Soil and perc tests in Comal County, Texas

What is a perc test and does Comal County require one?

A site evaluator must check the site and the soil. The county needs this check before it issues a permit.

The evaluator checks the soil. The evaluator also checks the water table, the slope, and the risk of a flood. Texas rules require this check under 30 TAC section 285.30.

Comal County Engineer's Office — Apply for Septic Permit · checked 2026-09-23

How USDA rates the ground in Comal County

Very limited across most of the county — 97.6% of the rated acres. A rating describes the ground, not a parcel. The county's site evaluation decides each lot.

• Very limited — 359,203 acres — 97.6% of 367,942 rated acres.
• Somewhat limited — 8,739 acres — 2.4% of 367,942 rated acres.
• Not rated — 66,272 acres, excluded from the denominator — mostly urban land and water.

97.6% of 367,942 rated acres. 66,272 acres unrated. Survey area TX604 version 22, established 2025-09-05.

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-12

What limits absorption here

The reasons USDA gives for the rating, by the acres they affect. A component can carry several, so the acres overlap.

• Depth to bedrock — 330,302 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Slow water movement — 132,600 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Large stones — 120,424 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Slope — 59,025 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Flooding — 9,881 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Depth to cemented pan — 4,207 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Seepage, bottom layer — 3,899 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Filtering capacity — 3,052 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Depth to saturated zone — 251 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Ponding — 30 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.

Ratings by soil map unit

The largest map units in the county, each with its rating. A soil survey names the ground. The county's evaluation of your lot is what a permit turns on.

• BtD — Brackett-Rock outcrop-Comfort complex, 1 to 8 percent slopes — 68,193 acres in this county — rated Very limited. Dominant component: Brackett (50% of the map unit).
• CrD — Comfort-Rock outcrop complex, 1 to 8 percent slopes — 66,648 acres in this county — rated Very limited. Dominant component: Comfort (70% of the map unit).
• RUD — Rumple-Comfort, rubbly association, 1 to 8 percent slopes — 60,035 acres in this county — rated Very limited. Dominant component: Rumple (60% of the map unit).
• BtG — Brackett-Rock outcrop-Real complex, 8 to 30 percent slopes — 49,203 acres in this county — rated Very limited. Dominant component: Brackett (38% of the map unit).
• RcD — Real-Comfort-Doss complex, 1 to 8 percent slopes — 30,707 acres in this county — rated Very limited. Dominant component: Real (40% of the map unit).
• HoB — Houston Black clay, 1 to 3 percent slopes — 16,029 acres in this county — rated Very limited. Dominant component: Houston Black (80% of the map unit).
• DoC — Doss silty clay, moist, 1 to 5 percent slopes — 13,197 acres in this county — rated Very limited. Dominant component: Doss (85% of the map unit).
• HeC3 — Heiden clay, 3 to 5 percent slopes, eroded — 11,265 acres in this county — rated Very limited. Dominant component: Heiden (85% of the map unit).

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-12

Sources

Each figure on this page has a government source and a checked-on date.

1. Comal County Environmental Health Department · checked 2026-09-23
2. Comal County Environmental Health Department — OSSF Information · checked 2026-09-23
3. Comal County Engineer's Office — Apply for Septic Permit · checked 2026-09-23
4. Comal County Environmental Health Department — List of Environmental Health Department Fees · checked 2026-09-23
5. 30 TAC §285.91(2), Table II — Septic Tank and Aerobic Treatment Unit Sizing · checked 2026-09-23
6. USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-12

Related pages

• Septic rules and requirements in Comal County, Texas
• Septic permits and fees in Comal County, Texas
• Septic rules and requirements in Texas
• Septic rules in Comal County