Which of the six counties are in the Edwards Aquifer program? Travis and Williamson.
The zone your parcel sits in is not a judgment call. TCEQ publishes a map viewer, and the answer it gives drives your permit path and your schedule. Review runs on a clock set by rule: as long as 30 days of administrative review, then 90 days of technical review, and no construction until approval issues. Check the map before you buy the land.
The Edwards Aquifer Protection Program covers eight Texas counties, which run from Williamson and Travis through Hays, Comal, Bexar, Medina and Uvalde to Kinney. Two of the six counties covered here are on that list. Travis County is in. So is Williamson County. Burnet, Llano, Bastrop and Caldwell are not.
Travis and Williamson are handled in the program's Austin region, along with Hays. The TCEQ Austin Regional Office takes those three at (512) 339-2929. The other five counties go to San Antonio.
Both counties name the program in their own permit material. Travis County lists the Edwards Aquifer Protection Program among its permit paths, and the aquifer plan question comes before the site work on the western side of the county. Williamson County lists it too, and adds that only a registered sanitarian or a professional engineer may design a septic system over the recharge zone.
Land in Burnet or Llano County can still sit under a water program, just not this one. The Lower Colorado River Authority's Highland Lakes Watershed Ordinance covers the Lake Travis watershed in Travis County, the Colorado River watershed in Burnet County and a portion of Llano County, above the Regulated Pool Elevation of the Highland Lakes. Different map, different rules, and a separate question for the Lower Colorado River Authority.
TCEQ GIS metadata, Edwards Aquifer Recharge Zone - Chapter 213 Rules (TSMS), quoting 30 TAC 213.3(8), as read September 13, 2026.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
LCRA Highland Lakes Watershed Ordinance, Section 1, Title and Scope, as read September 13, 2026.
Travis County Transportation and Natural Resources, Development Services, as read September 13, 2026.
Williamson County frequently asked questions, County Engineer, as read September 13, 2026.
What do the recharge, contributing and transition zones mean for a build? Three maps, three different answers.
The regulated area is drawn as three zones. They are not severity tiers of one rule. Each has its own test, and the zone your parcel sits in decides which plan you file, or whether you file one at all.
The contributing zone is defined by subtraction. In Travis and Hays counties it is all areas except the land that drains into the Colorado River upstream of a spot 1.3 miles above Tom Miller Dam. In Williamson County it is all areas except the watersheds draining to the Lampasas River above Stillhouse Hollow dam.
The rock is the reason the state regulates dirt work here. The Edwards (Balcones Fault Zone) Aquifer is a major aquifer in the southcentral part of Texas. Faulting along the Balcones Fault Zone followed uplift of the Edwards Plateau, and streams crossing the zone recharge the aquifer where permeability is enhanced by dissolution of limestone. Water moves from the surface into the aquifer through that limestone, so the state controls what happens on the surface.
Recharge zone: where the Edwards Aquifer rock layers surface, along with outcrops close by whose caves, sinkholes, faults or fractures could let surface water into the aquifer.
Contributing zone: the higher ground that drains down onto the recharge zone, mostly to its north and northwest, where rainfall runoff flows down to the recharge zone.
Transition zone: the area south and southeast of the recharge zone, where other formations crop out and faults or fractures give surface water a possible path into the aquifer.
TCEQ GIS metadata, quoting 30 TAC 213.3(25), as read September 13, 2026.
TCEQ GIS metadata, quoting 30 TAC 213.22(2), as read September 13, 2026.
TCEQ GIS metadata, quoting 30 TAC 213.3(34), as read September 13, 2026.
Texas Water Development Board, as read September 13, 2026.
USGS, Karst Aquifers: Edwards Balcones Fault Zone Aquifer, as read September 13, 2026.
What is an Edwards Aquifer contributing zone plan, and what triggers it? Five acres of disturbance.
A Contributing Zone Plan is the plan of best management practices required for a regulated activity proposed in the Edwards Aquifer contributing zone. It must be approved before any construction begins.
The trigger is acreage. A Contributing Zone Plan is required when activities disturb five or more acres, or are part of a larger plan to develop or sell land, under 30 TAC 213.21(b). Below that, no Edwards Aquifer protection plan is needed in the contributing zone.
Read the second half of that trigger slowly. The rule also reaches activities that are part of a larger plan to develop or sell land, so the acreage is not only your own dirt work. If your tract came out of a recent split, or sits in a platted subdivision still being developed, ask the TCEQ Austin Regional Office, phone (512) 339-2929, whether the larger plan of development applies to your build before you assume you are under the line.
Five acres is the aquifer number, not the stormwater number. The TPDES Construction General Permit TXR150000 covers construction that disturbs an acre or more, or part of a larger common development plan that will disturb at least an acre. Below one acre no coverage is required. Two programs, two thresholds. A barndominium with a long driveway and a big pad can clear one and not the other.
TCEQ, Contributing Zone Plan page, as read September 13, 2026.
TCEQ, Edwards Aquifer Protection Program: What Plans You Might Need, as read September 13, 2026.
TCEQ, Stormwater Discharges from Construction Activities: Am I Regulated?, as read September 13, 2026.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
Why is there no acreage floor for building in the Edwards Aquifer recharge zone? Every regulated activity needs a plan.
A Water Pollution Abatement Plan is the detailed best management practice plan required for any regulated activity proposed in the Edwards Aquifer recharge zone. Approval is required before any construction begins. There is no acreage floor. It applies to any regulated activity on the recharge zone.
On the recharge zone, every regulated activity needs an approved plan before construction. The five acre trigger is a contributing zone concept only, not a recharge zone one. Landowners carry that number across from one zone to the other and get caught by it. On the recharge zone the question is not how much dirt you move.
A water pollution abatement plan in Travis County is a front of project item, because the county puts the aquifer plan question before the site work on the western side of the county. Ask the TCEQ Austin Regional Office, phone (512) 339-2929, what counts as a regulated activity on your specific parcel, and write down the answer with the name of the person who gave it.
TCEQ, Water Pollution Abatement Plan page, as read September 13, 2026.
TCEQ, What Plans You Might Need, recharge zone branch, as read September 13, 2026.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
Travis County Transportation and Natural Resources, Development Services, as read September 13, 2026.
What if the lot straddles two zones? The whole site is treated as recharge zone.
A site that straddles the line, some of it contributing zone and some recharge zone, counts as recharge zone from end to end and a WPAP is required. The same escalation applies to a transition zone site that drains back to the recharge zone.
The test is the site, not the structure. Moving the house footprint off the recharge zone does not move the site off it. A parcel that clips the line anywhere converts the entire project to the stricter plan, and that changes what you file, not just where you build.
All of this is knowable before closing. Find out where the zone line crosses the tract, and in which zones the pad, the drive and the septic field would sit, before you sign anything.
TCEQ, What Plans You Might Need, contributing zone branch, as read September 13, 2026.
How long does the review take? Up to 30 days, then 90 days.
Administrative review of an Edwards Aquifer application takes up to 30 days under 30 TAC 213.4(e). That is the completeness check on the packet.
Technical review of an administratively complete application takes 90 days under the same rule. Construction cannot begin until approval issues. The 90 day clock runs on an administratively complete application, so a packet that comes back short does not start it.
Put the two together and the aquifer plan sits in front of your build for months, not weeks. Plan the money around that. Do not set a start date, book a concrete pour, or take delivery on a metal building package off a submittal date. Set those off an approval date.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
Can a single-family residence skip the plan? Three ways it can.
A single-family residence may not need its own Edwards Aquifer plan in three situations.
May not need is not the same as does not need. Confirm the answer with the TCEQ Austin Regional Office, phone (512) 339-2929, before you treat a build as exempt, and ask for it in writing.
Two questions are worth asking on the same call. Ask what counts toward impervious cover on your plan, since a barndominium brings slab, drive, shop and covered parking with it. And ask whether the subdivision you are buying into already has an approved plan on file. Ask the agency that answer, not only the seller.
The residence is in a master community that already has an approved plan.
The residence sits on a lot larger than five acres and is the only residence on it.
Impervious cover is kept to 20 percent or less of the legal property.
TCEQ, Edwards Aquifer Private Residences page, as read September 13, 2026.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
How do I find out whether my parcel needs an Edwards Aquifer contributing zone plan? Check the TCEQ map viewer.
A landowner checks whether a parcel falls in a regulated zone with the TCEQ Edwards Aquifer Map Viewer. You can print the map and submit it with an application, so the same step that answers your question also produces a document the agency wants.
Do this at the front of the deal. A lot listed as unrestricted acreage with a long view can be recharge zone, contributing zone, or split between them, and nothing in the listing will say so. The map viewer is where that answer comes from.
Zone status belongs on the same short list as flood zone, septic feasibility and road access when you are sizing up ground. That is the work covered on the land and lot evaluation page.
TCEQ, Edwards Aquifer Map Viewer page, as read September 13, 2026.
How does the recharge zone change the septic permit in Williamson County? A sanitarian or an engineer designs the system.
An OSSF permit is needed before anyone builds, installs, alters, extends or repairs a septic system, and local programs may be stricter than the state minimum. In Williamson County, only a registered sanitarian or a professional engineer may design a septic system over the recharge zone. That is a design cost and a calendar item, and it lands on top of the aquifer plan, not instead of it.
Who issues the septic permit is not the same question in the two counties. Williamson County has a single authorized agent, Williamson County itself, covering the entire county, with applications through the county's online portal and a Certificate of Compliance issued by the County Engineer processed first. Travis County has seven authorized agents: Travis County, the City of Austin, the Lower Colorado River Authority, West Lake Hills, Bee Cave, Mustang Ridge and Rollingwood.
Travis County states no lot-size exemption at all. Every system in its jurisdiction is covered whatever the size of the lot, and the minimum lot size for a home on a septic system there is one acre. Find out which agent covers your address before you pay anyone to design a system.
TCEQ, Getting a Permit for an On-Site Sewage Facility, as read September 13, 2026.
TCEQ OARS county search, Williamson County (CNTY_CD 246), as read September 13, 2026.
TCEQ OARS county search, Travis County (CNTY_CD 227), as read September 13, 2026.
Williamson County frequently asked questions, County Engineer, as read September 13, 2026.
Travis County Transportation and Natural Resources, Development Services, as read September 13, 2026.
What order do the permits go in on an aquifer lot? TCEQ first, then the county.
The sequence below is what keeps an aquifer parcel from stalling. It is the same logic as the rest of building a barndominium in Central Texas, with one extra agency in front of the county.
The county work does not stop while TCEQ reviews. In Travis County, any development requires a permit, and where a professional builder does the work at least three inspections by a third-party inspector are required: foundation before the concrete is placed, framing and mechanical before drywall, and completion of the residence. Williamson County has no county building permit to get and no county building code, but a Certificate of Compliance issued by the County Engineer has to be in hand before construction and before the septic application is processed.
Nothing is poured and no dirt moves until the aquifer approval issues. Everything that does not disturb soil, including plans, shell specification and pricing on turnkey barndominium construction, can run during the review.
Run the address through the TCEQ Edwards Aquifer Map Viewer and print the map.
Settle the zone question: contributing, recharge, transition, or split across two.
Call the TCEQ Austin Regional Office, phone (512) 339-2929, and confirm which plan applies and whether a residence exemption fits.
File the Contributing Zone Plan or the WPAP, and count as long as 30 days of administrative review plus 90 days of technical review.
Run the county track in parallel: 911 address, floodplain check, septic application and driveway.
Start construction only after the aquifer approval issues.
TCEQ, Edwards Aquifer Map Viewer page, as read September 13, 2026.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
TCEQ, Contributing Zone Plan page, as read September 13, 2026.
TCEQ, Water Pollution Abatement Plan page, as read September 13, 2026.
Travis County Transportation and Natural Resources, Development Services, as read September 13, 2026.
Williamson County frequently asked questions, County Engineer, as read September 13, 2026.
Who do you call first? The TCEQ Austin Regional Office.
Three offices carry this work. Call them in the order below and you will not repeat yourself.
Bring the same three things to every call: the address or the legal description, the printed map viewer result, and a rough number for how many acres the build will disturb. Those three answers decide almost everything else.
TCEQ Austin Regional Office, (512) 339-2929, for Williamson, Travis and Hays counties. Ask which zone the parcel is in, which plan applies, and whether a single-family residence exemption fits your lot.
Travis County TNR Development Services, for the county development permit, the floodplain question, the septic permit in the unincorporated county and the driveway onto a county-maintained road. The Lower Colorado River Authority handles septic near Lake Travis.
Williamson County Engineer's Office, for the Certificate of Compliance, the septic program and the floodplain development permit. Williamson County Road and Bridge Division handles the county driveway permit.
TCEQ Edwards Aquifer Protection Program home page, as read September 13, 2026.
TCEQ, Edwards Aquifer Map Viewer page, as read September 13, 2026.
Travis County Transportation and Natural Resources, Development Services, as read September 13, 2026.
Williamson County frequently asked questions, County Engineer, as read September 13, 2026.
More for planning the house: design and plans.
Lot and permit questions
Is the Edwards Aquifer plan a county permit?
No. It is a state program run by TCEQ, and it covers eight Texas counties, which run from Williamson and Travis through Hays, Comal, Bexar, Medina and Uvalde to Kinney. Travis and Williamson are the two counties on this site that fall inside it, which the TCEQ Austin Regional Office handles (call 512-339-2929). The county permits still apply on top of it: a development permit and three third-party inspections in Travis County, and a Certificate of Compliance issued by the County Engineer in Williamson County.
My barndominium will disturb less than five acres in the contributing zone. Do I need a plan?
In the contributing zone, the Contributing Zone Plan kicks in when activities disturb five or more acres, or are part of a larger plan to develop or sell land, under 30 TAC 213.21(b). Below that, no Edwards Aquifer protection plan is needed in the contributing zone. Two cautions. If your lot is part of a subdivision or a larger development, ask the TCEQ Austin Regional Office whether the larger plan of development reaches your build. And stormwater is a separate program with a one acre threshold under the TPDES Construction General Permit TXR150000.
Does the five acre trigger apply on the recharge zone too?
No. There is no acreage floor on the recharge zone. Any regulated activity proposed there must have its Water Pollution Abatement Plan approved before any construction begins. The five acre number is a contributing zone concept only.
My tract is partly contributing zone and partly recharge zone. Which rule applies?
The stricter one. A site that straddles the line, some of it contributing zone and some recharge zone, counts as recharge zone from end to end and a WPAP is required. The same escalation applies to a transition zone site that drains back to the recharge zone. Moving the house footprint does not change the answer, because the test is the site.
How long before I can start building?
Administrative review can last as long as 30 days under 30 TAC 213.4(e), and technical review of an administratively complete application takes 90 days under the same rule. Construction cannot begin until approval issues. Set your start date off the approval, not the submittal.
How do I check which zone my land is in?
Use the TCEQ Edwards Aquifer Map Viewer. It tells a landowner whether a parcel falls in a regulated zone, and the printed map can be submitted with the application. Do it before you make an offer on the land.
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