Septic soil in Sullivan County, NH, by the numbers

Very limited

85.4% of Sullivan County, NH's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Practically, that rules out a simple gravity system for most of the county - 85.4% of it sits in USDA's most-constrained bucket. Sullivan County, NH is 537.882 square miles with a population of 44,012.

What Sullivan County's reading doesn't cover

This is a countywide, area-weighted figure across every soil survey map unit in Sullivan County, NH - never a reading for one specific parcel. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Sullivan County will actually do.

What a system would cost here

With 85.4% of Sullivan County rating "Very limited", a standard gravity system is not a safe assumption here. 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.

Where this sits nationally

Nationally, Sullivan County, NH is the 1,658-most-constrained of 3,058 rated counties for septic soil. Within New Hampshire alone it ranks 8 of 10.

Before you act on this

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