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Cross Mine(M1977-410) Technical Revision No. 5 <br /> prior to discharge into Coon Track Creek. The Idaho Tunnel water meets NPDES discharge requirement <br /> and reports to Pond #2 without treatment. However, the discharge from the Cross Mine workings <br /> requires the daily addition of lime (5 — 15 lbs./day) to reduce zinc concentrations prior to reporting to <br /> Pond#2 so that discharge standards are met after mixing with water from the Idaho Tunnel. As a result <br /> of the reduced flow from the Idaho Tunnel, discharge of water from Pond #2 exceeded the allowable <br /> levels of cadmium and zinc from December 21,2019 to January 23,2020. The flow of the discharge from <br /> the Caribou Mine to Pond#2 was partially re-established on January 29,2020. A new water quality sample <br /> was subsequently collected at the discharge point(see Figure 1)and sent to the laboratory on January 30, <br /> 2020. The laboratory results (Attachment 1) show that the water quality met the permit requirements. <br /> However, by late February 2020 approximately 39 inches of mine water had accumulated behind the <br /> collapse rubble pile,which is acting as a dam to confine water within the tunnel. In order to preclude the <br /> possibility of an uncontrolled blowout and sudden release of the water, The rubble pile was slowly <br /> breached from the top down on February 25, 2020 to let small amounts of water out in an incremental <br /> fashion and it no longer impedes flow from the tunnel. <br /> Farther into the tunnel, approximately 3 feet of mine water is presently pooled behind another rubble <br /> pile roughly 200 feet from the current portal. It is not known how long this rubble pile has existed but it <br /> is believed that this pool of water contains a much larger volume, possibly as much as approximately <br /> 20,000 to 22,000 gallons of mine water(Photograph 4). <br /> zit � <br /> 44. <br /> •*, ' 7714111‘ <br /> [[ ( T' <br /> •• <br /> Photograph 4—Water pooled behind a rubble pile approximately 200 ft into the Idaho Tunnel <br /> 6 <br />