Crawl space moisture in Merrick County, NE

Merrick County scores moderate: no single wet-soil signal dominates its mapped acres. Where a seasonal water table is reported — 68% of acres — it averages 2.7 ft below grade.

Size venting or encapsulation

1Water table 2.7 ft
2Wet soils 45%
3Moisture score 33
4EPA radon zone 2

Share of mapped soil acres in Merrick County, NE by NRCS drainage class (dominant condition), bars to scale; wetter classes highlighted. Covers 98% of mapped acres.

Dominant drainage

Somewhat poorly drained

38% of acres

Group D soils

10%

slow infiltration

Flood-prone acres

42%

any flooding frequency

Ponding

3.6%

acres where water ponds

Reading the Merrick County soil survey

The score of 33 combines four parts, each from the USDA survey: wet drainage classes contribute 39.7 points of 100 on their own scale, group D soils 17.7, a shallow water table 39.6, and flooding 27.3; the weights are on the methodology page. The dominant hydrologic group is C (36% of acres): slow infiltration (clay layers).

Hydrologic soil groups in Merrick 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 2.7 ft the seasonal water table is usually below a crawl-space floor, but the 68% 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.

Merrick County against the rest of Nebraska

Merrick County ranks 7 of 93 Nebraska counties, 23 points above the state median of 10. That puts it in the wettest quarter of the state. Statewide, 9% of mapped soil is in the wet drainage classes; here it is 45%, half again the state figure or more. After somewhat poorly drained, the next most common class is moderately well drained at 23%.

Flooding. 5.5% of acres with a flooding class are rated frequent; 36.1% of acres with a flooding class are rated occasional; 0.6% 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 3.6% 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. EPA radon zone 2. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.

Near Merrick County by score

Dodge County 33 Nemaha County 32 Richardson County 31 Lancaster County 36

All 93 Nebraska counties

Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area NE121; drainage covers 98% of 317,428 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.