.. 1/ TESTIMONY OF GARALD G. PARKER, SR., C.P. G.-ON .IMPACT OF CONSTRUCTION IN THE SUMMIT REACH OF THE CFBC ON THE FLORIDAN AQUIFER J:l (Presented at Cross-Florida Barge Canal Hearing, Tampa, September 24, 1976) Professor Garald G. Parker: Colonel Wisdom, my name is Garald G. Parker. I am a consulting hydrologist and certified professional geologist, C.P.G., 691, and Visiting Professor of Hydrology and Hydrogeology at the University of Florida, Gainesville, Florida. I am here as a private citizen, and I represent no interest except myself, but I am a Florida taxpayer. Incidentally, I live at 3303 McFarland Road, Tampa, Florida 33618. I deplore the proposed construction of the Cross-Florida Barge Canal in the unfinished, summit reach because I think it's going to be disaster for the area, chiefly caused by expected pollution of the ground water in the Floridan Aquifer. I'm no babe in the woods on the probable effect of the CFBC on hydrology of the area, because, after all, I'm the man, who in 1946, named and described the great Floridan Aquifer and its geologically complex capping-layer, the Floridan Aquiclude. I also, at the same time, named and described the Biscayne Aquifer, the source of water for the Gold Coast of southeastern Florida. I have worked with the Floridan and the Biscayne and the other aquifers here in Florida for some 30 years, and because of my knowledge of hydrologic cause and effect, I am very much alarmed at what is likely to happen to the water supply in the summit reach of the Cross-Florida Barge Canal. Certified Professional Geologist and Visiting Professor geology, University of Florida, Gainesville, FL 32611. Revised and grammatically corrected from the Tampa talk. 1
. / The eastern part of that area is shallowly covered with sand and clay, beginning about a mile or a mile-and-a-half west of the Dosh Lock and Dam. The rest of it to the west, some 26 to 27 miles in length, is shallowly covered with highly permeable sand or sandy loam. The Floridan Aquifer is right at, or very close to, the land surface throughout this area. The depth of the canal in the summit area is to be dredged 12 to 28 feet below the existing water table. This deep dredging will cause the canal to act as a big horizontal well, taking the water in from the higher end and transporting it down to the lower end. Then, in those places where the canal is naturally sealed by a clay layer of t h e Hawthorn Formation, if the canal bottom is breached by dredging or if the clay plugs in filled sinkholes become loosened and drop out, polluted water will be dis-charged into the Floridan Aquifer and be transported with the regional flow of the aquifer. And, in the eastern area of the summit reach, .the regional flow is directly to Silver Springs and to Ocala's city water supply. In the summit reach of the canal the limestone in most of that length of 28 miles is likely --quite likely --to be more or less permeable, with both large and small vertical solution cavities reaching to and connecting with horizontal solution cavities developed by ground-water solution of the limestone matrix. This has produced the highly permeable upper part of the Floridan Aquifer, to depths of about 100 to 150 feet, through which the principal flow to Ocala's water supply and to Silver Springs takes place. I suspect that the same kind of "accident" may happen to Silver Springs that has recently happened to Weeki Wachee Springs. As you may know, they've had to close their "mermaid" show because, apparently, silt and clay particles dislodged by construction activities some distance removed from the springs have 2 ..
moved1!aterally through the underground cavity system that feeds Weeki Wachee Springs and has so completely clouded the formerly crystal-clear water of the springs as to ruin the mermaid show. Now, I'm not saying that this is what will happen to Silver Springs â€¢ . What I'm saying is that it may. Literally, in that 28 miles of the summit reach of the canal which is to be excavated 12 to 28 feet below the water table, there are likely to.be hundreds if not thousands of vertical solution cavities that will appear in the bottom of that canal. And if you read carefully the U.S. Geological Survey's reports on this area, you will agree with this statement. They have found many of these channels,-theyknow -they-are there. Most oE these-vertical-channels, apparently, are now filled with clay or sand, but there is no guarantee that they are going to remain filled once excavation begins. The mere dredging and movement of heavy construction equipment could create vibrations in the rock and water beneath and adjacent to the canal to cause sand and clay plugs now sealing preexisting solution holes, to loosen and fall out. The water of the canal will be more or less polluted --as all busy waterways are --and the polluted water would simply flow down the hydraulic gradient, chiefly to Ocala and Silver Springs. I fear, Colonel, that if the Corps is permitted to go ahead, or is required to go ahead with this excavation, it may become an albatross about your and. the Corps' necks; I don't see that it can be any credit to the Corps. A couple of years ago, during my employment as Chief Hydrologist of the Southwest Florida Water Management District, we hired a driller to drill some exploratory wells in Hernando County along the Gulf Coast to determine the location. and depth of the salt-water--fresh-water contact at depth in the Floridan Aquifer. One of these wells was about half-a-mile west of U.S. Highway 19 and about five miles 3
northof State Road 52 and Weeki Wachee Springs. The drill rig penetrated an extremely hard layer of rock at about 101-102 feet below the land surface. Immediately the ground about the drill rig began . to crack and sink. Before the driller and his helper could move the rig or any of the adjacent equipment, which included a large flat-bed truck and a nearby water-tank truck, everything sank into the ground and disappeared into a great big elliptical sinkhole, about 200 feet wide in an east-west direction and 300 feet long, north-south. A 60-foot pine tree also was swallowed up and disappeared into the huge, deep cavity that underlay the site. Now, when all of this happened, a whole series of small satellite sinks opened_ up to the north and south of the main sink, about 18 in all. The satellite sinks were doubtless produced by shock waves sent out through the ground water in the Floridan Aquifer when the 100 or more feet of rock and soil, along with the trucks and drilling rig, plunged down into the water-filled cavern beneath the drilling site. Such an event could happen in the summit reach of the Cross-Florida Barge Canal because the solution-ridden limestone of the Floridan Aquifer underlies both areas. The Corps would be working with the very same type of karst topography near Ocala as that in which we were drilling north of Weeki Wachee Springs. When the Masaryktown Bypass Canal, a Corps of Engineers project near Masaryktown, Florida, was dredged past the site of the Wilson Avenue Bridge in June, 1971, no underground cavities were detected despite the numerous exploratory coring and foundation holes that were made at the site. The drillers found no s1nks or caverns with their drilling --and yet, eight sinkholes subsequently developed in the sides and bottom of the canal excavation in the vicinity of that bridge, one of them underneath a pier of the bridge. Dredging exposed the pitted 4
and pinnacled limestone of the top of the Floridan Aquifer beneath the sand and clay overburden, with the pits filled with sand and clay. It wa$ these earth plugs that dropped out of the dredged bottom and adjacent berms of the Masaryktown Canal that created the "nests" of sinkholes that developed subsequent to the first heavy rains following canal excavation. My concern regarding the CFBC is that similar sinkhole development may also follow dredging in the summit reach. Also, herein Tampa, while the Corps was doing the on the Tampa Bypass Canal and .the Buffalo Avenue Bridge was being built, a 15-to 20-foot diameter sink opened up right underneath one of the bridge piers; the hole was fully as big as this rostrum area. Yet, this sinkhole had not been discovered by the test.drilling that had been done. The hole became apparent only after the canal had been excavated and artesian water pressure forced the Hawthorn clay filling out of a large cavity in the limestone beneath the surface of the Floridan Aquifer, which had been uncovered by dredging of the canal. What I'm saying is that there are great differences in the permeability and stability o f these rocks from place to place. Now, Colonel, you said earlier that you got 300-and-some gallons of water, at the most, out of test wells in the summit area of the CFBC and that this was all. that could be pumped out of at least one of these wells. I've had the same kind of experience in many sites throughout the Florida Peninsula. If the drill rig were to be moved over 1,000 feet, or perhaps even as little as 10 feet, a well might be made that would produce 3,000 or more gallons in a minute. There's that much of a difference from place to place in well yields from the Floridan Aquifer. , 5
In summary, there is a great deal more information needed than what you now have to be able to proceed safely with dredging this section of the CFBC, and more needs to be done with the knowledge that is now available to the Corps. Even though I think that the information which the Geological Survey has given you in their several reports is excellent, still there isn't enough for the Corps to proceed safely with this construction. Thank you. (Applause.) Colonel Wisdom: Thank you. And Garald, we do appreciate your concern, really. , 6