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{' y�.W ` �'44 .,. F.R. * N y.� +� ;w, �3 ^,.'•,.- Rt'��' ,.� _ � R" ..� a. �,�.5 � � r Y, Site Assessment Report April 5, 1991 139 South Center,Stockton,CA Page E .. i laboratory analysis were collected from the oontinuous axe by driving a 2-Inch by 8 fth long brass liner into the core at the desired depth Interval. Due to an equipment malfunction,It wass not possible io use the continuous core barrel during the soil boring for Monitoring Well MW-4;however,soil samples Ware examined,screened and collected approximately every 5 feet in this soil boring,using a Modified California spit;spoon sampler. Copies of the boring logs are Included In Appendix B. 1 Soil samples were collected for the field screening and for possible i2bc3 story analyses from each borehole at approximately 5-foot Intervals below surface grade. The soil samples were screened in the field for the presence of volatile hydrocarbon vapor:using a photo-lonlzatlon detector(PID). Soil samples were selected for laboratory analyses based on field observations Including PID readings. At least one soil sample in the vadose zone immediately overlying the saturated zone was selected for laboratory analyses from each:f the four soil borings. These samples were collected in 2-inch-diameter by 8-inch-long brass tubes. The tunes were sealed with aluminum foil,capped,and sealed with duct tape. 1 ` The retained samples we. W*ed,stored on ice In an Insulated cooler,and transported under Chain-of-Custody Manifest to the Superior Analytical Laboratory In Martinez,Callfomla,a State of k Caldomia-certlrled laboratory,for analyses. Copies of applicable Groundwater Technology Standard F Operating Procedures(SOPS)are Included in Appendix C. i 3 # The selected samples were analyzed for the presence of benzene,toluene,ethyibenzene, i a xylenes(BTEX),and total petroleum hydrocarbons(TPH)-as•gasoline using modifled U.S.Environmental Protection Agency(EFA) Methods SC3018=18015. A sample from the soil boring for monitoring well 'p MW-4,which is nearest to the waste-nil tank,was also analyzed for the presence of chlorinated hydrocarbon using EPA Method 824. Copies of the laboratory reports and Chain-of-Custody Mangests are included In Appendix D. ` gills Weil Construction. Monitoring wells were Installed In the four soil borings on February 14 and 15, 1991 (MW-1,MW-2 and MW-3),and February 19, 1991 (MW-4). The wells were oonstmeed of 2-Inch-dismotor,O,020-inoh, machine slotted,Schedule 40 PVC well seen set from eo-feet below grade to 35-feet below grade and blank casing se[from 35-feet below grade to the surface. A well filter pack a;nsisting of Lapis Luster No.2 sand was placed In the annular space of each -. GR4UNDWOER i--•;TECHNUt.OGY,INC.