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Ms. Mary Meays <br /> May 29, 1991 <br /> Page 2 <br /> ethylbenzene, and toluene and a decrease in xylenes concentration was observed, it was not <br /> significant enough to warrant concern. The changes in constituent concentrations are probably <br /> due to the different solubilities in these constituents. <br /> Review of previous groundwater quality from wells on the west side of the site reveals that the <br /> dissolved constituent concentrations have not elevated appreciably. The concentrations in these <br /> wells will be further evaluated after two quarters of operation of the groundwater extraction <br /> system. If it is found that the dissolved constituent concentrations remain similar or increase, <br /> then the need for additional investigation to the west will be explored. <br /> The groundwater extraction system at this site will be operating within approximately one month. <br /> After two or three quarters of operation, the effectiveness of the system will be evaluated by <br /> looking at the laboratory results for those quarters and noting any trends in the concentrations. <br /> Also, at the end of three quarters it may be possible to predict an estimated schedule for <br /> completion of the investigation based on the trends in dissolved constituent concentrations. <br /> A 1,000-gallon underground holding tank exists near the extraction well. This tank was to be <br /> used for free product recovery. However, after the tank was installed it was no longer needed <br /> for storage of free product because free product was no longer observed in any of the wells <br /> including the extraction well. This tank was never used for any purpose. ARCO intends to <br /> remove the tank and since the bottom of the tank is well above groundwater the removal should <br /> not have any effect on the extraction system. <br /> Finally, a Draft Final Remediation Plan (FRP) will be prepared including an executive summary. <br /> The County requests that the FRP be submitted for review by June 3, 1991, however, because <br /> of the amount of time involved and the level of detail that is required in the FRP, it may not be <br /> possible to meet the June 3, 1991 deadline. Therefore, ARCO is requesting an extension for <br /> submittal of the FRP. The FRP will be submitted by July 3, 1991 provided all pertinent <br /> information is available. <br /> If you have any questions or comments regarding this site please call me or Mr. Douglas <br /> Wilkerson at (916) 444-0123. <br /> Very truly yours, <br /> BROWN AND CAA.L✓/DWELL <br /> Steve Misner <br /> Project Manager <br /> SDM:mkw <br /> cc: Mr. Chuck Carmel, ARCO Products Company <br /> Mr. Chris Winsor, ARCO Products Company <br /> Br"ARSIA Wilkerson, Brown and Caldwell <br /> Consultants <br />