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Septic Rules on the Edwards Aquifer Recharge Zone
A large part of Comal County sits over the Edwards Aquifer, and property on the Recharge Zone carries septic requirements that do not apply elsewhere in Texas. If your lot is in that zone, these rules shape your lot size, your system layout, and who is even allowed to file your plans.
30 TAC 285.40 — special requirements for OSSFs on the Recharge Zone of the
Edwards Aquifer, part of TCEQ's on-site sewage facility rules.
30 TAC Chapter 213 — the Edwards Aquifer Protection Program, which governs
regulated activity across the Recharge, Transition and Contributing Zones.
Why the aquifer changes everything
The Edwards Aquifer is the drinking water supply for a large part of south-central Texas, and the Recharge Zone is where surface water enters it. The same geology that makes it recharge so efficiently — fractured limestone, caves, sinkholes, faults — means anything released at the surface can reach the aquifer quickly and with very little natural filtration. A septic system that under-treats its effluent on a Recharge Zone lot is not a local nuisance; it is a direct contamination pathway into a regional water supply.
That is the reasoning behind every requirement below, and it is also why the county reviews these permits carefully. It is not bureaucracy for its own sake.
The specific requirements
Minimum lot size: one acre per dwelling
Each lot or tract on the Recharge Zone carrying an OSSF must have an area of at least one acre — 43,560 square feet — per single-family dwelling. Certain counties with pre-established plat records are exempted, which matters a great deal around older Canyon Lake-area subdivisions where lots are much smaller than an acre. Whether your plat qualifies is a question for the Engineer's Office.
Setbacks from recharge features
| Component | Minimum distance from a recharge feature |
|---|---|
| Sewage treatment tank or holding tank | 50 feet |
| Soil absorption system | 150 feet |
On a constrained lot these setbacks are usually the binding constraint. Once you subtract the exclusion zones around every recharge feature, well and boundary, the remaining buildable area sometimes only fits a more expensive system design — or nothing at all.
Only an engineer or sanitarian may file your plans
On the Recharge Zone, all planning materials must be submitted to the permitting authority by a professional engineer or a professional sanitarian. Your installer cannot self-certify the design the way they might for a standard system elsewhere. Budget for that professional involvement from the start, and be sceptical of any bid that leaves it out.
Authorization before construction, approval before use
As everywhere in Texas, you need an Authorization to Construct before installation starts and a Notice of Approval before the system may be operated. See the full nine-step county process →
Disclosure when land is divided
A property owner dividing land on the Recharge Zone must inform prospective buyers about the applicable restrictions and the regulatory status of the property. If you are buying raw land in this zone and no one has mentioned septic constraints, ask directly and get the answer in writing.
Section 285.40 itself sets lot size, setbacks and who files the plans. It does not itself enumerate which system types are permitted or mandate disinfection — those requirements live elsewhere in 30 TAC Chapter 285 and in the Chapter 213 Edwards rules. In practice Recharge Zone lots overwhelmingly end up on aerobic systems with surface or drip distribution because of the soil, not because 285.40 says so.
What this means for your budget
Recharge Zone properties sit at the top of the local cost range — the $13,000 to $22,000 band rather than the $11,000 to $13,000 one. The drivers are the engineered design, the likelihood of an aerobic system, and rock excavation on the same limestone that makes the zone a recharge zone in the first place. Cost breakdown →
Parts of Comal County most affected
Recharge Zone coverage does not follow city limits. Large-lot residential areas in Bulverde and Spring Branch are substantially affected, as are parts of the Canyon Lake and Fischer areas. The only reliable answer for a specific parcel comes from the county. See our area notes →
A licensed site evaluator has to answer that with a soil test — nobody can tell from a map. Send us your address and we will have local licensed pros quote the evaluation and the install. Request free quotes →
Recharge Zone questions
How do I find out if my property is on the Recharge Zone?
TCEQ maps the Edwards Aquifer Recharge, Transition and Contributing Zones, and the Comal County Engineer's Office works from those boundaries when it reviews your permit. Because the answer changes what you are legally required to build, confirm it with the county at 830-608-2090 rather than guessing from a map.
Does the one-acre rule apply to my lot if it was platted years ago?
Possibly not. The rule sets a minimum of one acre per single-family dwelling on the Recharge Zone, but counties with pre-established plat records can be exempted. Older subdivisions around Canyon Lake and Startzville are exactly the situation that exemption addresses. Ask the county how it treats your specific plat.
Can I still get a septic permit on a Recharge Zone lot smaller than an acre?
It depends on the plat exemption and on whether a compliant system will physically fit once every setback is applied. Small Recharge Zone lots are where design gets genuinely difficult and where an experienced engineer or sanitarian earns their fee.
What counts as a recharge feature?
Features such as caves, sinkholes, faults and fractures that provide a direct pathway for surface water into the aquifer. Identifying them on your property is part of the site evaluation, and their location dictates where a system may be placed.
Official sources
- 30 TAC 285.40 — OSSFs on the Recharge Zone of the Edwards Aquifer
- TCEQ — Edwards Aquifer Protection Program
- TCEQ — Edwards Aquifer rules (Chapter 213)
- Comal County Environmental Health
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