What San Juan County, UT's soil rates for a septic system
Very limited
Soil across 56.8% of San Juan County, UT rates "Very limited" in USDA's septic-absorption-field interpretation. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 56.8% of San Juan County's land. San Juan County, UT is 7,823.687 square miles with a population of 14,601.
What San Juan County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in San Juan County, UT - never a reading for one specific parcel. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in San Juan County will actually do.
What a system would cost here
With 56.8% of San Juan 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.
San Juan County's rank among Utah counties
Nationally, San Juan County, UT is the 2,786-most-constrained of 3,058 rated counties for septic soil. Within Utah alone it ranks 27 of 28.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems