According to Jay Troell, P.E. and Larry Fox, directors of the Evergreen Underground Water Conservation District representing Atascosa County, the San Antonio Water System (SAWS) made a “categorical statement” at a January 7 presentation given to their Board of Trustees that an impervious barrier lies between the Wilcox Aquifer and the Carrizo Aquifer.
In a press release from the Evergreen Underground Water Conservation District, Troell and Fox assert that “Yes, there are shale beds of varying thickness in some areas between the Carrizo sands and the Wilcox formation” but that such shale beds are not without “holes”. Fox explained in an interview that there used to be springs around Atascosa County up till the 1960s. The springs flowed because water in the Carrizo outcropping (where aquifers come to the surface), on the northern end of Atascosa County was under atmospheric pressure, which in a way pushes the water into the ground, through the formations, and back out to the surface. Since springs form at faults, or cracks in layers of rock, there must have been faults that traveled down to the Carrizo formation, if not the Wilcox. This means that any imperviously layer that SAWS says prevents Carrizo water from mixing with Wilcox water must not be contiguous. Troell and Fox said of the “impervious barrier” assertion, “Is this a dangerous assumption or an out-right fabrication for their own benefit? We question what geologic study this claim was based.
The 2011 South Central Texas Regional Water Plan Water Management Strategy Summary Sheet, written for the South Central Texas Regional Water Planning Group: Region L, (a group of stakeholders guided by the Texas Water Development Board) said of the SAWS project “The wells would be developed in the deep, confined section of the Wilcox, which is substantially removed from the outcrop area. There is concern about the possibility of interaction between the Wilcox and Carrizo layers of the Carrizo- Wilcox Aquifer. If the interaction is significant, pumping the Wilcox will cause some downward leakage of Carrizo water into the Wilcox, which will cause some lowering of water levels in the Carrizo.”
That document is available at www.regionltexas.org/2011_ RegWater- Plan/2011_ vol2/Section4C.32. pdf
Geologist Arthur Troell, Professor Emeritus of Geology at San Antonio College and a consulting geologist said in a March 27, 2013 article in the Pleasanton Express that “Wilcox brackish water underlies the Carrizo – pump out the brackish water – you will mine it and Carrizo fresh water will leak down into the Wilcox.” Arthur Troell wrote a series of articles on the geology of Atascosa County in the Pleasanton Express in March 2013.
A quote from SAWS’ webpage on the Brackish Groundwater Desalination Project reads “SAWS future desalination facility will generate about 11 million gallons of water per day, or 12,210 acre-feet per year, from the Wilcox Aquifer in Phase l. The plant will be located at the existing SAWS Twin Oaks Aquifer Storage & Recovery site.” SAWS says that the brackish water of the Wilcox Formation, which lies underneath the Carrizo Formation in Evergreen Underground Water District, “is a plentiful, previously untapped local source of water that will help diversify San Antonio’s supplies.” Phase 1 of the Desalination Project also includes disposing of the byproducts of desalination in Class I injection wells on SAWS land in Wilson County,
Fox and Jay Troell, who attended the January 7 meeting, said in their press release “SAWS has targeted the Wilcox south and east of Bexar County (read: Atascosa and Wilson County) for an additional 50,000 acre-feet, approximately 45,000,000 gallons per day. This will lower the Wilcox aquifer pressure providing a path for migration of our Carrizo fresh water into the Wilcox through the supposed ‘imperious barrier.” Jay Troell and Fox say that SAWS still needs to secure their permits to drill wells in Atascosa County.
You can read Troell’s discussion of the aquifers at these links: www.pleasantonexpress.com/ news/2013-03-27/Oil_ and_ Gas_ Report/Oil__ Gas_ Editor. html www.pleasantonexpress.com/news/2013-03- 20/News/Troell_ discusses_ geology_ of_ aquifers.html