Modoc County, California, Alturas Area
The most common soil here is Deven, on about 7% of the land: a loam, a balanced mix that crumbles in your hand. Karcal and Delma come next.
About 69% of the land drains well, and 11% stays wet for long stretches; groundwater comes within two feet of the surface under 2% of it.
USDA rates 85% of the land very limited for a standard septic drain field, and 77% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 9% of the land floods occasionally or more, and bedrock lies within 40 inches under 53% 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 Modoc County, California, Alturas Area, 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 D (very slow infiltration, high 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 Modoc County, California, Alturas Area. 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 |
|---|---|---|---|---|---|
| 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 |
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 77% 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 85% 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.