Boulder County Area, Colorado
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 Boulder County Area, Colorado.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Juget-Rock outcrop complex, 9 to 55 percent slopes | 21K | Somewhat excessively drained | D | Very limited | Very limited |
| Nunn clay loam, 1 to 3 percent slopes | 16K | Well drained | C | Somewhat limited | Very limited |
| Fern Cliff-Allens Park-Rock outcrop complex, 15 to 60 percent slopes | 13K | Well drained | A | Very limited | Very limited |
| Ascalon sandy loam, 0 to 3 percent slopes | 12K | Well drained | B | Not limited | Somewhat limited |
| Lefthand, very stony-Littlejames, extremely bouldery complex, 20 to 55 percent slopes | 12K | Somewhat excessively drained | B | Very limited | Very limited |
| Nederland very cobbly sandy loam, 1 to 12 percent slopes | 11K | Well drained | B | Very limited | Very limited |
| Niwot loam, 0 to 1 percent slopes | 9K | Poorly drained | C/D | Very limited | Very limited |
| Terrace escarpments | 8K | Excessively drained | A | Very limited | Very limited |
| Water | 8K | Not rated | Not rated | ||
| Nunn clay loam, 0 to 1 percent slopes | 7K | Well drained | C | Somewhat limited | Very limited |
| Rock outcrop | 7K | D | Not rated | Not rated | |
| Boulder, bouldery-Sylvandale complex, 9 to 45 percent slopes | 6K | Well drained | C | Very limited | Very limited |
| Valmont clay loam, 1 to 3 percent slopes | 6K | Well drained | C | Not limited | Very limited |
| Valmont cobbly clay loam, 1 to 5 percent slopes | 6K | Well drained | C | Not limited | Not limited |
| Samsil-Shingle complex, 5 to 25 percent slopes | 6K | Well drained | D | Very limited | Very limited |
| Carterlake, stony-Rock outcrop complex, 15 to 55 percent slopes | 5K | Well drained | D | Very limited | Very limited |
| Nunn clay loam, 3 to 5 percent slopes | 5K | Well drained | C | Somewhat limited | Very limited |
| Baller, bouldery-Rabbitmountain complex, 9 to 35 percent slopes | 5K | Well drained | D | Very limited | Very limited |
| Heldt clay, 0 to 3 percent slopes | 5K | Well drained | C | Somewhat limited | Very limited |
| Ascalon sandy loam, 3 to 5 percent slopes | 5K | Well drained | B | Not limited | Somewhat limited |
What This Means
Building & Foundations
About 55% 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 78% 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.