Helena National Forest Area, Montana
The dominant drainage class is and the dominant hydrologic group is B (moderate infiltration). 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 Helena National Forest Area, Montana.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Typic Ustochrepts, steep | 68K | B | Very limited | Very limited | |
| Typic Cryoboralfs and Mollic Cryoboralfs, steep | 57K | C | Very limited | Very limited | |
| Typic Cryoboralfs-Typic Cryochrepts complex, mountain slopes | 50K | B | Very limited | Very limited | |
| Typic Haploborolls-Typic Eutroboralfs complex, mountain slopes | 30K | C | Very limited | Very limited | |
| Typic Cryoboralfs, bouldery, granitic substratum | 26K | B | Very limited | Very limited | |
| Lithic Cryoborolls-Argic Cryoborolls complex, mountain slopes | 24K | D | Very limited | Very limited | |
| Typic Cryochrepts-Typic Cryoboralfs complex, mountain slopes | 21K | C | Very limited | Very limited | |
| Typic Cryochrepts-Rubble land complex, basaltic substratum, cold | 21K | A | Very limited | Very limited | |
| Typic Cryochrepts-Typic Cryoboralfs complex, glaciated mountain slopes | 20K | A | Very limited | Very limited | |
| Typic Cryoboralfs and Mollic Cryoboralfs, basaltic substratum | 20K | C | Very limited | Very limited | |
| Typic Cryochrepts, bouldery, granitic substratum, steep | 20K | B | Very limited | Very limited | |
| Typic Cryochrepts, channery-Typic Cryochrepts, extremely cobbly complex, mountain ridges | 19K | A | Very limited | Very limited | |
| Typic Ustochrepts-Rock outcrop complex, limestone substratum | 18K | B | Very limited | Very limited | |
| Typic Cryochrepts, basaltic substratum, steep | 17K | B | Very limited | Very limited | |
| Typic Cryochrepts, steep | 17K | B | Very limited | Very limited | |
| Lithic Ustochrepts, mountain slopes | 17K | D | Very limited | Very limited | |
| Calcic Cryoborolls-Mollic Cryoboralfs complex, limestone substratum | 17K | C | Very limited | Very limited | |
| Cirqueland | 17K | Not rated | Not rated | ||
| Typic Ustochrepts-Rock outcrop complex, glacial trough walls | 16K | A | Very limited | Very limited | |
| Typic Ustochrepts-Mollic Eutroboralfs complex, bouldery, granitic substratum | 15K | B | Very limited | Very limited |
What This Means
Building & Foundations
About 96% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes. A geotechnical assessment is recommended before building.
Septic Systems
About 96% of soils are rated "very limited" for septic absorption fields. 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.