Jan. 28, 2026 – A senior author of a 2020 Southwest Research Institute study showing that a development like Guajolote Ranch would degrade the Edwards Aquifer is refuting claims by the San Antonio Water System that nine “controls” it negotiated with developer Lennar Corp. would make the project acceptable.
In a 22-page technical letter sent this week to San Antonio Mayor Gina Ortiz Jones and all city council members, Ronald T. Green, Ph.D, now retired from SwRI, says that even with the stated controls, effluent from a wastewater treatment plant in the proposed northwest Bexar County development could reach either private wells or public supply wells in days or weeks.
And he repeatedly characterizes public assertions by SAWS CEO Robert Puente and SAWS executive Donovan Burton as “simplistic” or “not correct,” and lacking any scientific citations. In contrast, Green’s letter includes numerous study citations and exhibits throughout, and a listing of 37 references at the end.
“Even with the controls, the dominant factor will remain the total mass load of effluent released to the environment,” says Green, a licensed geoscientist who has spent three decades studying the Edwards and Trinity aquifers. “This is because the limited soil, karst limestone and rolling terrain of the Hill Country provide minimal retardation to water applied to the land surface, whether by precipitation or land application. The characteristics of the Hill Country in the Guajolote tract will remain dominant even with the nine controls.”
Florida-based Lennar wants to build 2,900 homes on 1,160 acres of Guajolote Ranch, west of the intersection of Scenic Loop and Babcock roads, and release an average of 1 million gallons a day of treated sewage into the Helotes Creek watershed, which directly recharges the Trinity Glen Rose Aquifer, the water supply for the immediate area, and contributes up to 15% of the total recharge of the Edwards Aquifer, principal water source for about 2.5 million people across multiple counties.
SwRI’s comprehensive hydrological study (noted in Green’s letter as “Flores et al., 2020”), funded through the city’s own Edwards Aquifer Protection Plan, concluded that additional wastewater systems from residential development in the Helotes Creek watershed, “regardless of type,” would “significantly degrade the watershed and the quality of water recharging the Edwards Aquifer.”
His letter this week is a response to an Oct. 10 letter from Puente to San Antonio City Councilwoman Marina Alderete Gavito, who sought SAWS’ position on the issue, and to recent public comments by Burton – both of which cast the nine conditions for wastewater treatment that SAWS reached in a water services agreement for Guajolote Ranch as providing for adequate protections.
“I believe comments and assertions in the Puente letter are not consistent with the current understanding of the Trinity and Edwards aquifers and how they interact,” he says, later adding that Puente’s account “is absent of supporting technical documentation and citations. Assertions and opinions presented in the Puente letter are based on limited data and unsupported conceptualizations.”
Green’s letter comes as San Antonio City Council prepares to vote Feb. 5 on a municipal utility district (MUD) application for Lennar and Guajolote Ranch. During a Jan. 22 special meeting on the matter, where Burton repeated claims that “a lot of the water quality risks have been mitigated” by the nine conditions, Jones noted the differing conclusions of SAWS and the SwRI study. See Green’s full letter, here: https://www.scenicloop.org/wp-content/uploads/Puente-letter-rebutal-Green.pdf
Central to SAWS’ claims is that the Haby Crossing Fault, which crosses the area, prevents flow from the Trinity Aquifer to the Edwards Aquifer. But Green called Puente’s description and visuals of the fault in the letter to Alderete Gavito “overly simplistic” and “not representative,” and he cited studies showing multiple faults comprising the offset between the two aquifers, some producing pathways to flow. He says those features are readily apparent in Helotes Creek where bedrock is exposed.
Both Green’s SwRI study and another one by the U.S. Geological Survey characterize the Haby Crossing Fault as a conduit rather than a barrier to flow, Green’s letter says. “What is not explained in the Puente letter is that if the groundwater is not going from the higher Trinity Aquifer to the lower Edwards Aquifer, where is it going?” he asks.
He also disputes Puente’s view that the two aquifers don’t communicate because samples from two wells, one on each side of the fault, have different water chemistry. Green notes there have been “hundreds, if not thousands” of water samples taken from the two aquifers and analyzed for chemistry, and ticked off 13 studies where that was done. He suggests that SAWS should avail itself of more data.
“The assertion that the Trinity Aquifer is separate from the Edwards Aquifer based on the water chemistry of two wells in the Puente letter is not technically defensible,” Green wrote.
He notes that dye-tracer studies by the Edwards Aquifer Authority further confirms the hydraulic relationship between the Trinity and Edwards aquifers, with travel times of the dye in groundwater of approximately one mile per day.
Puente argues in his letter that the distance from the proposed Guajolote Ranch wastewater treatment plant to the Edwards Aquifer recharge zone is 5.4 miles, far enough for the effluent to “naturally attenuate.” But Green says that pathogens, like bacteria and viruses, can persist in groundwater for weeks and months. And that karst aquifers like the Trinity and Edwards are particularly vulnerable to degradation because of rapid groundwater speeds and short travel times.
“The SAWS well located on Tippecanoe Street on the west side of San Antonio is approximately 14 miles from the proposed location of effluent discharge in the Helotes Creek watershed,” Green says, noting that the well already has been found with pollutants. “At a groundwater velocity of one mile per day, effluent discharged at Guajolote Ranch could reach the Edwards Aquifer recharge zone in less than a week, and the Tippecanoe SAWS well in two weeks.
“To claim that SAWS’ well fields are too distant to be impacted by pathogens released in Helotes Creek watershed is not correct,” he writes, later adding, “Communities reliant of centralized water supplies from karst aquifers are at risk when the rapid rates of recharge to public supply wells is not adequately managed and protected.”
Green also notes comments by Burton speaking on behalf of SAWS at a Dec. 11 city of San Antonio Governance Committee meeting, claiming that the local geology in the Helotes Creek watershed mitigates risks to the environment by contamination from an effluent discharge facility.
“Locating an effluent discharge facility over a karstic terrain in which groundwater velocities exceed a mile per day is the antithesis of the claim by Mr. Burton,” Green writes. “There is clearly nothing in the geology of Helotes Creek watershed that would impede, to any degree, effluent released in the Helotes Creek watershed from entering the Edwards Aquifer in a matter of days to weeks.”
Green said that in preparing two recent peer-reviewed texts on the Edwards Aquifer, one as recently as 2022, he reviewed all available and relevant technical reports and peer-reviewed journal articles on the Edwards and Trinity aquifers, particularly in the San Antonio segment.
“I encountered neither technical reports nor peer-reviewed journal articles by SAWS staff regarding the subjects that Mr. Puente opined in his letter,” Green says. “Nor am I aware of any technical reports or peer-reviewed journal articles by SAWS staff released since that time.
“Like any scientific evaluation,” he says, “my conclusions may be changed if and when contradictory evidence or data become available. Neither are provided in the Puente letter.”
Separately, Green said he’d welcome the opportunity to discuss with Puente, staff or both.
Randy Neumann, chair of the steering committee of the Scenic Loop-Helotes Creek Alliance, notes that one of the conditions of the SAWS agreement with Lennar calls for the developer’s wastewater operator to be “licensed at the A level,” when SAWS’ own Clouse/Dos Rios plant – managed by a Class A operator and considered one of the most advanced plants in the country – has experienced sewage spills in four of the last five years.
SAWS has operated under a consent decree, a court-ordered settlement, with the EPA since 2013 due to frequent sewer spills, main breaks and other failures.
“So the question becomes: Why should the people of San Antonio trust the opinion of a utility operating under a consent decree from the EPA for its history of sewer spills, instead of the data and conclusions of world-class scientists?” Neumann asked.
“We commend Councilwoman Alderete Gavito for encouraging SAWS into the open and forcing them to make their position known,” he said. “In so doing, she has exposed a massive lack of accountability, a lack of true transparency, a failure to grasp the true geological facts and surprising lack of enforceable protection and empty promises.”
See also, “Guajolote Ranch opponents sue the Texas Commission on Environmental Quality to reverse permit decision,” here: https://www.scenicloop.org/post/1938/guajolote-ranch-opponents-sue-the-texas-commission-on-environmental-quality-to-reverse-permit-decision/
The Scenic Loop-Helotes Creek Alliance is a nonpartisan, nonprofit 501(c)(3) group representing the largest neighborhood by square mile recognized by the San Antonio Neighborhood & Housing Services Department, a wide corridor along Scenic Loop Road from Bandera Road to north of Babcock Road.
Contacts:
Randy Neumann, SL-HCA steering committee chair, 210-867-2826, uhit@aol.com
Annalisa Peace, Executive Director, Greater Edwards Aquifer Alliance, 210-320-6294, annalisa@aquiferalliance.org
Steve Lee, 210-415-2402, text; media@scenicloop.org