SBCT Final EIS - Govsupport.us

Chapter 3 ⎯ Affected EnvironmentSoil monitoring is conducted through the Range and Training Land Assessment Program, which isthe monitoring component of ITAM. Annual Range and Training Land Assessment reports detail thelevels of current and past disturbance and land condition resulting from military training and recreationaluse on FRA. Soil resources management on FRA is achieved through prevention activities andactual restoration of disturbed areas by implementing BMPs in agreement with industry standard installationstorm water prevention techniques. Disturbed areas are restored by both erosion control andstreambank stabilization activities, which control installation sources of dust, runoff, silt, and erosiondebris to prevent damage to land, water, and air resources; equipment; and facilities (including thoseon adjacent properties). Relevant BMPs used at FRA are detailed in the USAGAK INRMP(USARAK 2007) and in the ITAM Five-Year Management Plan.Chemical Constituents in SoilsThe Army has identified three sources of contamination on FRA, but they do not represent all knownor suspected sources of contamination at the installation. The sources are the Eagle River Flats (ERF)ordinance impact area, the Pole Line Road Disposal Area (PRDA), and the Roosevelt Road TransmitterSite (RRTS). The ERF ordinance testing area, located in the northwestern corner of the FRA, consistsof approximately 2,500 acres of wetlands associated with the Eagle River Delta. Soil and surfacewater samples collected in 1989 and 1991 showed elevated levels of heavy metals, explosive compounds,and white phosphorous. Concentrations of the heavy metals copper, cadmium, nickel, zinc,and mercury in surface water samples exceeded the National Ambient Water Quality Criteria (GlobalSecurity 2007). A site investigation conducted in 1990 by the Army in the PRDA, located southwestof the Eagle River, identified volatile organic compounds (VOCs) in soil and shallow groundwater asa result of a hazardous substances disposal area used in the 1950s (Global Security 2007). The RRTSis a former bombproof underground bunker and associated support facilities constructed in the 1940s.The Army conducted sampling at the RRTS in May and June 1990 as part of a site investigation follow-up.Analytical results from the follow-up investigation revealed elevated concentrations of PCBs,VOCs, SVOCs, dioxins, asbestos, and inorganic elements throughout the site (Global Security 2007).Geologic Hazards and SeismicityFRA is seismically active and has experienced at least nine major earthquakes in the last 85 years, includingthe largest earthquake in U.S. history. Two faults border Anchorage: the Border Ranges Faultand the Bruin Bay-Castle Mountain Fault. The Border Ranges Fault bisects FRA, running parallel tothe base of the Chugach Mountains. The Castle Mountain fault zone is located between Anchorageand the Alaska Range. The Castle Mountain Fault is a recently active, high-angle fault that runsnortheast-to-southwest for more than 100 miles. Three of the 10 strongest earthquakes recorded in recenthistory occurred in Alaska. The earthquake of 1964 was the result of the northwestward motionof the Pacific Plate (compression) over a period of tens to hundreds of years that was relieved by thesudden southeastward motion of portions of coastal Alaska as they moved back over the Pacific Plate.As a result, the Pacific Plate moved under the North American Plate by about 30 feet on average. Theepicenter of the earthquake was about 75 miles east of Anchorage, but the effects were widespread.The area has also experienced tremors and ash fall from volcanic eruptions of Mount Spurr, MountSt. Augustine, and Mount Redoubt since 1954.3.2.1.2 Donnelly Training AreaPhysiography and GeologyThe DTA is located within the Yukon-Tanana terrain of the Yukon physiographic province. TheYukon-Tanana terrain is the largest of the terrains in the Yukon, extending from interior British Columbiainto Eastern Alaska (Hart 2002). DTA lies in the northern foothills of the Alaska Range andFebruary 2008 3–97 2/25th SBCT Final EIS