Soil and perc tests in Montgomery County, Texas

USDA rates most of the soil in Montgomery County Very limited for septic absorption fields — 95.3% of the rated acres. Texas requires a site evaluation before it issues a permit. USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-22

Very limited

USDA rating, 95.3% of rated acres

checked 2026-09-22

Slow water movement

Most common limiting reason

checked 2026-09-22

Yes

Site evaluation required

checked 2026-09-23

What is a perc test and does Montgomery 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.

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

How USDA rates the ground in Montgomery County

Very limited across most of the county — 95.3% of the rated acres. A rating describes the ground, not a parcel. The county's site evaluation decides each lot.

Very limited — 594,883 acres — 95.3% of 624,492 rated acres.
Not limited — 28,539 acres — 4.6% of 624,492 rated acres.
Somewhat limited — 1,070 acres — 0.2% of 624,492 rated acres.
Not rated — 64,250 acres, excluded from the denominator — mostly urban land and water.

95.3% of 624,492 rated acres. 64,250 acres unrated. Survey area TX339 version 23, established 2025-09-04.

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-22

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 — 549,575 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Depth to saturated zone — 497,792 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Flooding — 63,874 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Seepage, bottom layer — 46,377 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Filtering capacity — 32,867 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Slope — 12,399 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Ponding — 3,643 acres. Reasons overlap — a component can carry several — so these acres exceed rated acres.
Depth to bedrock — 2,579 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.

CoC — Conroe loamy fine sand, 0 to 5 percent slopes — 77,161 acres in this county — rated Very limited. Dominant component: Conroe (100% of the map unit).
WkC — Fetzer loamy fine sand, 1 to 5 percent slopes — 49,634 acres in this county — rated Very limited. Dominant component: Fetzer (85% of the map unit).
SplB — Splendora fine sandy loam, 0 to 2 percent slopes — 38,602 acres in this county — rated Very limited. Dominant component: Splendora (90% of the map unit).
SuC — Woodville fine sandy loam, 1 to 5 percent slopes — 35,327 acres in this county — rated Very limited. Dominant component: Woodville (90% of the map unit).
SosA — Sorter-Tarkington complex, 0 1 percent slopes — 32,661 acres in this county — rated Very limited. Dominant component: Sorter (60% of the map unit).
BoyC — Boy loamy fine sand, 1 to 5 percent slopes — 32,018 acres in this county — rated Very limited. Dominant component: Boy (95% of the map unit).
Fs — Lilbert loamy fine sand — 28,974 acres in this county — rated Very limited. Dominant component: Lilbert (100% of the map unit).
W — Water — 23,149 acres in this county — rated Not rated. Dominant component: Water (100% of the map unit).

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-22

Sources

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

Montgomery County Environmental Health Services — How to Obtain a Permit to Construct a Septic System · checked 2026-09-23
Texas Administrative Code, Title 30, Chapter 285, Section 285.30, Site Evaluation · checked 2026-09-23
USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-22

Verify before you act. Septic rules are set locally and they change. Check anything here before you spend money on it. Call the county environmental health office.