Modoc County, California, Alturas Area
The dominant drainage class is Well drained and the dominant hydrologic group is D (very slow infiltration, high 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 Modoc County, California, Alturas Area.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Karcal-Ninekar complex,0 to 9 percent slopes | 53K | Well drained | D | Very limited | Very limited |
| Water | 51K | D | Not rated | Not rated | |
| Deven-Rock outcrop complex, 2 to 30 percent slopes | 40K | Well drained | D | Very limited | Very limited |
| Bieber gravelly loam, 0 to 9 percent slopes | 28K | Well drained | D | Very limited | Very limited |
| Delma cobbly loam, 0 to 9 percent slopes | 19K | Well drained | D | Very limited | Very limited |
| Packwood-Rock outcrop complex | 13K | Well drained | D | Very limited | Very limited |
| Tuff outcrop-Casuse, eroded complex, 2 to 15 percent slopes | 12K | Somewhat limited | Somewhat limited | ||
| Barnard gravelly loam, 0 to 9 percent slopes | 12K | Well drained | D | Very limited | Very limited |
| Buntingville clay loam, 0 to 2 percent slopes | 11K | Somewhat poorly drained | C | Very limited | Very limited |
| Pit silty clay loam, 0 to 2 percent slopes | 11K | Somewhat poorly drained | C | Very limited | Very limited |
| Daphnedale stony loam, 30 to 50 percent slopes | 11K | Well drained | D | Very limited | Very limited |
| McQuarrie stony loam, 30 to 50 percent slopes | 10K | Well drained | D | Very limited | Very limited |
| Fluvaquents | 8K | Very poorly drained | D | Very limited | Very limited |
| McQuarrie sandy loam, 5 to 30 percent slopes | 7K | Well drained | D | Very limited | Very limited |
| Ladd sandy loam, 2 to 9 percent slopes | 7K | Well drained | C | Somewhat limited | Very limited |
| Delma cobbly loam, 9 to 30 percent slopes | 7K | Well drained | D | Very limited | Very limited |
| Casuse sandy loam, 2 to 9 percent slopes | 7K | Well drained | D | Very limited | Very limited |
| Deven very stony clay loam, 30 to 50 percent slopes | 7K | Well drained | D | Very limited | Very limited |
| Thoms-Exel complex | 7K | Well drained | D | Very limited | Very limited |
| Karcal very cobbly clay, 0 to 9 percent slopes | 6K | Well drained | D | Very limited | Very limited |
What This Means
Building & Foundations
About 78% 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 80% 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.