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2016 Recommended Modifications to the West Elk Mine Hydrologic Monitoring Network 38 <br />3.2 Raven Gulch Surface Water Monitoring Sites <br />There are currently two surface water monitoring sites in the Raven Gulch area; Lower Raven <br />Gulch and Upper Raven Gulch (Table 2). <br />3.2.1 Lower Raven Gulch <br />Raven Gulch is a perennial stream that drains the West Flatiron mine panels area and is tributary <br />to the North Fork of the Gunnison River. The Lower Raven Gulch monitoring site was <br />established in 2005 and is located at the mouth of Raven Gulch, near its confluence with the <br />North Fork (Map 1). The site is about 3,000 feet to the north-northeast of B -Seam Panel 18, <br />which was mined in February 2008. <br />Hydrologic monitoring at the Lower Raven Gulch monitoring station began in 2005. It should <br />be noted that CDRMS (2005) approved baseline monitoring for the Raven Gulch surface water <br />sites to be the same as routine monitoring (3 times per year and one low flow water quality <br />sample). Flow in Lower Raven Gulch is perennial, but diminishes significantly in the late <br />summer months. A time -series flow graph for Lower Raven Gulch is shown on Figure 30. <br />rtgure su. rtow to i ower maven tjutcn <br />Lower Raven Gulch <br />250 <br />zoo <br />3 <br />r- <br />E <br />^ 150 <br />^ <br />4 C 4 4 4 <br />c c c c c <br />Date <br />Time -series water quality data from Lower Raven Gulch do not indicate any adverse trends in <br />water quality. The baseline laboratory water quality values are very limited (recorded in May and <br />June 2005 only) (HydroGeo, 2016b). The laboratory ECs for this stream for the period of record <br />are variable, ranging from 145 to 322 µmhos/cm and averaging 198 µmhos/cm. In comparison, <br />the baseline laboratory EC values range from 145 to 170 µmhos/cm. TDS values for this stream <br />for the period of record are variable, ranging from 70 to 190 mg/L, and averaging 132 mg/L, <br />compared to baseline values ranging from 110 to 120 mg/L. The baseline field water quality <br />data for pH for this site are also limited (recorded in May, June and September 2005 only) <br />(HydroGeo, 2016b). The field pH values for this stream over the period of record are relatively <br />steady, ranging from 7.27 to 8.87 s.u., and averaging 8.29 s.u., compared to baseline field pH <br />August 2016 HydroGeo, Inc. <br />