SBCT Final EIS - Govsupport.us

Chapter 3 ⎯ Affected EnvironmentSurface Water QualityThe waters on FRA are protected by freshwater use classes (A), (B), and (C) as assigned by the Stateof Alaska. These include Class (A) Water supply; (B) Water recreation; and (C) Growth and propagationof fish, shellfish, other aquatic life, and wildlife. If any exceedances of the water quality standardsare found, the state designates the water body as “water quality limited.”Two stream segments on FRA have been listed as water quality limited by the Alaska Department ofEnvironmental Conservation (ADEC) (ADEC 1996). Eagle River Flats was listed as a Tier II waterbody due to white phosphorous contamination, and a comprehensive water quality assessment to determinethe best methods for restoration and recovery has been implemented. Contamination was determinedto be the result of prior military activities; therefore, the chemical is no longer used byUSARAK. Remediation activities began in 1999 and are ongoing. Upstream of the FRA boundary,the Eagle River was found to be typical of a pristine glacial-fed stream in Alaska (USARAK 2004).Ship Creek is listed as a Tier I water body from the Glenn Highway Bridge down to its mouth, and itis currently being assessed to determine the degree to which contaminants exceed water quality standards(ADEC 1998). The Water Quality Assessment of Ship Creek in 1996 prepared by ADEC determinedthat fecal coliform bacteria, petroleum products, and contaminants contributed by biologicalcommunity alteration at sites downstream of FRA exceeded water quality standards (ADEC 1996).According to ADEC studies, most of the pollutants entered Ship Creek as nonpoint sources from surfacewater runoff and groundwater downstream of the post, where the watershed is increasingly urbanized.After compiling and reviewing the data, the state concluded that no cumulative or increasingwater quality degradation was occurring in the lower portion of Ship Creek (ADEC 1996). There arecurrently no restoration plans for Ship Creek.Groundwater OccurrenceGroundwater on FRA is located in both an unconfined and a deeper, confined aquifer. Water rechargesthe groundwater on FRA and the Anchorage Bowl in several ways. Along the mountains,groundwater seeps from bedrock fractures into the sediments. In the foothills and lowlands, waterflows from streams into the unconfined aquifer where the water table is above the stream elevation. Inthe lowlands, rain and snowmelt percolate from the surface into the groundwater.The hydrogeology of FRA is complicated due to deposits from multiple glacial advances through theregion. There are multiple confined aquifers and an unconfined aquifer that connect in some places.The low-permeability confining clay layer is present at depths ranging from 30 to 175 feet (Astley etal. 2000). The hydraulic gradient of the unconfined aquifer trends northwesterly, generally followingthe area’s topography surface elevation. The overall trend in flow direction in the confined aquifer isto the northwest except north of Bryant Airfield, where groundwater flow patterns are unclear.Perched groundwater tables are common on FRA and are found at a higher elevation than the mainunconfined groundwater table. Measured groundwater depths on FRA range from near the surfacenear Ship Creek to 200 feet deep near Bryant Airfield (Astley et al. 2000).As mentioned above, Ship Creek loses more than 16 million gallons per day to the unconfined aquiferbetween the reservoir at the base of the mountains and the eastern boundary of Elmendorf Air ForceBase (AFB) (Barnwell et al. 1972). Therefore, the aquifer is greatly influenced by stream discharge(Astley et al. 2000).February 2008 3–101 2/25th SBCT Final EIS