Colorado / Rio Grande County
Score 25 · moderate · #3 of 45 in CO
Crawl space moisture in Rio Grande County, CO
Rio Grande County scores moderate: no single wet-soil signal dominates its mapped acres. Where a seasonal water table is reported — 45% of acres — it averages 2.8 ft below grade.
- 1Water table 2.8 ft
- 2Wet soils 19%
- 3Moisture score 25
- 4EPA radon zone 2
Reading the Rio Grande County soil survey
The score of 25 combines four parts, each from the USDA survey: wet drainage classes contribute 25 points of 100 on their own scale, group D soils 31.7, a shallow water table 26, and flooding 6.8; the weights are on the methodology page. The dominant hydrologic group is B (40% of acres): moderate infiltration.
At 2.8 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.
Rio Grande County against the rest of Colorado
Rio Grande County ranks 3 of 45 Colorado counties, 15 points above the state median of 10. Only 2 other counties in the state score higher. Statewide, 3% of mapped soil is in the wet drainage classes; here it is 19%, half again the state figure or more. After well drained, the next most common class is moderately well drained at 25%.
Flooding. 3.4% of acres with a flooding class are rated frequent; 5.4% of acres with a flooding class are rated occasional; 1% 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 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 Rio Grande County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area CO631; drainage covers 98% of 280,525 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.