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0 WE- IW- Y-� MRRW ,..i Site Assessment Report April 5, 1991 139 South Center,Stockton,CA„ Page 6 laboratory analysis were collected from the con`Jnuou,:core by driving a 2-inch by 6-hch Iong brass liner into the core at tt'`'te desired depth interval. Due to an equipment malfunction, it was not possible to y use the continuous core barrel during the soil boring for Monitoring Well MW-4;however,sail samples were examined,screened and collected approximately every 5 feet In this soil boring,using a rllodlfled California split spoon sampler. Copies of the boring logs are included In Appendix B. Soil samples were collected for the field screening and for possible laboratory enalyses from each borehole at approximately 5-foot Lntervals below surface grade. The soil samples were scrsened In the field for the presence of volatile hydrocarbon vapors using a photo-ionizaticn detector(PIA). Soil samples were selected;or laboratory analyses based on field obxervatlons Including PID readings. At least one soil sample in the vadose zone immediately overlying the saturated zone was selected for laboratory analyses from each of the four soil borings. These samples were collected In 2-Inch- diameter by 6-Inch-long brass tubes. The tubes were sealed with aluminum foil,capped, and sealed with duct tape µ' The retained samples were labeled,stored on ice in an insulated cooler,and transported under Chain-cf-Custody Manifest to the Superior Analytical Laboratory In Marti,iez,Califomla,a State of Cal€fornia-certlfied laboratory,for analyses. Copies of applicable Groundwater Techrciogy Standard Mill Operating Procedures(SOPS)are Included In Appendix C. The selected samples were analyzed for the presence of benzene,toluene,ethylbenzene, xylenes(BTEX),and total petroleum hydrocarbons(TPH)-as-gasoline using modifled U.S.Environmental Protection Agency(EPA)Mathods 5030/8020/8015. A sample from the soil boring for monitoring well MWA which Is nearest to the waste-oil tank,was also analyzed for the presence of chlorinated hydrocarbons using EPA Method 624. Copies of the laboratory, g reports and Chain-of-Custody Manifests are included In Appendix D. ab MenKgrIng Well . Monitoring wells were knstalled in the four so]]borings on 1,r February 14 and 15, 1991 (MW-1,MW-2 and MW-3),and February 19, 1991 OAW4). The wells were , a constructed of 2-ir.;h-diameter,0.020-inch, machine slotted,Schedule 40 PVC well screen set from €� Wfeet below grade to 35-feet below grade and blank casing set from 35-feet below grade to the surface. A well filter pack consisting of Lapis Luster No.2 sand was placed In the annular space of each �f GROUNDWATER .1_._.;TECHNOLOGY,INC.