Crawl space moisture in Leavenworth County, KS

53% of Leavenworth 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 — 53% of acres — it averages 2 ft below grade.

Size venting or encapsulation

1Water table 2 ft
2Wet soils 18%
3Moisture score 36
4EPA radon zone 1

Share of mapped soil acres in Leavenworth County, KS by NRCS drainage class (dominant condition), bars to scale; wetter classes highlighted. Covers 99% of mapped acres.

Dominant drainage

Moderately well drained

51% of acres

Group D soils

53%

slow infiltration

Flood-prone acres

18%

any flooding frequency

Ponding

2.8%

acres where water ponds

Reading the Leavenworth County soil survey

The score of 36 combines four parts, each from the USDA survey: wet drainage classes contribute 30 points of 100 on their own scale, group D soils 56.6, a shallow water table 36.7, and flooding 11.6; the weights are on the methodology page. The dominant hydrologic group is C (36% of acres): slow infiltration (clay layers).

Hydrologic soil groups in Leavenworth County by share of acres, columns to scale. Group D and dual groups (x/D) shed water slowly and hold it near the surface.

At 2 ft the seasonal water table is usually below a crawl-space floor, but the 53% 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.

Leavenworth County against the rest of Kansas

Leavenworth County ranks 29 of 105 Kansas counties, 23 points above the state median of 13. That places it in the middle range, nationally and for the state. Statewide, 8% of mapped soil is in the wet drainage classes; here it is 18%, half again the state figure or more. After moderately well drained, the next most common class is well drained at 27%.

Flooding. 4.2% of acres with a flooding class are rated frequent; 11.7% of acres with a flooding class are rated occasional; 1.8% of acres with a flooding class are rated rare; 0.1% of acres with a flooding class are rated very rare. 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. Ponding — water standing at the surface with nowhere to go — affects 2.8% of acres.

What it means for a crawl space here

In a moderate county the soil record is mixed rather than uniformly wet, so conditions vary from lot to lot. Where the lot drains, the model-code default — a vented crawl space with 1 sq ft of net vent per 150 sq ft of floor, or 1 per 1500 with a Class I vapor retarder on the ground — is a reasonable starting point; where the sections above point to a shallow water table or flood-prone soil on your lot, plan as for an elevated county. Either way, check the site first: grading that falls away from the foundation, gutters and downspouts that discharge well clear of it, and a ground cover over bare earth. A wet crawl space in a moderate county points to one of those first.

Radon. Leavenworth County is in EPA radon zone 1, the highest predicted potential. A sealed crawl space and a radon system share most of their parts — the liner, the sealed seams, a fan — so if you are encapsulating, test for radon first and design both together. EPA itself says the zone map is not a reason to skip testing in zones 2 and 3.

Near Leavenworth County by score

Brown County 37 Greenwood County 37 Atchison County 39 Douglas County 39

All 105 Kansas counties

Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area KS103; drainage covers 99% of 300,300 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.