Mr. E. M. Bramlitt October 19, 1976 Page 2 to the grid point are assigned the highest weights. As mentioned above, the data were transformed to logarithms before any calculations were made. Once the grid estimates are obtained the desired contour lines are drawn automatically by linear interpolation between grid estimates. We did not iterate on the residuals to produce the enclosed contours. Iteration does not seem to be required for these data, i.e. the contours obtained after iterating would, in my judgement, be about the same as those given here. The 239-240, data collected at 0-5 cm and 0-10 cm increments were adjusted to correspond more closely to the 0-15 cm increments used at most sample locations. This was done by dividing the 0-5 cm and 0-10 cm data by 1.88 and 1.26, respectively. The factor 1.88 is the median of the ratios of 0-5 cm to 0-15 cm concentrations obtained from the profile samples on Enjebi. Similarly, 1.26 is the median ratio of the 0-10 cm to 0-15 cm concentrations. The 0-5, 0-10, and 0-15 cm concentrations were weighted averages of concentrations obtained at 0-2, 2-5, 5-10, and 10-15 cm, the weights being 2/15, 3/15, 5/15, and 5/15 respectively. have been using. This is the same weighting procedure you I have enclosed the revised list of soil Pu concentrations dated September 1976 which you sent Pam Doctor in your letter of October 8, 1976. These are the data we used except for the circled data which are for the 0-5 or 0-10 cm samples. The data used for these values are indicated next to the circled concentration. Please note that the North coordinate for sample location 120 appears to be in error since this N-E location is off the island. Using Figure B.8.1.f as a guide I replaced N144480 with N144880 which puts the sample in about the right position according to the figure. Also we have switched the Pu concentrations for samples 89 and 90 and for 27 and 28 since the Am/Pu ratios then fall into line. Since samples 89 and 90 are spacially adjacent and 27 and 28 fairly near to each other I don't think the contours would change much if we hadn't switched those samples. Now concerning the interpretation of the contour maps: It appears that the computer contouring has done a reasonably good job of automatically estimating and drawing contours around the "hot spots". A major drawback, however, is the lack of confidence statements associated with the contours. As I have noted in our phone conversations, the method of contouring we have used does not provide for estimating these confidence intervals. This is most unfortunate since we are left with a pretty map with little to guide us concerning its accuracy. We should recall, also that these contours were drawn without knowledge of the locations of detonation points, wind patterns at time of detonation, and other "subjective" data that might possibly be useful in drawing contours. I think we need to seriously face the question of whether