Ketchikan Area, Alaska
The most common soil here is McGilvery, on about 5% of the land: a very gravelly silt loam, smooth, like flour. E20-maritime forest-loamy colluvial slopes, shallow and St. Nicholas come next.
About 14% of the land drains well, and 46% stays wet for long stretches; groundwater comes within two feet of the surface under 62% of it.
USDA rates 80% of the land very limited for a standard septic drain field, and 80% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 11% of the land floods occasionally or more, and bedrock lies within 40 inches under 63% 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 Ketchikan Area, Alaska, 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 Very poorly drained and the dominant hydrologic group is A/D (varies with drainage). The most common soil order is Spodosols — acidic forest soils with a distinctive leached layer, common under conifers. 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 Ketchikan Area, Alaska. 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 |
|---|---|---|---|---|---|
| Alexander Archipelago-Gulf of Alaska Coast-Maritime Upland and Subalpine-Rounded Mountains | 837K | Very poorly drained | A/D | Very limited | Very limited |
| Salt Water | 761K | Not rated | Not rated | ||
| Alexander Archipelago-Gulf of Alaska Coast-Maritime Subalpine and Alpine-Rounded Mountains | 486K | Very limited | Very limited | ||
| Alexander Archipelago-Gulf of Alaska Coast-Maritime Upland-Glaciated Hills and Plains | 205K | Very poorly drained | A/D | Very limited | Very limited |
| Southern Alaska Coastal Mountains-Maritime Subalpine and Alpine-Mountains | 175K | Very limited | Very limited | ||
| Southern Alaska Coastal Mountains-Maritime Upland-Mountains | 146K | Moderately well drained | B/D | Very limited | Very limited |
| Southern Alaska Coastal Mountains-Maritime Alpine-Barren Mountains | 121K | Not rated | Not rated | ||
| Ulloa-Sarkar complex, 5 to 75 percent slopes | 121K | Well drained | B | Very limited | Very limited |
| Kina-Maybeso association, 5 to 35 percent slopes | 112K | Very poorly drained | D | Very limited | Very limited |
| Rock outcrop | 88K | Not rated | Not rated | ||
| Kina peat, 0 to 35 percent slopes | 81K | Very poorly drained | D | Very limited | Very limited |
| Water | 80K | Not rated | Not rated | ||
| Karta-Tolstoi complex, 35 to 75 percent slopes | 71K | Moderately well drained | D | Very limited | Very limited |
| Alexander Archipelago-Gulf of Alaska Coast-Maritime Water, Saline | 71K | Very limited | Very limited | ||
| Tolstoi very fine sandy loam, 5 to 100 percent slopes | 58K | Well drained | D | Very limited | Very limited |
| Rock outcrop and Ice | 58K | Not rated | Not rated | ||
| McGilvery peat, 60 to 100 percent slopes | 57K | Well drained | D | Very limited | Very limited |
| Hydaburg-Sunnyhay association, 5 to 75 percent slopes | 56K | Very poorly drained | D | Very limited | Very limited |
| Shakan-McGilvery association, 60 to 150 percent slopes | 53K | Well drained | C | Very limited | Very limited |
| Tonowek and Tuxekan soils, 0 to 15 percent slopes | 51K | Well drained | B | 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 80% 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 80% of soils are rated "very limited" for septic absorption fields. Poorly drained soils can't absorb septic effluent effectively. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Many soils hold water for extended periods. Raised beds are highly recommended to improve drainage for vegetables. Well-adapted native plants and water-loving species will do best in natural conditions.