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<br />London Mountain Clean Up <br />July 2025 <br /> <br /> <br />G2-1 <br />Appendix G-2 Mosquito Creek Historical <br />Water Quality Data Summary <br /> <br />1. Regulatory Context <br />303(d) Listing Documentation <br />Mosquito Creek is listed on Colorado's 303(d) list of impaired waters for: <br />• Zinc (Zn) <br />• Lead (Pb) <br />• Cadmium (Cd) <br />Water Quality Classifications <br />• Designation: Cold water aquatic habitat Class 1 <br />• Uses: Aquatic life protection, wildlife watering <br />2. Data Sources and Station Information <br />USGS Station 06693800 - Mosquito Creek Near Alma, CO <br />• Location: 39.2699896°N, -106.0511297°W (NAD83) <br />• Elevation: 10,220 feet (±10 feet accuracy) <br />• Data Period: 1998 - Present <br />• Agency: U.S. Geological Survey - Colorado Water Science Center <br />• Station Type: Stream gauging and water quality monitoring <br />• Drainage Area: 16.2 square miles <br />• Hydrologic Unit Code: 10190001 (South Platte River basin) <br />• Site Access: https://waterdata.usgs.gov/monitoring-location/06693800/ <br />CDPHE Station 21COL001_WQX-5988A5 - Mosquito Creek D/S N. London <br />Mine <br />• Location: 39.2842170000°N, -106.1418610000°W <br />• Agency: Colorado Department of Public Health & Environment-WQCD <br />• Station Type: Water quality monitoring (downstream of North London Mine) <br />• Data Period: 1998-1999 (3 sampling events) <br />• Sampling Dates: September 9, 1998; June 16, 1999; September 14, 1999