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May 2013 Groundwater POC Memorandum ♦ 1 <br />1.0 INTRODUCTION <br />This Technical Memorandum has been prepared for Climax Molybdenum Company's <br />Henderson Mill Operation (Henderson) to evaluate appropriate locations for point of <br />compliance (POC) groundwater monitor wells downgradient of 1 -Dam and 3 -Dam areas <br />pursuant to the Division of Reclamation, Mining, and Safety (DRMS)- approved Henderson <br />Groundwater Management Plan, formally submitted as Technical Revision 16 (TR -16) to the <br />Henderson Mine and Mill Reclamation Permit No. M- 1977 -342. <br />The Henderson Mine and Mill is an underground mining operation that extracts <br />molybdenite ore from beneath Red Mountain and transports it via conveyor through a 9.6 <br />mile tunnel and 5 mile overland conveyor to the Henderson Mill for crushing, flotation <br />concentration and tailings disposal. This Technical Memorandum focuses on the area <br />surrounding the Henderson Mill tailings storage facility (TSF), located within the Ute Creek <br />Basin of the Williams Fork River Valley, south of Parshall, in Grand County, Colorado. <br />Figure 1 presents a regional map showing the location and geographic setting of the <br />Henderson Mill and TSF area. <br />1.1 BACKGROUND <br />Tailings storage began at the Henderson Mill site in the mid 1970's. Tailings related seep <br />water is currently collected downgradient of the storage area in a collection channel. The <br />collected seep water is then pumped back up to the TSF for re -use. In order to address <br />seepage - impacted groundwater migrating northeast and downgradient from 1 -Dam, an <br />inceptor wellfield, consisting of nine interceptor wells was installed during summer 2002. <br />The water from the interceptor system is combined with the surface seepage waters from the <br />canals and is also pumped back to the TSF. <br />Process water associated with the Henderson Mill may be discharged under the authority of <br />CDPS Wastewater Discharge Permit No. CO- 0000230; however, process water is <br />customarily captured and reused in the milling circuit. Storm water at the Henderson Mill is <br />discharged under the authority of Storm Water General Permit COR- 040079 and may be, in <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 />