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Section 3 Physical Environment of the Major River Basins segments in need of TMDLs, and those of concern with inadequate quantity or quality of data to assess impairment, are compiled into Regulation 93 and Regulation 94 lists, respectively. Figure 3-7 identifies the locations of surface waters in the Arkansas Basin that are listed on Colorado's 2002 303(d) list. Stream segments proposed for listing on the 303(d) list and the Monitoring and Evaluation list are described in Colorado WQCC Regulations 93 and 94. The state's 2004 proposed 303(d) list incorporates several additions from the 2002 list. It includes numerous stream segments of the mainstem and its tributaries listed for selenium, primarily in the middle and lower (eastern) portions of the basin. Proposed 2004 higher-priority listings in the basin are primarily associated with metals constituents in the upper basin. Groundwater in the upper Arkansas River Valley is generally suitable for use as potable water supply with a few exceptions caused by acid rock drainage and septic system effluent contamination. Groundwater in the lower Arkansas Basin alluvial aquifer is considered to be of fairly good quality (CGS 2003). However, similar to the river, the groundwater increases in salinity with distance downstream. Groundwater or surface water with TDS concentrations greater than 2,000 ppm is generally considered to be unsuitable for irrigation without further treatment (CDPHE 2002). 3.2.9 Arkansas Basin Areas of Environmental Concern, Special Attention Areas, and Threatened and Endangered Species A major concern for the Upper Arkansas River Valley is the acid-mine drainage from many of the historic mining locations surrounding the headwaters of the Arkansas River (CGS 2003). One of these sites is the California Gulch Superfund site near Leadville, Colorado. Large volumes of mining waste were left at the site due to the intense historical mining activities, contaminating soils and surface water runoff (EPA 2003). In 1990, the Yak Tunnel Treatment Plant was built, which greatly improved water quality, but sources still affect and degrade the soil and water quality in the California Gulch (EPA 2003). In addition to impaired areas, threatened and endangered species and areas of high environmental or recreational value require special attention when evaluating water supply projects and use patterns in the Arkansas Basin. Appendix C presents a complete list of federal and/or state listed threatened and endangered fish and other species in the Arkansas Basin. As discussed in Section 2.4, the CDOW awards the Gold Medal designation to waters that have high-quality aquatic habitat, a high percentage of trout 14 inches or longer, and the potential for trophy trout fishing and angling success. There are no Gold Medal designated waters in the Arkansas Basin. The Arkansas River has become one of the state's largest water-based recreational attractions. Areas of high recreational value in the basin, including the Arkansas headwaters, whitewater reaches on the Arkansas River, Lake Pueblo State Park, and Buffalo and Collegiate Peaks Wilderness areas, are discussed in the environmental report provided in Section 6. Figure 3-8 shows the locations of some of the basin's key aquatic species habitat. 3.2.10 Arkansas Basin Energy and Minera Resources The headwaters of the Arkansas have been impaired due to intense mining of molybdenum, gold, and silver. Waters that have been affected include most of the drainages in the Leadville area, Lake Creek, and Chalk Creek (Water Colorado 2003, CDPHE 2000). Colorado Springs Utilities operates three hydroelectric power plants in the basin capable of producing a total of 33 megawatts of electricity (Colorado Springs Utilities 2003). Xcel Energy operates a thermal-electric power generating facility in Pueblo. ~ $~olevi~ice Wo~e' $upplY Initia~ive ~~ S:\REPORT\WORD PROCESSING\REPORT\S3 11-8-04-WITH PAGE BREAKS.DOC 3-5