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sample ID, sample depth, GPS reading, general descriptions and observations). <br />In addition, the field work for this project was conducted concurrently with construction of new <br />groundwater collection sumps, along with the piping necessary to deliver the water to a new water <br />treatment plant. As a result, a 4 -5 foot deep trench, excavated for pipeline burial, was temporarily <br />open across the majority of the alluvial fill pad. This presented an opportunity to sample an <br />additional 18 depth profiles to depths of 4 -5 feet, and to perform in -situ gamma surveys at depth <br />along the entire length of this open trench. This provided additional information regarding the <br />subsurface distribution of radiologically elevated alluvial fill materials across the pad. All depth <br />profile sampling and measurement locations are shown in Figure 3. <br />3. All soil samples were analyzed for Ra -226 concentration in a small on -site field laboratory as <br />described in the next section. Screening estimates of uranium based on x -ray fluorescence (XRF) <br />measurements were also performed, but results proved unsatisfactory. Moisture content, material <br />particle size, and small -scale spatial variability in U -nat concentrations within given samples appear <br />to have limited the representativeness, and hence the reliability, of such measurements. However, <br />the data indicate that on average, U -nat in naturally mineralized geologic materials at the <br />Schwartzwalder Mine site occurs in approximate radiological equilibrium with Ra -226 and Ra -226 <br />measurements were thus used to estimate U -nat concentrations. <br />4. Aliquots of select representative samples (about 12% of all samples) were sent to a commercial <br />laboratory for additional testing, including independent uranium and Ra -226 analysis, along with <br />laboratory leaching tests (Synthetic Precipitation Leaching Procedure, EPA Method 1312). <br />Analytical results from the above sampling and measurements were used to create depth profiles and <br />three - dimensional schematic maps of the distribution of subsurface contamination. <br />4 <br />