NEWS MEDIA CONTACT:
FOR IMMEDIATE RELEASE
Audrey Berry, 970/248-7727

GRAND JUNCTION, CO —The U.S. Department of Energy Office of Legacy Management (DOE-LM) announces the availability of the final Environmental Assessment of Ground Water Compliance at the Monument Valley, Arizona, Uranium Mill Tailings Site and the Finding of No Significant Impact documents for the site. The Environmental Assessment provides information concerning the potential effects of the proposed pilot studies and the ground water compliance strategies for the Monument Valley Site. The Finding of No Significant Impact states that no significant adverse environmental effects will result from the planned pilot studies or compliance strategies.

The Monument Valley Site is a former uranium ore processing facility located on the Navajo Reservation in northeastern Arizona, about 15 miles south of Mexican Hat, Utah, and about 13 miles east of the Monument Valley tribal park. Contaminated surface materials at the site were removed in 1994 and disposed of in the Mexican Hat disposal cell. However, ground water at the site is contaminated as a result of historical uranium ore processing activities.

The aquifers beneath the Monument Valley Site are the alluvial (uppermost), the underlying Shinarump, and the De Chelly (the deepest of the three aquifers). Of these, only the alluvial and De Chelly show evidence of site-related contamination. An estimated 1,660 acre-feet (540 million gallons) of alluvial ground water is contaminated with sulfate, nitrate, and uranium; contaminants are present in both the shallow and deeper portions of the aquifer. A small, isolated area of the De Chelly aquifer is contaminated with uranium, although the concentration only slightly exceeds the U.S. Environmental Protection Agency (EPA) ground water standards. DOE is proposing compliance strategies that are protective of potential future uses of ground water in both aquifers. The Shinarump aquifer, which directly underlies the alluvial aquifer and is above the De Chelly, has slightly elevated concentrations of naturally occurring constituents that do not exceed EPA ground water standards. Therefore, no compliance strategy is proposed for this aquifer.

DOE has determined that additional pilot studies of the proposed ground water remediation methods should be conducted prior to final selection of the compliance strategy for nitrate and sulfate in the alluvial aquifer. Pilot studies are usually completed before an Environmental Assessment is initiated. However, the Navajo Nation has requested that an Environmental Assessment be completed to address the entire scope of DOE’s proposal, including the pilot studies and proposed compliance strategies. Navajo Nation officials have determined that this approach is necessary to demonstrate full disclosure to local residents who may be affected by DOE’s actions.

The proposed compliance strategies for the alluvial aquifer are contingent upon the results of the pilot studies, which are anticipated to be completed in 2 to 3 years. The proposed compliance strategy for remediating nitrate and sulfate in the shallow areas of the alluvial aquifer and the subpile soils area is passive remediation, including phytoremediation (uptake of contaminants by plants) and natural attenuation processes. Natural attenuation refers to natural physical, chemical, or biological processes that can reduce the concentrations of contaminants in soil or ground water. The proposed compliance strategy for all contaminants in the deeper portions of the alluvial aquifer is either passive or active remediation. An active remediation system would involve installation of extraction wells and pipelines to pump ground water from deeper portions of the aquifer. This active method is referred to as land farming. The proposed passive remediation compliance strategy for the De Chelly aquifer is natural flushing.

In conjunction with the selected compliance strategies, DOE will implement institutional controls and ground water monitoring for both aquifers. Institutional controls protect public health and the environment by limiting access to a contaminated medium. At the Monument Valley Site, institutional controls will likely include restrictions on access to, and use of, ground water during the remediation period.

Reference copies of the Environmental Assessment will be placed in the Flagstaff Coconino Public
Library, Burton Barr Central Library (Phoenix), Tuba City Public Library, Navajo Nation Library System,
Cortez Public Library, Dine’ College Library, Dine’ College Library Shiprock Branch, the University of New Mexico-Gallup Library, Mexican Hat Elementary School Library, Monument Valley High School, Shiprock Abandoned Mine Lands (AML) Program Office, Tuba City AML Program Office, Kayenta Chapter House,
Oljato Chapter House, and Dennehotso Chapter House. A copy will also be available in the
DOE Public Reading Room in Grand Junction, Colorado, and on the DOE-LM website at http://www.LM.doe.gov/land/sites/az/monvalley/monvalley.htm. Copies may be requested
by contacting DOE-LM toll free at 1–800–399–5618.