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The Iithology encountered <br /> consisted predominant) during the dr�llin <br /> Interbedded with reddish-brown son brown g °f inoriitoring wells <br /> aquifer Is i , brown, and reddish-browW-1 through l►'pW_3 <br /> orated within the , and overlying bluish- sandy and cla e <br /> about 45 feet below surface bluish-gray silts gmy> clayey slits The u Y y silts <br /> grade. Around water was encountered duan uppermost <br /> The ay In the borings <br /> neal'Ost surface water channel is the IUIarSlough, <br /> g drilling at <br /> the north The nearest mon Slou h <br /> associated tribe major navigable g , located aPPraximatel <br /> on-site runoff is directed ciate approximately s waterway IS the y 3,500 feet to <br /> etwo miles to the an Joaquin River, <br /> system along ernes of surface drains During Including its <br /> direction g the western perimeter which +r g Inclement weather, <br /> This drainage mPtY Into a subsurface drainagc <br /> g system is believed to <br /> ASSESS flow In a southerly��T H1STpRY <br /> 1,aitial UST Removal and Sam <br /> Pang Activities <br /> Originally, the site housed <br /> L1STs, one 5400-gallonthree diesel <br /> excavated and moved an J underground storage <br /> Pacify USTs, and one 515- tanks {two Ip <br /> PIPing and dispensers une 12, 1989 b gallon capacit '`gallon capacity <br /> were also removed y wathall ConstruCtron waste-oil UST) which were <br /> Analytical results of Stockton The attached <br /> of the of the soil samples collected In native soil a <br /> Of <br /> UST excavation revealed that elevated Hydrocarbons (TRPH ed levels of Ta th °f 121f feet at the bottom <br /> detected in the 's ) at 4,500 parts Total <br /> Recoverable Petroleum <br /> ample collected from Per million {ppin) were <br /> at a depth of 13 feet the center of present Soil contaminationwas <br /> 650 ppm Laboratory analytical the west wall of the diesel UST excavation was <br /> No detectable cal results revealed a <br /> collected from the northwest of suspected con d1esel exOavatron <br /> three rthwest, of p taminants (TPH-d) concentration of <br /> f piping samples, and one , and easternwere revealed In sample, <br /> f dispenser sample collected from Portions hof the diesel UST Ples <br /> sail Underlying excavation, all <br /> Water y g the easternmost <br /> followiWarks o f Escalan, California re <br /> 1959 g a completed Invests Prepared a Problem Assessment Re <br /> sail was ex <br /> Investigation of soil and ground-water contamination dated <br /> contamination excavated from the April 4, ISigp <br /> nation was detected In the ex waste- On November 27 <br /> P were collected, <br /> along the south ' <br /> Water Work,F then , the excavation and east Falls feet. Soli <br /> excavation completed one ground-�, was evident) APPaOntly,n s no <br /> area and one angled boring, ater MonitoringY backfilled with clean soil <br /> existing shop building g, ASB-1 well, MW-1 <br /> 1 revealed g Laboratory analyses of soil m e south east of the UST <br /> minor concentrations of TRA it was advanced ben <br /> PPM), <br /> revealed <br /> le feet (2 7 H in soil sam pies collected during Oath the <br /> PPnI), and 34 feet (4, 1 POs collected from g the drillinof 1 g o f MW_ <br /> �'y'I^". Inc <br /> pPm) No detectable concentrations depths of BTl feet (1 5 <br /> Project No 33236 pp <br /> May 1995 X were <br /> 2 <br />