Hecla Mining Company – Durita Facility

1.0 General Site Information

Site Location:	Montrose County, CO
Agreement State License Number:	317-02
Agreement State Contact:	Shiya Wang	Shiya.wang@state.co.us
NRC Agreement State Site Monitor:	Duncan White	Duncan.White@nrc.gov
NRC Site Monitor:	Martha Poston-Brown	Martha.Poston-Brown@nrc.gov

2.0 Site Description

The site occupies 192 acres in Montrose County, approximately 100 miles south of Grand Junction and 2.5 miles west of Naturita (Figure 1) and is about 2 road miles west from the San Miguel River Valley floor at an elevation of about 5600 feet. This location is within the Canyon Lands area of the Colorado Plateau.

3.0 Site History

The Durita facility was a secondary extraction heap leach operation built in 1977 by Ranchers Exploration and Development Corporation (Ranchers). The facility was operated by Ranchers from 1977 to 1979. Hecla Mining Company (Hecla) merged with Ranchers in 1984. The reclamation plan was developed and implemented by Hecla. All of the estimated 700,000 tons of feedstock "ore" for the mill were tailings from the Naturita mill site.  The tailings were trucked to the site and dumped into a crusher. The crushed tailings were conveyed to one of the three clay-lined heap leach tanks. When the tanks were full, the tailings surface was flooded with a dilute 5% sulfuric acid solution. The percolating acidic solution leached uranium and vanadium from the tailings. This solution was collected by slotted pipes in the bottom of each leach tank and then transferred by gravity flow to the extraction plant. Uranium and vanadium were recovered by ion exchange and solvent extraction. The waste liquid was stored in six onsite evaporation ponds. After operations ceased, the leach tanks were covered. The evaporation ponds were left uncovered to allow liquids to evaporate.

Formal decommissioning and reclamation of the site began in 1992. Equipment and facilities in the process plant and tailings process areas were demolished or salvaged. The salvaged items were decontaminated and removed from the site in accordance with the release criteria. Non-salvaged equipment and structures were buried onsite, in place, or if contaminated, buried in the leach tanks. Contaminated soils were excavated and placed in either the leach tanks or a disposal cell. During reclamation, no evidence of leakage from the evaporation ponds was noted, and material beneath the ponds was dry. Final reclamation construction activities were completed in 1999.

Reclamation at the Durita mill facility in Montrose County, Colorado, consisted of stabilizing three heap leach tanks, salvaging equipment that could be decontaminated, demolishing the remaining site structures and equipment, and disposing of contaminated equipment and debris onsite. Contaminated mill site soils also were disposed of onsite. The surface was contoured to establish positive drainage, and disturbed areas were seeded with endemic plant species. All disposed of materials are isolated from the environment in buried, engineered disposal structures.

Image from U.S. Department of Energy Draft Long-term Surveillance Plan for the Durita Colorado UMTRCA Title II Disposal Site, Montrose County CO, November 2020 LMS/DTA/S01514-0.0

4.0 Current NRC actions/status

In April 2021 the NRC staff completed it's review of the Completion Review Report (CRR) developed by the Colorado Department of Public Health and the Environment (CDPHE) for the Durita site.  NRC based it's review on The Office of Nuclear Material Safety and Safeguards (NMSS) Procedure SA-900, "Termination of Uranium Mills in Agreement States.

As summarized below, this review of the final CRR was based on three factors:

1. The NRC staff's evaluation of CDPHE's conclusion that all standards and requirements have been met;

2. The performance of CDPHE's uranium recovery program as evaluated under the Integrated Materials Performance Evaluation Program (IMPEP), which evaluates NRC and Agreement State materials programs; and,

3. Given unique circumstances at the Durita site, a supplemental technical review of the groundwater system at the Durita site.

The NRC staff determined that CDPHE's review covered all necessary technical areas and regulatory requirements relating to geotechnical engineering, surface water hydrology and erosion protection, radiation cleanup and control, and groundwater monitoring program. The CDPHE conducted appropriate inspections of site reclamation activities at the Durita site.

Under the NRC's IMPEP program, CDPHE's overall program has been determined to be adequate to protect public health and safety in all reviews to date. In addition, the CDPHE regulations were found to be compatible with the NRC's program in every review, except in the April 19, 2021 case of a 2014 finding regarding legislative issues that have since been resolved. The March case of a 2014 finding regarding legislative issues that have since been resolved (ADAMS Accession No. ML17065A376). Additionally, every IMPEP review of the CDPHE's uranium recovery program to date has resulted in a satisfactory rating (the highest performance rating possible).  These consistent satisfactory ratings provide a basis for the NRC staff's confidence that the CDPHE's licensing reviews, inspections, and CRR conclusions for the Durita site have been conducted appropriately.

The NRC staff also conducted an independent review and analysis of the groundwater system at the Durita site, which is documented in the enclosed evaluation report.  The NRC staff's report is based on an extensive document review and site observations. The NRC also conducted independent calculations to characterize the Durita site features, groundwater monitoring history, tailings and impoundment features, and the behavior of radionuclides in the groundwater system. The report quantifies the consequences of hypothetical historical and future releases from the Durita site using flow and transport modeling. The results of the modeling were used to support the NRC staff's determination that the Durita site does not and will not adversely affect the water quality of usable groundwater at or beyond the site boundary, and the evaluation concludes that the Durita site does not pose a risk to the public health and safety or environment.

In May 2021 the NRC staff informed the U.S. Department of Energy that they did not have any significant concerns with the DOE's Long-term Surveillance Plan for the Durita site.

5.0 Expected Transition to DOE for LTS&M

2024 (See DOE LM Site Management Guide, June 2022)