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[ LEWSkILL•HERXENHOFF, 1W. <br /> i <br /> REGULATORY GUIDELINES <br /> s <br /> 5. 1 EVALUATION OF SOIL <br /> In 1985, State of California Department of Health Services (DONS) and the State <br /> ' Water Resources Control BoardSWRCB <br /> ( ) jointly published the LUFT Field Manual as <br /> a guidance manual to aid representatives of the state and local agencies and <br /> consultants in conducting underground tank investigations and the evaluation of <br /> hazards created by unauthorized releases of gasoline and diesel products. <br /> One section of the LUFT Manual provides guidance in establishing site-specific <br /> soil clean-up levels for BTX&E and TPH. The manual suggests the investigator use <br /> two analyses for determining appropriate clean-up levels, first a leaching <br /> potential analysis and second, a general risk appraisal . The leaching potential <br /> analysis will result in maximum allowable residual soil levels obtained for each <br /> discrete sample. The general risk appraisal is then used to determine whether <br /> the BTX&E residuals left in the soil will pose a continuing threat to groundwater <br /> resources. <br /> I <br /> The leaching potential analysis looks at five site specific characteristics which <br /> tend to greatly increase vertical contaminant migration: (1) groundwater depth, <br /> (2) average annual precipitation, (3) subsurface fractures, (4) man-made <br /> conduits, and (5) unique site features. Each of the—"aforementioned <br /> • characteristics is evaluated using a numerical scoring system from 0 to l0, w1 <br /> a score of 10 indicating low potential for leaching. The LUFT Manual sets <br /> guidelines for scoring each of the characteristics. The sum of each of the <br /> individual scores is then used to set maximum allowable residual BTX&E and TPH <br /> levels that can be left in place without posing a threat to the groundwater <br /> resources of the area. <br /> Using the recommended LUFT procedure, the following table lists the site feature, <br /> LH's interpretation of the score and the sum for the Weber Point Property: <br /> - Site Feature Score <br /> I . Minimum Distance to Groundwater from soil sample 0 <br /> (less than 25 feet) <br /> I <br /> 2. Fractures in subsurface(none) 10 <br /> (applies to foothills and mountain areas) <br /> 3. Average Annual Precipitation (14.4 inches) 9 <br /> i <br /> 4. Man-made conduits (none) 10 <br /> 5. Unique site features (none) <br /> 10 <br /> ( includes recharge area, nearby well , coarse <br /> soil , etc. ) <br /> Approximate score by LH following LUFT recommendations - Total 39 <br /> J 23 <br />