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10/8/2020 Federal Register::National Oil and Hazardous Substance Pollution Contingency Plan Partial Deletion of the California Gulch Superfund . <br /> measuring devices,at key locations in the Yak Tunnel.The weir locations were selected during an initial <br /> inspection of the tunnel;(5)Periodic inspection of the Yak Tunnel.Qualified mining crews will enter the <br /> tunnel annually to inspect and maintain weirs and other structures in the tunnel.Crews will also enter the <br /> tunnel to determine the cause of unexpected increases or decreased in flow within the Yak Tunnel;and(5) <br /> Development and implementation,as necessary,of a contingency plan to address any adverse ❑effects on ❑Start Printed <br /> surface or groundwater resulting from tunnel blockage.The implementation would be based upon decrease Page 6772 <br /> in flow from Yak Tunnel,rise in water levels in monitoring wells located near mine workings,indication of <br /> gradient reversal,or degradation of water quality. <br /> Because the selected remedy in the 1988 OU1 ROD left wastes in place but did not include institutional <br /> controls(ICs),a second ESD was signed on July 29,2013 to include ICs.The objectives of ICs for OU1 are as <br /> follows: (1)Reduce or control human exposure to contaminants of concern;and(2)Maintain the integrity of <br /> and prevent disturbances to engineered features or structures established as part of the current remedy or <br /> future remedies.The properties that comprise most of OU1 are owned by Resurrection/Newmont. <br /> OU1 Cleanup Standards <br /> The OU1 remedy was the first source control remedy at the Site that addressed the Yak Tunnel discharge as <br /> the largest single source of contamination to surface water and groundwater but did not contain numeric <br /> cleanup standards for those media.Numeric cleanup standards for site-wide surface water and groundwater <br /> contamination were established in the OU12 Record of Decision. <br /> OU1 Response Actions <br /> The EPA issued a Unilateral Administrative Order(UAO)to ASARCO Incorporated,Newmont Mining <br /> Corporation,Res-ASARCO Joint Venture and Resurrection Mining Company on March 29,1989 ordering <br /> these parties to perform the remedial design and remedial action for the Yak Tunnel.Two amendments were <br /> made to the UAO on April 30,1993 and June 16,1993•The UAO was replaced and terminated in a 2oo8 <br /> Consent Decree settlement(2oo8 CD)by and among the United States,State of Colorado,Newmont USA <br /> Limited and Resurrection Mining Company.Under the 20o8 CD,Newmont USA Limited and Resurrection <br /> Mining Company assumed responsibility for the OU1 remedy.Construction of a surge pond and permanent <br /> water treatment plant began in September 1988 and was completed in June i99i.The construction efforts <br /> included four main elements:(1)A surface water conveyance system,(2)the surge pond itself,(3)a barge <br /> transfer system and(4)installation of gravity filters.The water treatment facility to treat waters emanating <br /> from the Yak Tunnel was constructed over a two-year period and the Yak Tunnel Water Treatment Plant has <br /> been in operation since construction was completed in February 1992.The Yak Tunnel Bulkhead was <br /> constructed in 1994 to control surges of water coming from the Yak Tunnel,particularly during spring melt. <br /> The bulkhead is located approximately 1,68o feet into the tunnel from the portal.Additional efforts were <br /> made in 1995 and 1996 to reduce metals loading into the Arkansas River from ephemeral tributaries.As part <br /> of a Consent Decree settlement with Resurrection/Newmont,Resurrection/Newmont placed environmental <br /> covenants on its properties in OU1 on July 31,2012 and October 1,2012 that meets the IC objectives above. <br /> All remedial components described in the 1988 OU1 ROD and subsequent 1989 OUi AROD,1991 OU1 ESD, <br /> and the 2013 OU1 ESD have been implemented. <br /> OU1 Operation and Maintenance <br /> The potentially responsible parties'(PRPs)operations and maintenance(O&M)responsibilities were first <br /> defined under the UAO and then updated in the 20o8 CD.In accordance with the terms of the 2oo8 CD,the <br /> Routine Monitoring Plan(RMP),Contingency Plan(CP)and the OU1 Work Plan(Work Plan)govern the <br /> https//www.federalregister.gov/documents/2016/02/09/2016-02601/national-oil-and-hazardous-substance-pollution-contingency-plan-partial-deletion-... 9/16 <br />