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CAMBRIA report for the required monthly samples, taken on April 4, 2003, is presented as Appendix A Monthly Flow Data• Between March 25, 2003 and April 28, 2003, the total discharge was 180,952 gallons, which corresponds to an average flow rate of 3 70 gallons per minute Discussion The LEL meter was calibrated by Aqua Sierra Controls, Inc on Wednesday, April 16, 2003 The LEL meter calibration results are included as Appendix B Cambria believes that monthly laboratory pH analysis should not be required for the subject site We have analyzed groundwater samples for pH (by EPA Method 150 l) per our discharge permit requirements since August 2002 and have found that the pH of our discharge stream ranges from 6 63 to 7 21 The average pH between August 2002 and April 2003 has been 6 93 These findings are well within the permit pH range of 5 0 to 10 0 Since we only pump groundwater from one extraction well there is no reason to expect that our influent stream would have a variable pH Correspondingly,we would expect that our discharge stream would not vary much from the 6 95 average The pH data is presented in Table 1 If the City of Stockton Department of Municipal Utilities requires us to continue to monitor pH levels, please consider accepting pH data collected by Cambna technicians in the field using a field pH meter rather than the laboratory analytical method We have been collecting pH values using a field pH meter for the past five months to compare with the laboratory pH results As shown in the table below, the two sets of pH data are very similar Cambna will await your response to this request before altering our self-monitoring program We appreciate your consideration in this matter Date pH by EPA Field pH % Difference from Method Meter Lab Results 1501 12/04/03 699 74 59% 01/24/03 721 76 54% 02/21/03 694 68 20% 03/25/03 663 72 86% 04/04/03 697 72 33% Average: 6.95 7.24 50% • 0783 2