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ATC Associates Inc <br /> M%TC <br /> 1117 Lone Palm Avenue, Suite B <br /> Modesto, California 95351 <br /> 209-579-2221 <br /> fax 209-579-2225 <br /> A 5 S O C I A T E S I N C <br /> numbers 7505755364 and 5104236304, respectively) Documentation of the data submittal is contained <br /> in Attachment 3 <br /> CONCLUSIONS <br /> The laboratory analytical results of the groundwater samples collected from MWl, and MW4 through <br /> MW8 in March 2006 are generally consistent with recent historical analytical results MW2 and MW3 <br /> were not chemically sampled this quarter because they are sampled on an annual schedule MTBE <br /> concentrations detected in the groundwater samples collected from MW4 and MW5 decreased with <br /> respect to the last time these wells were sampled, however increased concentrations were observed in <br /> monitoring wells MW1, MW6, MW7, and MW8 TPHg detected in the groundwater sample collected <br /> from MW4 increased with respect to the previous sampling event The lateral extent of the groundwater <br /> plume appears to be adequately assessed The direction of groundwater flow was fairly consistent with <br /> respect to recent monitoring events The hydraulic gradient on March 8, 2006, was calculated to be <br /> 0 0017 feet per foot, or approximately 8 97 feet per mile Groundwater elevations have increased since <br /> December 2005 <br /> RECOMMENDATIONS <br /> Based on the results of the first quarter 2006 monitoring episode,we recommend the following <br /> • Conduct the second quarter 2006 groundwater monitoring and sampling of MW 1 and MW4 <br /> through MW8 and analyze samples for TPHg and BTEX by EPA Method 8015M/8021B and <br /> MTBE, ETBE,DIPE, TBA, TAME, 1,2-DCA, and EDB by EPA Method 8260B <br /> e Prepare an Interim Remedial Action Plan to address the MTBE hot spot concentrations <br /> Please contact our office at(209) 579-2221 if you have any questions or comments <br /> Respectfully submitted, <br /> ATC Associates Inc <br /> 1 <br /> ,i�¢ra GE040 <br /> David Scrirnger / <br /> Staff Scientist <br /> � F, No 445o � 7k <br /> l � <br /> F C ti <br /> Lorraine Sawyer, P G <br /> wy � <br /> CA Professional Geologist#4450 <br /> cc Mr John Johnson,The Customer Company <br /> Mr Bob Matthews, More 4 Less <br /> Jim Barton, RWQCB <br /> sIenviromenia1125847\00371reportsllstQTR-2006 doe 4 <br />