FIELD INSPECTION OF GRID STAKES AND PORTABLE INSTRUMENT(PG-2) SURVEY OF FIG/QUINCE AREA ON YVONNE DOE/ERSP TECH NOTE NO. 16.0 DATED: 8 June 1979 AUTHOR: D. H. Denham, PNL In reviewing the Fig/Quince IMP data, both pre- and post-lift, it was apparent that a numberof potentially key locations were missed. Hence, it was assumed these grid locations along both sides of the island were not measured because of missing stakes, terrain too difficult for the IMPs, or physical barriers like bunkers or roadways. Previously it had been decided no soil lifts or further meaurements would be made in roadwayssince they werelaid out in the "cleanest"part of the area. Methods On 28 May 1979, the DOE Tech Advisor (Denham) and EG&G Scientist (Jobst) were deployed to Yvonne to determine why no post-lift IMP values exist for certain grid locations (see Figure B-16-1). This was an on-foot survey in which the location of missing stakes was estimated by stepping off the distance from existing stake locations. In addition, a PG-2 survey instrument (low-energy gamma detector and count rate meter) and petri dishes were taken along during the on-foot survey. PG-2 measurements were made with the detector positioned 1 meter above grade at a number of marked locations and at 25-meter unmarked locations missed during the post-lift IMP survey. Another more extensive PG-2 survey was conducted by the DOE Tech Advisor (Denham) and EG&G Scientist (Tipton) on 1 and 2 June over much of the Fig/Quince area. This second mission was launched to better define potential excision areas on Yvonne, especially those with activity levels greater than 400 pCi/g TRU. This latter survey was made on a 12.5 m grid (6.25 m grid around the 12 NE 12 location). Results and Discussion The "no measurement" locations along both sides of the island from the 8 South line to the 28 North line were examined to determinesuitability for staking and IMPing. Of the 19 locations so checked, 4 had stakes in place (of which 3 were in unlifted areas), 7 may be in the water or below the high-water mark, and 1 each may fall on a roadway or at a cliff-beach interface. There were no indications of stakes at the remaining questionable locations. Specific grid data and comments concerning the reasons for not IMPing these locations are presented in Table B-16-1. Although these were not "hot-spot" surveys, the PG-2s were carried between locations with the detector about 40 em above grade and the count rate speaker turned on. Hence, the surveyors were at least aware of those areas traversed in which significant contamination levels existed. Only one "hot-spot" was detected beyond those areas previously identified by the IMP surveys. This was observed on the 2 June survey at approximately grid location 4-SE-6. The estimated (PG-2) soil TRU concentration at that location and the two others identified by the IMP are listed below: Location Estimated Max. TRU, pCi/g 4-SE-6 5,800 13-NE-12 24,000 0-0 140,000 In addition to the PG-2 fine-grid survey in the 12-NE-12 area, we took three samples of the roadway lip material (ocean side) along the stretch from about the 10 N to 16 N lines. A concrete bunkeris on the opposite side of the roadway on roughly the 16 N line. The results from those soil samples (petri dishes) ranged from 25 to 100 pCi/g* 241Am. Using the previously established TRU/Am ratio of 14 (NVO-140), the approximate TRU concentrations along that roadway ranged from 300 to 1400 pCi/g, with the highest concentration about 15 m from stake number 12-NE-12. * Calibration factor for 241Am for PG-2 in contact with the petri dish is approximately 31 pCi/cpm. B-16-1