Washington County, OK's soil, for a septic absorption field

Very limited

In Washington County, OK, 95.5% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Practically, that rules out a simple gravity system for most of the county - 95.5% of it sits in USDA's most-constrained bucket. Washington County covers 415.524 square miles and counts 54,060 residents.

This is a county figure, not a parcel figure

USDA's survey covers the whole of Washington County, OK at once, not any single address. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Washington County.

System cost, conventional vs. engineered

Given Washington County's rating, plan for the engineered-system range rather than the conventional one. The engineered-system range, $10,000-$40,000 (mound or aerobic treatment), is the more realistic number to plan around, against $3,000-$8,000 for a conventional system on the rare lot that passes.

How Washington County, OK compares

Nationally, Washington County, OK is the 595-most-constrained of 3,058 rated counties for septic soil. Within Oklahoma alone it ranks 3 of 77.

Further reading

How this rating is built, and its real limits · Conventional vs. engineered septic systems