Hawaii County, HI's soil, for a septic absorption field

Very limited

92.8% of Hawaii County, HI's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Practically, that rules out a simple gravity system for most of the county - 92.8% of it sits in USDA's most-constrained bucket. Hawaii County, HI is 4,028.431 square miles with a population of 209,790.

What Hawaii County's reading doesn't cover

Two lots a mile apart in Hawaii County can carry different soil, even though they share one countywide rating. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Hawaii County will actually do.

What a system would cost here

With 92.8% of Hawaii County rating "Very limited", a standard gravity system is not a safe assumption here. 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.

Hawaii County's rank among Hawaii counties

Nationally, Hawaii County, HI is the 947-most-constrained of 3,058 rated counties for septic soil. Within Hawaii alone it ranks 2 of 3.

Before you act on this

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