Arkansas / Columbia County
Score 47 · elevated · #25 of 67 in AR
Crawl space moisture in Columbia County, AR
51% of Columbia County's soil falls in hydrologic group D or a dual D group: clays and high water tables that shed water slowly. Where a seasonal water table is reported — 90% of acres — it averages 2.1 ft below grade.
- 1Water table 2.1 ft
- 2Wet soils 32%
- 3Moisture score 47
- 4EPA radon zone 3
Reading the Columbia County soil survey
The score of 47 combines four parts, each from the USDA survey: wet drainage classes contribute 44.8 points of 100 on their own scale, group D soils 46, a shallow water table 60.4, and flooding 20.5; the weights are on the methodology page. The dominant hydrologic group is C/D (26% of acres): D when undrained, C when drained.
At 2.1 ft the seasonal water table is usually below a crawl-space floor, but the 90% of acres that report one are by definition the wettest parts of the county; on those lots, a wet spring can bring water close to the footings.
Columbia County against the rest of Arkansas
Columbia County ranks 25 of 67 Arkansas counties, 13 points above the state median of 34. Wetter counties exist in Arkansas, but the soil here still sits well above the national middle. Statewide, 33% of mapped soil is in the wet drainage classes; here it is 32%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After moderately well drained, the next most common class is poorly drained at 30%.
Flooding. 20.5% of acres with a flooding class are rated frequent. That is a large flood-prone share; a crawl space in the floodplain needs flood vents under most local floodplain ordinances, which is a separate rule from R408 and can rule out a fully sealed design.
What it means for a crawl space here
In an elevated county the soil supplies more moisture than average, but a vented crawl space can work if the ground is covered: the code lets vent area drop from 1 sq ft per 150 to 1 per 1500 with a Class I vapor retarder on the ground, which is an admission of how much moisture comes from below. Grading, gutters and a ground cover usually decide whether a crawl space here stays dry before any decision about sealing it.
Radon. EPA radon zone 3. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.
Near Columbia County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area AR027; drainage covers 99% of 490,944 mapped acres); EPA Map of Radon Zones, county table (June 2024 JSON); IRC R408.3 Unvented crawl space, as adopted in S.C. Code Regs. 8-1221 (LII). Checked 2026-10-23.