Poet and Martell (1974) estimated that 80 percent of the activity from the top 10 cm was in the upper 0.3 cm. An uncertainty is not associated with this statement, but it would appear to be significantly different from the results observed in the above studies. Bernhardt (1976) summarizes values from various sites indicating the average depth distribution. These values indicate about 50 percent of the total inventory in the upper centimeter and 70 percent in the upper 5 em. The variations on these values are about plus and minus 50 percent (numeric range) or more. Cesium-137 results for selected samples from this study are given in Table 4. Values are given for the top l-cm and 5-cm samples and for samples from the 5- to 10-cm depth interval. The average of the sample results for each technique and site has been used to estimate the activi-~ ty in the upper 10-cm depth interval for that site (column on right). The percent distribution at various depths from this data is plotted on Figure 7. The distribution is very similar to that indicated for pluto- nium-239 reported by Harley (1975). Error terms are not indicated for the accumulative cesium-137 values because some of the estimates are based on only one or two data points. The coefficients of variation (where there are several values) range from around 20 to 50 percent. The cesium-137 data appear to be from the same population unlike the plutonium-239 data in Table 1, suggesting the absence of a significant point source (e.g., Rocky Flats) contribution. Figure 8 is a log-probability plot of the cesium-137 data in the top 5 em of soil. The good fit of the data to a lognormal distribution is a strong indication of the data relating to a single uniformly dispersed distribution (Denham and Waite, 1975). Hardy (1976) reports an average deposition value of 100 nCi/m? (surface to 15- or 30-em sampling depth, northern Nevada and Utah). The Rocky Flats values are similar too, but appear to be somewhat lower (shallower sampling depth) than this value. SUMMARY AND CONCLUSIONS This is a status report of the EPA segment of a cooperative soil sampling evaluation study conducted at Rocky Flats, Colorado. The study was based on five duplicate samples by five different techniques from four sites around the Department of Energy's Rocky Flats Plant (see Figure 1). Undisturbed areas were selected for the sampling sites. The two EPA sampling techniques discussed in this report are: 664