Hays County’s five septic-permitting authorities together authorized 169 systems in 2025, down from 677 in 2022, a drop of about 75 percent in four years. The count comes from TCEQ’s own “Types of Systems Installed by Time Period” reports, re-summed row by row for this piece: Hays County Development Services (agent 620098) alone went from 569 authorizations to 131, and the four cities that run their own septic-permitting programs inside the county, Dripping Springs, Niederwald, San Marcos and Uhland, made up the rest. The pattern is not one office losing ground to another.
Every one of the five fell over the years it operated, including Dripping Springs, the city with the longest track record (99, then 34, then 24, then 28), and Uhland, the newest of the four agents, first appeared in TCEQ’s reports in 2024 and added too few authorizations to move the total either way. Statewide, authorizations fell about 21 percent over the same span. Hays County’s own drop ran more than three times as steep, and nothing TCEQ or the county publishes says why.
Rock explains most of what does get built. The Balcones fault zone crosses Hays County, and the U.S. Geological Survey’s 1963 study of the county’s geology describes the Edwards limestone belt through the west and center as covered in “thin, rocky soil,” with “an abundance of solution and fracture openings” where the aquifer reaches the surface. East of the fault, the same study found softer ground, the Taylor marl and Navarro group, underlying the plains toward Caldwell County.
A Soil Data Access query of the joint Comal-Hays soil survey area (TX604; the two counties were mapped as one unit and NRCS does not split the results back out by county) rates 44 of the area’s 51 soil map units “Very limited” for a septic tank absorption field, a count run directly by this pass, not an NRCS-published county percentage. Hays County’s own 2025 numbers track it: drip and surface irrigation, both aerobic-treatment methods, made up 108 of the county authority’s 131 authorizations, while standard trench-and-bed systems ran 3, 7, 2 and 0 across the last four years. The ground here mostly forces an aerobic system instead of a conventional drainfield.
Hays is one of eight counties, alongside Medina, Bexar, Comal, Kinney, Uvalde, Travis and Williamson, that TCEQ’s Edwards Aquifer rules name directly: 30 TAC §213.1 for the recharge zone and §213.20 for the contributing zone. Where a lot falls inside either zone, Hays County’s Order sets minimum lot size by aquifer zone and water source instead of a single countywide number, so two half-acre lots on opposite sides of a zone boundary can have very different acreage requirements. Acreage buys no exemption regardless of where the lot sits: Section 10.W.1 of the county’s Order requires a permit “regardless of the size of the lot or acreage,” closing the state’s ten-acre exemption inside Hays County entirely.
None of this tracks a shrinking county. The Census Bureau’s Vintage 2025 estimate puts Hays County at 304,390 residents, up 10,051 that year alone and up about 26 percent from the 2020 estimates base of 241,064. Fees, the zone-based lot-size table, and Hays County Development Services’ contact information are on the Hays County permit guide.
Outside Dripping Springs, Niederwald, San Marcos and Uhland, septic permits come from Hays County Development Services, 2171 Yarrington Rd, Suite 100, Kyle. Inside those four cities, that city’s own office issues permits instead. Full sequence here.
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New installs and major repairs need a permit from the local authorized agent — usually the county, sometimes a city — and the rules that bind are the local ones.
Our permit guide covers fees, required professionals and every step.
Four things decide what you can build and what it costs: zoning, environmental protections, power for aerobic systems, and the ground itself. We publish each one only where we have checked it — and say so plainly where the answer is “same as the rest of Texas”.
Zoning & land use
Hays County issues the septic permit for the whole county outside several named cities. It holds that job only because the commissioners court adopted an on-site sewage facility order and TCEQ approved it (Health and Safety Code § 366.031), and § 366.032(b) makes that order prevail wherever it is stricter than 30 TAC Chapter 285. Ask the office for its current order — Texas counties have no general zoning power, so the order, not zoning, is where a local siting rule sits.
Hays County is inside the area 30 TAC Chapter 213 covers. The contributing zone takes in all of it except the watersheds draining to the Colorado River above a point 1.3 miles upstream of Tom Miller Dam. On the recharge zone §285.40's siting rules apply, and where the site needs a TCEQ protection plan the Austin regional office must approve it before the authorized agent issues a permit. §213.5(h)(2) exempts an owner building their own single-family home at 20 percent impervious cover or less. Check the parcel on TCEQ's Edwards map viewer first.
The dominant constraint here is bedrock close to the surface (83.4% of rated soils), followed by clayey subsoil that water moves through too slowly (21.8%). NRCS rates 91.9% of rated ground very limited for a standard soil absorption field, 80.9% for subsurface drip and 12.3% for surface application with disinfection. Where a conventional field will not pass, surface application is usually the route that does.
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