Crawl space moisture in Tooele County, UT

67% of Tooele 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 — 37% of acres — it averages 0.1 ft below grade, shallow enough to reach a typical crawl-space footing.

Size venting or encapsulation

1Water table 0.1 ft
2Wet soils 39%
3Moisture score 43
4EPA radon zone 2

Share of mapped soil acres in Tooele County, UT by NRCS drainage class (dominant condition), bars to scale; wetter classes highlighted. Covers 92% of mapped acres.

Dominant drainage

Well drained

42% of acres

Group D soils

67%

slow infiltration

Flood-prone acres

any flooding frequency

Ponding

0.5%

acres where water ponds

Reading the Tooele County soil survey

The score of 43 combines four parts, each from the USDA survey: wet drainage classes contribute 38.7 points of 100 on their own scale, group D soils 73.4, a shallow water table 36.1, and flooding 3.6; the weights are on the methodology page. The dominant hydrologic group is D (67% of acres): very slow infiltration, high runoff (clays, high water table).

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

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 on the soils that report a water table — about 37% of Tooele County's acres. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.

Tooele County against the rest of Utah

Tooele County ranks 1 of 18 Utah counties, 27 points above the state median of 16. Only no other county in the state scores higher. Statewide, 13% of mapped soil is in the wet drainage classes; here it is 39%, half again the state figure or more. After well drained, the next most common class is very poorly drained at 34%.

Flooding. 3.5% of acres with a flooding class are rated frequent; 0.3% of acres with a flooding class are rated rare. Flood-prone soils are a minority here, concentrated along streams; the score mostly reflects what happens between floods.

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 2. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.

Near Tooele County by score

Box Elder County 33 Utah County 33 Salt Lake County 29Washington County 19

All 18 Utah counties

Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area UT611; drainage covers 92% of 5,124,559 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.