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x <br /> 29 December 1999 <br /> '. AGE-NC Project No 97-0312 <br />' Page %of 9 <br /> } <br /> • 1,2-DCA was detected in UST-5 at a concentration of 1,000 ppb, exceeding the State of <br />' California drinking water maximum contaminant level (MCL) of 0 5 ppb <br /> • Primarily clayey silt was encountered from surface grade to 80 feet bsg Silty sand was <br />' encountered from 80 feet to 100 feet bsg <br /> • The greatest concentrations of hydrocarbons in soil were detected in soil samples collected <br /> beneath the former UST locations High concentrations were also detected in the shallow <br />' piping samples and in borings UST-1 and UST-5 , <br /> • The lateral and vertical extent of Impacted soil at the former UST and dispenser locations has <br />' been defined and are Illustrated on Figures 5 through 11 _ <br /> • Approximately 416 gallons of gasoline'are estimated to Impact a total of 3167 cubic yards , <br />' of soil, approximately 2495 gallons of diesel are estimated to Impact a total of 7495 cubic <br /> yards of soil <br /> • Approximately 73 percent of the gasoline and 90 percent of the diesel in soil Is contained <br />' within approximately 1230 cubic yards of soil located within 25 feet of surface grade <br /> 6.0. RECOMMENDATIONS' <br />' Based upon data obtained from the site, AGE recommends the following <br /> • In preparation for site closure, performance of"fate and transport" modeling to determine <br />' possible future effects of impacted soil on groundwater through leaching of contaminants <br /> • Continuation of quarterly monitoring event in accordance with monitoring requirements from <br /> the PHS-EHD <br /> S <br /> 7.0. LIMITATIONS <br /> r <br /> Our professional services were performed'using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities, The findings were based mainly <br /> upon analytical results provided by an ' ,independent laboratory _ Evaluation of the <br /> geologic/hydrogeologic conditions at the site for the purpose of this Investigation was made from <br />' a limited number of available data points (i a ground water samples, soil samples) and subsurface <br /> conditions may vary away from these data points No other warranty, expressed or Implied, is made <br />' as to the professional recommendations contained in this report <br /> r <br />' - Advanced GeoEnviron mental,Inc <br />