Petroleum County, MT Shrink-Swell Risk

What Petroleum County, MT's soil means for a foundation

Moderate

USDA's SSURGO data puts Petroleum County, MT's soil at "Moderate" shrink-swell potential, an area-weighted linear extensibility of 5.82% across 36.7% of the county's surveyed land. That's a middle reading: not the sharp swings that crack a foundation outright, but enough that grading and drainage are worth getting right.

This is a county figure, not a lot figure

USDA's survey covers the whole of Petroleum County, MT at once, not any single address. A site-specific soil report, usually $1,000-$5,000, is what an engineer would actually pull before designing a foundation on a lot in Petroleum County.

Report cost vs. repair cost

With Petroleum County, MT rating "Moderate", a geotechnical report is still worthwhile before a build, just less urgent than in a high-risk county. A geotechnical report runs $1,000-$5,000, typically around $2,700. Foundation repair, if a specific lot turns out to differ from the county average, runs $5,000-$15,000.

Where this sits nationally

Nationally, Petroleum County, MT is the 153-most-constrained of 3,085 rated counties for shrink-swell soil. Within Montana alone it ranks 1 of 54. The county spans 1,656 square miles, home to 525 people.

Before you act on this

Orleans Parish, LA carries this site's most-constrained reading. Lexington County, SC and Warren County, OH are worth a look for comparison.

How this reading is built, and its real limits · Moisture management: the cheap fix that works on any soil

More of Montana

Every county in Montana is on this site, including Mineral County, MT and Jefferson County, MT. The full underlying dataset is downloadable directly, one row per county.