Maine / Kennebec County
Score 42 · elevated · #7 of 10 in ME
Crawl space moisture in Kennebec County, ME
85% of Kennebec 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 — 62% of acres — it averages 1.4 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.4 ft
- 2Wet soils 27%
- 3Moisture score 42
- 4EPA radon zone 1
Reading the Kennebec County soil survey
The score of 42 combines four parts, each from the USDA survey: wet drainage classes contribute 32.9 points of 100 on their own scale, group D soils 66.3, a shallow water table 48.4, and flooding 0.8; the weights are on the methodology page. The dominant hydrologic group is C/D (48% of acres): D when undrained, C when drained.
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 across much of Kennebec County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Kennebec County against the rest of Maine
Kennebec County ranks 7 of 10 Maine counties, 4 points below the state median of 46. Wetter counties exist in Maine, but the soil here still sits well above the national middle. Statewide, 37% of mapped soil is in the wet drainage classes; here it is 27%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After moderately well drained, the next most common class is well drained at 23%.
Flooding. 0.7% of acres with a flooding class are rated frequent; 0.2% of acres with a flooding class are rated occasional. Flood-prone soils are a minority here, concentrated along streams; the score mostly reflects what happens between floods. Ponding — water standing at the surface with nowhere to go — affects 6.3% of acres.
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. Kennebec 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 Kennebec County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area ME011; drainage covers 91% of 609,197 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.