Middlesex County, MA: the USDA septic-suitability picture

Very limited

Middlesex County, MA: USDA's soil survey calls 76% of the county "Very limited" for a septic leach field. That reading means a conventional system is a poor bet here - 76% of Middlesex County lands in the strictest "very limited" bucket USDA uses. For scale: 817.905 square miles and 1,668,956 people call Middlesex County home.

Before you rely on this for one lot

Middlesex County's rating is an average across the whole county, not a promise about any one lot inside it. The real answer for one lot is still a site-specific perc test, running about $750-$1,850 (typically near $1,300).

Budgeting for a system in Middlesex County, MA

Middlesex County's soil reading pushes the likely outcome toward an engineered system rather than a conventional one. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.

Where this sits nationally

Among the 3,058 rated counties on this site, Middlesex County, MA ranks 2,232 most-constrained nationally, and 11 of 14 within Massachusetts.

Related guides

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