Soil and perc tests in Hays County, Texas

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

Yes. Texas requires a site evaluation before it issues a permit.

A site evaluator or an engineer checks the soil in two pits or borings. Hays County uses this report to size the system.

Texas Administrative Code, Title 30, Chapter 285, Section 285.30, Site Evaluation · checked 2026-09-23

How USDA rates the ground in Hays County

Very limited across most of the county — 98.1% of the rated acres. A rating describes the ground, not a parcel. The county's site evaluation decides each lot.

• Very limited — 301,167 acres — 98.1% of 307,031 rated acres.
• Somewhat limited — 5,864 acres — 1.9% of 307,031 rated acres.
• Not rated — 61,040 acres, excluded from the denominator — mostly urban land and water.

98.1% of 307,031 rated acres. 61,040 acres unrated. Survey area TX604 version 22, established 2025-09-05.

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-24

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 — 299,221 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Large stones — 125,539 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Slow water movement — 86,974 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Slope — 80,004 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Flooding — 6,727 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Seepage, bottom layer — 4,925 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Filtering capacity — 2,783 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Depth to cemented pan — 963 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Depth to saturated zone — 87 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Ponding — 21 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.

• CrD — Comfort-Rock outcrop complex, 1 to 8 percent slopes — 87,040 acres in this county — rated Very limited. Dominant component: Comfort (70% of the map unit).
• BtG — Brackett-Rock outcrop-Real complex, 8 to 30 percent slopes — 55,430 acres in this county — rated Very limited. Dominant component: Brackett (38% of the map unit).
• RUD — Rumple-Comfort, rubbly association, 1 to 8 percent slopes — 46,348 acres in this county — rated Very limited. Dominant component: Rumple (60% of the map unit).
• BtD — Brackett-Rock outcrop-Comfort complex, 1 to 8 percent slopes — 42,187 acres in this county — rated Very limited. Dominant component: Brackett (50% of the map unit).
• ErG — Eckrant-Rock outcrop association, 8 to 30 percent slopes — 24,347 acres in this county — rated Very limited. Dominant component: Eckrant (65% of the map unit).
• RcD — Real-Comfort-Doss complex, 1 to 8 percent slopes — 13,517 acres in this county — rated Very limited. Dominant component: Real (40% of the map unit).
• W — Water — 9,205 acres in this county — rated Not rated. Dominant component: Water (100% of the map unit).
• BrB — Bolar clay loam, 1 to 3 percent slopes — 7,150 acres in this county — rated Very limited. Dominant component: Bolar (90% of the map unit).

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-24

Sources

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

1. Hays County Development Services — Contact Us · checked 2026-09-24
2. Hays County Development Services — On-Site Sewage Facilities · checked 2026-09-24
3. Order Adopting Rules for Hays County, Texas for On-Site Sewage Facilities, Exhibit A, Table 10-2 · checked 2026-09-24
4. Hays County Development Services Fee Schedule, effective January 1, 2026 · checked 2026-09-24
5. Texas Administrative Code, Title 30, Chapter 285, Section 285.30, Site Evaluation · checked 2026-09-23
6. Hays County Development Services — Septic Permits · checked 2026-09-24
7. USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-24

Related pages

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