Spokane County, Washington
The most common soil here is Naff, on about 6% of the land: a silt loam, smooth, like flour. Rockly and Cheney come next.
About 81% of the land drains well, and 6% stays wet for long stretches; groundwater comes within two feet of the surface under 11% of it.
USDA rates 91% of the land very limited for a standard septic drain field, and 60% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 6% of the land floods occasionally or more, and bedrock lies within 40 inches under 30% 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 Spokane 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 Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Mollisols — grassland soils with a thick, dark, fertile topsoil rich in organic matter. 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 Spokane 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 |
|---|---|---|---|---|---|
| Naff-Garfield complex, 3 to 15 percent slopes | 40K | Well drained | C | Somewhat limited | Very limited |
| Rockly-Fourmound complex, 0 to 15 percent slopes | 38K | Well drained | D | Very limited | Very limited |
| Rockly-Deno complex, 0 to 15 percent slopes | 31K | Well drained | D | Very limited | Very limited |
| Northstar-Rock outcrop complex, 3 to 15 percent slopes | 30K | Well drained | C | Very limited | Very limited |
| Naff-Thatuna complex, 8 to 25 percent slopes | 27K | Well drained | C | Very limited | Very limited |
| Cheney ashy silt loam, 0 to 8 percent slopes | 25K | Well drained | B | Not limited | Very limited |
| Northstar-Rock outcrop-Rockly complex, 0 to 15 percent slopes | 21K | Well drained | C | Very limited | Very limited |
| Urban land-Opportunity, disturbed complex, 0 to 3 percent slopes | 18K | Not rated | Not rated | ||
| Naff-Garfield complex, 15 to 25 percent slopes | 17K | Well drained | C | Very limited | Very limited |
| Larkin-Southwick complex, 8 to 15 percent slopes | 17K | Well drained | C | Somewhat limited | Very limited |
| Stutler-Springdale complex, 3 to 15 percent slopes | 17K | Well drained | B | Somewhat limited | Very limited |
| Cheney-Alecanyon complex, 0 to 8 percent slopes | 16K | Well drained | B | Not limited | Very limited |
| Cocolalla-Hardesty complex, 0 to 3 percent slopes | 15K | Poorly drained | B/D | Very limited | Very limited |
| Springdale gravelly ashy coarse sandy loam, 0 to 8 percent slopes | 14K | Somewhat excessively drained | A | Not limited | Very limited |
| Alecanyon, very stony-Cheney complex, 0 to 8 percent slopes | 13K | Somewhat excessively drained | A | Very limited | Very limited |
| Kramerhill-Spokane complex, 8 to 25 percent slopes | 12K | Well drained | C | Very limited | Very limited |
| Water | 12K | Not rated | Not rated | ||
| Caldwell-Thatuna complex, 0 to 8 percent slopes | 11K | Somewhat poorly drained | C | Very limited | Very limited |
| Freeman ashy silt loam, 8 to 15 percent slopes | 10K | Moderately well drained | C/D | Very limited | Very limited |
| Marble loamy sand, 0 to 8 percent slopes | 10K | Well drained | A | Not 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 60% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 91% 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.