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C-SHADRIFS.6/WPADD.8 <br /> 05/17/90 <br /> 3.0 ARSENIC IN SOIL INVESTIGATION <br /> Arsenic concentrations in SHAD soils have been investigated on two <br /> separate occasions, once in 1987 and again in 1989. Three purposes were <br /> stated for the 1989 investigation: <br /> 1. Establish any correlation between arsenic in groundwater and <br /> arsenic in soils, <br /> ' 2. Establish if the SHAD soils are statistically different in <br /> their arsenic content from the offsite soils, and <br /> 3. Map the distribution of arsenic in shallow depressions to <br /> determine if any arsenical pesticides have been concentrated by <br /> runoff. <br /> The results of that investigation are currently being prepared. <br /> However, the preliminary indications are as follows: <br /> 1. Arsenic concentrations in the soil range between 0.7 and <br /> ' 109 ppm. <br /> 2. The distribution of arsenic concentrations is strongly skewed <br /> ' toward low concentrations, with the average arsenic <br /> concentration of SHAD soils approximately 5 to 6 ppm. <br /> 3. All of the measured values are consistent with a normal <br /> ' distribution of naturally occurring arsenic-enriched minerals <br /> in SHAD soils. <br /> ' 4. The SHAD soils are statistically indistinguishable from the <br /> offpost soils. <br /> ' Although all of the data are consistent with these conclusions, a single <br /> high value of 109 ppm needs to be investigated further in order to <br /> ' increase the level of confidence regarding the conclusions. <br /> ' Environmental Science & Engineering, Inc. (ESE) proposes to complete a <br /> statistically rigorous investigation based on sampling methodology <br /> 1 8 <br /> 1 <br /> 1 <br />