Purcell Mountains, Pah River Flats and Koyukuk River Area, Alaska
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 Purcell Mountains, Pah River Flats and Koyukuk River Area, Alaska.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Interior Alaska Highlands-Boreal Upland and Subalpine-Rounded Mountains | 763K | Well drained | B | Not limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Upland and Lowland-Glaciated Valleys | 697K | Poorly drained | D | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Upland-Hills and Plains | 419K | Poorly drained | D | Very limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Alpine-Rounded Mountains, Acid | 362K | Well drained | C | Very limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Alpine-Glaciated Valleys | 288K | Poorly drained | D | Very limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Upland and Alpine-Rounded Mountains | 268K | Well drained | B | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Upland and Alpine-Rugged Mountains | 232K | Well drained | A | Very limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Alpine-Rounded Mountains | 210K | Well drained | B | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Upland-Loess Plains and Peat Plateaus | 118K | Poorly drained | C/D | Very limited | Very limited |
| Northern Seward Peninsula-Selawik Lowlands-Arctic Upland-Plains, Gravelly | 95K | Very poorly drained | D | Very limited | Very limited |
| Western Brooks Range Mountains, Foothills, and Valleys-Boreal Upland and Lowland-Glaciated Valleys | 95K | Poorly drained | D | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Alpine and Upland-Rugged Mountains | 88K | Well drained | B | Very limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Lowland-Flood Plains and Terraces | 83K | Poorly drained | D | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Upland-Hills and Plains, Acid | 70K | Well drained | D | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Lowland-Flood Plains and Terraces | 66K | Poorly drained | D | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Upland-Rounded Mountains, Acid | 41K | Well drained | A | Very limited | Very limited |
| Upper Kobuk and Koyukuk Hills and Valleys-Boreal Alpine-Rugged Mountains | 40K | Well drained | B | Very limited | Very limited |
| Interior Alaska Highlands-Boreal Upland and Lowland-Mountain Valleys | 31K | Poorly drained | D | Very limited | Very limited |
| Interior Alaska Lowlands-Boreal Lowland-Fan Terraces and Stream Terraces | 22K | Poorly drained | D | Very limited | Very limited |
| Interior Alaska Lowlands-Boreal Lowland-Flood Plains and Terraces | 22K | Poorly drained | B | Very limited | Very limited |
What This Means
Building & Foundations
About 80% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 100% 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.