Callahan County, Texas
The most common soil here is Throck, on about 16% of the land: a clay, sticky when wet and rock-hard when dry. Pedernales and Speck come next.
About 91% of the land drains well.
USDA rates 99% of the land very limited for a standard septic drain field, and 66% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 7% of the land floods occasionally or more, and bedrock lies within 40 inches under 55% 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 Callahan County, Texas, 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 Callahan County, Texas. 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 |
|---|---|---|---|---|---|
| Throck-Speck association, undulating | 64K | Well drained | D | Very limited | Very limited |
| Throck-Owens-Lueders association, hilly | 50K | Well drained | D | Very limited | Very limited |
| Lueders-Speck association, undulating | 49K | Well drained | D | Very limited | Very limited |
| Throck-Callahan-Owens association, undulating | 33K | Well drained | D | Very limited | Very limited |
| Chaney loamy fine sand, 0 to 3 percent slopes | 33K | Moderately well drained | C | Somewhat limited | Very limited |
| Leeray clay, 1 to 3 percent slopes | 30K | Well drained | D | Very limited | Very limited |
| Pedernales fine sandy loam, 1 to 3 percent slopes | 25K | Well drained | C | Somewhat limited | Very limited |
| Frio-Gageby association, frequently flooded | 25K | Well drained | C | Very limited | Very limited |
| Speck-Throck association, gently undulating | 24K | Well drained | D | Very limited | Very limited |
| Sagerton loam, 1 to 3 percent slopes | 22K | Well drained | C | Somewhat limited | Very limited |
| Cisco-Hext-Pedernales association, undulating | 20K | Well drained | C | Somewhat limited | Very limited |
| Pedernales fine sandy loam, 1 to 5 percent slopes, moderately eroded | 14K | Well drained | C | Somewhat limited | Very limited |
| Rowden clay loam, 0 to 3 percent slopes | 13K | Well drained | D | Very limited | Very limited |
| Hext-Oplin-Brackett association, hilly | 13K | Well drained | D | Very limited | Very limited |
| Pedernales loamy fine sand, 1 to 5 percent slopes | 12K | Well drained | C | Somewhat limited | Very limited |
| Cisco-Hext-Pedernales complex, 1 to 5 percent slopes | 12K | Well drained | C | Somewhat limited | Very limited |
| Nukrum clay, 1 to 3 percent slopes | 12K | Well drained | C | Very limited | Very limited |
| Demona-Patilo complex, 1 to 5 percent slopes | 11K | Moderately well drained | A | Very limited | Very limited |
| Owens-Throck association, hilly | 10K | Well drained | D | Very limited | Very limited |
| Frio clay loam, occasionally flooded | 9K | Well drained | C | 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 66% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 99% 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
Drainage is generally favorable for gardening. Adding compost and mulch will improve fertility and water retention. Test your soil's pH before planting — most vegetables prefer 6.0-7.0.