Mason County, Washington
The most common soil here is Alderwood, on about 19% of the land: a gravelly sandy loam, gritty and crumbly. Grove and Shelton come next.
About 45% of the land drains well, and 4% stays wet for long stretches; groundwater comes within two feet of the surface under 14% of it.
USDA rates 95% of the land very limited for a standard septic drain field, and 74% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 3% of the land floods occasionally or more, and bedrock lies within 40 inches under 10% of it.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in Mason County, Washington, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Moderately well drained and the dominant hydrologic group is A (high infiltration, low runoff). The most common soil order is Inceptisols — young soils with minimal horizon development but more than Entisols. This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in Mason County, Washington. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Alderwood gravelly sandy loam, 8 to 15 percent slopes | 85K | Moderately well drained | B | Very limited | Very limited |
| Rough mountainous land, Tebo soil material | 46K | Excessively drained | Very limited | Very limited | |
| Grove gravelly sandy loam, 0 to 5 percent slopes | 44K | Somewhat excessively drained | A | Not limited | Very limited |
| Shelton gravelly sandy loam, 5 to 15 percent slopes | 41K | Moderately well drained | A | Very limited | Very limited |
| Hoodsport gravelly sandy loam, 5 to 15 percent slopes | 14K | Moderately well drained | B/D | Very limited | Very limited |
| Grove gravelly sandy loam, 5 to 15 percent slopes | 10K | Somewhat excessively drained | A | Somewhat limited | Very limited |
| Astoria silt loam, 15 to 30 percent slopes | 9K | Well drained | B | Very limited | Very limited |
| Cloquallum silt loam, 5 to 15 percent slopes | 9K | Moderately well drained | C | Very limited | Very limited |
| Hoodsport gravelly sandy loam, 30 to 45 percent slopes | 9K | Moderately well drained | B/D | Very limited | Very limited |
| Alderwood gravelly sandy loam, 15 to 30 percent slopes | 9K | Moderately well drained | B | Very limited | Very limited |
| Everett very gravelly sandy loam, 8 to 15 percent slopes | 8K | Somewhat excessively drained | A | Somewhat limited | Very limited |
| Rough mountainous land, Hoodsport soil material | 8K | Excessively drained | A | Very limited | Very limited |
| Water | 7K | Not rated | Not rated | ||
| Shelton gravelly sandy loam, 15 to 30 percent slopes | 7K | Moderately well drained | A | Very limited | Very limited |
| Everett very gravelly sandy loam, 15 to 30 percent slopes | 7K | Somewhat excessively drained | A | Very limited | Very limited |
| Harstine gravelly ashy sandy loam, 6 to 15 percent slopes | 6K | Moderately well drained | C | Very limited | Very limited |
| Rough broken land | 6K | Well drained | B | Very limited | Very limited |
| Hoodsport stony sandy loam, 5 to 15 percent slopes | 6K | Moderately well drained | B/D | Very limited | Very limited |
| Carstairs gravelly loam, 0 to 5 percent slopes | 6K | Excessively drained | A | Not limited | Very limited |
| Hoquiam silt loam, 5 to 15 percent slopes | 5K | Well drained | B | Somewhat limited | Somewhat limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 74% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes. A geotechnical assessment is recommended before building.
Septic Systems
About 95% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.