Snoqualmie Pass Area, Washington (Parts of King and Pierce Counties)
The most common soil here is Playco, on about 9% of the land: a ashy loamy sand, gritty and loose. Nimue and Pitcher come next.
About 76% of the land drains well, and 3% stays wet for long stretches; groundwater comes within two feet of the surface under 4% of it.
USDA rates 98% of the land very limited for a standard septic drain field, and 90% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 2% of the land floods occasionally or more, and bedrock lies within 40 inches under 22% 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 Snoqualmie Pass Area, Washington (Parts of King and Pierce Counties), 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 Well drained and the dominant hydrologic group is B (moderate infiltration). The most common soil order is Spodosols — acidic forest soils with a distinctive leached layer, common under conifers. 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 Snoqualmie Pass Area, Washington (Parts of King and Pierce Counties). 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 |
|---|---|---|---|---|---|
| Playco loamy sand, 30 to 65 percent slopes | 46K | Well drained | B | Very limited | Very limited |
| Nimue loamy sand, 30 to 65 percent slopes | 40K | Well drained | B | Very limited | Very limited |
| Playco very gravelly loamy sand, tuff substratum, 30 to 65 percent slopes | 40K | Well drained | B | Very limited | Very limited |
| Tokul gravelly medial loam, 8 to 15 percent slopes | 34K | Moderately well drained | B | Very limited | Very limited |
| Nimue loamy sand, tuff substratum, 30 to 65 percent slopes | 32K | Well drained | B | Very limited | Very limited |
| Pitcher sandy loam, 30 to 65 percent slopes | 28K | Well drained | B | Very limited | Very limited |
| Pitcher sandy loam, tuff substratum, 30 to 65 percent slopes | 28K | Well drained | B | Very limited | Very limited |
| Kaleetan sandy loam, 30 to 65 percent slopes | 24K | Well drained | B | Very limited | Very limited |
| Barneston gravelly ashy coarse sandy loam, 0 to 8 percent slopes | 23K | Somewhat excessively drained | A | Not limited | Very limited |
| Reggad very cobbly muck, 30 to 90 percent slopes | 21K | Excessively drained | A | Very limited | Very limited |
| Barneston gravelly ashy coarse sandy loam, 8 to 15 percent slopes | 20K | Somewhat excessively drained | A | Somewhat limited | Very limited |
| Haywire sandy loam, 30 to 65 percent slopes | 16K | Well drained | C | Very limited | Very limited |
| Tokul gravelly medial loam, 15 to 30 percent slopes | 16K | Moderately well drained | B | Very limited | Very limited |
| Nagrom sandy loam, 30 to 65 percent slopes | 16K | Well drained | C | Very limited | Very limited |
| Rock outcrop-Rubble land-Serene complex, 45 to 90 percent slopes | 15K | Very limited | Very limited | ||
| Elwell silt loam, 6 to 30 percent slopes | 15K | Moderately well drained | C | Very limited | Very limited |
| Water | 15K | Not rated | Not rated | ||
| Altapeak gravelly sandy loam, 30 to 65 percent slopes | 15K | Well drained | A | Very limited | Very limited |
| Zynbar loam, 6 to 30 percent slopes | 15K | Well drained | B | Very limited | Very limited |
| Index loamy sand, 30 to 65 percent slopes | 14K | Well drained | A | Very limited | Very 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 90% 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 98% 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.