le, - Chapter 4—Monitoring Accidental Radiation Releases © 7/ Photo creat! Sanco wananm | 388 Whole Body Counter, Environmental Protection Agency. managed by the Environmental Protection Agency at the Departmentof Energy’s direction with advice on sampling locations being obtained from the U.S. Geological Survey. Whenever possible, water samples are collected from wells downstream (in the direction of movement of underground water) from sites of nuclear detonations. On the Nevada Test Site, about 22 wells are sampled monthly (figure 4-15). The 29 wells around the Nevada Test Site (figure 4-16) are also sampled monthly and analyzed for tritium semiannually. The flow of groundwater through the NevadaTest Site is in a south-southwesterly direction. The flow speed is estimated to be about 10 feet per year, although in some areas it may move as fast as 600 feet per year. To study the migration of radionu- clides from underground tests. DOE dniled a test well near a nuclear weapons test named “Cambri Cambric had a yield of 0.75 kilotons and was detonated in a vertical drill hole in 1965 A test well was drilled to a depth of 200 feet below the casity created by Cambnic. It was found that most ot the radioactivity produced by the test was retuned within the fused rock formed by the explosion. although low concentrations of radioactuye matenal were foundin the waterat the bottom ofthe cavity A satellite well was also drilled 300 teet trom the cavity. More than 3 billion gallons of water were pumped from.the satellite well in an effort to draw water from the region of the nuclear explosion The only radioactive materials found in the water were extremely small quantities (below the permitted '5See ‘*Radionuchde Migration in Groundwater at NTS,” U.S. Department of Energy, September, 1987.