Septic soil in Plymouth County, IA, by the numbers

Very limited

83.1% of Plymouth County, IA's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 83.1% of the county. Plymouth County covers 862.828 square miles and counts 25,825 residents.

This is a county figure, not a parcel figure

Nothing about Plymouth County, IA's SSURGO figure applies to a specific address - it's a county-wide average. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Plymouth County.

System cost, conventional vs. engineered

Given Plymouth 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.

Where this sits nationally

Nationally, Plymouth County, IA is the 1,849-most-constrained of 3,058 rated counties for septic soil. Within Iowa alone it ranks 81 of 99.

Related guides

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