California / Imperial County
Score 30 · moderate · #10 of 48 in CA
Crawl space moisture in Imperial County, CA
Imperial County scores moderate: no single wet-soil signal dominates its mapped acres. Where a seasonal water table is reported — 45% of acres — it averages 2.6 ft below grade.
- 1Water table 2.6 ft
- 2Wet soils 36%
- 3Moisture score 30
- 4EPA radon zone 3
Reading the Imperial County soil survey
The score of 30 combines four parts, each from the USDA survey: wet drainage classes contribute 31.8 points of 100 on their own scale, group D soils 42.9, a shallow water table 27.1, and flooding 0; the weights are on the methodology page. The dominant hydrologic group is A (37% of acres): high infiltration, low runoff (sands, gravels).
At 2.6 ft the seasonal water table is usually below a crawl-space floor, but the 45% 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.
Imperial County against the rest of California
Imperial County ranks 10 of 48 California counties, 12 points above the state median of 18. That puts it in the wettest quarter of the state. Statewide, 11% of mapped soil is in the wet drainage classes; here it is 36%, half again the state figure or more. After somewhat poorly drained, the next most common class is somewhat excessively drained at 29%.
Flooding. No mapped soil in Imperial County carries a flooding frequency above "none", so the score here is about water held in and under the soil rather than water arriving over it.
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 3. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.
Near Imperial County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area CA683; drainage covers 99% of 990,338 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.