Jump to main content or area navigation.

Contact Us

EPA's Region 6 Office

Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations

United Nuclear Corporation Mill Site, New Mexico


The Issue: Human health related to uranium mining.

The Area: Vicinity around State Highway Route 566 and intersection with the Puerco River which is located approximately 17 miles northeast of Gallup, McKinley County, New Mexico.

The Inhabitants: Approximately 250 to 500 predominantly Navajo people live within two miles of the area. This area includes the Navajo Nation's Pinedale, Church Rock, Coyote Canyon, Standing Rock, Nahodishgish Chapters and the residences along Route 566 south of the mill site. The Red Water Pond Road Community lies between the Northeast Church Rock Mine and the Quivira Church Rock I Mine, just west of the Pipeline Canyon Road.

United Nuclear Corporation Mill Superfund Site - Section 2 contains the former uranium ore processing mill facilities and a byproduct material (tailings) disposal site which cover about 25 and 100 acres, respectively. Section 36 adjoins the southern border of the Navajo Reservation.

Two underground uranium mines were formerly operated in the vicinity of the Site. UNC operated the former Northeast Church Rock (NECR) mine, which is located to the northwest and adjacent to the Site, and Quivira (formerly Kerr-McGee) operated a mine to the north of the Site (Figure 2).

The UNC uranium mill was operated from 1977 to 1982. Uranium ore was processed at the facility using a combination of crushing, grinding, and acid-leach solvent extraction methods. The milling operation produced acidic slurry of ground rock and fluid (tailings) that was pumped into the tailings impoundments, into which an estimated 3.5 million tons of tailings were disposed.

Uranium Mines in the Area (see Figure 1): Uranium mines in the Area

Nearby Uranium Mines

Northeast Church Rock Mine (NECR) — is a former uranium mine that operated from 1967 to 1982. Most of the 125-acre mine permit area is held in trust for the Navajo Nation by the United States Government. Approximately 40 acres are patented mining claim land owned by the United Nuclear Corporation (UNC). There is a small community of residents that live immediately next to the mine site on the Navajo reservation, downstream and downwind of the waste piles. The residents graze sheep, cattle and horses, and collect herbs around the area. Due to the proximity of the residents to the mine site, this mine was identified as the highest priority for cleanup by US EPA and Navajo Nation EPA of over 500 abandoned uranium mines on the Navajo Nation.

The uranium ore body is located up to 1,800 feet below grade at the NECR Mine Site. Therefore, the mining was conducted over 1,000 feet below the ground surface accessed through two main underground shafts. Other mining features included several vent holes, support buildings, roads and water extraction wells and treatment facilities. Portions of the site are located within an arroyo. Approximately 3.5 million tons of uranium ore from the UNC mine was processed at the adjacent UNC Mill Site, located on private property across Highway 566.

NECR site

Quivira Mines (Quivira Church Rock I and Quivira Church Rock IE) - are two former uranium mines that were operated by Kerr McGee Corporation (Kerr McGee) from 1974-1986. Rio Algom Mining LLC (RAML) received the property in 1985 and relinquished the lease in 1987. The Quivira mine areas contain abandoned uranium mines and are considered to be the major sources of the soil contamination at the Site. All the uranium ore from the mines, approximately five-million pounds, was processed at the Quivira Mining Corporation (QMC) Ambrosia Lake Mill located in Grants, New Mexico.

Quivira Site

UNC Mill Site
NECR Mine Site
Quiviria Mine Site
Regulatory Agency U.S. EPA Region 6 and Nuclear Regulatory Commission U.S. EPA Region 9

U.S. EPA Region 9

Potential Responsible Party UNC United Nuclear Corporation (UNC)

Rio Algom Mining LLC

Land Owner UNC Navajo Indian Trust Land with 40-acres of patented mining claim land owned by UNC

Navajo Indian Reservation

Contaminants Uranium, Radium, gross Alpha and Metals Uranium, Radium and gross Alpha

Uranium, Radium and gross Alpha

For more information, see the Contaminant Sources and Impacted Areas webpage.

Top of Page


The surface reclamation actions performed by UNC under the direction and oversight of the U.S. Nuclear Regulatory Commission (NRC) at the Site between 1988 and 1996 have stabilized the mill tailings and have protected the Rio Puerco from contamination spills like the one that occurred in 1979.

Top of Page

National Priorities Listing (NPL) History

NPL Proposed Date: 12/30/82
NPL Final Date: 9/08/83

Location: The Site is located 17 miles northeast of Gallup, New Mexico and on the southern border of the Navajo Indian Reservation.
Population: The surrounding area is sparsely populated, with the nearest residence located 1.5 miles north of the Site.

The Site includes a former uranium ore processing mill and tailings disposal area, which covers about 25 and 100 acres, respectively. The tailings disposal area is subdivided into three cells by dikes. The cells are identified as the South Cell, Central Cell, and North Cell. The tailings cells have been capped with an interim radon barrier cover as part of the reclamation activities directed by the NRC. Two evaporation ponds have been constructed on top of the cells as part of the EPA's ground-water remedy.

The surrounding lands include Indian Tribal Land, Indian Allotment Land and UNC-owned property. The land use near the Site is primarily grazing for sheep, cattle and horses. It is noted that the Ft. Defiance Housing Corporation, in conjunction with the U.S. Department of Housing and Urban Development and the Navajo Housing Authority, is planning to develop a 1000-unit housing complex, called the Springstead Estates Project, in the vicinity of Springstead (seven miles to the southwest of the Site).

Four water wells are within a 4-mile radius, the nearest being 1.7 miles northeast of the Site; however, nearby residents generally have used bottled water for drinking since the well water has a bad taste.

Hydrogeology: Three shallow water-bearing units beneath the Site were significantly recharged by mine water that was discharged into a local arroyo prior to and during Site milling operations. They are Zone 1 and Zone 3 of the Upper Gallup Sandstone Formations and the shallow alluvium (referred to as the Southwest Alluvium). These recharged units were then contaminated by tailings seepage from the Site. Underlying the Upper Gallup Sandstone Formation is the Mancos Shale. The Mancos Shale acts as an aquitard to prevent or retard the downward migration of contamination.

Principal pollutants:

Acidic mill tailings, total dissolved solids, sulfate, thorium, radium, aluminum, ammonia, and iron.

Top of Page

Proposed Plan

Surface Soil Operable Unit Proposed Plan released July 20, 2012.

Preferred Alternative: On-Site Disposal at the UNC Site within the Tailings Disposal Area.

Public Comment Period: July 20, 2012 through September 21, 2012.

Public Meetings:

August 29, 2012
Pindale Chapter House
1149 Mile Marker 5
Church Rock, New Mexico
Meeting begins at 6:00 p.m.

August 30, 2012
Octavia Fellin Public Library
115 West hill Avenu
Gallup, New Mexico
Meeting begins at 6:00 p.m. and ends 8:00 pm

Site Repositories:

Octavia Fellin Public Library
115 West Hill Avenue
Gallup, NM 87310

Navajo Nation Superfund Office
Highway 264/43 Crest Road
St. Michaels, Arizona 86511

Top of Page

Record of Decision

EPA signed the ROD on September 30, 1988.

    The selected remedy included:
  1. Containment and removal of contaminated ground water in the Southwest Alluvium and Zones 1 and 3 of the Upper Gallup Sandstone utilizing existing and additional wells.
  2. Evaporation of ground water removed from aquifers using evaporation ponds supplemented with mist or spray systems to enhance the rate of evaporation.
  3. Implementation of a monitoring program to detect any increases in the areal extent, or concentration of ground water contamination at, and outside of, the boundary of the tailings disposal area.
  4. Implementation of a performance monitoring and evaluation program to determine water levels and contaminant reductions in each aquifer, and the extent and duration of pumping actually required outside the tailings disposal area.

Top of Page

Ready-for-Reuse Determination

A Ready-for-Reuse Determination has not been made. The Site will be turned over to the Department of Energy for long-term care and monitoring of the tailings cells following closure.

Top of Page

Documents and Reports

Administrative Records
4/11/2013 Administrative Record for United Nuclear Corporation Superfund Site

7/20/2012 Proposed Plan Administrative Record File for United Nuclear Corporation Superfund Site

11/7/2012 NRC Final Comments on Surface Soil Operable Unit Proposed Plan

10/2/2012 TASC Comments on Surface Soil Operable Unit Proposed Plan

10/1/2012 Janet Greenwald Comments on Surface Soil Operable Unit Proposed Plan

10/1/2012 Robert Tohe Comments on Surface Soil Operable Unit Proposed Plan on the Surface Operable Unit Proposed Plan for the United Nuclear Corporation Superfund Site

9/27/2012 NMED Comments on Surface Soil Operable Unit Proposed Plan

9/26/2012 LBecenti Comments on Suface Soil Operable Unit Proposed Plan

9/21/2012 DOE Comments on Surface Soil Operable Unit Proposed Plan

9/18/2012 UNC/GE Comments on Surface Soil Operable Unit Proposed Plan

9/18/2012 UNC/GE Transmittal Letter for Comments

9/4/2012 Leona Morgan Comments on Surface Soil Operable Unit Proposed Plan

8/29/2012 Hand Delivered Comments on Surface Spol Operable Unit Proposed Plan at Public Meeting

8/29/2012 Verbal Comments Offered to Cynthia Wetmore at Public Meeting

8/20/2012 RWPRCA Comments on Surface Soil Operable Unit Proposed Plan

Fact Sheets
2/2015 Site Status Summary

10/2014 Site Status Summary

3/29/2013 Fact Sheet

7/2012 EPA Seeks Comment on the Surface Soil Proposed Plan for the United Nuclear Corporation Superfund Site

Five-Year Review Reports
9/2013 Fourth Five-Year Review

9/2008 Third Five-Year Review

9/2003 Second Five-Year Review

9/1998 First Five-Year Review


Legal Documents
6/29/1989 Administrative Order - United Nuclear Corporation - Docket No. CERCLA 6-11-89


Memorandum of Understanding
7/26/1988 Memorandum of Understanding between Region VI of U.S. EPA and Region IV of the US Nuclear Regulatory Commission for Remedial Action at United Nuclear Corporation

Proposed Plan
7/20/2012 U.S. Environmental Protection Agency Announces the Surface Soil Operable Unit Proposed Plan

Records of Decision
3/29/2013 Record of Decision for Operable Unit 2 Surface Soil Operable Unit

9/30/1988 Record Of Decision for the Ground Water Operable Unit Remedial Action - United Nuclear Corporation

Technical Documents

2/20/2015 2014 Groundwater Corrective Action Annual Review Report

6/3/2014 Groundwater Flow Model of the Church Rock Site and Local Area, Church Rock, New Mexico – Revised Appendices

1/29/2014 2013 Groundwater Corrective Action Annual Review Report

1/2013 Navajo Uranium Report Five-Year Plan Summary Report

8/13/2012 Updated Baseline Human Health Risk Assessment - Final

4/17/2012 NRC License Amendment Request for Revised Groundwater Protection Standards Based on Updated Background Concentrations, Source Materials License SUA-1475, Groundwater Corrective Action Program, United Nuclear Corporation Church Rock Mill and Tailing Site

1/2012 Annual Review Report 2011: Groundwater Corrective Action Church Rock Site - United Nuclear Corporation

10/14/2011 EPA email Re: Comments on the Site-Wide Supplemental Feasibility Study Revised Parts 1 and 2 document dated April 2011 for the UNC Church Rock Mill Superfund Site located in Gallup, New Mexico, and related to Source Materials License SUA-1475, Docket No: 040-08907

8/18/2011 Technical Memorandum Summarizing Two Reports on Zone 3 Tailings Seepage Sourcing and Groundwater Recharge with Information Update United Nuclear Corporation

4/26/2011 Revised Submittal: Site-Wide Supplemental Feasibility Study Parts I and II

1/2009 Annual Review Report – 2008 Groundwater Corrective Action, Church Rock Site, Church Rock, New Mexico

1/19/2004 Rationale and Field Investigation Work Plan to Evaluate Recharge and Potential Cell Sourcing to the Zone 3 Plume Church Rock Site, Gallup, New Mexico

9/30/1987 Impact on the Standing Rock Community Regarding Spill of Contaminated Drinking Water at the Church Rock Mill United Nuclear Site

8/27/1987 Justification for Request of Superfund Monies; Map Attached Depicting Area Where the People Affected by the Spill Reside

5/1/1987 Geohydrologic Report, Church Rock Site, Gallup, New Mexico

1/9/1984 Reports Related to Impact of July 16, 1979 Spill at the Site

11/8/1983 Potential Long-Term Contamination of Water Resources Resulting from 7/16/1979 Uranium Tailings Spill

9/1/1983 The Church Rock Uranium Mill Tailings Spill: A Health and Environmental Assessment Summary Report

11/4/1982 Response to Geotechnical Concerns - August Report on Church Rock Tailings Dam Failure and Ancillary Concerns

8/9/1982 Regarding Outstanding Issues and problems Related to July 16, 1979 UNC Tailings Dam Failure

8/1/1982 Unresolved Issues and Recommendations for Resolution Concerning the Church Rock, New Mexico Uranium Tailings Dam Failure of July 16, 1979

6/2/1982 The Assessment of Human Exposure from a Uranium Mill Tailings Release and Mine Dewatering Effluent

12/1/1981 Survey Of Radionuclide Distributions Resulting From The Church Rock, New Mexico, Uranium Mill Tailings Pond Dam Failure

9/4/1981 Rio Puerco Monitoring Program Executive Summary

12/24/1980 Biological Assessment After Uranium Mill Tailings Spill

4/2/1980 Radium Concentration Levels in the Rio Puerco River and Representative Data Depicting a Three-Year Period Pre-Spill

10/16/1979 Joint Statement of EPA and the Navajo nation on Current Status of the Spill and Clean-Up

10/4/1979 Comments on Spill Response

9/16/1979 Draft Joint Statement on the Current Status of the Spill and Clean-Up

9/12/1979 Programs Summary Relating to Spill of July 16, 1979 Which Includes Data From EPA, UNC, State of New Mexico, and Arizona

9/7/1979 Tailings Spill Hydraulic Assessment Report

8/24/1979 Transmittal of Weekly Tailings Breach Follow-Up Reports of August 10, 1979 Through August 23, 1979

8/23/1979 Background and Analysis of Tailings Spill Actions Taken by UNC

8/21/1979 Summary of State Action in Reponses to Spill on July 16, 1979

Top of Page

Community Involvement

5/13/2014 Ground Water Education Session #2

12/12/2013 Ground Water Education Session #1

12/1/2012 Community Involvement Plan

9/18/2012 Transmittal of Public Meetings Transcripts

8/30/2012 Transcript from Public Meeting

8/29/2012 Transcript from Public Meeting

8/20/2012 Response to Red Water Pond Road Community Association Comments

8/8/2012 TASC Meeting Minutes

Top of Page


EPA Remedial Project Manager: Janet Brooks 214.665.7598
EPA Community Involvement Coordinator: Jason McKinney 214.665.8132
EPA Attorney: James Costello 214.665.8045
EPA Region Public Liaison: Donn R. Walters 214-665-6483
EPA State Coordinator: Kathy Gibson 214.665.7196
New Mexico Environment Department: Earle Dixon 505.827.2980
Navajo Nation Superfund Contact: Freida White 928.871.6859
EPA Region 6 Superfund Toll Free Number: 800.533.3508

Top of Page

Jump to main content.