2008-03-13_PERMIT FILE - C1992081 (8)

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In response to these requirements as they relate to existing conditions, a network of monitoring stations was installed to ' ~ describe pre-mining conditions.,. .The location o£ the sites is shown on Figure 1. 1.4 Regional Description The project -region is in the low mountains and plains between the Yampa River and the Williams Fork of the Yampa River, as seen on Figure 1. The proposed Hayden Gulcfi Mine is situated at the head of Hayden Gulch, at the crest of the divide between the drainages, and the transportation corridor is to the north and east (Figure 2). 2.0 HYDROLOGY 2.1 Drainages The project area drainages are shown on Figure 1. Drainage is to the north and south from the crest of the divide about 7500 ft. Hayden Gulch and Dowden Gulch ,join the Williams Fork at about 6800 ft after flowing approximately 4 mi, and Sage Creek and Dry Creek join the Yampa River at about 6400 ft after flowing approximately 11 mi. The mining area is within the southern drainage to the Williams Fork, at the headwater:. of Hayden Gulch and Dowden Gulch, both ephemeral streams. The monitoring network consisted of two gauging stations on each drainage. Four monitoring stations were installed on Hayden and Dowden gulches (two on each) downstream of the mine site, and four were installed in the vicinity of the transportation corridor, one upstream and one downstream on Sage Creek, and an upper and lower station on Dry Creek. Two stations consisting of a crest stage gage and single staff;e sediment sampler arrangement, one on Hayden Gulch and one on Dowden Gulch, were installed to monitor close to the mine (tliax is, the drainage immediately below it). Since at the time the flow regime of the stream was unknown, and similarly the amo~~nt of flow that would occur, two grab sample stations were located near the mouth of each stream in case the other sites did .not have flow, The four stations on Sage and Dry creeks were placed so that one station on each drainage would sample the quality of water from the mountainous pastures and one would monitor the water from the plains cultivated land. The stations were also placed to monitor the effect of the different geological features of • L J