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59 <br /> 7-Elever►/Stockton 23 <br /> August 1990 <br /> Groundwater extracted from the pumping wells is treated <br /> through an air-stripping tower prior to discharg% to the sanitary <br /> sewer system. Once a month, laboratory analyses are conducted on <br /> samples of the influent-to and effluent-from the air-stripping <br /> tower to check for the presence of concentrations of BTEX and <br /> - TPH-as-gasoline in order to verify compliance with the <br /> requirements imposed by the Stockton Municipal Utilities District <br /> and the San Joaquin County Air Pollution Control District. The <br /> ry concentrations of BTEX and TPH-as-gasoline for the influent and <br /> effluent samples analyzed during this period are tabulated in <br /> Appendix D, and the laboratory results are included in Appendix <br /> -- E. The air-stripping tower effluent sample results were below <br /> the laboratory MDL for BTEX and TPH-as-gasoline durilig April and <br /> May. The air-stripper effluent sample for June showed a TPH-as- <br /> gasoline concentration of 21 ppb, which is well below the <br /> - allowable limit. In addition to the monthly BTEX and TPH-as- <br /> 4' <br /> gasoline analyses, the air-stripping tower effluent is also <br /> sampled and analyzed once Each quarter for the presence of <br /> metals. Laboratory analyses are performed for the presence of <br /> lead, cadmium, chromium, copper, nickel, and zinc. For all <br /> sampling rounds, the sample analyses results indicate that the <br /> 7 <br /> levels of these metals in the discharge were below the specified <br /> discharge limits. These results document that the air-stripping <br /> system is not exceeding the permitted discharge requirements. <br /> The results of the analyses metals are tabulated on Table 3 <br /> and the laboratory results for BTEX and TPH-as-gasoline are <br /> included in Appendix E. <br /> E� <br /> TABLE 3 <br /> ' AIR STRIPPER EFFLUENT ?WTALS <br /> �,. {micrograms per liter} <br /> DATE LEAD CADMIUM CHROMIUM COPPER NICKEL ZINC <br /> 5/1/90 8 50 <100 <100 <100 <100 <br /> Gkul'�u11',1TEk <br />