BasementSoil

“Somewhat poorly drained” soil: Wet long enough that ordinary use needs artificial drainage

Water is removed slowly enough that the profile is wet at shallow depth for significant periods. Almost always a slowly permeable layer, a high water table, or both.

What it means for a basement

Expect real hydrostatic pressure at times. Perimeter drainage — inside or outside — is a legitimate recommendation here, not an upsell. A sump pump is a normal part of the house, not an admission of failure.

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 “somewhat poorly drained” is the dominant class

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

Page data updated