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2001 Hydra(ogic Report <br />Vegetation varies from riparian and blue grama complexes in the valley bottoms to pinion juniper, <br />oak brush, and pine cover on the side slopes. Vegetation cover ranges from 100 percent in the valley <br />bottoms to none on the steeper side slope rock outcrop areas. <br />The nearest weather station to the mine site is located at the Trinidad Airport (elevation 5,746 feet) <br />approximately 30 miles east. Over a recording period from 1961 to 1990, total annual precipitation <br />averaged 13.5 inches. The majority of this precipitation (65%) occurs from May to September. July <br />usually has the most rainfall. The mean annual temperature is 51.8°F. January is the coldest month <br />with a mean temperature of 32.9° F, and July is the warmest month, showing a mean of 60.2° F <br />(Owenby and Ezell, 1992). The project area is approximately 1650 feet higher in elevation than the <br />Trinidad Airport and can be considered to have 5° F lower mean temperatures and higher average <br />precipitation. <br />Surface water availability is directly related to precipitation received in the drainage. The climate <br />summary, as described in the mine permit document, projects a mean annual precipitation near the <br />mine of 16.92 inches. <br />The United States Geological Survey (USGS) monitored the flow of the Middle Fork of the <br />Purgatoire at Stonewall (07124050), approximately four miles upstream from the New Elk Mine, <br />from May 1978 to September 1981. The Purgatoire River at Madrid (07124200), approximately 15 <br />miles downstream of the Golden Eagle Mine, has been monitored since 1972. The size of the <br />drainage area above the Stonewall station is 52.1 square miles (miZ). There are some diversions for <br />imgation above the station. Recorded discharges during the three-and-a-half year period ranged <br />from 2.8 cfs to 522 cfs (USGS, Water Resources Division, 1982). The size of the drainage area <br />above the Madrid station is 505 miZ. There are diversions for irrigation for about 6,000 acres <br />upstream of the Madrid station. The average annual discharge between ] 972 and 1995 at Madrid <br />was 71.4 cfs and the average annual runoff was 51,740 ac ft (Crowfoot et al, 1995). The annual <br />runoff in the Purgatoire is dominated by snowmelt, with peak flows occurring in May and June. <br />Summer and fall thunderstorms generally produce smaller peaks of short duration. <br />1.2 MONITORING PROGRAM <br />Monitoring programs have been conducted since February 1984 to assess the effects of past, present, <br />and future mining operations on surface and groundwater quality and quantity. These programs <br />provide information to Basin and to regulatory agencies such as the Colorado Division of Minerals <br />and Geology (CDMG) and the Colorado Department of Public Health and Environment (CDPHE). <br />CDMG programs are designed to monitor past and present, and to anticipate fixture, effects ofmining <br />activities on the hydrologic regime of the area. One aspect of the CDPHE program addresses water <br />quality as required by the National Pollution Discharge Elimination System (NPDES) permit <br />program. These stations are shown in Map 8, Regional Hydrology (see Permit Document). <br />The monitoring program has undergone several revisions. The revisions have resulted from data <br />review by Basin, CDMG, and CDPHE. The monitoring program of springs and seeps is presented <br />2000AHR dui-RPT(191)/April /9. 20!12 4 <br />