2024 – 2025: On May 14, 2025, ADEQ and the United States Army Corps of Engineers (USACE) documented the conclusion of the formal dispute resolution regarding risk at the site. Details of the documented terms and conditions may be requested through ADEQ’s Record Center or submission of a Freedom of Information Act request to the Army Corps. 

2023: The USACE completed the Final Remedial Investigation (RI) Addendum Number 2 Report in April 2023 to document the investigation activities conducted at 37 additional residential parcels between March and July 2022. The updated Human Health Risk Assessment (HHRA) concluded that 9 parcels of the 37 investigated had cancer-causing risk greater than the acceptable residential exposure level. Clay pigeon fragments occurred on the surface of 10 parcels and in the subsurface of 6 parcels investigated during the RI Addendum 2. The Time-Critical Removal Action (TCRA) parcels were also inspected at this time to confirm the presence of clay pigeon fragments. The site inspection identified areas, typically near foundations, fence lines, crawl spaces, and trees, where accumulation of clay pigeon fragments persist.

2022: The USACE submitted the RI Addendum Report in February 2022 to document the additional investigation activities conducted at 30 additional parcels and one easement area between January 2020 and April 2021. The updated HHRA concluded that 79 parcels investigated during all TCRA and RI phases conducted between April 2013 and April 2021 had cancer-causing risk greater than the acceptable residential exposure level. The highest carcinogenic risk was reported at Thompson Easement Parcel L. Clay pigeon fragments occurred on the surface of 71 parcels and in the subsurface of 15 parcels investigated during all investigation phases. Based on the results of the RI to date, the USACE will continue to investigate residential parcels bordering those investigated during the RI, as well as TCRA parcels where clay pigeon fragments persist. 

2021: The USACE submitted the Final RI Report documenting the results of the initial activities (2014-2019). The results of the initial HHRA indicated 72 parcels were identified with a cancer-causing risk greater than the acceptable residential exposure level. Confirmation soil sample results from the 55 TCRA parcels were also compared to acceptable human health risk levels for polyaromatic hydrocarbons (PAHs) in soil. Subsurface soil in 50 of the 55 parcels had confirmation sample results with PAHs in soil above the 2014 established cleanup levels. Non-cancer human health risks associated with metals were below the acceptable noncarcinogenic risk level, and lead concentrations were below the United States Environmental Protection Agency’s residential soil screening level at all parcels. 

2020 – 2021: The USACE conducted RI Addendum activities at 30 additional parcels and the Thompson Easement between January 2020 and April 2021. The USACE collected soil samples to characterize the environmental conditions at the RI Addendum parcels and easement area, and to incorporate the RI Addendum results into an updated HHRA. During the RI Addendum, clay pigeon fragments were observed on eight of the 30 parcels and on the easement surface. One of the 30 parcels had clay pigeon fragments in the subsurface.

2019: The USACE continued the RI with the investigation of an additional 60 parcels between January and October 2019. As with the previous RI, the USACE collected soil samples from the surface and subsurface at parcels where right-of-entry was granted. Clay pigeon fragments were observed on the surface at 44 of the 60 parcels and in the subsurface at eight of the 60 RI parcels.

2014– 2017: Between December 2014 and February 2017, the USACE investigated 66 parcels during the initial RI program. Surface and subsurface soil samples were collected using Incremental Sampling Methodology (ISM) and analyzed for PAHs and metals. Results of visual observations indicated clay pigeon fragments on the surface at 21 of the 66 parcels and in the subsurface at five of the 66 parcels.

2013: The USACE performed a TCRA in two phases to remove clay pigeon fragments from the ground surface of the most impacted properties. The TCRA included excavation of contaminated soil from the upper two feet of properties having the greatest potential for human activities and exposure. PAH-impacted soil from 55 properties was excavated and transported off-site for proper disposal.

2011: The Final Site Inspection Report, Kingman Ground-to-Ground Gunnery Range, was submitted on September 21, 2011 describing Site Inspection (SI) field activities completed in 2010. Based on the analytical results presented in the SI report, the USACE concluded there was a potentially unacceptable risk to human health due to exposure to PAHs in the surface soil at the site. The USACE recommended conducting a Remedial Investigation/Feasibility Study (RI/FS) to evaluate the extent of clay pigeon debris and soil contamination, and also concluded that an expedited evaluation of a removal action for clay pigeon debris was warranted.

2010: SI field work began in September 2010 on residential properties where USACE and its contractor obtained right-of-entry. The SI evaluation included approximately 33.6 miles of visual inspections within the Munitions Response Sites (MRSs) In addition, 65 surface soil samples were collected using ISM. Samples were analyzed for PAHs and metals. The USACE conducted the investigation. 

2006: The Final Archives Search Report (ASR), completed in March 2006, documents a site visit, community interviews, and confirmation of munitions debris (MD) findings. It updates previous information and includes updated risk assessment code (RAC) scores. The ASR team found MD (in the form of spent small arms projectiles), but no munitions and explosives of concern. 

2004: The ASR Supplement, completed in November 2004, identified five MRSs at the site. According to the ASR Supplement, the suspected munitions used at all five MRSs were .50 caliber machine gun ammunition and/or general small arms.

1993: The USACE completed the Inventory Project Report INPR in 1993 and established the Kingman Ground-to-Ground Gunnery Range as a formerly used defense site (FUDS). The USACE set the preliminary site boundary, assigned the FUDS Project Number, and completed RAC scoring. The site was assigned a RAC score of 4 based on a hazard severity of negligible and a hazard probability of probable. The following 5 MRSs were established: MRS01 — Malfunction Range No. 1, MRS02 - Malfunction Range No. 2, MRS03 — 15 Skeet Ranges, MRS04 — Moving Base Range, and MRS05 — Range Complex No. 1. 

1943: Training began in January 1943. The Army created the Kingman Flexible Gunnery School to train gunners to use the defensive turrets and armaments of the B-17 bomber. The school built and utilized several ranges near Kingman Army Airfield (AAF), including the Kingman Ground-to-Ground Gunnery Range. While under Department of Defense control, approximately 89 buildings were constructed in an area referred to as the Ordnance Magazine and Target Range. This area also included jeep-type moving target ranges, two .22 caliber moving target ranges, one five-foot high tower turret shotgun range, 15 Skeet Ranges, and one 50-trap moving base range, as well as two malfunction ranges and a range estimation course.

1945: The Army classified the site as surplus in November 1945 and returned the land to its prior owners between 1946 and 1947.

1942: An Army Air Forces Flexible Gunnery School began operations at Kingman AAF on Aug. 4, 1942. The Army established a ground-to-ground gunnery range on Aug. 5, 1942.