By Anton Riecher
A more specific outline of the massive 50,000 acre-feet per year storage project being proposed by the recently formed Medina County Regional Water Alliance took shape August 12 during the alliance’s monthly meeting in Hondo.
Listed as one of the principals on the Medina County Regional Aquifer Storage Recovery Project (MCRASR) team, Russell Persyn presented a PowerPoint presentation updating the project’s pre-feasibility report.
“We’ve made a lot of good progress on the front end but a lot of the tough decisions are coming up as far as determining locations where things might be feasible and how this will play with all the partners,” he said.
However, some “partners” have yet to commit. Of the nine elgible to join–listed by Persyn – the cities including Hondo, Castroville, Devine, Natalia and La Coste and water supply operations including East Medina County Special Utility District, Yancey Water Supply Corporation, West Medina WSC and Atascosa Rural WSC – neither Devine nor Natalia have agreed to participate.
In November, the Texas Water Development Board will review regional water planning throughout Texas in anticipation of adopting an updated state water plan. With hopes of qualifying for funding, a draft report on MCRASR project is expected to be completed by Sept. 20.
A final report on the project is due on October 18, Persyn said.
“Trying to find grant funds is the importance of getting (the report) into the state water plans, so we’re eligible for cost sharing and those types of things for our project,” he said.
The project has been compared to the city of Kerrville which has stored more than one billion gallons using an aquifer storage and recovery (ASR) system that diverts surface water into the Ellenburger aquifer. Such a system serves as a “bank account,” allowing water deposited during wet years to be withdrawn when drought prevails.
What the MCRWA proposes is a minimum storage of 50,000 acre-feet per year of water using the Trinity Aquifer in the near term, Persyn said. The Trinity is a group of smaller aquifers that combine into a major group extending across much of the central and northeastern part of Texas.
“Initially, I set the yield at about 12,500 (acre-feet per year),” Persyn said. “That’s roughly a little higher than your 2070 projection for annual need (in Medina County) in the state water plan.”
The expected 50,000 acre-feet per year minimum storage will depend on the results from research by hydrogeologic experts, he said. Beyond utilizing the Trinity, more storage might be found in brackish regions of the Edwards aquifer or by using the Carrizo-Wilcox, a major aquifer extending from the Louisiana border to Mexico.
“Carrizo is further to the south so transmission (costs) might be a bit more but, again, these are all from a long term perspective,” Persyn said. “These are things we should at least keep on the radar.”
Storing water in the aquifer will require a field of at least 10 ASR wells with a total recovery capacity of almost 20 million gallons per day, he said. It would be financially desirable to locate these wells are close to the point of demand as possible.
“The next step that would probably be recommended is to do some type of test site to work out the details,” Persyn said. “This is not uncommon in a project like this. The target flow rate would be around one million to two million gallons a day.”
Research on where to place that test well should be located is still in progress, he said. In addition, the test well will require construction of a production facility to be operated by one of the partners in the project.
Another objective is to minimize the long distance transmission of the water to be stored and recovered.
“Obviously, putting in large diameter pipeline is not an inexpensive task, especially if you’ve got to consider right-of-way,” Persyn said.
To keep those costs in check, the project will seek to maximize the use of existing interconnections between the various partners involved, he said. This may also involve the transfer of water rights among those entities to better serve the long term objective.
The other anticipated facilities that will be required for the project will include treatment plants, booster stations, and possibly additional above ground and elevated storage, Persyn said. Also necessary will be high service pumps and additional interconnection transmission lines.
Persyn is senior vice president of the water and natural resouces unit of PESPEC, a global engineering and consulting firm. PESPEC, together with ASR Systems LLC, specialists in water resources development, make up the MCRASR project team.
Persyn also serves on the Edwards Aquifer Authority board of directors representing district 13 including Medina and Atascosa counties.
As a prelude to details of the project, Persyn reviewed population projections for Medina County through 2070 and the impact on water requirements citing research by the South Central Texas (Region L) Regional Water Planning Group.
“If you start diving into municipal demands … you can see the demands are going to increase from really around 7,800 (acre-feet per year) to really around 11,000 (acre-feet per year) as we move into 2070,” Persyn said.
Shortages for some of the water suppliers operating in Medina County will become apparent in the next 50 years, he said. However, projects intended to serve Medina County in the future such as expanded ASR treatment, recycled water programs and expanded use of the Carrizo-Wilcox are presently dominated by the San Antonio Water System (SAWS).
“So the anticipated way to meet your needs is (SAWS) is going to do things in order to help you meet your needs,” Persyn said. “I think that lends itself to why all of you are here today – to try to maybe dictate your own future as opposed to relying upon others.”
The 2021 Region L plan shows that municipal water needs for East Medina County Special Utility District will expand from 140 acre-feet per year in 2020 to 455 acre-feet per year in 2070. Lytle will increase from 70 acre-feet per year to 192 acre-feet per year in 2070. Likewise, Natalia will increase from 106 acre-feet per year to 250 acre-feet per year in 2070.
La Coste is expected to jump from 38 acre-feet per year to 92 acre-feet per year. Figures for the city of Devine were not included in the 2021 Region L plan as presented.
Municipal needs for Medina County are expected to reach 3,255 acre-feet per year in 2070. That excludes water used for crop irrigation.
“If you look at where (South Central Texas Regional Water Planning Group) say the water is at, they’re not estimating a lot of ground water and surface water being available other than what we have today,” Persyn said.
The reason the MCRWA is looking at an ASR project “is to either use ground or surface water more effectively in times where we do have plenty in order to support those times during drought,” he said.
During a question and answer period, Medina County Precinct 2 Commissioner Larry Sittre challenged the populations figures used in the Region L plan.
“I’d say your estimates are off 75 to 80 percent,” Sittre said, charging that the numbers were low.”
Bruce Alexander, superintendent of East Medina County SUD, and others agreed with Sittre.
“The last time we submitted information on regional population centers we were experiencing about two percent annual growth,” Alexander said. “In the last three years we’ve probably had 15 to 20 percent annual growth.”
Persyn said the rapid growth in recent years means that demand will come quicker than what is being projected.
“That’s why I’m signaling to you that the short term is what you are working on now but it’s not the end of the road,” he said. “It’s to buy you the time you need.”
The meeting concluded with a presentation by Enriqueta Caballero, outreach specialist with the Texas Water Development Board detailing the TWDB’s financial assistance programs involving loans, principal forgiveness and grants.
TWDB has committed more than $35.4 billion in funding for water, wastewater and stormwater projects throughout the state.