BasementSoil

“Moderately well drained” soil: Wet in the lower profile for part of the year

Water is removed somewhat slowly, usually because of a slowly permeable layer within or just below the profile, or seepage from higher ground.

What it means for a basement

This is the tipping point class. The ground is not aggressive, but a seasonally saturated zone can sit at footing depth in spring. Most basements here are dry for years and then leak in one wet March.

Where the USDA definition comes from

Drainage class is assigned per soil component in the national soil survey and describes frequency and duration of wet periods under conditions similar to those under which the soil formed. It is not a measurement taken at your house; it is a classification of a mapped soil body. That distinction is why we phrase every county page as a statement about soil, never as a statement about your basement.

USDA NRCS, National Soil Survey Handbook, part 618. Delivered per map unit in SSURGO.

Counties where “moderately well drained” is the dominant class

300 counties in our coverage, highest-risk 60 shown.

Page data updated