San Marcos Mercury | Local News from San Marcos and Hays County, Texas
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The city of Kyle is looking to drill a test well in the lower Trinity Aquifer in an effort to buy time before a much more costly longer-term supply is needed for the burgeoning Austin exurb.

The Trinity “is not going to be anything that’s going to be a longtime supply fix for the city,” said James Earp, the assistant Kyle city manager. “All the Trinity wells might do for us is give us an alternative water supply during times of drought so we don’t have to invest the hundreds of millions of dollars way in advance of when we really need the water.”

The Hays Caldwell Public Utility Agency, of which Kyle is a member, has been buying up water rights in eastern Caldwell County in an effort to tap into the prolific Carrizo Wilcox Aquifer. But the first phase of a 40-mile pipeline to bring the water across Caldwell County to the corridor cities of Kyle, Buda and San Marcos in Hays County is projected to cost $108 million. Last year, the partners agreed to put off the pipeline project for at least five years and look for ways to make ends meet in the meantime, a prospect that mainly affects Kyle since San Marcos and Buda officials say they are set water-wise for the near and intermediate future.

In September, the city of Kyle inked a deal with the Guadalupe Blanco River Authority to buy an additional 810 million gallons a year of Canyon Lake water, a 54 percent increase in surface water it buys directly from the authority. Also last year, the city of Kyle won its lawsuit against the Barton Springs Edwards Aquifer Conservation District — and the right to pump an additional 165 million gallons a year.

The third stop-gap measure could be tapping into the lower or middle Trinity Aquifer, which lies below the Edwards Aquifer in eastern Hays County and has not been seriously tested as a potential water source.

“There’s never been any need to drill into the lower Trinity before because the Edwards was fairly shallow and there was no need to drill beyond that,” said Brian Hunt, the senior hydrogeologist at the Barton Springs Edwards Aquifer Conservation District. “Consequently, the middle trinity, and especially the lower Trinity, are relatively unknown.”

A residential or commercial well in the Edwards Aquifer in the Buda or Kyle area might be anywhere from 300 to 800 feet deep with a rough average somewhere around 400 feet, Hunt said. By contrast, a middle Trinity well would need to be 1,000 to 1,200 feet or more and a lower Trinity well at least 1,400 feet deep.

Said Hunt, “It’s more expensive to get to the Trinity water and from what we know about it, it’s lower quality. But as water becomes more scarce, it’s really elevated the value of water in the Trinity as an additional source.”

Earp said the city has met with the Texas Lehigh Cement Co. and Centex Materials near Buda to see if the industrial players might be willing to share part of the $250,000 to $300,000 cost of a lower Trinity test well. The city has also met with the BSEACD to clear the way for permits to drill the test well, if it is done within the conservation district’s geographic boundaries.

The conservation district has two middle Trinity monitoring wells, one near the Ruby Ranch subdivision and a second just west of Buda. The Ruby Ranch subdivision has a middle Trinity well that produces about 100 gallons a minute — a tenth of what a high-producing Edwards well might yield but still a significant amount of water, especially in time of drought. But no one has ever really tapped the lower Trinity in this area.

“We think it’s a viable project but there’s just more we need to know. Ultimately we will have to answer the question of if the lower Trinity is a cost-effective option for us,” Earp said.

Although geologists don’t know in detail how the upper, middle and lower Trinity aquifers interact with each other, Hunt said “the likelihood is very small” that pumping from the lower Trinity in eastern Hays County would impact water availability in the Wimberley valley and elsewhere in western Hays County where the middle and lower Trinity are the only water sources.

“You really are not going to be impacting the middle Trinity out there” with Trinity wells in the Kyle or Buda area, Hunt said.

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