Septic soil in Lewis County, TN, by the numbers

Very limited

In Lewis County, TN, 77.5% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 77.5% of the county. Lewis County covers 282.092 square miles and counts 13,418 residents.

This is a county figure, not a parcel figure

Two lots a mile apart in Lewis County can carry different soil, even though they share one countywide rating. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Lewis County.

System cost, conventional vs. engineered

Given Lewis 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 Lewis County, TN compares

Nationally, Lewis County, TN is the 2,160-most-constrained of 3,058 rated counties for septic soil. Within Tennessee alone it ranks 63 of 95.

Before you act on this

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