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.q <br /> n <br /> KLLINFELDER <br /> fi <br /> 1 EXECUTIVE SUMMARY <br /> This is report of ground water assessment activities conducted at the Nomellini <br /> Construction facility in Stockton, California. Nomellini Construction retained Klcinfelder <br /> to assess ground water beneath the site that may have been affected by an u►:derground <br /> �. storage tank removed in 1988. 'I`lle scope at work was based on a work plan approved by <br /> the San Joaquin County Public Health Service,Environmental Health Department. <br /> In February 1991, Kleinfelder installed, developed and sampled three monitoring wells <br /> triangulated around the tank excavation. Analytical results of the water samples collected <br /> - as been affected b gasoline and its <br /> from the monitor wells indicate that ground water h Y S , <br /> S-QrlipvuriUsttLilS�ti�[Y�jt1G'_grd�it2"kat„ I17�7p.Q�,;� t>ze:`east;:EliettIle5i �i'�1tC�tltlatt4llS.�WOICf <br /> detected.in Ynoniter3ng ell.N[W-2.approxtnately 70 feet north of the forrner,ankV Total <br /> Petroleum Hyrdrocarbons (TIPH) as gasoline was detected at 10,000 ug/l, while benzene <br /> was delcted at 13,(}00 ug/I. The concentrations of benzene detected was at concentrations <br /> significantly above the California Title 22,Maximum Contaminant Level(MCI.)of 1.0 ug/1 <br /> for drinking wau.r as established by the California Department of 1Iealth Services. Due to <br /> the apparent discr:pancy between the measured gradient on February 21, 1991 and the <br /> analytical results of samples collected that day, Meinfelder collected additional ground <br /> water gradient information on April 9 and 19, 1991 <br /> 'fie gro he site s',ppcs generally to the east but#luctuktes from <br /> ' g <br /> east-north asftd`astsou hea t. Based'on the ground water flow direction,MW-1,the well <br /> approximately 30 feet downgradient of the excavation should have had the greatest <br /> concentrations of petroleum hydrocarbons. It is not clear why MW-2 reported the highest <br /> -• lin the wells in <br /> , <br /> concentrations duringhe Februarysem lin event;hpwpyepon.Xcaamp l3 ,. <br /> asbltr�e w:”-'served fioatin on:the watcr.sutface to K'W <br /> ifne-1991",1 layer of product (II � <br /> gasoline and its components had also increased in water samples <br /> ,1„Concentrations of <br /> ' collected from the other two wells on that date. <br /> Based on the observed ground water flow direction and analytical results, it appears that <br /> ground water affected by petroleum hydrocarbons extends laterally east from the <br /> excavation possibly off site beyond MW-j. .1Kleitifelder.recommends rurthec sse�sme>?ti`;oF ; <br /> ground.waterjo-,assess,;the,lateral extent,of-contarainant.itligratil tz'nrd fine potential far: <br /> downward rnigratitsn'fo`deeper,aquif s. Efforts should be made to remediate the soil and <br /> ground water beneath the site. <br /> F18-91-62 1 <br /> copyright 1991 Kleinfelder, Inc. <br />