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Arizona Army National Guard Maroon Crater Artillery Range


The Arizona Army National Guard (ARNG) Maroon Crater Artillery Range Munitions Response Site (MRS) is located approximately 7 miles northeast of Flagstaff, Coconino County, Arizona within Coconino National Forest’s San Francisco Volcanic Field. Maroon Crater MRS is a Non-Department of Defense Owned, Non-Operational Defense Site (NDNODS). The 12,177 acres of formally used artillery range land is owned by the U.S. Forest Service.

Maroon Crater was utilized for artillery training of howitzers, mortars, and machine guns from 1948 to 1950. The firing points are unknown for the mortars and machine guns. Historical documents indicate the howitzer firing point was located on the western edge of the MRS and directed east toward an impact point on Maroon Crater.

Contaminants of Concern

The contaminants of concern (COCs) includes munitions and explosives of concern (MEC) and associated munitions constituents (MC). COCs at the site may change as new data become available.

Public Health Impact

Military munition and unexploded ordinance (UXO) debris may pose an explosive hazard. Discovery of these materials should be reported to the local law enforcement authorities and left untouched.

Action Taken

The ARNG conducted site assessments of Maroon Crater Artillery Range between 2011 and 2012. In 2016, ARNG submitted a Remedial Investigation (RI) Work Plan for ADEQ’s review. RI field activities were conducted during the summer months of 2016. The activities involved utilizing Digital Geophysical Mapping (DGM) and analog geophysical transects to survey and map anomalies in the investigation areas. A Feasibility Study (FS) was finalized in 2017 and presented four remedial action alternatives. Alternative 4A and 4B were selected as the preferred remedial action methods in the 2017 Proposed Plan (PP). The 2018 Record of Decision (ROD) finalized the remedy decisions by recommending Alternative 4B, which included land use controls (LUCs) and surface/subsurface removal of military munitions using advanced geophysical classification (AGC) methods, as the preferred alternative for the Maroon Crater Artillery Range.


ARNG completed site characterization for Maroon Crater Artillery Range in 2017 and finalized the remedy decisions in 2018. A Community Relations Plan was accepted in March 2020. The Plan was developed to inform and involve the community during the Remedial Design/Remedial Action (RD/RA) phase. ARNG is currently working on completing the RD Work Plan. Once finalized the first phase of the RA field work will begin, pending weather and DoD COVID-19 guidelines.