Lehigh County, PA's soil, for a septic absorption field

Very limited

Soil across 79.4% of Lehigh County, PA rates "Very limited" in USDA's septic-absorption-field interpretation. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. Lehigh County covers 345.336 square miles and counts 385,655 residents.

This is a county figure, not a parcel figure

USDA's survey covers the whole of Lehigh County, PA 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 Lehigh County.

System cost, conventional vs. engineered

Given Lehigh 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, Lehigh County, PA is the 2,068-most-constrained of 3,058 rated counties for septic soil. Within Pennsylvania alone it ranks 54 of 66.

Further reading

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