Tribal EPA


From Wednesday, October 23 2019 at 05:00 pm until Thursday, October 24 2019 at 09:00 pm

The Cyprus Tohono Mine (CTC) Site (Site) is located within three miles of the village of North Komelik in the Sif Oidak District of the Tohono O’odham Nation (Nation), approximately thirty-two miles southwest of the town of Casa Grande, Arizona. CTC maintains a copper mine and processing facility in “care and maintenance status” on lands leased from the Nation. Development of the Site began in the 1880s when low-grade copper oxide ore was mined from the surface. Beginning in 1996, various activities at the mine site resulted in the discovery of groundwater contamination underneath the village of North Komelik. Over more than a ten year period of investigation, CTC conducted numerous environmental fact-finding activities and installed numerous groundwater monitor wells. As a result, during 2006–2008 CTC removed contaminated soils from their evaporation ponds and mill tailings impoundment areas and redisposed of these wastes in a properly lined containment cell. CTC placed an Evapotranspiration (ET) cover over the former ponds and impoundment which is inspected semi-annually. These actions removed the primary source of groundwater contamination. In 2009, CTC voluntarily entered into a Groundwater Remedial Investigation/ Feasibility Study (RI/FS) with USEPA under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly referred to as Superfund. The Site is classified as a Superfund Alternative Approach site which uses the same process as sites on the National Priorities List (NPL), however, this site is not listed on the NPL. The next step is a “Proposed Plan” which identifies USEPA’s preferred alternative for cleanup of the basin-fill aquifer. Successful cleanups are done through collaboration. USEPA works closely with the Nation’s Environmental Protection Office, Mineral Resources Program, and Water Resources Department.

8:00 am – Departing

9:00 am – Arrive at Sif Oidak District Office

9:00 am to 9:10 am – Attendee will ride in transportation provided by Cyprus Tohono Mine site

9:30 am – Arrive at Cyprus Tohono Mine site

9:30 am to 9:45 am – Introductions

9:45 am to 10:00 am – Start Tour

10:00 am to 11:00 – Tour

11:00 am to noon – Return