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f� r�f A S S O C I A T E S I NI C constituents Detectable concentrations of TPHg ranged from 130 micrograms per liter (ug/L) in the sample collected from MW 10, to 150,000 ug/L in the sample collected from MW2 Detectable concentrations of benzene ranged from 1 1 ug/L in the sample collected from MW 10, to 25,000 ug/L in the sample collected from MW2 The groundwater samples collected from MW5 and MW9 contained no detectable concentrations of TPHg or BTEX Groundwater samples collected from wells MW4 and MW7 contained detectable concentrations of MTBE at 14 ppb and 100 ppb, respectively EPA Method 8021B is a screening method with respect to FtifD�f MTBE and without confirmation by EPA Method 8260B, the MTBE results may be false positives Confirmation of any positive 8021B detection of MTBE requires confirmation by 3��z EPA Method 8260B Analytical results of groundwater samples are summarized in Table 2 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 FILTRATION SYSTEM �� filtrations stem was installed to remove petroleum hydrocarbons from In May 2002, a carbony the water in domestic well DW On April 29 and May 28, 2004, water samples were collected Vhy from the first and second effluent ports identified as ICC Effluent and 2CC Effluent in the filtration system During the April 29, 2004, sampling event, all constituents from ICC. Effluent and 2CC Effluent were reported as not detected During the May 28, 2004, sampling event, all constituents from ICC Effluent and 2CC Effluent were reported as not detected, except for benzene which was detected at a concentration of 0 7 ug/L in the sample collected from carbon filter 1 CC It appears the filtration system is effective in removing petroleum products from groundwater extracted by well DW Analytical results are summarized in Table 2 CONCLUSIONS Concentrations from wells MW 1 through MW 10 remain generally consistent with the results from the previous sampling event The direction of groundwater flow continues to be variable across the site, with a general southerly gradient The MTBE detected in MW4 and MW7 was not confirmed by EPA Method 8260B due to an oversight MTBE has never been detected in groundwater samples collected at tre srtceanc- therefore are considered to be spurious Groundwater elevations have decreased since March 2004 RECOMMENDATIONS Based on the results of the second quarter 2004 monitoring episode, we recommend the following Conduct the third quarter 2004 groundwater monitoring and sampling of wells MW1 through MW 10 and DW and analyze samples for TPHg, BTEX, and MTBE by EPA method 8015B / 8260B Inspect well box conditions and maintain all well boxes in a water tight state S IEnviromenta11163931REPORTS12gr-2004 doc 4