Sherman County, TX's soil, for a septic absorption field
Very limited
In Sherman County, TX, 51.6% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Practically, that rules out a simple gravity system for most of the county - 51.6% of it sits in USDA's most-constrained bucket. Sherman County, TX is 922.86 square miles with a population of 2,771.
What Sherman County's reading doesn't cover
Two lots a mile apart in Sherman 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 Sherman County will actually do.
What a system would cost here
With 51.6% of Sherman 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.
Sherman County's rank among Texas counties
Nationally, Sherman County, TX is the 2,850-most-constrained of 3,058 rated counties for septic soil. Within Texas alone it ranks 227 of 253.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems