Spokane County, Washington
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). 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.
| 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 |
What This Means
Building & Foundations
About 57% 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 92% 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.