Why does the Edwards Aquifer matter for a Comal County lot?
It matters because part of Comal County sits on ground where the state regulates what you can build and how you build it. If the lot you want is on the Edwards Aquifer recharge zone, building a house and putting in a septic system can both fall under rules from the Texas Commission on Environmental Quality (TCEQ). Those rules can add a plan, a review period and a minimum lot size before anyone pours a slab.
The reason is the rock. On the recharge zone, caves, sinkholes and fractures can carry water from the surface into the aquifer, and that aquifer is a water source for central Texas communities. That is why the state regulates activities on top of it that could pollute the water.
The rules sit in Chapter 213 of the Texas Administrative Code. They apply to the Edwards Aquifer in eight counties, and Comal County is one of them. That does not mean every acre in Comal County is covered. TCEQ says only portions of the aquifer are regulated.
So the first question for any Hill Country lot is which zone, if any, it sits on. TCEQ’s Edwards Aquifer Map Viewer shows the areas subject to regulation under the program. This post focuses on the recharge zone. Pull it up with the parcel boundary in front of you. A tract can straddle a line, and you want to know which part of the land you plan to build on.
I spent more than 20 years as an oil and gas landman, and one habit stuck. Find out what the ground lets you do before you talk price. A lot that looks perfect from the road can carry rules that change the cost and the calendar of building on it.
When does building a home need a TCEQ plan?
Building on the recharge zone is a regulated activity unless an exclusion fits. TCEQ’s rules list construction of buildings on the recharge zone as a regulated activity, and TCEQ’s guidance for private residences says construction at a home on the recharge or contributing zones is subject to these rules. The house itself is covered, not only a subdivision or a commercial project.
One exclusion is tied to lot size. The definition leaves out construction of single-family residences on lots larger than five acres, where no more than one single-family residence is on each lot. TCEQ’s private-residence guidance lists the same condition, a lot larger than five acres with no more than one single-family residence on it, as one where an individual plan may not be required.
Read that wording closely. The rule says “larger than five acres,” so check the acreage on the survey or plat against those exact words. The exclusion also is tied to one single-family residence per lot. If you are thinking about a guest house, a second home for family or splitting the tract later, take that plan to TCEQ before you count on the exclusion.
If you are buying in a subdivision on the recharge zone, ask the seller or developer whether the subdivision has an approved Edwards Aquifer plan and what it requires of each lot. TCEQ’s private-residence page explains the other situations where an individual plan may not be required, so read it with your builder rather than assume one applies.
If none of those conditions fit, plan on an application. TCEQ’s rules say no one may start construction of a regulated activity until the Edwards Aquifer protection plan is approved.
That approval takes time. Under the rule, TCEQ has 30 days to declare an application administratively complete or deficient, and then 90 days to finish its review of a complete application. The program page lists the same turnaround times. If your build schedule assumes you break ground right after closing, put that review window on the calendar first.
How does the recharge zone change the septic plan?
If the lot will not connect to a sewer, the septic system gets its own set of recharge zone rules. TCEQ’s on-site sewage facility (OSSF) rules have a section just for the Edwards Aquifer recharge zone, separate from the general septic rules.
Here is what the rule requires for a new system on the recharge zone:
- A professional submits the plans. All planning materials must be submitted to the permitting authority by a professional engineer or professional sanitarian.
- One acre per home. Each lot or tract on the recharge zone where a septic system will be located must have at least one acre, 43,560 square feet, per single-family dwelling.
- Distance from recharge features. No sewage treatment tank or holding tank may sit within 50 feet of a recharge feature, and no soil absorption system may sit within 150 feet of one. The rule adds further separation distances from a table elsewhere in the septic rules.
- Edwards plan first. A companion rule says an Edwards Aquifer protection plan shall be approved by the regional office before a permitting authority may issue an authorization to construct the septic system.
There is a local twist for Comal County. Lots platted and recorded in Comal County before March 26, 1974 are exempt from the one-acre minimum, under conditions in the rule. That same section says an Edwards Aquifer protection plan may still be required for home construction. So an older, smaller lot is not automatically off the hook.
The rule also puts a duty on whoever divided the land. An owner who divides property into two or more residential lots, where any part of a septic system will be on the recharge zone, must tell each prospective purchaser in writing which lots are subject to these terms, that an authorization to construct is required before a septic system can be built, that a notice of approval is required to operate one, and whether a water pollution abatement plan was applied for, approved or conditioned.
If you are buying a lot that came out of a subdivided tract, ask for the written notice that owner had to give. It shows what paperwork was already done and what is still left for you.
What should you check before you commit to the land?
Treat the recharge zone like any other condition of the property. Get answers while your money and your deadlines are still flexible. Here is the order I would work through:
- Map the lot. Check the parcel on the TCEQ Edwards Aquifer Map Viewer and note whether the building area falls on the recharge zone.
- Measure against the five-acre line. Get the acreage from the survey or plat, not the listing. Then compare it to “larger than five acres” and your plan for one home or more.
- Ask about an existing plan. Ask whether the subdivision or tract already has an approved Edwards Aquifer protection plan, and get a copy of the approval and its conditions.
- Ask for the septic notice. On a lot from a divided tract, ask for the dividing owner’s written recharge zone notice and check the plat date against March 26, 1974.
- Talk to the right people. Call TCEQ’s San Antonio Regional Office about the Edwards rules, and hire a professional engineer or professional sanitarian to look at the septic site.
- Ask the title company. Ask whether the county deed records show anything about an Edwards Aquifer plan on the tract. My guide to what a title company does in a Texas home purchase explains its role.
- Line it up with your contract dates. Run these checks while you can still walk away under your contract. My guide to option fees and earnest money in Texas explains how those windows work.
A recharge zone lot comes with a process, with a review period and professionals attached to it. Put those in your budget and your calendar early.
If you are weighing a larger tract, the land questions stack up fast. My post on reading a Texas land listing with a landman’s eye walks through the other things I check on raw land, and the ag valuation guide covers the tax side of Hill Country acreage. Add the Edwards Aquifer Map Viewer check and the plat date to that list for any raw land you are considering.
