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The Cimarron Mining Corporation site is located in Carrizozo, New Mexico. The site includes two areas: the 10.6-acre Cimmaron Mill site, located on the north side of Highway 380, and the 7.5-acre Sierra Blanca Mill site, located east of Highway 54. Milling operations took place from 1960 to 1982. Operations at the Cimarron Mill recovered iron and precious metals from ores. In 1979, use of cyanide to extract precious metals from the ore began. Operations at the Sierra Blanca Mill site recovered a variety of metals from ore transported to the site, although the process apparently did not use cyanide. Milling operations contaminated soil, sediment and groundwater. Following cleanup, operation and maintenance activities and groundwater monitoring are ongoing.

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What Is Being Done to Clean Up the Site?

The site is being addressed through federal and state actions.

Drinking water for 1,000 residents drawn from public and private wells within three miles of the site has been protected from contamination.

EPA has conducted several five-year reviews of the site’s remedy. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review concluded that response actions at the site are in accordance with the remedy selected by EPA and that the remedy continues to be protective of human health and the environment.

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What Is the Current Site Status?

NMED continues to perform O&M activities and ground water monitoring.  NMED increased the frequency of groundwater monitoring to quarterly for the last two years to determine if cyanide concentrations remain below the remedial goal of 200 micrograms/liter for eight consecutive quarters to satisfy New Mexico water quality requirements.  The last quarterly sampling was performed in the summer of 2015.   NMED will provide a report to EPA on the results of the quarterly monitoring by early 2016. 

Both mill sites are currently inactive.  OU-1 is currently used as an auto repair shop and salvage yard.  OU-2 is fenced and not in use.  About 1,500 people live within a two-mile radius of the site.  People obtain drinking water from 29 municipal wells within three miles of the site.  Current land uses in the surrounding area include residential, range land, agricultural and some recreational uses.

Two restrictive covenants were recorded by the town of Carrizozo in 2006. While the covenant for OU-1 prohibits drilling less than 100 feet below ground surface for obtaining ground water, it does not restrict well drilling in general.  It only serves to protect the present remedy in place.  The covenant for OU-2 also protects the remedy by prohibiting drilling near the disposal cells on or near their perimeters.

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EPA’s Involvement at the Site

EPA divided the site cleanup into two phases or operable units: OU-1 includes the Cimmaron Mill site and OU-2 includes the Sierra Blanca Mill site.  The remedy for OU-1 consisted primarily of extraction of cyanide-contaminated groundwater and its discharge to the publically-owned treatment works facility.  The construction of the remedy was completed in 1993.  The ground water extraction system was operated for approximately nine years and shut down in 2001 due to diminished extraction rates, with groundwater monitoring continuing.  Soil remediation was also performed at OU-1 similar to OU-2 and consisted of excavation, stabilization and on-site disposal.  A partial deletion of OU-1 from the NPL for soil was completed in August 2001.

Solidification and stabilization of contaminated soil and waste rock with cement was the major component of the remedy selected by EPA for OU-2.  The OU-2 cleanup was performed by the Department of the Interior's Bureau of Reclamation under an interagency agreement with EPA.  The cleanup consisted of excavation, solidification and disposal of contaminated soil and waste rock at an on-site repository followed by placement of a low permeability cap on the repository area and establishement of a vegetative cover.  This work was completed in 1992.  Additional work to excavate, stabilize and disposed of additional contaminated soil in a second repository follwed by capping and revegetation was completed in 1997.  OU-2 was deleted from the NPL by EPA in August 2001. 

Responsibility for site O&M and ground water monitoring at OU-1 and OU-2 was transferred to the State of New Mexico in 2005 and is currently performed by NMED.  Groundwater near the soil repositories is monitored to ensure a breach from the repository or a release to groundwater has not occurred. 

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