Soil and perc tests in Grayson County, Texas

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

Yes. A licensed site evaluator or engineer must do a site evaluation first.

Grayson County OSSF Division — OSSF Permitting Requirements · checked 2026-10-05

How USDA rates the ground in Grayson County

Very limited across most of the county — 92.6% of the rated acres. A rating describes the ground, not a parcel. The county's site evaluation decides each lot.

• Very limited — 510,587 acres — 92.6% of 551,463 rated acres.
• Somewhat limited — 40,876 acres — 7.4% of 551,463 rated acres.
• Not rated — 74,643 acres, excluded from the denominator — mostly urban land and water.

92.6% of 551,463 rated acres. 74,643 acres unrated. Survey area TX181 version 23, established 2026-09-03.

USDA NRCS Soil Data Access (SSURGO) · checked 2026-10-05

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.

• Slow water movement — 492,776 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Depth to bedrock — 320,175 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Flooding — 51,486 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Slope — 46,049 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Depth to saturated zone — 26,438 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Seepage, bottom layer — 11,980 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Filtering capacity — 8,724 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
• Large stones — 3,285 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.

• 33 — Fairlie and Houston Black clays, 1 to 3 percent slopes — 64,423 acres in this county — rated Very limited. Dominant component: Fairlie (58% of the map unit).
• 52 — Normangee clay loam, 1 to 3 percent slopes — 47,490 acres in this county — rated Very limited. Dominant component: Normangee (85% of the map unit).
• W — Water — 31,337 acres in this county — rated Not rated. Dominant component: Water (100% of the map unit).
• 23 — Crockett loam, 2 to 5 percent slopes, eroded — 24,855 acres in this county — rated Very limited. Dominant component: Crockett (85% of the map unit).
• 80 — Wilson silty clay loam, 1 to 3 percent slopes — 22,751 acres in this county — rated Very limited. Dominant component: Wilson (100% of the map unit).
• 77 — Whitewright-Eddy-Howe complex, 5 to 12 percent slopes — 20,925 acres in this county — rated Very limited. Dominant component: Whitewright (41% of the map unit).
• 22 — Crockett loam, 1 to 3 percent slopes — 20,197 acres in this county — rated Very limited. Dominant component: Crockett (85% of the map unit).
• 71 — Vertel clay, 3 to 5 percent slopes — 19,053 acres in this county — rated Very limited. Dominant component: Vertel (100% of the map unit).

USDA NRCS Soil Data Access (SSURGO) · checked 2026-10-05

Sources

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

1. Grayson County OSSF Division — OSSF Permitting Requirements · checked 2026-10-05
2. Grayson County Development Services · checked 2026-10-05
3. Order Adopting Rules of Grayson County, Texas for On-Site Sewage Facilities, Section 10(E)(1)(a) · checked 2026-10-05
4. Grayson County Development Services Fees (revised 04/14/2026) · checked 2026-10-05
5. Grayson County — MyPermitNow Navigation Guide · checked 2026-10-05
6. 30 TAC §285.91(2), Table II -- Septic Tank and Aerobic Treatment Unit Sizing · checked 2026-09-23
7. USDA NRCS Soil Data Access (SSURGO) · checked 2026-10-05

Related pages

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