Draft Environmental Impact Statement for Roca Honda Mine

Chapter 2. Alternatives, Including the Proposed Action
material, with total radioactivity of 1,850 curies of radium-226. The uppermost aquifer beneath
the site consists of alluvium (river deposits), sandstone, and weathered shale. This uppermost
aquifer is not a current or potential source of drinking water because of its low yield (DOE,
2011).
Rising about 50 feet above the surrounding flat terrain, the rectangular disposal cell is
approximately 2,500 feet long by 1,600 feet wide, including the toe apron. Its cover consists of
several layers designed to encapsulate and seal off the contaminated materials. The disposal cell
cover includes a low-permeability radon barrier (first layer placed over compacted tailings)
comprised of compacted clayey soil, a bedding layer of granular bedding material, and a rock
(riprap) erosion protection layer for the top and side slopes (figure 24). In accordance with 40
CFR 192.32, the disposal cell is designed to last 1,000 years, to the extent reasonably achievable,
and, in any event, for at least 200 years (DOE, 2011).
Figure 24. South-north cross-section of Ambrosia Lake disposal cell
The DOE’s Office of Legacy Management (LM) manages the Ambrosia Lake disposal site
according to a site-specific long-term surveillance plan to prevent the release of radioactive
contaminants to the environment. Under provisions of this plan, LM conducts annual inspections
of the site to evaluate the condition of surface features, performs site maintenance as necessary,
and samples two monitoring wells every 3 years. The encapsulated tailings will remain
potentially hazardous for thousands of years. However, the NRC general license for UMTRCA
Title I sites has no expiration date, and LM’s responsibility for the safety and integrity of the
Ambrosia Lake disposal site will last indefinitely (DOE, 2011).
Rio Algom Mine and Mill Tailings Site (Ambrosia Lake area)
Past; Current Reclamation
The Rio Algom Mine and mill tailings site is in the Ambrosia Lake uranium district. Located
about 25 miles north of Grants, this tailings impoundment contains 33 million tons of uranium
ore and covers an area of approximately 370 acres.
The site status changed from standby to reclamation in 2003, reflecting the licensee’s intent to
begin full demolition and reclamation. The mill was demolished and disposed of in the tailings
88 DEIS for Roca Honda Mine, Cibola National Forest