2020-12-02_PERMIT FILE - M2020061

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10/8/2020 Federal Register::National Oil and Hazardous Substance Pollution Contingency Plan: Partial Deletion of the California Gulch Superfund ... (5)If adverse comments are received within the 3o-day public comment period on this partial deletion action,EPA will publish a timely notice of withdrawal of this direct final Notice of Partial Deletion before its effective date and will prepare a response to comments and continue with the deletion process on the basis of the Notice of Intent for Partial Deletion and the comments already received. Deletion of a portion of a site from the NPL does not itself create,alter,or revoke any individual's rights or obligations.Deletion of a portion of a site from the NPL does not in any way alter EPA's right to take enforcement actions,as appropriate.The NPL is designed primarily for informational purposes and to assist EPA management.Section 300.425(e)(3)of the NCP states that the deletion of a site from the NPL does not preclude eligibility for further response actions,should future conditions warrant such actions. IV. Basis for Partial Site Deletion The following information provides EPA's rationale for deleting OU1 and OU3 of the Site from the NPL. Site Background and History The California Gulch Superfund Site,EPA ID No.COD980717938,CERCLIS Site ID o801478,is located in Lake County,Colorado approximately ioo miles southwest of Denver.The Site was proposed for inclusion on the NPL on December 30,1982,(47 FR 58476),and listed on September 8,1983,(48 FR 4o658).The Site is in a highly mineralized area of the Colorado Rocky Mountains covering approximately 18 square miles of a watershed that drains along California Gulch to the Arkansas River.The Site includes the City of Leadville, various parts of the Leadville Historic Mining District,Stringtown,and a section of the Arkansas River from the confluence of California Gulch to the confluence of Two-Bit Gulch.Mining,mineral processing,and smelting activities have occurred at the Site for more than 130 years.Mining in the district began in 186o, when placer gold was discovered in California Gulch.As the placer deposits were exhausted,underground mine workings became the principal method for removing gold,silver,lead and zinc ore.As these mines were developed,waste rock was excavated along with the ore and placed near the mine entrances.Ore was crushed and separated into metallic concentrates at mills,with mill tailing generally released into surrounding streams and after about 1930 slurried into tailing impoundments.Many of the mining operations ceased operations around igoo,although several smelters continued operations into the 1920E (Western Zinc)and the i96os(AV Smelter)and the last active mine,the Black Cloud,shut down in 1999. All of the mines within the Site boundaries are presently inactive,and all of the mills and smelters have been demolished.Mining remains that contributed to environmental contamination are(i)mill tailing(the fine- grained residue remaining after milling has removed the metal concentrates form the ore)in impoundments and fluvial deposits;(2)mine waste rock piles(mine development rock and low grade ore removed to gain access to an ore body,and often deposited near adits and shaft openings);(3)mine water drainage tunnels; (4)draining adits;and(5)various smelter wastes including slag piles,flue dust and fallout from stack emissions. The Site was placed on the NPL due to concerns regarding the impact of acidic and metals laden mine drainage on surface waters leading to California Gulch and the impact of heavy metals loading into the Arkansas River.A Site-wide Phase I Remedial Investigation(Phase I RI),which primarily addressed surface water and groundwater contamination,was issued in January 1987.As a result of the Phase I RI,EPA identified the first operable unit,the Yak Tunnel,to address the largest single source of metallic loading.A number of additional Site-wide studies followed the Phase I RI. https:/Iwww.federalregister.gov/documents/2016/02/09/2016-02601/national-oil-and-hazardous-substance-pollution-contingency-plan-partial-deletion 6/16