Septic soil in Suffolk County, MA, by the numbers

Very limited

Soil across 65.5% of Suffolk County, MA rates "Very limited" in USDA's septic-absorption-field interpretation. Practically, that rules out a simple gravity system for most of the county - 65.5% of it sits in USDA's most-constrained bucket. Suffolk County covers 58.257 square miles and counts 793,144 residents.

This is a county figure, not a parcel figure

This is a countywide, area-weighted figure across every soil survey map unit in Suffolk County, MA - never a reading for one specific parcel. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Suffolk County.

System cost, conventional vs. engineered

Given Suffolk 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 Suffolk County, MA compares

Nationally, Suffolk County, MA is the 2,594-most-constrained of 3,058 rated counties for septic soil. Within Massachusetts alone it ranks 13 of 14.

Before you act on this

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