventional water quality controls, the best management practice is to eliminate the sources of these pollutants. The construction sites will be revegetated using only native materials, and turf areas will be minimized to eliminate the need for fertilizers. Pest control will be accomplished using the least toxic alternative. These measures to minimize or eliminate the sources of fertilizer and pesticiderelated pollutants are best achieved through adoption and strict enforcement of an Integrated Pest Management Plan (IPMP) that will guide the design, construction, and management of the JTM. Implement erosion and sedimentation controls and surface/groundwater quality protection systems. Erosion and sedimentation controls and water quality protection system items, if required, shall meet guidelines established by the responsible governmental authority and shall be installed prior to starting construction. The erosion and sedimentation controls and water quality protection systems shall be maintained until revegetat ion is established and restoration is accepted by the BCCP Coordinating Committee Secretary.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 54 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Develop Jollyville Plateau Salamander Contingency Plan. A contingency plan will be developed and implemented to address potential effects to Jollyville Plateau Salamander habitat and populations from the construction of the JTM and to address potential scenarios regarding imminent danger to surface water and groundwater. Develop a groundwater monitoring plan and establish baseline conditions to address Jollyville Plateau Salamander protection. A groundwater monitoring plan will be designed to identify baseline conditions for hydrology and water quality and to set the frequency and parameters for monitoring during the construction phase. Hydrologic and water quality data for groundwater, springs, and streams at selected historical and new locations will be documented to define baseline conditions prior to the start of transmission main construction activities. The monitoring shall be conducted according to the plan developed during the design phase and will continue until disturbed soils within the project area are stabilized. Use shaft construction methods that avoid or minimize disruption of existing groundwater flow paths. The portion of each shaft that spans the Edwards and Walnut formations is required to be water-tight (engineering term for shaft support installations to cut off water inflow and exfiltration) and lined with gasketed steel liner plates and steel ring beams as shown in Technical Memorandum No. 9 from the BDR (Black and Veatch, 2010a). If preferential flow pathways or karst features are encountered during shaft construction, the annular space behind the liner plates will be backfilled with pea gravel. For larger voids, 4-inch-diameter perforated high-density polyethylene (HDPE) pipes wrapped in Type II geotextile fabric will ring the shaft (at that elevation); that is, the pipe will be constructed in such a way that it connects back to itself and creates a ring. In this way, the active voids would be reconnected through the perforations in the pipe (or the pea gravel backfill) around the shaft and the pipe would direct (or connect) groundwater regardless of the groundwater gradient direction, or if the gradient changes direction. These methods may also be used in other zones based on field observations during construction. Appropriately manage construction water. Water encountered during construction of the shafts and tunnel will require appropriate controls before discharge. Tunnel and shaft construction water will be collected and pumped to the surface. Treatment and preapproved discharge of extracted water will be required at all four shaft sites. Water encountered during excavation will be laden with sediment due to rock cuttings carried with it. In addition to rock cuttings, the water may contain trace amounts of oil and grease, largely due to lubricants used for bearings in the tunnel boring machine and other moving machinery. Section 5 of

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 55 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 the BDR provides groundwater management and tunnel and shaft construction water handling procedures, and Technical Memorandum No. 5 (Groundwater Inflow Mitigation Plan) provides a detailed discussion of shaft and tunnel construction water quantity and control within the tunnel. No uncontrolled discharges of water that exceed the limits developed by the EC Team will be released to surface waters. Shaft and tunnel water at the Four Points, PARD, and Jollyville Reservoir shafts will likely be treated for sediments and discharged to sanitary sewers nearby. Once a connection is made between the WTP4 and Four Points shafts, construction water from the WTP4 shaft and tunnel will be discharged at Lake Travis along with the water generated during construction of the WTP4 facilities. Other BMPs for storm water quality management, including soil erosion and sedimentation controls, will be implemented and checked throughout the construction and operational phases to protect karst and related recharge zones. Strategies such as routing runoff water from roads and parking areas away from karst feature catchment areas, limiting activities that disturb the natural vegetation within catchment areas, and restricting the use of pesticides, herbicides, fertilizers, and other potentially harmful substances should be used to protect recharge features. Additional measures regarding void mitigation (including void description, biological assessment, etc.) are included in Technical Memorandum 9 in the BDR, but these are not directly applicable to groundwater impacts and so are not included in this assessment. The BMPs and mitigation strategies discussed above and in the EC Plan and BDR were developed based on the best information available at the date this document was prepared. As the project proceeds through design, construction, and operation, and as more information becomes available, modifications to the BMPs and mitigation strategies may become necessary to achieve the project environmental goals and project requirements. The process of adapt ive management will be used to implement changes to the EC process if required. If, despite the best efforts, the EC goals are not being met, alternatives measures shall be implemented to achieve those goals. Changes will be discussed and cooperatively developed through the EC process. 4.2 SURFACE AND GROUNDWATER MONITORING A plan for monitoring surface and groundwater quality and quantity is being developed consistent with environmental protection and EC goals established for the JTM project. Hydrologic and water quality data for groundwater, springs, and streams at selected historical and new locations will be documented to define baseline conditions prior to start of construction activities. The monitoring shall be conducted according to the plan

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 56 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 developed during the design phase and will continue until disturbed soils within the project area are stabilized. The City of Austin Team is leading the development of the monitoring plan to include the baseline conditions (Section 4.3) and construction monitoring requirements for the following: Groundwater elevations at existing and additional piezometers and monitoring wells as necessary, Bull Creek and spring flows, Shaft and tunnel construction water discharges, and Monitor water quality indicator parameters (TSS, DO, pH, TDS, TPH, and fecal coliform). The details of the surface and groundwater monitoring plan will be outlined by the City of Austin Team, and appropriate water quantity and quality monitoring efforts will be coordinated with design and construction ins pection activities. Minimum requirements will be established in the contract specifications as necessary based on discharge locations. 4.3 BASELINE ENVIRONMENTAL CONDITIONS The baseline environmental conditions assessment included a comprehensive environmental assessment of critical environment al features near the project facilities. This report addresses specific baseline conditions for Bull Creek and spring flows and groundwater elevations at shaft and tunnel locations. The groundwater levels are currently moni tored on a monthly basis using existing piezometers to establish baseline groundwater levels at shaft and tunnel locations. Groundwater quality sampling to date included a number of parameters to check for corrosion protection of the system and will be further expanded to include the baseline water quality indicator parameters (TSS, DO, pH, TDS, TPH, and fecal coliform). Following completion of the preconstruction monitoring and sampling, a baseline conditions report will be developed for the project. 4.4 CONTINGENCY MEASURES While the design and construction of the JTM project are consistent with environmental protection objectives and the EC goals, additional contingency measures are planned to avoid or otherwise minimize potential construction impacts of the project, specifically for

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 57 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 the Jollyville Plateau Salamander habitat. A contingency plan will be developed to outline the contingency measures that will include the following: Design modifications to address EC adaptive management practices, Tunnel probe drilling and monitoring of potential tunnel inflows ahead of tunneling excavations, Means to further reduce shaft and tunnel water inflows by implementation of preand post-excavation grouting, and Means for emergency augmentation of Bull Creek base flows ( viability to be discussed ). 4.5 CONSTRUCTION MONITORING AND INSPECTIONS Construction monitoring and inspections are critical to the success of the project environmental protection measures The scope of construction monitoring and inspections is under development and shall be consistent with this Groundwater Assessment Report and the goals established in the EC Plan. In addition to the City staff, the construction inspection team will include a dedicated environmental coordinator reporting to the Project Manager and a dedicated field inspector. The environmental coordinator will provide weekly updates to the BCCP Coordinator and the EC Team and will coordinate and facilitate inspections by the City and BCCP staff as necessary. 4.6 SHAFT AND TUNNEL INFLOW ASSESSMENT Potential sources of construction shaft and tunnel water are described in Sections 2 and 3 of this report. Tunnel inflows are generally expected throughout the alignment. The quantity will vary along the alignment according to the hydraulic conductivity and storativity of the rock surrounding the tunnel. Packer testing has identified areas of relatively higher hydraulic conductivity in the Glen Rose Formation along the east and west ends of the alignment. These areas are coincident with areas where the Edwards and Walnut formations are present above the Glen Rose. Reach 2, generally located within the BCP and lowlands area near Bull Creek and its tributaries, has noticeably lower hydraulic conductivity, corresponding to areas where the Edwards and Walnut formations have been eroded away. Analyzing potential groundwater inflows from fractured and vuggy rock has its inherent limitations. The high variability in the spacing, connectivity, and character of rock mass discontinuities adds uncertainty to estimati ng the locations and likelihood of any inflows and the sustainability of those inflows into the tunnel.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 58 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 A modified radial flow equation was used to calculate potential groundwater inflows (Heuer, 1995, 2005). Heuers method uses a one-eighth reduction factor (based on empirical evidence) for radial steady-state flow (continuous recharge). The tunnel heading inflow factors suggested by Heuer, varying from 1 for low-permeability to 4 for high-permeability rock, were also used. The two groundwater inflow conditions to be considered are initial heading flush inflow and long-term steady-state inflow. The longterm, steady-state inflow condition is reached with time and the distance from the face. The time between the initial heading inflow condition and the long-term, steady-state inflow condition may vary from a day to a month depending on the ground and recharge conditions. The calculated flows represent average tunnel inflow assuming instantaneous excavation without any mitigation techniques. The steps taken to assess the groundwater inflow into the tunnel were as follows: 1. Lugeon tests were performed in most of the exploration boreholes. Except for the first test at the bottom of each boring, the tests were done with a straddle packer system spanning a length of 12 to 17 feet. Generally, each test had five steps, with pressures ranging from to 1 pound per square inch (psi) per foot of depth to the center of the test interval. Overlapping tests were run throughout the Glen Rose Formation. 2. Lugeon tests were analyzed using the Houlsby method (Houlsby, 1976) to choose the representative apparent hydraulic conductivity for each test interval. The thickness of limestone/dolomite interbedding was too thin compared to the length of the test intervals to allow a separate calculation for each lithology. 3. Tunnel inflows were calculated based on Heuers method, as described above, for both sustained and heading flush flows. The tunnel inflows calculated using these steps are presented in Table 4-1. The packer test data set from which these calculations were made is presented in the GDM. Additional packer test data will be collected from borings to be drilled in the near future, which could affect the calculated inflows. When available, these data will be added to the current data set and the calculations rerun. Additionally, water level data are being collected. The inflow calculations were done assuming maximum groundwater head, so the tunnel flow rates may be revised when equilibrated groundwater depths are determined from the piezometers along the alignment.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 59 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Table 4-1 Tunnel Inflow Calculations Reach Average Unmitigated Sustained Inflow (gpm) per 100 feet of Tunnel Maximum Unmitigated Flush Flow (gpm) 1 14 950 2 1 580 3 5 920 gpm = Gallons per minute The inflows shown in Table 4-1 are for unmitigated conditions, meaning that no measures are taken to reduce inflows during construction. Inflows were estimated along the three reaches of tunnel. It is important to note that these are maximum unmitigated flows, that mitigation measures will be employed for large inflows, and that at no time will the entire length of the tunnel ever be open. These reaches correspond with proposed shafts and with variations seen in the hydraulic conductivity data, which is presented in the GDM. It was observed from the data collected to date that lower hydraulic conductivity is observed in the Glen Rose Formation through the BCP, where the Edwards and Walnut have been eroded, exposing the Glen Rose. Higher hydraulic conductivity was observed on both ends of the tunnel alignment. The shaft inflows will be significantly reduced using water-tight construction systems through the shallow groundwater system as discussed above and in the BDR. No significant shaft inflows or potential groundwater impacts are anticipated in the Glen Rose or deeper groundwater system.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 60 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 5.0 SUMMARY AND CONCLUSIONS The City of Austin is undertaking the design and construction of a tunnel to move water from WTP4 to the Jollyville Reservoir for distribution to the City of Austin. Although the final design has not yet been completed, the project involves tunneling beneath the BCP, which contains known habitat locations of the Jollyville Plateau Salamander, a species that is a candidate species for listing under the Endangered Species Act. The salamander habitat is along Bull Creek, a creek that originates as groundwater discharge from the hillsides whose base flow is seasonally supplied by discharge from springs along the creek. This preconstruction groundwater assessment evaluated the groundwater conditions in the project area and assessed the potential impacts of the tunnel and shaft construction on groundwater flow in the project area, in particular impacts on springs that are found on hillsides in the area and on flow in Bull Creek. The objective is to identify appropriate protection measures so that the installation of the shafts and tunnel does not alter groundwater flow to spring locations in the area. Sections of the tunnel will be parallel to and cross Bull Creek within the boundaries of the BCP, and the potential impact of the tunnel construction on Bull Creek and spring flows is of particular importance toward protection of environmental habitat, specifically that of the Jollyville Plateau Salamander. The rocks present in the study area include the Edwards, Comanche Peak, Walnut, and Glen Rose formations: The Edwards Formation is the uppermost unit and is up to 200 feet thick in the study area. It is a more resistant unit and is typically found at the higher elevations on hilltops in the area. Solution features are common within the Edwards. The Comanche Peak Formation is a limestone unit often placed in the stratigraphic sequence between the Edwards and Walnut formations. Within this study area, however, it becomes interfingered within the Edwards. This unit is present only at the eastern end of the tunnel alignment. The Walnut Formation is a nodular and marly limestone found beneath the Edwards Formation and is between 90 and 100 feet thick in the study area. It includes three individual members, from oldest to youngest, the Bull Creek, Bee Cave, and Cedar Park. Compared to the overlying Edwards formation, the Walnut is less permeable; limited groundwater movement occurs vertically along discrete joints and/or fractures and then laterally along the surface of less permeable horizons, discharging at springs and seeps. However, significant

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 61 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 water movement through fractures in the Walnut has been observed in some locations in the study area, including one boring completed as part of the Forest Ridge site evaluation where 100% of circulation was lost within the Walnut and a packer test was not able to be performed. The upper Glen Rose Formation is only present at land surface at the lowest elevations in the study area. It is estimated to be more than 600 feet thick in the study area, although no borings have penetrated below the base of this unit, and appears to be fairly tight in the study area with only a limited number of enlarged joints and fractures being observed in outcrops or cores collected from boreholes. Hydraulic conductivities are much lower than in the Edwards Formation, although the upper 50 feet appeared to be more permeable than the rest of the Glen Rose Formation. Small springs and seeps have been observed to occur from the Glen Rose, presumably from this more permeable zone. Two different groundwater flow regimes are described in the area of interest, a flow system that occurs primarily in the Edwards and Walnut formations, and a deeper flow system present in the upper Glen Rose Formation: The Edwards/Walnut flow system is the source of spring discharge in much of the study area. Precipitation enters the Edwards as recharge in areas where it crops out and moves downward through the unit through preferential flow pathways (such as conduits) until encountering a less permeable layer. Groundwater then moves laterally, primarily discharging as springs and seeps along the hillsides found in the area. Groundwater can also move vertically into the Walnut through fractures or joints, subsequently moving laterally to discharge from the middle or base of the Walnut Formation. Springs and seeps may also discharge from the upper Glen Rose Formation. This appears to be where groundwater moving laterally encounters fractures in these formations that allow downward movement through an otherwise tight formation, ultimately discharging on hillsides or along creeks in the area. Very few wells and very little groundwater pumpage occur in the study area, and so most of the discharge from these formations occurs from springs and seeps. The second groundwater flow regime described in the study area is found within the upper Glen Rose Formation, located beneath the Edwards and Walnut formations. Groundwater within the upper Glen Rose Formation appears to be largely hydrologically disconnected from that within the Edwards and Walnut formations. Nested piezometers in the study area generally show a strong downward hydraulic gradient within the upper Glen Rose Formation, making the

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 62 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 creation of a "regional" picture of groundwater elevations within the Glen Rose very difficult. Hydraulic characteristics of the formations within the study area are variable based on the available data. Dye-tracing studies in the Edwards/Walnut flow system indicate groundwater flow velocities of tens of feet per day, indicating that flow in this upper system is typical of a karst system. Packer testing on the Edwards was largely unsuccessful during the geotechnical investigation because of these high hydraulic conductivities. Hydraulic conductivities in the Glen Rose are generally much lower. The upper 50 feet of the upper Glen Rose Formation appears to be more permeable, but below this zone the Glen Rose was consistently very tight, often yielding estimated hydraulic conductivities too low to be measured during packer tests. The study area is mostly contained within the Bull Creek watershed. Surface water flow within Bull Creek is supported by spring discharge from the groundwater flow system found within the Edwards, Walnut, and upper Glen Rose formations. This spring discharge also provides important habitat for the Jollyville Plateau Salamander and ultimately discharges into the Colorado River/Lake Austin. A detailed evaluation of flow in Bull Creek was able to provide good baseline data on surface water flow and water quality conditions at various locations along Bull Creek within the study area. The water in Bull Creek is mostly a calcium-bicarbonate type water. This is distinct from groundwater in the Glen Rose Formation, which tended to have more sulfate and magnesium than surface water from Bull Creek. No water quality data for the Edwards or Walnut formations were available. The JTM project can generally be divided up into five individual components: the main transmission tunnel and four shaft locations associated with it. In addition, this assessment covers the Forest Ridge Transmission Main and shaft, which are part of a separate project but whose impacts on the grou ndwater system are similar to those of the JTM project. The four shafts that are required as part of the JTM projectthe WTP4, Four Points, PARD, and Jollyville Reservoir shaftsare between 20 and 40 feet in diameter and 130 and 340 feet deep, although these depths may be changed in the final design. The main questions about the proposed shafts are their potential impact on groundwater and the subsequent impact on Jollyville Plateau Salamander habitat. Three of the four proposed shafts (WTP4, Four Points, and Jollyville Reservoir shafts) will be completed in the Edwards Formation, and because of the karstic nature of the formations underlying these shaft locations, the specific impact of each of the individual

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 63 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 shaft locations cannot be definitively quantified. For each of the shafts installed through the Edwards Formation it is possible that no individual conduits are intersected; an individual conduit is intersected, but the groundwater finds an alternate path to the same spring or springs after the installation of the shaft; an individual conduit is intersected, but the groundwater flow is restored through mitigation measures employed during shaft construction; an individual conduit is intersected and groundwater flow is not restored along the same path, but does not result in any springs going dry; or an individual conduit is intersected, groundwater flow is not restored, and the spring eventually goes dry. No definitive conclusions can be reached as to which, if any, of these scenarios will occur in the Edwards/Walnut groundwater flow system with the installation of the shafts. Mitigation techniques will be used to minimize groundwater inflow to the shafts, and therefore groundwater inflow into the shafts will be minimal, and they are not expected to dewater the formation. Therefore, any potentia l impact of the shafts would occur during installation. While no definitive conclusions can be reached as to whether springs in the Edwards/Walnut groundwater flow system will be impacted due to the installation of each shaft, the deep flow system in the upper Glen Rose Formation is not expected to be adversely impacted during the construction of the shafts. The main transmission tunnel alignment will be approximately 10 feet in excavated diameter and 34,600 feet in length. The tunnel depth is variable, with the current design specifying depths of more than 250 feet in the plateau portions at both the eastern and western ends of the alignment, to between 100 and 150 feet in the central portion of the alignment. Because the deeper portions of the Glen Rose Formation, where the tunnel will be located, tend to be fairly tight, and because hydraulic gradients in the Glen Rose Formation are strongly downward, significant impacts on springs and seeps in the Edwards/Walnut flow system are not be expected during the boring and completion of the proposed tunnel. The proposed Forest Ridge shaft is located within the boundaries of the BCP and will be completed through the Edwards, Walnut, and Glen Rose formations. The conclusions regarding potential impacts from this shaft location are similar to those for the three JTM shaft locations completed in the Edwards Formation, in particular the Four Points shaft. It is possible that specific conduits may be intercepted by the installation of this shaft; however it is not possible to determine whether this will occur and, if it does, whether spring discharge in the area will be impacted. Because specifics of the design of the Forest Ridge tunnel were not available, an assessment of its impact is not included in this assessment.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 64 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 In order to achieve the environmental goals of the JTM project, a number of general mitigation measures were developed for use during the project. To the maximum extent practicable, the JTM will be designed, constructed, and operated to prevent adverse impacts to downstream surface and subsurface water quality and quantity. The Final EC Plan and BDR present the techniques developed for this project. These techniques were developed through a collaborative effort between the environmental and engineering project teams.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 65 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 6.0 REFERENCES Baker, E.T., Jr., R.M. Slade, Jr., M.E. Dorsey, and L.M. Ruiz, 1986. Geohydrology of the Edwards Aquifer in the Austin Area, Texas. Texas Water Development Board Report 293, 82 pp. Black & Veatch, 2009. Preliminary Geotechnical Memorandum, Jollyville Transmission Project. Black and Veatch, 2010a. Basis of Design Report. Prepared for the City of Austin, 140 pp. Black and Veatch, 2010b. Geotechnical Design Memorandum, Jollyville Transmission Main Project. Draft report prepared for the City of Austin, 79 pp. Brune, Gunnar, and Gail L. Duffin, 1983. Occurrence, Availability, and Quality of Ground Water in Travis County, Texas. Texas Department of Water Resources Report 276, 103 pp. City of Austin, 2001. Jollyville Plateau Water Quality and Salamander Assessment. Water Quality Report Series Report No. COA-ERM 1999-01, Watershed Protection Department, Austin, Texas, 141 pp. Duffin, Gail, and Steven P. Musick, 1992. Evaluation of Water Resources in Bell, Burnet, Travis, Williamson, and Parts of Adjacent Counties. Texas Water Development Board Report 326, 105 pp. Fugro Consultants, Inc., 2008. Geotechnical Data Report, City of Austin Water Treatment Plant No. 4, Austin, Texas. Submitted to Carollo Engineers, February 18, 2008. Fugro Consultants, Inc., 2009. Geotechnical Data Report, City of Austin Water Treatment Plant No. 4, Raw Water Facilities and Tunnel, Austin, Texas (REVISED). Submitted to AECOM, October 20, 2009. Garner, L.E., and K.P. Young, 1976. Environmental Geology of the Austin Area: An Aid to Urban Planning. Bureau of Economic Geology Report of Investigations No. 86, 39pp. Ging, Patricia Bauer, 1995. A Water Quality Study of the Upper Bull Creek Watershed, Austin, Texas. May 1995, 127 pp.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 66 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Harper, Jackson, 2001. Review of Ground Water Quality Data for the Bull and West Bull Creek Watersheds, Austin, Texas (PBS&J Job No. 440606.00). Memorandum prepared for Pat Hardigan (City of Austin), October 31, 2001. 5 p. Hauwert, Nico M., 2009. Groundwater Flow and Recharge within the Barton Springs Segment of the Edwards Aquifer, Southern Travis and Northern Hays Counties, Texas. University of Texas dissertation, May 2009, 328 pp. Heuer, R.E., 1995. Estimating Rock Tunnel Water Inflow. Proceedings, Rapid Excavation and Tunneling Conference (RETC), San Francisco, California. Society for Mining, Metallurgy, and Exploration, Inc., Littleton, Colorado. Heuer, R.E., 2005. Estimating Rock Tunnel Water Inflow-II. Proceedings of RETC Conference, Seattle, Washington, pp. 394-407. Hicks and Company, 2010a. Final Environmental Commissioning Plan, Jollyville and Forest Ridge Transmission Mains. Prepared for the City of Austin, September 2010, 60 pp. Hicks and Company, 2010b. Endangered Species Habitat Assessment & CEF Investigations PARD Shaft for the Jollyville Transmission Main, Austin, Texas. Technical Memorandum prepared for Black & Veatch, December 3, 2010, 12 pp. Houlsby, A.C., 1976. Routine Interpretation of the Lugeon Water-Test. Quarterly Journal of Engineering Geology, Vol. 9, pp. 303-313. Holt Engineering, 2009. Subsurface Investigation and Preliminary Geotechnical Data Report for Forest Ridge Transmission Main. Prepared for Lockwood, Andrews & Newnam, Inc. HVJ Associates, Inc. (HVJ), 2007. Geotechnical Investigation, Travis County Water Treatment Plant #4, City of Austin, Aust in, Texas. Submitted to Carollo Engineers. HVJ Associates, Inc. (HVJ), 2009. Preliminary Geotechnical Investigation, Travis County Water Treatment Plant #4, Site 34, Austin, Texas. Submitted to Carollo Engineers. Ikins, W.C., 1941. Stratigraphy and Paleontology of the Walnut and Comanche Peak Formations. Ph. D. dissertation, University of Texas (includes excerpts of Hill, R.T. 1891 The Comanche Series of the Texas-Arkansas region, Bulletin of the Geological Society of America 2:503-528).

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 67 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 Klemt, William B., Robert D. Perkins, and Henry J. Alvarez,1975. Ground-water resources of part of Central Texas with emphasis on the Antlers and Travis Peak Formations. Texas Water Development Board Report 195, 25 pp. Lindgren, R.J., A.R. Dutton, S.D. Hovorka, S.R.H. Worthington, and Scott Painter, 2004. Conceptualization and Simulation of the Edwards Aquifer, San Antonio Region, Texas. USGS Scientific Investigations Report 2004-5277, 143 pp. Moore, C.H., 1964. Stratigraphy of the Fredericksburg Division, South-Central Texas. University of Texas, Bureau of Economic Geol ogy Report of Investigations no. 52, 37 pp. Rodda, P.U., L.E. Garner, and G.L. Dawe, 1970. Austin West, Travis County, Texas. The University of Texas at Austin Bur eau of Economic Geology, Geologic Quadrangle Map 38, 11 pp. Rogers, Margaret Anne Christie, 1969. Stratigraphy and structure of the Fredericksburg Division (Lower Cretaceous), northeast quarter Lake Travis quadrangle, Travis and Williamson counties, Texas. Masters thesis, The University of Texas at Austin, 49 pp. Rose, P.R., 1972. Edwards Group, Surface and Subsurface, Central Texas. The University of Texas Bureau of Economic Geology Report of Investigations 74, 198 pp. Scanlon, Bridget R., Robert E. Mace, Michael E. Barrett, and Brian Smith, 2003a. Can We Simulate Regional Groundwater Flow in a Karst System Using Equivalent Porous Media Models? Case study, Barton Springs Edwards Aquifer, Texas. Journal of Hydrology 276 (2003):137-158. Scanlon, Bridget R., Dutton, Alan, and Sophocleous, Marios, 2003b. Groundwater Recharge in Texas. Prepared for the Texas Water Development Board, 62 pp. Slade, Raymond, 2010. Documentation and Recommendations for Water-Resource Data Collected in the Bull Creek Basin for the Jollyville Transmission Project, April 2009 through March 2010. Prepared for Black and Veatch, 42 pp. Small, T.A., J.A. Hanson, and N.M. Hauwert, 1996. Geologic Framework and Hydrogeologic Characteristics of the Edwards Aquifer Outcrop (Barton Springs Segment), Northeastern Hays and Southwestern Travis Counties, Texas. U.S. Geological Survey Water Resources Investigations 96-4306, 15 pp. Stricklin, F.L., C.I. Smith, and F. E. Lozo, 1971. Stratigraphy of Lower Cretaceous Trinity Deposits of Central Texas. Bureau of Economic Geology Report of Investigations No. 71, 63 pp.

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JOLLYVILLE TRANSMISSION MAIN DECEMBER 2010 68 Preconstruction Groundwater Assessment B&V PROJECT NUMBER 167760 The Student Geology Society, 1977. Guidebook to the Geology of Travis County. The University of Texas, online edition, http://www.lib.utexas.edu/geo/ggtc/toc.html. Woodruff, Jr., M., F. Snyder, L. De La Garza, and R.M. Slade, Jr. 1985. Edwards AquiferNorthern Segment, Travis, Williamson, and Bell Counties, Texas. Austin Geological Society, Guidebook 8, 104 pp. Woodward Clyde Consultants, 1986a. Geotechnical Report, Raw Water Intake Facilities Water Treatment Plant No. 4 Austin, Texas. Prepared for Lake Travis Consultants. Two volumes. Woodward Clyde Consultants, 1986b. Geotechnical Report, North Zone Transmission Tunnel Water Treatment Plant No. 4 Austin, Texas. Prepared for Lake Travis Consultants; two volumes. Woodward Clyde Consultants, 1986c. Geotechnical Report, Northwest A Transmission Tunnels Water Treatment Plant No. 4 Austin, Texas. Prepared for Lake Travis Consultants; two volumes.

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FM 620 FM 2222 360 360 360 183 PARD site WTP4 Site Four Points Site Jollyville Reservoir Site Figure 1-1Jollyville Alignment and Shaft LocationsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 015003000FeetImage source: NAIP, 2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_1-01_JOLLYVILLE_ALIGNMENT_AND_SHAFT_LOCATIONS.MXD Explanation Shaft Jollyville alignment

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183 360 FM 2222 FM 620 PARD site WTP4 Site Four Points Site Jollyville Reservoir Site Figure 2-1Study Area LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 015003000FeetImage source: NAIP, 2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-01_STUDY_AREA_LOCATION.MXD Explanation Shaft Jollyville alignment Study Area Austin TRAVIS HAYS WILLIAMSON BASTROP BURNET CALDWELL

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JN LT04.0008 12/9/2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-02_PHYSIOGRAPHIC_PROVINCES.MXD JOLLYVILLE TRANSMISSION MAINPhysiographic ProvincesDaniel B. Stephens & Associates, Inc. Figure 2-2

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PARD site WTP4 Site Four Points Site Jollyville Reservoir Site WTP 4 Site Figure 2-3Study Area with Surface GeologyJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/13/2010Daniel B. Stephens & Associates, Inc. N 015003000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-03_STUDY_AREA_SURFACE_GEOLOGY.MXD 013121Explanation Shaft Jollyville alignment Lake Glen Rose formation Comanche Peak formation Edwards formation Walnut formation Based on Garner and Young (1976)

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PARD site WTP4 Site Four Points Site Jollyville Reservoir Site 800 780 920 960 980 760 840 860 720 740 880 900 1000 820 660 1020 700 680 940 640 1040 1060 620 1080 600 1100 611 1000 740 700 900 880 720 820 960 1080 900 860 1100 860 840 960 780 680 900 820 780 860 980 880 880 940 900 880 1060 900 1040 920 1080 660 860 740 860 860 940 980 940 820 960 720 980 611 1000 760 920 1020 1080 760 1060 1000 700 920 920 960 840 860 840 900 800 840 960 880 1020 1020 880 720 820 900 840 900 740 820 840 800 1000 960 840 800 940 960 820 1040 980 940 611 900 980 800 780 800 880 980 740 820 880 920 740 900 860 880 800 840 900 1100 820 880 1100 880 820 940 840 1000 960 920 960 940 940 940 760 860 1000 960 960 860 820 860 700 920 780 880 880 980 840 820 820 Figure 2-4Study Area TopographyJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 010002000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-04_STUDY_AREA_TOPOGRAPHY.MXD Explanation Shaft Jollyville alignment

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 5 G e n e r a l S t r a t S e c t i o n m x d F i g u r e 2 5 G e n e r a l i z e d S t r a t i g r a p h i c S e c t i o n J O L L Y V I L L E T R A N S M I S S I O N M A I N J N W R 1 0 0 1 3 8 0 0 1 2 / 9 / 2 0 1 0 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c G r o u p R o c k D e s c r i p t i o n H y d r o l o g i c U n i t T h i c k n e s s f e e t C o m a n c h e P e a k F m L i m e s t o n e a r g i l l a c e o u s l i m e s t o n e M o t t l e d a n d b u r r o w e d o c c a s i o n a l l y f o s s i l i f e r o u s o c c a s i o n a l l y v u g g y u p t o 1 2 0 T r i n i t y G r o u p G l e n R o s e F o r m a t i o n U p p e r M e m b e r A l t e r n a t i n g b e d s o f d o l o m i t e a n d l i m e s t o n e o c c a s i o n a l l y a r g i l l a c e o u s m o t t l e d f o s s i l i f e r o u s b u r r o w e d D o l o m i t e i s g e n e r a l l y v u g g y U p p e r T r i n i t y A q u i f e r m o r e t h a n 5 0 0 S o u r c e : B a s e d o n H a r p e r 2 0 0 1 ; B r u n e a n d D u f f i n 1 9 8 3 u p t o 2 0 0 E d w a r d s F o r m a t i o n W a l n u t F o r m a t i o n F o r m a t i o n F r e d e r i c k s b u r g G r o u p D o l o m i t e d o l o m i t i c l i m e s t o n e l i m e s t o n e S o m e b e d s f o s s i l i f e r o u s C a v e r n s a n d s o l u t i o n f e a t u r e s c o m m o n E d w a r d s A q u i f e r

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JT-108-A JT-107S-A JT-106 JT-105 JT-109 JT-110-A JT-111 JT-112 JT-100 JT-101-A JT-102 JT-103-A JT-104-A JT-113 JT-114 JT-115 JT-116 JT-117 JT-118 JT-119 JT-120-A JT-121 JT-122 JT-123 JT-124-A JT-125-A JT-126 JT-127 JT-107PZ-A JT-107D-A JT-107ITW-A B-9 B-8 B-5 B-13 B-10 B-8A Lake Travis B-16 B-02 B-01 B-02A Figure 2-6Boring LocationsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/13/2010Daniel B. Stephens & Associates, Inc. S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-06_BORING_LOCATIONS.MXD Note: Borings with an "-A" in the boring name are replacement borings and were not cored. N 012502500FeetExplanation Borings Borings not yet installed Jollyville alignment Fugro borings Forest Ridge borings

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TextTextText Explanation Explanation Source:N 80 ft Text Modified from DRI, 1991 TextTextTextText 0 12/10/10 JN WR10.0138 Not to Scale Daniel B. Stephens &Associates, Inc. S:\Projects\WR10.0138_Jollyville_Transmission_Main\VR_Drawings\WR10_0138_Graphs_Figure_2-7.cdr City ofAustin, Texas Water Treatment Plant 4 JollyvilleTransmission Main Geologic Profile StratLithCrossSectionver93_11x17 J.Young 12/07/10 Data source: BV, City ofAustin, CAPCOG, Fugro DRAFT November 20, 2010 Ground Surface ProposedTunnelAlignment JT-127 To Be Drilled JT-115 To Be Drilled JT-106 (119 ft from alignment) Inclined 20 deg., S 50 E JT-105 (323 ft from alignment) Inclined 20 deg., N 60 W JT-119 (5 ft from alignment) JT-120 (4 ft from alignment) JT-118 (36 ft from alignment) JT-108 (308 ft from alignment) JT-116 (358 ft from alignment) JT-117 (239 ft from alignment) JT-107D (77 ft from alignment) JT-100 (313 ft from alignment) JT-109 (26 ft from alignment) JT-104 (573 ft from alignment) JT-121 (1063 ft from alignment) JT-123 (61 ft from alignment) JT-101 (864 ft from alignment) JT-102 (163 ft from alignment) JT-122 (1126 ft from alignment) JT-125 (119 ft from alignment) JT-113 (10 ft from alignment) JT-110 (123 ft from alignment) JT-126 (69 ft from alignment) JT-112 (21 ft from alignment) JT-124 (164 ft from alignment) JT-111 (117 ft from alignment) JT-114 (7 ft from alignment) B-10 (68 ft from alignment) -2000 0 1000 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 22000 24000 26000 28000 30000 32000 34000 36000 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 B-8 B-9 B-10 JT-108 JT-106 JT-105 JT-109 JT-110 JT-111 JT-112 JT-100 JT-101 JT-102 JT-103 JT-104 JT-113 JT-114 JT-116 JT-117 JT-118 JT-119 JT-120 JT-121 JT-122 JT-123 JT-124 JT-125 JT-126 JT-107D JT-115 JT-127 Legend Contact Uncertain Contact Tunnel Lithology No Core Recovered Overburden Limestone Dolomite Argillaceous Rocks Stratigraphy Edwards Walnut Glen Rose Notes: 1.This is our interpretation of the subsurface conditions encountered during the investigation. 2. Maximum depth drilled: 553.4 ft (B-10). Feet 01,000 Feet 0 50 Vertical Exaggeration: 24x Stratigraphic SectionAlongAlignment Figure 2-7JOLL YVILLE TRANSMISSION MAIN

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5834802 5834803 5833901 5834706 5834708 5834714 5834711 5834705 5834701 5834707 5834713 5834712 5834903 5834905 5834702 5834704 5834703 5834710 5834709 5834904 5834801 5835711 5833907 5833908 5835710 5834606 5835413 5834608 5834504 5834503 5834607 5834601 5834614 5834615 5834618 5834613 5834403 5834603 5834604 5834509 5834508 5834502 5834406 5834506 5834507 5834514 5834616 5834619 5834620 5834621 5834611 5834303 WTP4 Site Jollyville Reservoir Site PARD site Four Points Site Lake Travis Figure 2-8TWDB Wells Within Two Miles of AlignmentJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 020004000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-08_WELLS_WITHIN_TWO_MILES_OF_ALIGNMENT.MXD Explanation Shaft Wells within two miles of alignment Jollyville alignment

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BH-3 BH-14 BH-2 BH-8 Windmill S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-09_DYE_TRACING_GEOLOGY.MXD Figure 2-9 JN WR10.0138.00 12/13/2010Daniel B. Stephens & Associates, Inc. N 05001000FeetExplanation Springs and seeps Dye tracing sites monitored Dye tracing injection borings/wells Jollyville alignment Edwards Limestone Walnut Cedar Park Member Walnut Bee Cave Member Walnut Bull Creek Member Glen Rose Limestone JOLLYVILLE TRANSMISSION MAINDetailed Surface Geology and Monitoring Locations at Former WTP4 SiteNote: Topography shading is included on figure.

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BH-8 BH-2 BH-3 BH-14 Windmill Explanation Springs and seeps Dye tracing sites monitored Dye tracing injection borings/wells Dye Trace Results JollyvilleAlignment N 05001000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-10_DYE_TRACING_RESULTS.MXD Figure 2-10Dye tracing resultsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/13/2010Daniel B. Stephens & Associates, Inc.

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 1 1 D y e T r a c i n g C r o s s S e c t i o n m x d F i g u r e 2 1 1 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c 1 2 / 9 / 2 0 1 0 J N W R 1 0 0 1 3 8 0 0 J O L L Y V I L L E T R A N S M I S S I O N M A I N C r o s s S e c t i o n V i e w o f D y e T r a c i n g R e s u l t s S o u r c e : C i t y o f A u s t i n

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Lake Travis B-5 B-8A B-10 B-8 B-9 Old WTP 4 Site WTP 4 Site S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-12_NESTED_PIEZOMETERS_LOCATIONS.MXD Figure 2-12Nested Piezometers LocationsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 012502500FeetExplanation Nested piezometers Shaft JollyvilleAlignment

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Lake Travis WTP 4 Site S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-13_NESTED_PIEZOMETERS_B-5_B-8A.MXD Figure 2-13Nested Piezometers B-5 and B-8AJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 07501500FeetExplanation Nested piezometer Shaft JollyvilleAlignment B-5500.0 550.0 600.0 650.0 700.0 750.0 Apr07 Aug07 Dec07 Apr08 Aug08 Dec08 Apr09 Aug09 Dec09 Apr10 Aug10Pressure Elevation (ft) piezometer elevation = 652.9 piezometer elevation = 492.9 B-8A500.0 550.0 600.0 650.0 700.0 Apr-07May-07Jun-07Jul-07Aug-07Sep-07Oct-07Pressure Elevation (ft) piezometer elevation = 599.1 piezometer elevation = 474.1

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WTP 4 Site Old WTP 4 Site S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-14_NESTED_PIEZOMETERS_B-8_B-9_B-10.MXD Figure 2-14Nested Piezometers B-8, B-9, and B-10JOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/13/2010Daniel B. Stephens & Associates, Inc. N 07501500FeetExplanation Nested piezometer Shaft JollyvilleAlignment B-9450.0 500.0 550.0 600.0 650.0 700.0 750.0 800.0 850.0 900.0 950.0 1000.0 Apr-07Oct-07Apr-08Oct-08Apr-09Oct-09Apr-10Oct-10Pressure Elevation (ft) piezometer elevation = 930 piezometer elevation = 662 piezometer elevation = 600 piezometer elevation = 475 B-10400.0 500.0 600.0 700.0 800.0 900.0 1000.0 Apr-07Oct-07Apr-08Oct-08Apr-09Oct-09Apr-10Oct-10Pressure Elevation (ft) piezometer elevation = 916.5 piezometer elevation = 636.5 piezometer elevation = 461.5 B-8600.0 650.0 700.0 750.0 800.0 850.0 900.0 950.0 1000.0 Apr-07Oct-07Apr-08Oct-08Apr-09Oct-09Apr-10Oct-10Pressure Elevation (ft) piezometer elevation = 929.7 piezometer elevation = 699.7 piezometer elevation = 479.7

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Cross-SectionAlongAlignment TextTextText Explanation Figure 2-15JOLLYVILLE TRANSMISSION MAIN Explanation Source:N 80 ft Text Modified from DRI, 1991 TextTextTextText 0 12/10/10 JN WR10.0138 Not to Scale Daniel B. Stephens &Associates, Inc. S:\Projects\WR10.0138_Jollyville_Transmission_Main\VR_Drawings\WR10_0138_Graphs_Figure_2-15.cdr B-8 B-9 B-10 JT-115 JT-127 JT-108 JT-106 JT-105 JT-109 JT-110 JT-111 JT-112 JT-100 JT-101 JT-102 JT-103 JT-104 JT-113 JT-114 JT-116 JT-117 JT-118 JT-119 JT-120 JT-121 JT-122 JT-123 JT-124 JT-125 JT-126 JT-107D 01,1002,200 Feet 1 inch = 2,200 feet Austin Lakeway Lakeway 183 Travis Williamson City ofAustin, Texas Water Treatment Plant 4 JollyvilleTransmission Main GeotechCrossSectionver93NoRQD_11x17 J.Young 12/06/10 Data source: BV, City ofAustin, CAPCOG, ESRI DRAFT November 22, 2010Vertical Exaggeration = 12X ProposedTunnelAlignment Ground Surface JT-127 (To Be Drilled) JT-115 (To Be Drilled) JT-106 (119 ft) Inclined 20 deg., S 50 E JT-105 (323 ft) Inclined 20 deg., N 60 W JT-119 (5 ft) JT-120 (4 ft) JT-118 (36 ft) JT-108 (308 ft) JT-116 (358 ft) JT-117 (239 ft) JT-107D (77 ft) JT-100 (313 ft) JT-109 (26 ft) JT-104 (573 ft) JT-121 (1063 ft) JT-123 (61 ft) JT-101 (864 ft) JT-102 (163 ft) JT-122 (1126 ft) JT-125 (119 ft) JT-113 (10 ft) JT-110 (123 ft) JT-126 (69 ft) JT-112 (21 ft) JT-124 (164 ft) JT-111 (117 ft) JT-114 (7 ft) B-10 (68 ft) -1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000 26000 27000 28000 29000 30000 31000 32000 33000 34000 35000 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 Geotechnical ProfileLegend Existing B&V Borehole or Piezo Planned B&V Piezo Existing Borehole by Others Retrieval Shaft Working Shaft RecommendedAlignment Reservoir and WTP4 Old WTP4 Site Creeks Water City ofAustin Parks BCP Potential Future BCP Property Lines/ROWCross-Section Tunnel Formations Overburden Edwards Walnut Glen Rose K HydraulicConductivity (cm/s) Less than 1x10-6 1x10-6to 3x10-6 3x10-6to 1x10-5 1x10-5to 3x10-5 3x10-5to 1x10-4 1x10-4to 3x10-4 3x10-4to 1x10-3 1x10-3to 3x10-3 JT-XXX (xx ft) Boring Log Detail Borehole ID Distance to Alignment RQD 100 to 0% Hydraulic Conductivity 0 to 3x10-3 Stratigraphy

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S:\PROJECTS\WR10.138_JOLLYVILLE_TRANSMISSION_MAIN\VR_DRAWING\WR10_0138_04W_Graphs_figures_2-16_2-17_2-18.cdrFigure 2-16JOLLYVILLE TRANSMISSION MAIN Daniel B. Stephens &Associates, Inc.12/09/10 JN WR10.0138 PRELIMINARYSUBJECT TO REVISIONPRIVILEGEDAND CONFIDENTIAL Overall Distribution of Hydraulic Conductivity in Glen Rose Formation63% 4% 3%3% 9% 6% 6% 7% 0% 20% 40% 60% 80% 100% <1E-61E-6 to 3E-63E-6 to 1E-51E-5 to 3E-53E-5 to 1E-41E-4 to 3E-43E-4 to 1E -31E-3 to 3E-3Hydraulic Conductivity (cm/s)Percentage Note:Number of samples = 180

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S:\PROJECTS\WR10.138_JOLLYVILLE_TRANSMISSION_MAIN\VR_DRAWING\WR10_0138_04W_Graphs_figures_2-16_2-17_2-18.cdrFigure 2-17JOLLYVILLE TRANSMISSION MAIN Daniel B. Stephens &Associates, Inc.12/09/10 JN WR10.0138 PRELIMINARYSUBJECT TO REVISIONPRIVILEGEDAND CONFIDENTIAL Distribution of High Hydraulic Conductivity Values for the GlenRose Formation4 3 2 1 2 6 1E-4 to 3E-43E-4 to 1E-31E-3 to 3E-3Hydraulic Conductivity (cm/s)DolomiteLimestone Explanation 5 0 2 4Frequency

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S:\PROJECTS\WR10.138_JOLLYVILLE_TRANSMISSION_MAIN\VR_DRAWING\WR10_0138_04W_Graphs_figures_2-16_2-17_2-18.cdrFigure 2-18JOLLYVILLE TRANSMISSION MAIN Daniel B. Stephens &Associates, Inc.12/09/10 JN WR10.0138 PRELIMINARYSUBJECT TO REVISIONPRIVILEGEDAND CONFIDENTIAL Distribution of Hydraulic Conductivity for Walnut Formation9% 13% 4% 74% 0% 20% 40% 60% 80% 100% <1E-61E-6 to 3E-63E-6 to 1E-51E-5 to 3E-53E-5 to 1E-41E-4 to 3E-43E-4 to 1E -31E-3 to 3E-3Hydraulic Conductivity (cm/s)Percentage Note:Number of samples = 23

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WTP4 Site Jollyville Reservoir Site PARD site Four Points Site 966 JT-109 11/30/2010 977 JT-112 11/30/2010 957 JT-114 11/30/2010 966 JT-113 11/30/2010 871 5834513 01/04/2008 911 5834601 05/12/1983 884 5834613 02/24/1993 822 5834614 07/24/1972 912 5834618 05/02/1996 899 5834622 01/04/2008 871 5834902 03/01/1978 781 5835413 08/24/1978 850 5835702 05/12/2005 843 5835711 11/15/1939 979 JT-101A 11/30/2010 854 JT-124A 11/30/2010 925 NW-8 1/18/1986 917 NW-9 1/18/1986 939 B-8 9/5/2007 944 B-9 9/5/2007 942 B-10 9/5/2007 884 Long Hog Hollow Spring 779 Wall Hill Cove Spring 834 Elm Spring 853 Canyon Creek Spring 3 754 Raindrop Cove Spring 827 Tanglewood Spring 860 Grace Covenant Church Spring 864 Spicewood Parkway Spring 881 Ivanhoe Spring 2 836 Bronc Spring 824 Fire Oak Spring 751 Great Hills Spring 875 Canyon Creek Spring 1 (Tubb Spring) 785 Texas Plume Spring 834 Quarry Lake Spring 745 Small Sylvia Spring 899 Ivanhoe X Spring 894 Spanish Oak Spring 891 Canyon Creek Spring 5 886 Ivanhoe Spring 884 Fern Gully Spring 860 Cistern (Pipe) Spring 855 Irena Spring 936 Park West Spring 916 Plum Spring 888 Moss Gully Spring 861 Plunge Pool Spring 880 Stock Pond Spring 872 Honeycomb Spring 905 SAS Canyon Spring (Grandview Hills Spg) 847 Ribelin Spring 2 (Lower Ribelin) 861 Burr Oak Spring 891 Unnamed seep 872 Unnamed seep 880 Seeking Tank Spring 861 Canyon Creek Spring 2 894 Canyon Creek Spring 6 879 Canyon Creek Spring 4 923 Powerline Spring 789 Lanier Spring 1007 Davis Spring 962 Hampton Spring 964 Lloyd Spring 779 Canyon Creek 2 Spring 812 Bull Creek Spring Pool 919 Concordia Spring X 866 Concordia Spring Y (aka SS-6) 758 Sierra Spring 725 Hearth Spring 832 Canyon Head Seep/Spring 915 Schlumberger Spring 1 901 Schlumberger Spring 1 (aka SS-10) 969 Unnamed spring 976 Unnamed spring 972 Unnamed spring Figure 2-19Water Levels in the Edwards/Walnut Groundwater Flow SystemJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/13/2010Daniel B. Stephens & Associates, Inc. N 015003000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-19_WATER_LEVELS_IN_THE_SHALLOW_GROUNDWATER_FLOW_SYSTEM.MXD Explanation Shafts Well or boring Spring Piezometer Jollyville alignment963 JT-109 10/15/2010Date Designation Water level or spring elevation

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WTP4 Site Jollyville Reservoir Site PARD site Four Points Site 676 B-5 11/23/2010 682 B-8A 9/5/2007 762 B-8 11/23/2010 681 B-9 11/23/2010 688 B-10 11/23/2010 768 NW-3 10/3/1985 749 NW-4 10/3/1985 813 BH-7 12/5/1985 525 B-13 9/16/2009 720 JT-118A 11/30/2010 822 JT-125A 11/30/2010 802 JT-126 11/30/2010 823 JT-110A 11/30/2010 720 JT-120A 11/30/2010 828 JT-103A 11/30/2010 779 JT-104A 11/30/2010 Figure 2-20Water Levels in the Upper Glen Rose Groundwater Flow SystemJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/13/2010 N 015003000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-20_WATER_LEVELS_IN_THE_DEEP_GROUNDWATER_FLOW_SYSTEM.MXD 01 3121Explanation Well or boring Piezometer Shafts Jollyville alignment525 B-13 9/16/2009Date Designation Water level or spring elevationDaniel B. Stephens & Associates, Inc.

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923 891 923 947 906 947 801 794 844 830 849 904 868 890 897 906 989 894 970 968 995 971 971 906 846 906 969 976 972 962 958 994 977 JT-112 11/30/2010 979 JT-101A 11/30/2010 957 JT-114 11/30/2010 966 JT-109 11/30/2010 966 JT-113 11/30/2010 WTP4 Site Four Points Site Explanation Springs and seeps Well Shaft Surface watershed Jollyville alignment N 05001000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-21_DIVIDES.MXD 013121 Figure 2-21Approximate Four Point Surface and Groundwater DividesJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/13/2010Daniel B. Stephens & Associates, Inc. 977JT-11211/30/2010Date Designation Water level or spring elevation

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Panther Hollow West Bull Creek Bull Creek Rattan Creek Lake Travis WTP4 Site Jollyville Reservoir Site PARD site Four Points Site Figure 2-22Surface WatershedsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 015003000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-22_SURFACE_WATERSHEDS.MXD Explanation Shafts Jollyville alignment Watershed

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Long Hog Hollow Spring Elm Spring Wedgewood Spring Canyon Creek Spring 3 Tanglewood Spring Spicewood Parkway Spring Muddy Spring Vista Spring Ivanhoe Spring 2 Bronc Spring Fire Oak Spring Canyon Creek Spring 1 (Tubb Spring) Texas Plume Spring Spicewood Valley Park Spring Small Sylvia Spring Ivanhoe X Spring Spanish Oak Spring Canyon Creek Spring 5 Ivanhoe Spring Fern Gully Spring Cistern (Pipe) Spring Park West Spring Plum Spring Buzzard Spring Moss Gully Spring Plunge Pool Spring Stock Pond Spring Honeycomb Spring SAS Canyon Spring (Grandview Hills Spg) Ribelin Spring 2 (Lower Ribelin) Burr Oak Spring Ribelin Spring Powerline Spring Seeking Tank Spring Canyon Creek Spring 2 Canyon Creek Spring 6 Canyon Creek Spring 4 Pit Spring Lanier Spring Davis Spring Hampton Spring Lloyd Spring Canyon Creek 2 Spring Bull Creek Spring Pool Concordia Spring X Concordia Spring Y (aka SS-6) Schlumberger Spring 1 WTP4 Site Jollyville Reservoir Site PARD site Four Points Site Figure 2-23Springs and SeepsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 010002000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-23_SPRINGS_AND_SEEPS.MXD Explanation Springs and Seeps Shafts Jollyville alignment

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Bowman well Open bore Bull creek upstream WTP4 Old WTP4 well Old WTP site Lanier springs Lanier well Pit springs Spicewood springs crossing 7 PARD site Four Points Site Figure 2-24Bull Creek Low Flow Study Measurement LocationsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 07501500FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-24_BULL_CREEK_FLOW_STUDY_MEASUREMENT_LOCATIONS.MXD Explanation Bull Creek flow study location Shaft Jollyville alignment

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 2 5 B u l l C r e e k F l w o v s P r e c i p m x d F i g u r e 2 2 5 S t r e a m f l o w v s P r e c i p i t a t i o n i n u p p e r B u l l C r e e k J O L L Y V I L L E T R A N S M I S S I O N M A I N J N W R 1 0 0 1 3 8 0 0 1 2 / 9 / 2 0 1 0 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c 0 0 5 1 1 5 2 2 5 3 3 5 4 0 0 5 1 1 5 2 2 5 3 3 5 4 4 5 5 J a n 0 7 J u l 0 7 J a n 0 8 J u l 0 8 J a n 0 9 J u l 0 9 J a n 1 0 J u l 1 0 P r e c i p i t a t o i n i n c h e s S t r e a m f l o w c f s P r e c i p i t a t i o n B u l l C r e e k S t r e a m f l o w R a i n f a l l o n 9 / 6 t o 7 / 2 0 1 0 w a s 9 8 i n c h e s a n d t h e a v e r a g e d a i l y f l o w o n 9 / 8 / 2 0 1 0 w a s 7 8 c f s

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 2 5 B u l l C r e e k F l w o v s P r e c i p m x d F i g u r e 2 2 6 B u l l C r e e k S t r e a m f l o w s v s D r a i n a g e A r e a J O L L Y V I L L E T R A N S M I S S I O N M A I N J N W R 1 0 0 1 3 8 0 0 1 2 / 9 / 2 0 1 0 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c 0 5 1 0 1 5 2 0 2 5 3 0 0 7 7 4 0 3 8 4 1 2 2 3 0 S t r e a m f l o w c f s D r a i n a g e A r e a s q m i 4 / 2 5 / 2 0 0 9 5 / 3 0 / 2 0 0 9 6 / 2 0 / 2 0 0 9 7 / 2 5 / 2 0 0 9 8 / 2 2 / 2 0 0 9 9 / 1 9 / 2 0 0 9 1 0 / 1 7 / 2 0 0 9 1 1 / 1 4 / 2 0 0 9 1 2 / 1 3 / 2 0 0 9 1 / 2 3 / 2 0 1 0 2 / 2 7 / 2 0 1 0 3 / 2 7 / 2 0 1 0

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S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_2-27_STREAM_FLOW.MXD Bull Creek Gain-Loss Study ResultsJOLLYVILLE TRANSMISSION MAIN PRELIMINARY SUBJECT TO REVISION JN WR10.0138 105 Bull ck 0.343 Ribelin trib 0.041 Lanier Spring 0.232 206 Bull ck crossing 1 3.007 204 Bull ck crossing 3 2.550 203 Bull ck crossing 4 3.641 202 Bull ck crossing 5 2.522 101 Bull ck upst WTP4 0.019 201 Bull ck crossing 6 2.735 109 Bull ck crossing 7 2.376 108 Bull ck dnst tub 5 1.424 207 Bull ck crossing 11 2.749 205 Bull ck crossing 2 2.665 104 Bull ck dnst Lanier 0.423 107 Bull ck dnst pf Pit spring 0.674 208 Bull ck @ lakewood/loop 360 2.935 102 Bull ck dnst WTP4 (former gage) 0.420 106 Bull ck upst of Pit spring 0.000 Figure 2-2712/10/2010Daniel B. Stephens & Associates, Inc. N 015003000FeetExplanation Stream flow measurement site JollyvilleAlignmentNote: Stream flow measured May 13, 2010 105 Bull ck 0.343Site name Stream flow (CFS)

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 2 8 B u l l C r e e k P r o f i l e m x d F i g u r e 2 2 8 P r o f i l e o f S t r e a m f l o w i n B u l l C r e e k J O L L Y V I L L E T R A N S M I S S I O N M A I N J N W R 1 0 0 1 3 8 0 0 1 2 / 9 / 2 0 1 0 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c 0 0 5 1 1 5 2 2 5 3 3 5 4 S t r e a m f l o w c f s U S G S g a g e r e p o r t s 4 5

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 2 9 B u l l C r e e k P i p e r D i a g r a m m x d G o n z a l e s G o n z a l e s D e w i t t D e w i t t G u a d a l u p e G u a d a l u p e W i l s o n W i l s o n K a r n e s K a r n e s C a l d w e l l C a l d w e l l G o n z a l e s N i x o n S m i l e y P i p e r d i a g r a m o f B u l l C r e e k S a m p l e s J O L L Y V I L L E T R A N S M I S S I O N M A I N J N W R 1 0 0 1 3 8 0 0 1 2 / 9 / 2 0 1 0 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c F i g u r e 2 2 9

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N : / C l i e n t / W a t e r R e s o u r c e s / C O A J o l l y v i l l e T r a n s m i s s i o n M a i n / G I S / M X D s / F i g u r e 2 3 0 G l e n R o s e P i p e r D i a g r a m m x d G o n z a l e s G o n z a l e s D e w i t t D e w i t t G u a d a l u p e G u a d a l u p e W i l s o n W i l s o n K a r n e s K a r n e s C a l d w e l l C a l d w e l l G o n z a l e s N i x o n S m i l e y F i g u r e 2 3 0 P i p e r d i a g r a m o f G l e n R o s e S a m p l e s J O L L Y V I L L E T R A N S M I S S I O N M A I N J N W R 1 0 0 1 3 8 0 0 1 2 / 9 / 2 0 1 0 D a n i e l B S t e p h e n s & A s s o c i a t e s I n c

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PARD site WTP4 Site Four Points Site Jollyville Reservoir Site Figure 3-1Location of Alignment and Proposed Shaft LocationsJOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 010002000FeetImage source: NAIP, 2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-01_LOCATION_OF_ALIGNMENT_AND_PROPOSED_SHAFT_LOCATIONS.MXD Explanation Shafts Jollyville alignment Reach 1 Reach 2 Reach 3

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FM 620 FM 2222WTP 4 WTP4 Site Four Points Site JT-115 JT-114 JT-113 JT-102 JT-100 JT-112 JT-111 JT-109 JT-105 JT-106 JT-103-A JT-101-A JT-110-A Explanation Springs and seeps Boring Shaft Jollyville alignment N 010002000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-02WTP4.MXD 010121 Figure 3-2Proposed WTP4 Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/10/2010Daniel B. Stephens & Associates, Inc.

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JT-100 JT-112 JT-111 JT-109 JT-101-A JT-110-A WTP4 Site Four Points Site Explanation Shaft Boring Springs and seeps Jollyville alignment Potential area of groundwater discharge N 0375750FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-03WTP4 IMPACT AREAS.MXD Figure 3-3Potential Areas of Groundwater Discharge from Proposed WTP4 Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/10/2010Daniel B. Stephens & Associates, Inc.

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FM 2222FM 620Highway RR 620 JT-115 JT-114 JT-113 JT-102 JT-100 JT-112 JT-111 JT-109 JT-103-A JT-101-A JT-110-A WTP4 Site Four Points Site WTP 4 Site Explanation Shaft Boring Springs and seeps Jollyville alignment N 05001000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-04-FOUR POINTS.MXD Figure 3-4Proposed Four Points Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/10/2010Daniel B. Stephens & Associates, Inc.

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? JT-115 JT-114 JT-113 JT-102 JT-112 JT-111 JT-101-A JT-110-A Four Points Site Explanation Springs and seeps Boring Shaft Jollyville alignment Potential area of groundwater discharge N 0400800FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-05FOUR POINTS IMPACT AREAS.MXD Figure 3-5 JN WR10.0138.00 12/10/2010Daniel B. Stephens & Associates, Inc. Potential Areas of Groundwater Discharge from Proposed Four Points Shaft LocationJOLLYVILLE TRANSMISSION MAIN

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BULL CREEK JT-123 JT-122 JT-121 JT-119 JT-118 JT-117 JT-124-A JT-120-A JT-116-A JT-104-A Bronc Spring Muddy Spring Tanglewood Spring Texas Plume Spring Small Sylvia Spring Spicewood Parkway Spring Spicewood Valley Park Spring PARD site Explanation Springs and seeps Boring Shaft Jollyville alignment N 05001000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-06-PARD.MXD 013121 Figure 3-6Proposed PARD Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/13/2010Daniel B. Stephens & Associates, Inc.

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JT-127 (Not yet drilled) JT-126 JT-123 JT-125-A JT-124-ASpicewood Springs RoadUS Hwy 183 Jollyville Reservoir Site Tanglewood Spring Explanation Springs and seeps Boring Shaft Jollyville alignment N 0300600FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-07-JR.MXD Figure 3-7Proposed Jollyville Reservoir Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/10/2010Daniel B. Stephens & Associates, Inc.

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Four Points Dr. WTP4 Site Four Points Site Figure 3-8Reach 1JOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 0200400FeetImage source: NAIP, 2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-08_REACH_1.MXD Explanation Shafts Jollyville alignment

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TextTextText Explanation Explanation Source:N 80 ft Text Modified from DRI, 1991 TextTextTextText 0 12/10/10 JN WR10.0138 Not to Scale Daniel B. Stephens &Associates, Inc. S:\Projects\WR10.0138_Jollyville_Transmission_Main\VR_Drawings\WR10_0138_Graphs_Figure_3-9.cdrCross-SectionAlong Reach 1 Figure 3-9JOLL YVILLE TRANSMISSION MAIN JT-109 JT-112 City ofAustin, Texas Water Treatment Plant 4 JollyvilleTransmission Main GeotechCrossSectionver93_West-112 J.Young 12/07/10Data source: BV, City ofAustin, CAPCOG, Fugro DRAFT November 22, 2010 JT-100 (313 ft) JT-109 (26 ft) JT-101 (864 ft) JT-110 (123 ft) JT-112 (21 ft) JT-111 (117 ft) -2000 -1000 0 1000 2000 3000 4000 5000 800 850 900 950 1000 1050 Geotechnical Profile Cross-Section TunnelFormations Overburden Edwards Walnut Glen RoseK HydraulicConductivity (cm/s) Less than 1x10-6 1x10-6to 3x10-6 3x10-6to 1x10-5 1x10-5to 3x10-5 3x10-5to 1x10-4 1x10-4to 3x10-4 3x10-4to 1x10-3 1x10-3to 3x10-3West end to Borehole JT-112 JT-XXX (xx ft) Boring Log Detail Borehole ID Distance to Alignment RQD 100 to 0% Hydraulic Conductivity 0 to 3x10 -3 Stratigraphy 50 Vertical Exaggeration = 12X Feet25 Feet 0 5001,000

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S:\PROJECTS\WR10.138_JOLLYVILLE_TRANSMISSION_MAIN\VR_DRAWING\WR10_0138_05W_HYDRAULIC_CONDUCTIVITY_3-10_3-13_3-16.CDRFigure 3-10JOLLYVILLE TRANSMISSION MAIN Daniel B. Stephens &Associates, Inc.11/24/10 JN WR10.0138 PRELIMINARYSUBJECT TO REVISIONPRIVILEGEDAND CONFIDENTIAL Distribution of Hydraulic Conductivities along Reach 1 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% <1x10-61x10to 3x10-6 -63x10to 1x10-6 -51x10to 3x10-5 -53x10to 1x10-5 -41x10to 3x10-4 -43x10to 1x10-4 -31x10to 3x10-3 -3Hydraulic Conductivity (cm/s)ProportionofTesting

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Spicewood Springs Rd. Ranch Road 620 North Four Points Dr. River Place Blvd. PARD site Four Points Site Figure 3-11Reach 2JOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 07501500FeetImage source: NAIP, 2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-11_REACH_2.MXD Explanation Shafts Jollyville alignment

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Cross-SectionAlong Reach 2 TextTextText Explanation Figure 3-12JOLLYVILLE TRANSMISSION MAIN Explanation Source:N 80 ft Text Modified from DRI, 1991 TextTextTextText 0 12/10/10 JN WR10.0138 Not to Scale Daniel B. Stephens &Associates, Inc. S:\Projects\WR10.0138_Jollyville_Transmission_Main\VR_Drawings\WR10_0138_Graphs_Figure_3-12.cdr JT-112 JT-120 City ofAustin, Texas Water Treatment Plant 4 JollyvilleTransmission Main GeotechCrossSectionver93_112-120 J.Young 12/07/10Data source: BV, City ofAustin, CAPCOG, ESRI DRAFT November 22, 2010Vertical Exaggeration = 12X ProposedTunnelAlignment Ground Surface JT-115 (To Be Drilled) JT-106 (119 ft) Inclined 20 deg., S 50 E JT-105 (323 ft) Inclined 20 deg., N 60 W JT-119 (5 ft) JT-120 (4 ft) JT-118 (36 ft) JT-108 (308 ft) JT-116 (358 ft) JT-117 (239 ft) JT-107D (77 ft) JT-102 (163 ft) JT-113 (10 ft) JT-112 (21 ft) JT-114 (7 ft) B-10 (68 ft) 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 Geotechnical ProfileCross-Section Tunnel Formations Overburden Edwards Walnut Glen Rose K HydraulicConductivity (cm/s) Less than 1x10-6 1x10-6to 3x10-6 3x10-6to 1x10-5 1x10-5to 3x10-5 3x10-5to 1x10-4 1x10-4to 3x10-4 3x10-4to 1x10-3 1x10-3to 3x10-3 Boreholes JT-112 to JT-120 JT-XXX(xx ft) Boring Log Detail Borehole ID Distance to Alignment RQD 100 to 0% Hydraulic Conductivity 0 to 3x10 -3 Stratigraphy Feet 05001,000 Feet 0 25 50

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Figure 3-13JOLLYVILLE TRANSMISSION MAIN Daniel B. Stephens &Associates, Inc.11/24/10 JN WR10.0138 PRELIMINARYSUBJECT TO REVISIONPRIVILEGEDAND CONFIDENTIAL S:\PROJECTS\WR10.138_JOLLYVILLE_TRANSMISSION_MAIN\VR_DRAWING\WR10_0138_05W_HYDRAULIC_CONDUCTIVITY_3-10_3-13_3-16.CDR Distribution of Hydraulic Conductivities along Reach 2 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%ProportionofTesting<1x10-61x10to 3x10-6 -63x10to 1x10-6 -51x10to 3x10-5 -53x10to 1x10-5 -41x10to 3x10-4 -43x10to 1x10-4 -31x10to 3x10-3 -3Hydraulic Conductivity (cm/s)

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Jollyville Reservoir Site PARD site Figure 3-14Reach 3JOLLYVILLE TRANSMISSION MAIN JN WR10.0138 12/9/2010Daniel B. Stephens & Associates, Inc. N 0350700FeetImage source: NAIP, 2010S:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-14_REACH_3.MXD Explanation Shafts Jollyville alignment

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Cross-SectionAlong Reach 3 TextTextText Explanation Figure 3-15JOLLYVILLE TRANSMISSION MAIN Explanation Source:N 80 ft Text Modified from DRI, 1991 TextTextTextText 0 12/10/10 JN WR10.0138 Not to Scale Daniel B. Stephens &Associates, Inc. S:\Projects\WR10.0138_Jollyville_Transmission_Main\VR_Drawings\WR10_0138_Graphs_Figure_3-15.cdr JT-127 JT-120 City ofAustin, Texas Water Treatment Plant 4 JollyvilleTransmission Main GeotechCrossSectionver93_112-120 J.Young 12/07/10 Data source: BV, City ofAustin, CAPCOG, ESRI DRAFT November 22, 2010 JT-127 (To Be Drilled) JT-120 (4 ft) JT-104 (573 ft) JT-121 (1063 ft) JT-123 (61 ft) JT-122 (1126 ft) JT-125 (119 ft) JT-126 (69 ft) JT-124 (164 ft) 25000 26000 27000 28000 29000 30000 31000 32000 33000 34000 35000 550 600 650 700 750 800 850 900 950 1000 Geotechnical ProfileCross-Section Tunnel Formations Overburden Edwards Walnut Glen Rose K HydraulicConductivity (cm/s) Less than 1x10 -6 1x10 -6 to 3x10 -6 3x10 -6 to 1x10 -5 1x10 -5 to 3x10 -5 3x10 -5 to 1x10 -4 1x10 -4 to 3x10 -4 3x10 -4 to 1x10 -3 1x10 -3 to 3x10 -3 Borehole JT-120 to East end JT-XXX (xx ft) Boring Log Detail Borehole ID Distance to Alignment RQD 100 to 0% Hydraulic Conductivity 0 to 3x10 -3 Stratigraphy Vertical Exaggeration = 12X 05001,000 Feet Feet0 25 50

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Figure 3-16JOLLYVILLE TRANSMISSION MAIN Daniel B. Stephens &Associates, Inc.11/24/10 JN WR10.0138 PRELIMINARYSUBJECT TO REVISIONPRIVILEGEDAND CONFIDENTIAL S:\PROJECTS\WR10.138_JOLLYVILLE_TRANSMISSION_MAIN\VR_DRAWING\WR10_0138_05W_HYDRAULIC_CONDUCTIVITY_3-10_3-13_3-16.CDR Distribution of Hydraulic Conductivities along Reach 3 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% <1x10-61x10-6 to 3x10-63x10-6 to 1x10-51x10-5 to 3x10-53x10-5 to 1x 10-41x10-4 to 3x10-43x10-4 to 1x10-31x10-3 to 3x10-3 Hydraulic Conductivity (cm/s)ProportionofTesting

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Ribelin Spring Ivanhoe Spring 2 Wedgewood Spring Ribelin Spring 2 (Lower Ribelin) B-02 B-01 B-02A Forest Ridge Site Explanation Springs and seeps Shaft Forest Ridge borings Jollyville alignment Forest Ridge alignment N 05001000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-17-FOREST RIDGE.MXD Figure 3-17Proposed Forest Ridge Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/13/2010Daniel B. Stephens & Associates, Inc.

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Ribelin Spring Ivanhoe Spring 2 Wedgewood Spring Ribelin Spring 2 (Lower Ribelin) B-02 B-01 B-02A Forest Ridge Site Explanation Springs and seeps Shaft Forest Ridge borings Jollyville alignment Forest Ridge alignment Potential area of groundwater discharge N 05001000FeetS:/PROJECTS/WR10.0138_JOLLYVILLE_TRANSMISSION_MAIN/GIS/MXDS/FIGURE_3-18-POTENTIAL_GW_DISCHARGE_AREA.MXD 013121 Figure 3-18Potential Area of Groundwater Discharge from Proposed Forest Ridge Shaft LocationJOLLYVILLE TRANSMISSION MAIN JN WR10.0138.00 12/13/2010Daniel B. Stephens & Associates, Inc.


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