otra tt: ee2 CEESUES Pacific Northwest Laboratories Battelle Boulevard Richland, Washington 99352 Telephone (509) 946-2378 Telex 32-6345 October 19, 1976 Mr. E. M. Bramlitt Defense Nuclear Agency Field Command Kirtland Air Force Base, NM 87115 Dear Ed: Enclosed are the 239-2405 in soil contours Dr. Pam Doctor and I obtained using the data you sent us that were collected at random soil locations on the island of Enjebi (Janet) Enewetak Atoll in 1972. The enclosure labeled "A" gives estimated contours in units of pCi/gram; in addition, the location of data points are indicated by a cross. Three contour levels in log, scale are indicated; 2.08, 2.71 and 3.56. These are rounded from actual contour levels of 2.079442, 2.70805, and 3.555348, which when antilogs are taken, correspond to 8, 15, and 35 pCi/gram, respectively. The contours on the plot are in log, units since the contours were obtained on the logarithms of the data. The coordinates around the plot correspond to the North and East coordinate system you supplied with the data. Enclosure "B" gives the same contour lines as "A" and in addition plots the value of the 239-240py soil concentrations (pCi/gram) at-collection locations. These are the data used to estimate the contours. Enclosure "C" is identical to "B" except that Pam has roughed in the shoreline of Enjebi and colored the four bands of estimated concentrations (<8, 8-15, 15-35, >35 pCi/gram). contour lines extending off the island should be ignored. The The estimated contours were obtained using a nearest-neighbor estimation routine on the SURFACE II Graphics System developed by the Kansas Geological Survey. This system is described in "The SURFACE II Graphics System" by R. J. Sampson, pp. 244-266 in Displayand Analysis of Spatial Data (J. C. Davis and M. J. McCullogh, eds.), John Wiley and Sons, 1975. The specific Sub- routines used were GRID and NEAR. The basic idea is to estimate 239-240py concentrations at equally spaced grid points over the island. The grid size used here was 100 feet. The estimate at each grid point was obtained as a weighted average of the eight nearest data points, where the data nearest