TCEQ credited Montgomery County’s Authorized Agent, agent 620145, with 1,821 septic authorizations in 2025: 1,469 surface irrigation, 336 drip irrigation, just 11 standard trench-or-bed. A second agent works inside the same county line: the San Jacinto River Authority, listed in the same TCEQ report as agent 620146, cleared 29 systems that year, 15 surface irrigation and 14 drip, none conventional. SJRA regulates anything within 2,075 feet of Lake Conroe outside a city limit, under its own Order Adopting Rules for On-Site Sewage Facilities, passed December 10, 2015 and in force since June 1, 2016, with a flat $300 fee SJRA still posts itself.
Montgomery County sits in the Gulf Coastal Plain’s Pineywoods, and its own USDA-NRCS soil survey explains why spray and drip dominate that permit mix. Sandy units cover the ridges: Conroe loamy fine sand runs across roughly 11 percent of the mapped county at 46 percent sand by weight, Fetzer loamy fine sand another 10 percent at 51 percent sand, Splendora and Woodville fine sandy loams about 7 and 6 percent apiece. Drop into the creek bottoms and the same survey turns to heavy, frequently flooded clay: Kaufman clay tests at 8 percent sand, Kaman clay at 6 percent, both mapped as frequently flooded. A conventional trench needs two feet of usable soil above a restrictive layer or the water table, and ground that swings from loose sand to standing-water clay within a single square mile rarely supplies it.
Neither authority in Montgomery County honors the state’s ten-acre exemption. The county’s Order, adopted by Commissioners Court in December 2020, requires a permit “regardless of the size of the lot or acreage,” and SJRA’s rules close the same door inside its own 2,075-foot ring. Address, not acreage, is what decides whether a lot needs a permit here, because every developable lot does.
Reach the county’s Authorized Agent at Montgomery County Environmental Health Services, 501 N. Thompson St., Suite 100, Conroe, (936) 539-7839. Inside the Lake Conroe ring, the San Jacinto River Authority permits instead, from its Lake Conroe office at 1561 Damsite Rd., Conroe, (936) 588-1111. Fees, forms, and lot-size minimums are in our Montgomery County permit guide. Price aerobic systems and new installs early; the statewide ten-acre exemption reaches neither side of the lake line here.
Montgomery County’s population reached 781,194 on July 1, 2025, up from 620,443 at the 2020 Census: a 25.9 percent gain in five years. Septic permits are following rooftops faster than sewer lines, and a lot with public water and sewer last year is no guarantee for the lot next to it this year.
Unincorporated Montgomery County: Environmental Health Services, 501 N. Thompson St., Suite 100, Conroe, (936) 539-7839. Within 2,075 feet of Lake Conroe outside a city limit, the San Jacinto River Authority permits instead. Full sequence in the permit guide.
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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
Montgomery County permits septic in the whole county outside several named cities under its own Montgomery County OSSF Local Order. Texas designates a county an authorized agent only after the commissioners court adopts such an order and TCEQ approves it (Health and Safety Code § 366.031), and § 366.032(b) makes that order prevail wherever it is stricter than the state rules in 30 TAC Chapter 285. Read the order before siting a system.
Nothing in Montgomery County changes this.
Texas adds a separate approval path over the Edwards Aquifer recharge, transition and contributing zones, where TCEQ requires an Edwards Aquifer Protection Plan under 30 TAC Chapter 213. Elsewhere the Chapter 285 rules stand on their own.
The dominant constraint here is a seasonal high water table (36.8% of rated soils), followed by clayey subsoil that water moves through too slowly (18.7%). NRCS rates 46.6% of rated ground very limited for a standard soil absorption field, 93.6% for subsurface drip and 93.6% for surface application with disinfection.
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