San Juan County's SSURGO septic rating
Very limited
USDA puts San Juan County, CO at "Very limited" for septic absorption fields, the dominant reading across 95.3% of the county's soil. That reading means a conventional system is a poor bet here - 95.3% of San Juan County lands in the strictest "very limited" bucket USDA uses. The county spans 387.516 square miles, home to 821 people.
What this number does and doesn't tell you
This is a countywide, area-weighted figure across every soil survey map unit in San Juan County, CO - 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.
San Juan County: conventional vs. engineered cost
95.3% of San Juan 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.
How San Juan County, CO compares
Among the 3,058 rated counties on this site, San Juan County, CO ranks 647 most-constrained nationally, and 4 of 63 within Colorado.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems