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J <br /> f <br /> a� � �� cleanup Decision <br /> Fact Sheet <br /> y <br /> 'yooya�� <br /> Treatability studies were conducted on the-iDDT-contannnate soil removed from Sites 4,5G,and 5H. <br /> Treatability studies are experiments in which.possiblepl anuprmtk ods are tested. Several treatment methods exist <br /> to reduce or remove DDT from soil;howeve4,each methods off reness depends on soil type and level of DDT, <br /> among other factors. For example,some treattnent:me&io&w* w:'ell to remove DDT from sandy soils but don't <br /> work well on soils that contain large amounts-ofclay,,s& *iii s8ils at NCS Stockton. The treatment methods <br /> used in the treatability studies for DDT-conlatnitedsdl-atStockton were chemical oxidation and solvent <br /> extraction. The chemical oxidation methoddidnotremoveMOU&DDT,but the solvent extraction method was <br /> successful in treating 360 cubic yards of the°stoc7e&,p tas levels of DDT that the Navy,DTSC, and RWQCB <br /> consider protective of human health. Still,1,,1100>ciiKd yards oscn7 continue to be stockpiled and require treat- <br /> ment. Because of the High DDT levels,the`soll stb&uvat*reduce the DDT to levels protective of human <br /> health and the environment. <br /> Site IAS-9 ° <br /> Site IAS-9 is a dirt road approximately 1.25>niles longwestern portion of NCS Stockton that was <br /> constructed in 1945. According to base personnel,from I945'. 1970,DDT and other pesticides were mixed with <br /> waste oil and solvents and sprayed on the road fur-dnst:caz6L <br /> Soil samples collected during the site investi.gao6tuindicaft-,fliatthodirt surface of the road contains levels.of DDT' <br /> that pose a risk to human health and the envJr f�ocl' gates were subsequently put up to restrict access to <br /> the road. Warning signs have been posted,iand-s"&fy- r for traveling on IAS-9 have been issued to <br /> personnel required to use the road. <br /> SUMMARYOF • <br /> As part of its evaluation of Sites 4,5G,5H,,and:IAS-9,Ahe1 ,conducted a human health risk assessment. <br /> The human health risk assessment was conducted`according-to guidelines published by DTSC and the U.S.Envi- <br /> ronmental Protection Agency(EFA). The human healt riskcassessment is an important step in the cleanup process <br /> for three reasons: <br /> It identifies the ways a persotimightcome ifitorncoidact with the DDT(exposure pathways) <br /> It estimates the potential harm,to human:health as:a result of exposure to DDT(potential risk) <br /> It calculates the level to which the DDT mu'stibe cleaned up to be considered protective of human <br /> health(cleanup goal) <br /> *Words in bold are defined in the glossary <br /> 5 <br />