5. The chairman asked participants to consider the question of what can be concluded from the available data and whether that data can lead to a better definition of the scope of work under conditions prevailing on Runit Island. There were discussions of the methods used to obtain available data; the relative degree of preciseness of aerial in-situ survey and van in-situ survey. The aerial survey technique integrates readings over approximately one hectare each second to approximately three centimeters depth. Aerial survey isopleth lines are probably limited to an accuracy of + 100 feet. The in-situ survey integrates over a field of view of 68.8 feet diameter and approximately three centimeters depth. It was concluded that the data presently available would not support refinement of the scope of work involved. 6. Further data is highly desirable. The chairman then addressed the obtaining of such data. discussion of methods of measuring both surface level and contamination levels and the specified removal criteria. read extracts from the four removal criteria contained in plan (OPLAN 600-77) (encl 6). Miss Barnes stated that it There was subsurface Mr. McCraw the operations would be impossible to reach even the 50 percent confidence level of not having missed significant subsurface contamination without doing much more profile sampling. A lower density of measurements would result in lower confidence in the estimate and a greater error term. For example, to find a particular region of contamination two feet wide, under worst case with the seam parallel to the grid lines, would require sampling every four feet. To provide such characterization would require commit- ment of substantial resources. a. If the characterization is done on a simple yes-no criteria i.e. contamination exceeds a specified level, the sampling need not be so precise. Using the highest contamination level recorded on the island, 3200 pCi/g, Dr. Crites demonstrated a calculation showing that a pocket of contamination which would average greater than 400 pCi/g over a 21 meter (68.8 ft) field of view would be approximately seven meters in diameter. Thus sampling on a grid of less than seven meters should locate such a minimum pocket size subsurface contamination of interest (see also encl 8). b. There was discussion on the one half distance technique for determining the presence or absence (yes-no) of subsurface contamination. Available data indicates only a few sample locations showing subsurface contamination at greater than 400 pCi/g levels. Sample locations are spaced on approximately a 200 foot grid. Moving one half the distance between greater than and less than sample points iteratively should provide boundary definition of contamination areas of interest (see encl 8). This investigation would be limited to those areas where Sry em mnmmner carmen, came a Te Rm pres RRG TE Bet aR ater en ay AER mene Ima ete ae ar PTE eae etat serene “ . my ‘ OS not oan ;. ttm Te Lone oS so, foe \ sow,: ‘ : nn og , . . . tel og, . yg am ye to ee, noe “ . te . : h , .