Polk County, OR: the USDA septic-suitability picture

Very limited

Polk County, OR's SSURGO dominant class comes back "Very limited", covering 95.7% of the county. Practically, that rules out a simple gravity system for most of the county - 95.7% of it sits in USDA's most-constrained bucket. The county spans 740.924 square miles, home to 90,549 people.

What this number does and doesn't tell you

This is a countywide, area-weighted figure across every soil survey map unit in Polk County, OR - never a reading for one specific parcel. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.

Polk County: conventional vs. engineered cost

95.7% of Polk 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, Polk County, OR ranks 561 most-constrained nationally, and 14 of 36 within Oregon.

Further reading

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