Laserfiche WebLink
March 2014 Mill MLGW -7 Groundwater Quality Assessment ♦ 1 <br />1.0 INTRODUCTION <br />This Technical Memorandum has been prepared for Climax Molybdenum Company's <br />Henderson Operations (Henderson) to summarize groundwater quality downgradient of the <br />Henderson Mill 1 -Dam Tailing Storage Facility (TSF) located within the Ute Creek Basin of <br />the Williams Fork River Valley, south of Parshall, in Grand County, Colorado. Figure 1 <br />presents a regional map showing the location and geographic setting of the Henderson Mill <br />and TSF area. Monitoring and reporting requirements for the Mill are pursuant to the <br />Division of Reclamation, Mining, and Safety (DRMS)- approved Henderson Groundwater <br />Management Plan (GWMP), formally submitted as Technical Revision 16 (TR -16) to the <br />Henderson Mine and Mill Reclamation Permit No. M- 1977 -342 (Henderson, 2012). <br />1.1 BACKGROUND <br />Groundwater quality downgradient of the 1 -Dam area has historically been, and continues to <br />be, monitored at Point of Compliance (POC) well MLGW -7. The location of MLGW -7 in <br />relation to 1 -Dam is shown on Figure 2. The monitor well is constructed in glacial drift and <br />outwash deposits (Qd) and is representative of shallow groundwater conditions <br />downgradient of 1 -Dam operations. MGLW -7 is screened between 30 and 40 feet below <br />ground surface (bgs) and the depth to water is approximately 22.5 feet bgs (water elev. of <br />8520.51 feet amsl in February 2014). A deeper Qd well, MLGW -15, that was constructed in <br />2012 is paired with MLGW -7 and has been proposed to DRMS as a second POC monitor <br />well (AJAX and Clear Creek, 2013). <br />Beginning in the third quarter 2012, MLGW -7 has been sampled triannually per Henderson's <br />GWMP. A sample collected on July 31, 2013, had a measured pH value of 6.1. and a follow - <br />up sample on August 14, 2013 also reported a pH value of 6.2. Based on these deviations <br />from the numeric protection limit of 6.5 -8.5, Henderson provided verbal notification to <br />DRMS on August 7 and 22, 2013 and written notification (dated September 12, 2013; <br />Henderson 2013b) per Section 5.3 of the GWMP. <br />AJAX Ltd ♦ 28828 Cedar Circle ♦ Evergreen, CO 80439 ♦ (303) 241 -2057 <br />Clear Creek Associates* 6155 E. Indian School Rd. ♦ Scottsdale, AZ 85251 ♦ (480) 659 -7131 <br />