Grays Harbor County's SSURGO septic rating
Very limited
Grays Harbor County, WA: USDA's soil survey calls 92.8% of the county "Very limited" for a septic leach field. 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. The county spans 1,902.268 square miles, home to 77,893 people.
What this number does and doesn't tell you
Two lots a mile apart in Grays Harbor County can carry different soil, even though they share one countywide rating. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Grays Harbor County: conventional vs. engineered cost
92.8% of Grays Harbor County carrying a "Very limited" reading changes the realistic budget here. 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, Grays Harbor County, WA ranks 949 most-constrained nationally, and 15 of 39 within Washington.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems