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AOC 36 - Mustard Gas Investigation Report
Section 9.0 - Soil Sifting
The magnetic “signature” of large metal objects, such as mustard gas shells potentially buried at CSSA, is easily detected. Because no large metal objects were detected during the magnetometer survey or during the trench excavation, the field crew had a high degree of confidence that buried shells did not exist at the site. The final step taken at the site to ensure no mustard gas shells or other UXO remained was to sift all soils within the B-28 trenches, as well as on the top six to twelve inches of the entire site. These soils were excavated, large pieces of metal slag were removed, and the remaining material was stockpiled on the site for sifting.
Soil sifting at suspected mustard gas burial area.
The soil was first loaded into a hopper that encased bars which broke the soil into small particles. The soil was then carried up a conveyor belt to a shaker screening plant equipped with a ¾-inch mesh screen. The fine size soil fell through the shaker screen onto a conveyor “stacker”, which stockpiled the sifted soil. The material that remained over the screen (“the overs”) was spread out and metal debris/UXO was removed by a trailer mounted electromagnet and/or hand picked. The overs were then visually inspected to ensure that they were free of UXO. The overs consisted primarily of rock and metal debris.
In June 1997, 12 potential UXO items recovered from the B-28 trenches, categorized, and destroyed.. The potential UXO items found at the site primarily included small arms munitions (20mm projectiles, .50 caliber projectiles/cartridges and .30 caliber projectiles/cartridges) and numerous UXO related parts, such as .30 caliber stripper clips spent cartridges, empty rifle grenades and practice hand grenades. All 20mm projectiles found were still considered live ordnance due to the fact that some contained high explosives in the nose of the projectile. All of the UXO items recovered were destroyed by detonation. No evidence of mustard gas shells was found during the sifting operations.
All items that were not considered to be live, or did not resembled live ordnance, were taken off-site for recycling as scrap metal. Approximately 1,300 cubic yards of soil and debris were sifted. A total of 8,000 pounds of metal debris were removed, and 12 UXO items were located.