The large undetonated ordnances (B52 drops) are usually found 5 meters to 10 meters in the stick clay layers below the topsoil. The locals look for them with metal detectors, then dig them up, and defuse them. The shells are used or are sold for scrap. The majority of the UXO's and casings are from the Lam Son 719 operation which started in late January, 1971 and was completed by early April. Some of these shells are cluster bomb canisters.