Plutonium in surface soil near the southwestern boundary of the Hanford project

Samples of airborne particles collected near the Prosser Barricade in another study showed low /sup 240/Pu//sup 239/Pu ratios that are indicative of Hanford-produced plutonium. In an effort to locate evidence of a trail or the remains of a large short-term release of plutonium that may have occurred during past Hanford operations, surface soil samples were collected along the southweastern boundary of the Hanford Site in December 1979. Results indicated the possibility of slightly elevated levels of /sup 239/ /sup 240/Pu (0.016 pCi/g) occurring in the general vicinity of the Arid Land Ecology Field lab extending to the junction of Highway 240 and Horn Rapids Road as compared to lower levels (0.006 pCi/g) in a northwesterly direction along the base of Rattlesnake Mountain and the eastern slope of Yakima Ridge. Assuming the worldwide average /sup 240/Pu//sup 239/Pu ratio of 0.18 for soil of the Pacific Northwest, the plutonium in these soil samples may be slightly less enriched with /sup 240/Pu (/sup 240/Pu//sup 239/Pu = 0.16). No evidence was discovered of an acute release remaining intact and crossing the southwestern boundary during the operating history of plutonium facilities in the 200 Areas.