Arkansas / Grant County
Score 53 · elevated · #22 of 67 in AR
Crawl space moisture in Grant County, AR
51% of Grant County's mapped soil is somewhat poorly to very poorly drained, which means ground that stays wet near the surface for significant periods. Where a seasonal water table is reported — 88% of acres — it averages 1.7 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.7 ft
- 2Wet soils 51%
- 3Moisture score 53
- 4EPA radon zone 3
Reading the Grant County soil survey
The score of 53 combines four parts, each from the USDA survey: wet drainage classes contribute 56.6 points of 100 on their own scale, group D soils 45.9, a shallow water table 65.3, and flooding 27.9; the weights are on the methodology page. The dominant hydrologic group is C (42% of acres): slow infiltration (clay layers).
A water table under two feet is the single most important number here. A crawl-space floor is usually 18 to 36 inches below the joists and often below outside grade, so in a wet season groundwater can stand at or above the crawl-space floor across much of Grant County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Grant County against the rest of Arkansas
Grant County ranks 22 of 67 Arkansas counties, 19 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 51%, half again the state figure or more. After moderately well drained, the next most common class is poorly drained at 32%.
Flooding. 27.9% 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 Grant County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area AR053; drainage covers 99% of 405,401 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.