Hunterdon County, NJ: the USDA septic-suitability picture
Very limited
Hunterdon County, NJ's SSURGO dominant class comes back "Very limited", covering 87.4% of the county. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 87.4% of the county. The county spans 427.835 square miles, home to 131,708 people.
What this number does and doesn't tell you
USDA's survey covers the whole of Hunterdon County, NJ at once, not any single address. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Hunterdon County: conventional vs. engineered cost
87.4% of Hunterdon 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, Hunterdon County, NJ ranks 1,516 most-constrained nationally, and 5 of 21 within New Jersey.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems