Integrated Training Area Management EA and Final FNSI

3.1 SOIL RESOURCES3.1.1 Affected EnvironmentSoil is a dynamic medium made of mineral and biological matter, organic material, water, and air. Soilsare produced by the continual interaction of five soil-forming factors: climate, vegetation, organisms,parent material, and topography. Climate is the most important soil-forming factor for Alaska.Differences in soil composition and formation result in soils of differing properties, which are alsocontinually altered by natural processes. Soil properties ultimately determine the natural and humanactivities that can take place in a given area.Permafrost is defined as soil, silt, and rock that remain frozen year-round. Though a thin layer may thawduring summer months, the majority of permafrost remains frozen until the local climate changes or itmelts due to disturbance of the insulating peat and vegetation above it. Permafrost is a major factorinfluencing the distribution of vegetation and human activities in Alaska. It typically exists in multiplelayers of varying thickness ranging from less than one foot to more than 150 feet. Permafrost hasimportant influences on soil processes including cryoturbation (the mixing of soil due to freezing andthawing which results in contorted and broken horizons), rapid water runoff, ground subsidence andrestriction of drainage. Thermokarst is the process and range of features resulting from irregularsubsidence of permafrost. These features include hummocks and mounds, water-filled depressions,flooded forests, and mudflows on sloping ground.More information can be found in the Transformation of U.S. Army Alaska Final Environmental ImpactStatement (USARAK 2004).Fort RichardsonSoil maps utilizing the Unified Soil Classification System describe a wide variety of engineering soiltypes on Fort Richardson. Glacial moraines, outwash, tidal flats, and peat bogs all provide a wide varietyof parent material for soils at the installation (USARAK 2004). The soils are shallow, immature, anddeficient in primary plant nutrients and water retention ability, making them a primary limiting factor forvegetative growth during dry periods. In depressions and saturated areas, such as wetlands, surfacehorizons may be covered with peat (USARAK 2002e). A soil survey of the Anchorage area conducted bythe Natural Resources Conservation Service identified two distinct climatic zones along with theirassociated soil types (Moore 2002) – the lowlands surrounding Anchorage (including Fort Richardson)and the adjacent Chugach Mountains.Permafrost is found in less than 1% of Fort Richardson. It occurs primarily in patches of forested bogsnear Muldoon Road, with some permafrost persisting at high elevations. Although thermokarst hasoccurred in the forested bog areas, the effects of thermokarst have been negligible (