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1 <br /> REQUEST FOR SITE CLOSURE <br /> Genesi Mills Facihty <br /> 2000 West Turner Road <br /> Lodi, Caufomm <br /> Delta P-oject No 4.0-92-708 <br /> Page-1 <br /> At the April 15, 1993 meeting, the County suggested that we present our case for leaving soil in place <br /> with concentrations of TPH as diesel No 6 over IGO ppm to the Technical Advisory Committee After <br /> consideration, General Mills has decided to proceed with this suggestion. To support our case, General <br /> Risk Appraisal analyses were performed <br />' 2.7 Leaching Potential Anal s <br />' The Leaching Potential Analysis, presented in the LUFT Manual was developed to estimate the <br /> concentration of BTEX, TPH as gasoline, and TPH as diesel that can be safely left in soil at a site <br />' without posing a risk to ;round water quality It is used as a screening method to determine whether <br /> additional site analyses are necessary As stated by Odencrantz, et. al , "This screening table is <br /> t incorrectly used throughout California by a wide variety of agencies and private entities to determine TPH <br /> and BTEX cleanup concentrations If it is found during the screening step using Table 2-1 (LUFT <br /> Manual) that additional detailed analysts are required, the I =manual provides a more detailed analysis <br /> that compares "cumulative concentrations" of BTEX to compound-specific tables for determinations of <br /> appropriate cleanup levels. This second, more involved analysis, termed the General Risk Appraisal, is <br />' rarely performed or enforced" <br /> The County is incorrectly applying the screening table to trigger further remediation, which is clearly not <br /> the intent of the LUFT manual. <br /> 3.0 GENERAL RISK APPRAISAL <br />' Proceeding on the premise that the County's Leaching Potential Analysis results are appropriate <br /> (maximum allowable concentration of TPH as diesel No 6 should be 100 ppm), the next step <br />' recommended in the L= Manual is either cleanup or additional site analysis such as a General Risk <br /> Appraisal. Delta has performed a General Risk Appraisal as described on pages 36 through 46 of the <br />' LUFT manual <br />' The General Risk Appraisal is more sophisticated than the Leaching Potential Analysis. It was developed <br /> to evaluate the risk of ground water pollution at an underground fuel storage tank site from BTEX <br /> concentrations to soil Delta performed three analyses: one for toluene, one for ethylbenzene, and one <br />' RPT076 TA <br />