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C A M B R I A <br /> on the extracted volume and sample analytical results, interim remediation removed <br /> approximately 3 33 pounds of MTBE(Table 1) <br /> Figure 3 presents a graph of monitoring well MW-4 MTBE concentrations versus time As <br /> anticipated, the MTBE concentrations during the test were higher than the third quarter 2002 <br /> monitoring event MTBE concentration This occurrence is typical as contanunants are drawn <br /> towards the extraction point at the outset of pumping Although MTBE concentrations have <br /> increased in well MW-4 since the third quarter 2002 monitoring event, the MTBE concentrations <br /> over the course of the test demonstrated a decreasing trend As anticipated, the MW4 MTBE \J <br /> concentration from the fourth quarter 2002 monitoring event was higher than the MTBE <br /> concentration at the end of the test This rebound effect is typical as the groundwater <br /> equilibrates after extraction <br /> RECOMMENDATIONS <br /> Given the MTBE concentrations remaining in groundwater in the vicinity of well MW4 and <br /> piezometer P-1, further remediation may be warranted Based on the effectiveness of the aquifer <br /> • pump test in removing MTBE mass and decreasing MTBE concentrations over the course of the <br /> test, Cambna recommends implementing a temporary groundwater extraction program <br /> This program would consist of extracting groundwater from monitoring well MW4 for one <br /> week, once per quarter Groundwater would be extracted using a two-inch diameter Grundfos <br /> electric submersible pump The extracted groundwater would be temporarily stored on site in a <br /> 6,000-gallon tank A flow-totalizing meter will be used to measure the extracted volume At the <br /> end of the week, the tank will be emptied and the groundwater transported via vacuum truck to <br /> the Shell refinery to Martinez, California for recycling Cambna will collect beginning and <br /> ending groundwater samples from the process stream The samples will be analyzed for TPHg, <br /> BTEX, MTBE, TAME, and TBA by EPA Method 8260 Cambna will include the extraction <br /> data, an evaluation of the program's effectiveness, and any recommendations with the quarterly <br /> monitoring reports <br /> I <br /> Cambria will implement this program upon receiving approval from SJCE> D <br /> 0955 6 <br />