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Waste Programs Division: Hazardous Waste Management: Camp Navajo Munitions Disposal

Camp Navajo Munitions Disposal
EPA ID No: AZ7 213 820 635

Facility Description

Camp Navajo is located at 1 Hughes Avenue (Ave), approximately 12 miles west of Flagstaff, south of Interstate 40 at Exit 185, in Bellemont, Arizona (Figure 1). The facility encompasses 28,347 acres and is situated in heavily forested to grassy, gently rolling to steep hilly terrain approximately 7,100 feet above mean sea level. The global position of the facility is approximately 35 degrees, 12 minutes, 48 seconds north latitude and 111 degrees, 49 minutes, 50.6 seconds west longitude.

Military facilities present at Camp Navajo include approximately 170 buildings of which 32 are currently used for administration, maintenance, operations, and storage. The northern part of the installation includes the Limited Area, which is used for a variety of storage missions. Over 17,000 acres are laid out as a Buffer Area to act as a protective barrier for the Limited Area. The Buffer Area is located between the perimeter fence and the Limited Area fence and is used by the Arizona Army National Guard and visiting military units for field training, as well as hunting and camping. The Open Burn/Open Detonation (OB/OD) Area is located adjacent to the southern Limited Area fence line and is estimated to be approximately 2,000 acres (Figure 2). It was initially established as a disposal location for old and obsolete munitions returned from active military operations. Past disposal practices have resulted in unexploded ordnance (UXO), munitions and explosives of concern (MEC), and munitions constituents (MC) contamination.

The Arizona Department of Environmental Quality (ADEQ) Federal Projects Unit (FPU) has been working with the Army National Guard Directorate (ANGD) (formerly National Guard Bureau (NGB) and Army National Guard (ARNG)) to complete environmental closure at Camp Navajo Army Depot for approximately 65 sites (Table 1) within the installation. The FPU is using the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Risk Based Cleanup process to remediate the site and will transfer the site to the ADEQ Hazardous Waste Permits Unit (HWPU) upon completion. An Arizona Hazardous Waste Management Act (AHWMA) (i.e., Resource Conservation and Recovery Act (RCRA)) post-closure permit (Permit) is required to properly manage any sites long-term where hazardous waste will remain in place upon closure. Approximately 700 acres will have MC and MEC left in place. Areas planned to be covered under the post-closure Permit are munitions response work area (MRWA) 02-01 and MRWA 02-03, with a corrective action plan to also include MRWA 02-02 (Figure 3).

  • MRWA 02-01 includes Navajo Army Depot (NAAD) 02 (Figure 4), which was an open detonation area, and some open burn areas and waste piles.
  • MRWA 02-03 consists of NAAD 03, the Former White Phosphorus Open Detonation and Burn Area, which is referred to as Chemical Canyon. Investigations and munitions clearance activities were conducted, but some subsurface munitions remain in the area.
  • MRWA 02-02 is a kick-out area that resulted from open detonations conducted within NAAD 02. Surface sweeps with MEC and UXO removal have been conducted, but there is the possibility of some subsurface munitions remaining within MRWA 02-02 that could migrate to the surface as a result of erosion and frost heaving over time. Therefore, measures are planned to be included in the Permit in the rare event MEC/UXO is discovered in this area.

Facility History

Camp Navajo was established in 1942 and was originally known as the Navajo Army Depot. The facility operated as a reserve supply depot for the receipt, shipping, storage, surveillance, minor maintenance and demilitarization of obsolete ammunition/explosives and assigned commodities. The OB/OD Area was formerly used for demilitarization and land disposal of obsolete and unserviceable conventional ammunition, explosives, and limited chemical warfare agents. Areas containing ordnance and visible UXO are present in the OB/OD area. Improper disposal occurred in the OB/OD area at sites including the trinitrotoluene (TNT) washout lagoons and the Former White Phosphorus Detonation and Burn Area (a.k.a. Chemical Canyon). Environmental studies of the facility began in 1979. Besides the OB/OD Area, studies and investigations at the facility included tank areas, landfills, waste and ash piles, igloos, storage areas, burn pads, paint and maintenance shops, wastewater lagoons, retention ponds, demolition and demilitarization areas, training areas, and asphalt plants. Since 1980, Camp Navajo has been in RCRA interim status while undergoing closure.

In 1982, operational control of the base was transferred under an Intra-State Support Agreement from the Secretary of the Army to the Arizona Army National Guard (AZ ARNG). After the transfer, the missions for the National Guard were training, continuing depot activities, and facilities maintenance. Past activities led to known and suspected contamination of several environmental media outside the ammunition demolition areas. These areas included: ammunition workshops, munitions storage, munitions testing and training ranges, operations facilities (including automotive maintenance and fueling), hazardous materials storage, and solid waste disposal facilities. The Army’s demilitarization activities in the OB/OD Area were regulated under RCRA interim status. The United States Environmental Protection Agency (EPA) and ADEQ completed the RCRA facilities assessment and visual inspection at Camp Navajo in 1993. EPA also completed a preliminary assessment/site inspection re-evaluation of Camp Navajo under CERCLA in April 1993. The report incorporated records contained in the 1991 Master Environmental Plan and subjected available sampling data to Hazard Ranking System scoring. In October 1993, EPA notified the AZ ARNG that Camp Navajo did not score high enough to be placed on the EPA’s National Priorities List (NPL). However, the facility is subject to all state and federal laws and is being cleaned up and closed to federal standards as part of the Department of Defense’s (DoD’s) Installation, Restoration Project (IRP) for non-NPL sites as authorized by the Defense Environmental Restoration Program, 10 USC Chapter § 2701-2708 and 2810). Operational control was transferred under the Base Realignment and Closure Act of 1988 (BRAC 1) to the AZ ARNG in 1993, and the name was changed to Camp Navajo.

Demilitarization activities ceased in September 1994 in connection with the closure of Camp Navajo under BRAC 1. A Closure Plan was submitted to ADEQ, which was determined to be insufficient. Between 1995 and 2002, the Army Environmental Center conducted a Closure Plan Investigation to collect sufficient data to support an appropriate Closure Plan. Preliminary geophysical work revealed potential UXO in the OB/OD area was worse than previously suspected. Since 2002, remedial activities in the OB/OD Area have continued. These activities included repair and replacement of the fence around the OB/OD Area, conducting an airborne ordnance detection survey, posting warning signs around the OB/OD Area in English and Spanish, conducting an archive search report, performing detonation pit sampling, consulting with the U.S. Fish and Wildlife Service, conducting a biological survey, updating the community relations plan, and distributing a hunting advisory flyer, conducting soil and surface water sampling, removal actions (e.g., contaminated soils, buried drums, munitions), surface sweeps with munitions removal, debris management, risk assessments, and associated reporting aiming towards closure. Submunitions were encountered in the historical OB/OD Area in January 2003, upon which ANGD obtained the required approval of a Department of Army waiver, which allowed access back into the area for environmental cleanup activities.

In July 2004, the ANGD began a two-year surface water and groundwater investigation in the OB/OD Area. Perchlorate was analyzed in this investigation, and with the exception of surface water in the open detonation pits, the results have been non-detect for contaminants of concern. In October, the ANGD began a soil investigation in NAAD 02 (i.e., open detonation pits). Both surface and subsurface samples were collected and reported in the RI Report. In October, the ANGD began investigations at four of the open burn areas (NAADs 05, 06, 08B, and 09D) that were operated under RCRA interim status. The investigation consisted of surface and subsurface soil sampling, and additional trenching in NAAD 08B to investigate numerous historical trenches.

During the Open Burn Area’s Phase I sampling in April 2005, NAADs 05 and 06 had contaminant levels above regulatory levels which, led to a Phase II vertical extent investigation in October. In June, ADEQ met with the ANGD to discuss investigation activities in NAADs 01, 04, 07, 08A, 09A, 10, and E76. These sites were not operated under the RCRA interim status permit, but were investigated under a performance-based contract. In 2006, ANGD continued investigations at NAADs 01, 02, 04, 05, and E76, and also conducted interim removal actions to remove lead-, arsenic-, and TNT-impacted soil.

In 2009, twenty vadose zone monitor wells were installed in the OB/OD area in the vicinity of NAAD 02 to determine whether contaminants are transported through the subsurface and to set-up the site for long-term post-closure care (Figure 5).

All remaining field activities including screening, sampling, and off-site disposal of stockpiled soil from NAAD 09C and NAAD 02 removal actions, backfilling the NAAD 02 pits, on-site detonation of all MEC, and collecting all scrap munitions debris (MD) for off-site recycling were completed in the summer of 2010. The MRWA 02 Engineering Evaluation/Cost Analysis (EE/CA) was approved by FPU in the winter of 2010. Several closure documents, including the NAAD 02 risk assessment associated with the revised NAAD 02 Decision Document (DD), are pending before the post-closure application may be submitted; however, some of the critical portions of the permit application are being discussed in advance. The site is expected to transfer to the Hazardous Waste Permits Unit for post-closure in spring 2014. IRP sites with waste remaining will continue to be managed under Five-Year Reviews (FYRs). The installation continues as a major training site, and also performs a depot-level storage service for the DoD, other government, and civilian entities. Long-term management and monitoring will be conducted by the AZ ARNG.


The contaminants of concern in the OB/OD Area include metals, explosives, perchlorate, semi-volatile organic compounds (SVOCs) such as pesticides and herbicides, white phosphorus, nitrate, dioxin/furans, and UXO. Additional contaminants of concern associated with installation operations include volatile organic compounds (VOCs) and polychlorinated biphenyls (PCBs). Contaminants of concern at both sites may change as new data become available.

Public Health Impacts

A public health risk exists due to UXO in the OB/OD Area. This risk is managed by restricting public access to the area; only AZ ARNG and ANGD personnel with a UXO escort are allowed. In addition, fencing with warning signs is located around the OB/OD Area and is maintained regularly by Camp Navajo personnel. Warning signs have also been placed around the area to be covered under a post-closure permit. Monitoring and corrective action plans will be in place for contaminated groundwater that may be detected during long term management and post-closure care.

A public health risk may exist by ingestion of contaminated soils or groundwater at the IRP sites. This risk is managed by restricting site access to AZ ARNG and ANGD personnel only. Land use at the installation will be non-residential for the foreseeable future.

Ecological and Cultural Impacts

Camp Navajo is home of several threatened and endangered species, including the bald eagle, northern goshawk, ferruginous hawk, osprey, peregrine falcon, the Mexican spotted owl and the Arizona toad. Other inhabitants include the pronghorn and elk. A protected activity center and critical habitat for the Mexican spotted owl is located in the south-eastern portion of the OB/OD Area. Due to the weather in the Bellemont area, the field season would normally last from May thru November. Because the Mexican spotted owl’s mating season is from March 1st to August 31st, conservation measures are implemented in consultation with the U.S. Fish and Wildlife Service.

Cultural sites are located within the boundary of the Camp Navajo installation, including within the OB/OD Area. Camp Navajo has been working with the Arizona State Historical Preservation Office for management cultural resources and mostly identifies and avoids cultural sites. More than 200 archaeological sites have been identified on the Camp Navajo facility.

Site Hydrogeology

The Camp Navajo area is underlain by unconsolidated Quaternary alluvial deposits, volcanic rocks of Quaternary and Tertiary age, and Paleozoic sedimentary rocks, mostly sandstones, limestones and shales. Outcrops of the volcanic unit are predominantly basaltic and range from lava flows to cinder cones. Thirteen volcanic vents have been identified within Camp Navajo’s boundaries. Several faults have been identified cutting Paleozoic sedimentary rocks and Quaternary-Tertiary volcanic rocks. These faults are regionally important with respect to groundwater sources and recharge.

The regional water table, occurring in the Coconino-Supai sandstone aquifer, is encountered at approximately 1,500 feet below ground surface. The City of Flagstaff relies on the Coconino aquifer for its municipal drinking water; its production wells are located at the Woody Mountain Wellfield, three miles southeast of the eastern boundary of Camp Navajo. Since 2003, Camp Navajo and the town of Bellemont have also tapped the regional aquifer. Regional groundwater flow is north to northeast. Several perched water tables, controlled by local geologic conditions, are present above the regional unconfined aquifer. These perched saturated zones have been identified at various depths to 350 feet and have historically been the predominant source of groundwater in wells immediately adjacent to Camp Navajo.

The OB/OD area contains two canyons, the Former White Phosphorous Detonation and Burn Area (a.k.a. Chemical Canyon) and Volunteer Canyon. The Former White Phosphorous Detonation and Burn Area Canyon is a tributary of Volunteer Canyon. Volunteer Canyon joins Sycamore Canyon and Sycamore Creek only 5.5 miles downstream of Camp Navajo. Within the OB/OD area, the Fossil Mountain and the Harrisburg members of the Kaibab Formation are the dominant rock units present. These units are bisected by several northeast striking normal faults and associated fracture sets that are surficially exposed in outcrop.

Community Involvement Activities

In February of 2002, a Stakeholder’s Advisory Group (SAG) was formed to assist the ANGD with stakeholder concerns through most of the closure process and met on a consistent basis. The SAG consisted of members from agencies such as the U.S. Fish and Wildlife Service, ADEQ, the Arizona Game and Fish Department, the U.S. Forest Service, the Arizona Army National Guard (AZ ARNG), as well as three community members. All SAG meetings were open to the public. Investigation and remediation activities are conducted in accordance with Camp Navajo’s Community Relations Plan which was finalized in March 2003. A couple of site tours were setup and attended by the public. The last SAG meeting was held June 9, 2011.

Information Repository

Interested parties may view select site documents at the Northern Arizona University Cline Library located at 901 S. Knoles Drive, Building 28, in Flagstaff, (928) 523-4459.

Site information is also available at the ADEQ Main Office located at 1110 W. Washington Street in Phoenix. Please contact (602) 771-4380 or (800) 234-5677 to schedule an appointment with 24-hour notice to review these documents. Once all documents requested have been collected, you will be contacted for a review Monday through Friday from 8:30 a.m. to 4:30 p.m. at the ADEQ Records Management Center, 1110 W. Washington Street in Phoenix, AZ.

For more information

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