SBCT Final EIS - Govsupport.us

Chapter 3 ⎯ Affected Environmentfloods can occur intermittently during high rainfall-runoff events; however, flooding is rare and notsevere (USACE 2007a).The downrange area includes Rock Creek and Little Fountain Creek, intermittent streams that convergeand drain into Fountain Creek approximately 10 miles east of FTC. Turkey Creek flowsthrough the center of the installation and enters the Arkansas River to the south. Red Creek flowsthrough the western portion of the installation and enters Beaver Creek to the south. In general, thesites drain to the south through Beaver Creek and Turkey Creek, eventually emptying into the ArkansasRiver south of FTC. Floodplains in the southern part of the installation have not been delineated(USACE 2007a).Surface Water Quality and UseTeller Reservoir, the largest downrange water body, is listed as an impaired water body on Colorado’sSection 303(d) list. The impairment has resulted in a fish consumption advisory that has been imposedbecause of a biological accumulation of mercury in soil, terrestrial plants, and fish tissues. FTChas mandated a catch-and-release fishing program in this body of water to reduce the potential for apublic health issue. Although the Teller Reservoir has a capacity of approximately 2,600 acre-feet, itfrequently contains no water and, in fact, has been dry since 2002 (USACE 2007a).Although the quality of the surface water is good, it is not a source of domestic water at FTC (DE-CAM 2002a). Water from most streams and surficial aquifers on the western portion of the installationis suitable for irrigation and would be potable. Surface water that flows eastward across FTC accumulatessediments (i.e., dissolved and suspended solids) that are then concentrated through evaporation.Water from the eastern portion of FTC, however, is still suitable for irrigation with propermanagement practices. FTC retains 34 surface water rights as specified by the Colorado Division ofWater Resources. Of these surface water rights, 20 are surface diversion ditches and 14 are reservoirstorage rights (DECAM 2002a).Groundwater OccurrenceGroundwater at FTC exists in both alluvial and bedrock aquifers. Alluvial aquifers are formed fromunconsolidated deposits of stream alluvium and residuum derived from Pierre Shale that are moderatelypermeable. The alluvial aquifers can provide well yields from 10 to more than 100 gallons perminute (gpm) (Leonard 1984).In much of the Arkansas River Basin, hydraulic heads are lower in the deep bedrock aquifers thanthose in the shallow formations, which indicate that deep bedrock aquifers are not in communicationwith the shallow formations. The primary bedrock aquifer at FTC is the Dakota-Purgatoire aquifer,which can yield 10 gpm, although local fracturing can increase permeability and yield more than200 gpm. Precipitation and stream flow infiltration recharge the bedrock aquifers (Leonard 1984).Groundwater Quality and UseHistorically, the quality of groundwater on FTC has been good. Nitrates, however, have recently beendetected in the groundwater at multiple locations higher than the regulatory standard of 10 mg/L. Currently,FTC and the Colorado Department of Public Health and the Environment (CDPHE) are collaboratingto evaluate the possibility that elevated concentrations of nitrates may be naturally occurringas a result of groundwater coming in direct contact with the shale bedrock (DECAM 2005c).The Army has 16 subsurface water rights, including nine wells for domestic or military use, at FTC.Seven wells classified as future wells are planned for installation when determined to be neededFebruary 2008 3–144 2/25th SBCT Final EIS