OSWER/OSRTI 

Washington, DC 20460 

NATIONAL PRIORITIES LIST (NPL) 

[The description of the site (release) is based on information available at the time the site was evaluated with the HRS. The description may change 

as additional information is gathered on the sources and extent of contamination.]

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these 

substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet 

at http://www.atsdr.cdc.gov/toxfaq.html or by telephone at 1-888-42-ATSDR or 1-888-422-8737.

***Proposed Site*** March 2011 

MOLYCORP, INC. Questa, New Mexico 

Taos County 

à Site Location:

The MolyCorp, Inc. site (MolyCorp) is a molybdenum mining site located near the village of Questa, Taos County, New 

Mexico and consists of two separate areas: the mine and the tailing ponds. The mine itself is approximately 3 square miles 

in size and is surrounded by the Carson National Forest and the state-designated Latir Peak Wilderness Area, which is 

located approximately two miles north of the mine. The tailing facility, which is approximately one square mile in size, is 

located 6 miles west of the mine site in the village of Questa. The mine is located near the Red River and includes several 

side drainages, including Sulfur Gulch, Spring Gulch, Goathill Gulch, and Capulin Canyon. 

 ́ Site History:

Chevron Mining, Inc. (CMI), currently owns and operates the MolyCorp mine site. The mining operation has been active 

for the last 90 years, with three distinct operational phases: (1) conventional underground mining, which occurred from 

about 1919 to 1958, (2) open pit mining, which was conducted from 1965 to 1981, and (3) underground block cave mining, 

which started in 1983 and continues to the present. As part of the current operations, the facility also consists of a mill, a

tailing facility, and a tailing pipeline that runs between the mine and the tailing facility. 

r Site Contamination/Contaminants:

Sources evaluated include the open pit mine, waste rock piles, contaminated soil in the mill area, tailing impoundments, 

and the tailing pipeline. Primary contaminants present in on-site sources include polychlorinated bi-phenyls (PCBs), 

molybdenum, and other heavy metals. Antimony, boron, cadmium, cobalt, manganese, molybdenum, nickel, vanadium, 

and zinc were detected in the Red River. 

v Potential Impacts on Surrounding Community/Environment: 

Hazardous substances, contaminants and pollutants from the mining-related sources have released into the soil, ground 

water, surface water and sediment at and in the vicinity of the mine site and tailing facility, including the surface water of 

the Red River, which flows in a westerly direction just south of the site. A release of hazardous substances has been 

documented in both surface water and sediment within the Red River, including the Red River Fish Hatchery, which is 

located downstream of the site. Both a Human Health and Ecological Risk Assessment have been completed at the site, 

and identified unacceptable risks to human health and the environment. 

3 Response Activities (to date):

An RI/FS has been conducted through an Administrative Order on Consent between EPA and Chevron. Chevron currently 

is working in conjunction with the State and EPA to address ongoing releases. 

} Need for NPL Listing: 

The site was initially proposed to the NPL in May 2000. EPA is re-proposing to ensure that site score more accurately 

reflects current site conditions obtained since the May 2000 proposal.