Septic soil in Musselshell County, MT, by the numbers
Very limited
Soil across 74.7% of Musselshell County, MT rates "Very limited" in USDA's septic-absorption-field interpretation. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 74.7% of the county. Musselshell County, MT is 1,868.958 square miles with a population of 5,452.
What Musselshell County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in Musselshell County, MT - 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 Musselshell County will actually do.
What a system would cost here
With 74.7% of Musselshell 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.
How Musselshell County, MT compares
Nationally, Musselshell County, MT is the 2,302-most-constrained of 3,058 rated counties for septic soil. Within Montana alone it ranks 37 of 54.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems