Septic soil in Johnston County, NC, by the numbers

Very limited

In Johnston County, NC, 62.7% of the surveyed land carries a "Very limited" rating for a standard septic drain field. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 62.7% of Johnston County's land. Johnston County covers 792.017 square miles and counts 249,794 residents.

This is a county figure, not a parcel figure

USDA's survey covers the whole of Johnston County, NC 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 Johnston County.

System cost, conventional vs. engineered

Given Johnston 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 Johnston County, NC compares

Nationally, Johnston County, NC is the 2,671-most-constrained of 3,058 rated counties for septic soil. Within North Carolina alone it ranks 64 of 97.

Before you act on this

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