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1 <br /> • Page 7 September 16,2002 <br /> zone and MW No 2 near the east fence in June 2002 Earlier borings by Gallardo and <br /> • Barber found diesel at the 13,000 to 15,000 mg/kg levels in the same area <br /> ' Earlier borings by Gallardo and Barber found concentrations of upwards to 30,000 <br /> mg/kg in the vicinity of MW No 1 and BH No B-1 at similar depths <br /> Review of previous geological findings and field findings in June support the <br /> contention that there was dispersion of diesel in the 25 FT to 35 FT bgs zone atop an <br /> ' aquatard, possibly with perched waters Perched waters were not found at this depth <br /> by Stellar or Barber in December 2000 or the later June 2002 exploration <br /> ' Near the east fence during construction of MW No 2 in June 2002, minor seepage of <br /> product (diesel like) and shallow water were apparent in the upper 0 to 10 FT bgs <br /> ' region <br /> The low concentrations of "diesel" petroleum hydrocarbons may reflect natural <br /> attenuation of hydrocarbons released from the adjacent contaminated soil masses <br /> ' Characterization of mobilityand direction of an non-volatile advancing plume at this <br /> Y <br /> site will require additional monitoring Definition of the leading edge will require <br /> ' additional sampling beyond the plant site's property line or recognition of diminishing <br /> levels with expected attrition and projected plume within a short distance further north <br /> of the property line The availability of the Victor information presents a clearer picture <br /> of the seasonal gradient and direction of groundwater movement <br /> ' Recommendations <br /> Groundwater monitoring should continue Use of common elevation datum and <br /> ' assignment of elevations to ground water surface should be continued <br /> Attenuation of hydrocarbons in the ground water should be reviewed after the <br /> September sampling of monitoring wells <br /> Alternative remediation plans should be considered leading to development of an <br /> ' approved work plan and closure of the site <br /> Seek guidance from EHS and submit"GeoTracket" formatted information on findings <br /> ' and MW locations for electronic data submittal requirement to State of California <br /> t <br /> • <br />