The PG-2 survey data are summarized in Tables B-16-2 and 3. To estimate the background count rate at each location we rotated the detector from the down-facing to up-facing position, Maintaining it at 1 meter above grade. For those few locations at which we didn't make both up and down measurements, we took the average of the "up" values from locations where the "down" values were less than 400 cpm. The post-lift IMP data (pCi/g) are also included in Tables B-16-2 and 3. From these data it is possible to estimate a minimum sensitivity and calibration factor for the PG-2. The minimum sensitivity for the PG-2 was taken to be the average value of the IMP readings at grid locations at which the "up" exceeded or was nearly the same as the "down" count rate with the PG-2. This value was 110 + 70 pCi/g TRU. Approximate field calibration factors for the PG-2 were calculated as follows: (1) Ratio of the IMP pCi/g to PG-2 net epm at specific 25 meter IMP stake locations (Table (2) Ratio of the IMP pCi/g to the average PG-2 net cpm from the five PG-2 12.5 meter B-16-2); or measurements centered on eachIMP stake location (Table B-16-3). The average calibration factors so calculated are 2.6 (+ 80%) and 3.3 (+ 30%) pCi/g per epm, respectively. PG-2 measurements were made on both dates at some grid ijiocations. These paired values are compared in Table B-16~4, showing reasonable agreement (within less than + 40% of the respective averages) between the two data sets, The PG-2 survey data, converted to pCi/g TRU, are presented in Figure B-16-2. This map is an expanded version of the one shown in Figure B-16-1 (IMP data only). From Figure B-16-2 it is evident that the highest surface contamination levels in the Fig/Quince area occur in areas along the two shorelines. Contours encompassing different degrees of surface contamination are shown on the map in Figure B-16-3. The contamination contours chosen (namely, 400, 1000, and 3000 pCi TRU/g) eneompass areas of about 12,500 (1.25 ha), 3750 (0.38 ha), and 375 (0.04 ha) square meters, respectively. These surface areas agree with those determined from IMP data, but provide a more refined estimate of the boundaries between different contamination levels. In particular, the PG-2 data showed that there are inhomogeneities over the Fig/Quince area. Most notable of these are the "hot-spots" at 0 - 0 and 4-SE-6, and the larger "hot-zone" at 13-NE-12. This latter zone definitely is distributed, covering an area perhaps 5 to 10 meters on a side, while the two former areas are discrete spots, no more than a meter or two across. Conclusions The PG-2 surveys of 28 May and 2 June confirm that the surface TRU contamination in the Fig/Quince area on Yvonne is very inhomogenous, with zones of contamination ranging from "hot-spots" of the order of a meter across to zones of 50 to a few hundred square meters. Based on the data presented herein, it is recommended that JTG plan a several tier strategy for cleanup, taking into account the available space remaining in the Cactus Crater dome. A suggested plan and estimated volumes of soil to be excised (single lift only) are shown below in orderof priority: Priority Area to Excise/Location Estimated Volume (m3) 1 3 "hot-spots"; 0-0, 4-SE-6, 13-NE-12 2 >3000 pCi/g; 6-NE-2 to 10-NW-2 80 3 >1000 pCi/g; 3-NE-3 to 16-NW-6 12-NE-6 to 14-NE-12 500 150 4 >400 pCi/g; lagoon side ocean side 8-15 1000 (balance after 700 removing items 1 to 3 above) * Does not include beach areas but assumes once an area is lifted, no further lift will be made in that region. B-16-3