to determine the hole volume and the procedures followed were those specified in ASTM D 1556-64. A portion of soil removed was used to determine the moisture content by weighing the sample before and after drying, according to procedures given in ASTM D 2216-71. Soil samples were taken at two of the three locations within each area where soil density measurements were made. Soil samples were also taken at each location where a sand-cone comparison was made. The samples were taken to a depth of 5 em and included all organic material, roots and any aggregate which might have been present at the location. Each sample was sealed in a plastic bag ana then inserted into a l-gailon paint can. A total of 124 samples, taken from ¥ islands, were optained and shipped to LLL for composition analysis. Eleven of these samples were split, witn half going to LLL and the other half going to EG&G, Las Vegas for direct soil attenuation measurements. At LLL the samples were dried at 75° C for 48 hours in commercial ovens. The samples were then ballmilled for 48 hours. After this preparation, the samples were sent to a commercial laboratory for composition analysis, including a determination of the percent organic material within each sample. Results 1. Soil Density and Soil Moisture Average soil density and soil moisture results were obtained over the top 5 em, the top 10 em and the top 15 em of soil. A summary of the results for the 5 em average is given in Table B-22-1. The 10 cm average gave a value of 1.56 g/em3 and the average for the 15 em measurements was 1.59 g/em3, compared to a value of 1.53 g/em3 for the 5 em measurements. Thus, there appears to be a slight inerease in the density with depth. Figures B-22-1 and 2 show the distribution obtained for the area-averaged wet soil density and percent soil moisture, respectively, over the 73 areas which were measured. A standard deviation of 0.14 g/em3 was obtained for the soil density and 5% for the percent moisture. As shown in Table B-22-1, almost half of the measurements were made on Janet. A grid pattern was established to provide uniform coverage over the island (see Figure B-22-3). Similar coverage was also obtained over Irene, Pearl and Sally. measured on the other islands. Only a few representative areas, however, were Two types of calibration experiments were also conducted on Janet. The first was a check on repeatability for the nuciear density/moisture gauge. A series of 12 repeat measurements were made at the same location for each of the three source depths of interest. The results showed that the error associated with counting statistics was approximately 0.5% and, hence, negligible for all practical purposes. The second experiment was performed to cross-check the data obtained from the nuclear density/moisture gauge with another independent technique used for obtaining in situ density measurements. A total of 12 comparison measurements were made on Janet and one on Enewetak. The locations on Janet were spread around to provide a reasonable cross section for the island (see Figure B-22-3), The sand-cone measurements were taken to a depth of 10 em or 15 em depending on soil compaction. In all cases, the comparison was made with results from the nuclear gauge taken at the same depth as the sand-cone. Table B-22-2 shows the results of the comparison. It can be seen that both the density and soil moisture data compare quite well. The only exception is the percent moisture comparison at location 6. The soil sample sent to LLL from this location had a soil moisture content of 13%, which compares well with the nuclear moisture gauge results. It is not known why the field measurement for soil moisture was so much different for this particular location. There was no correlation observed between the comparison data and the radiation levels which were also measured at each location using a Ludlum Model 19 MicroR Meter, calibrated for 137Cs. This indicates that the rather low !3%Cs levels in the soil at Enewetak did not significantly contribute to the nuclear density gauge detector compared to the counts from the built-in 8 millicurie source. 2. Mass Attenuation Coefficient Two methods were used to determine the mass attenuation coefficient for 60 keV gamma rays in Enewetak soil. The first, and primary method, was to determine the elemental composition of the soil through chemical analysis. The soil mass attenuation coefficient can then be obtained from a B-22-2