2012-10-01_REVISION - M1977306 (23)

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1.0 Introduction The Colorado Department of Reclamation, Mining and Safety's (DRMS) revised regulations for a Designated Mining Operation (DMO) require an Engineered Stormwater Management Plan (ESWMP), commonly referred to as a Drainage Design Plan, to ensure that waste rock and ore stockpiles are protected from design storm events that could potentially erode and transport materials offsite from mining operations. In addition, this plan provides site information and plans to control stormwater runoff from the site, including best management practices (BMPs) to minimize soil disturbances, control erosion and sedimentation during operation and post - reclamation, prevent run -on from offsite areas which could flow across the site, and reduce the potential for pollutants possibly being transported by stormwater runoff. The improvements proposed by this document should be implemented prior to initiating new mining activity for the site given that it has been previously reclaimed and is currently in a stable condition with no apparent signs of significant stormwater erosion. No drainage improvements are required for the mine site in the current condition. 2.0 Approach The goal of the ESWMP is to protect the waste rock stockpile and ore stockpile areas during mining operations and long -term protection of the waste rock area after remediation has been completed. The approach used in this plan is to prevent offsite run -on from entering the active surface mining area by diverting offsite surface flows above the stockpile areas via berms or diversion ditches, and preventing onsite runoff from leaving the site, or containing it long enough to allow sediment to settle in the retention pond. This plan defines the drainage areas above the mining site, delineates the onsite drainage area, determines the amount of runoff from 10 -year, 24 -hour and 100 -year, 24 -hour precipitation events, routes offsite runoff around the site, and contains or controls onsite precipitation and subsequent runoff. Similar to the SWMP regulated by the Colorado Department of Public Health and Environment (CDHPE), this plan also focuses on potential sources of pollution, particularly petroleum compounds and other potentially hazardous materials. Prevention of unintended discharge using secondary containment structures to minimize the potential for spills or leaks from containment structures, reporting requirements to the CDPHE, and BMPs related to storage and containment are important components of a conventional SWMP regulated by CDPHE and incorporated into this plan. 3.0 Location The JD -9 Mine is located in southwestern Colorado approximately 6 miles southeast of the unincorporated town of Bedrock. Access to the mine is from Colorado Hwy 90 on County Road EE21 to the southwest onto Monogram Mesa and entering Bull Canyon where the mine is located on the northern hillside of the canyon. Bull Canyon is an ephemeral drainage that empties to the Dolores River approximately 4 miles southwest of the mine site. The mine has surface facilities found in two general locations. Water treatment facilities for mine water are located above, on Monogram Mesa, and the portal and mine yard are on the ESWMP -1