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is I� i � h QUARTERLY GROUNDWATER MONITORING PROGRAM - AND TIDAL STUDY REPORT - SECOND QUARTER 1992 1.0 INTRODUCTION As required by San Joaquin County Environmental Health Division's (the County's) letter dated w March 27, 1992 issued to East Bay Municipal Utility District(EBMUD), seven monitoring wells located at the EBMUD Stockton Center facility in Stockton, California are tested quarterly. The testing includes sampling of the groundwater and chemical analysis of the samples for Benzene, Toluene, Ethylbenzene, Xylene (BTEX, EPA Method 8020), Total Petroleum Hydrocarbons.as gasoline (TPH-G, Method 8015-M1)':and Soluble Lead (EPA Method 239.2). The results from the second quarter 1992 sampling are presented in Section 2 of this report. Duringthis quarter, a tidal influence stud was also completed as requested by the County to q � Y P evaluate possible tidal effects on the groundwater beneath the site. The study was completed during July 1992 and the results of the study, which included nine rounds of groundwater levels R collected from the seven monitoring'wells during an approximate 12 hour period (one complete { tidal cycle), are presented in Section 3.0. 2.0 GROUNDWATER MONITORING SUMMARY Sampling of five of the seven monitoring wells (MW-1, MW-2, MW-3, MW-4, MW-7) was completed on July 2, 1992. Two i wells, MW-5 and MW-6, were not sampled due to the (' presence of asphaltic material in and around the well casings which could impact the water ' L quality in the well causing the analysis to be unrepresentative of groundwater conditions. These two wells will be cleaned and re-developed prior to the next quarterly sampling. The monitoring program consisted of two aspects: 1} field measurement of physical parameters and 2} the collection and analysis of water samples for specific analytes. Two quality control samples were also collected. One sample (coded MW-8) was collected as a blind duplicate from MW-1 to evaluate analytical reproducibility and one sample (coded MW-9) was taken to evaluate field decontamination procedures. A detailed description of the field activities is presented in Appendix A. 2.1 Physical Parameters Summary + i Field measurement of physical parameters included groundwater elevation, temperature, pH and 1 electrical conductivity. These data are presented in Table 1. } 2.2 Chemical Analysis Summary LConcurrent with the measurement of the physical parameters, groundwater samples were collected and analyzed for BTEX, TPH-G and soluble lead. The resultant data is summarized in Table 2 and the complete analytical report is presented in Appendix B. 1 RPTS/ERMUDRFF.WP 1 08/27192 L I� �