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mit iwu Is k- ~� Lammersvilie School District 2 Jwy 16, 1990 02/899.7004 9 observations,one sample from each boring was selected for laboratory analysis. Samples wr:re preserved on ice and delivered with the appropriate Chain-ol-Custody manifest to GTEL Environmental Laboratories, Inc, (GTEL),a State-certified laboratory,in Concord,California. The sail samples obtained from the three borings (MW-6, MW-7 and MW-8) were analyzed for TPH-G and BTEX using U, S. Environmental Protection Agency (EPA) Methods 5030/8015/8020. 5.5 MONITORING WELL INSTALLATION The three soil borings were completed as monitoring wells(MW-6, MW-7, and MW-8)to provide groundwater sampling points east of the site, The wells were in_!alled to a total depth of 20 feet a io were constructed of 15 feet of 0.020-inch, machine-slotted PVC screen threaded to blank PVC casing to the surface. The annular space from the bottom of the yells to approximately 1 foot above the slotted interval was filled with number 2/12 grain-size sand. The wells were then sealed with approximately 2 feet of bentonite,overlain by sand-cement grout to the surface. The drilling and construc,ion of the welly, and placement of the annular seals, was inspected by Mr. Gregory Lyon of the SJCPHS-Eho. Locking caps and traffic-rated street boxes were installed to provide access to a' _ wells. Specific well construction details, which are shown on the drill logs, aro included in Appendin,I. ` 5.6 GROUNDWATER MONITORING On June 19, 1990,the wells were c .veloped using bailing and surging techniques to remove fine particulates and to accelerate proper settling of the sand pack. Groundwater collected during well development was stored on site in DOT-approved containers for disposal or remediation at a later date, depending on the results of laboratory analyses. On June 21,1990,depth to groundwater was measured to determine static water table elevations and the presence of any separate-phase petroleum hydrocarbons(fable 4). Prior to monitoring,all eiqht wells were surveyed to grade level for elevation control. An arbitrary datum of 100 feet was used for elevation control, using MW-1 as a benchmark, The depth to water was measurad using an interface probe, consisting of a dus.1 optical sensor and electrical conductivity probe,that distinguishes between water and petroleum products. The monitoring data was combined%Lith the survey results to determine the water tabl-2 elevation in each of the monitoring wells. Figure 3 presents a Potentiometric Surface Map of the wa!er table elevations measured on June 21, 1990, No separate-phase petroleum hydrocarbons were measured on the groundwater surface. GROuNmvvra TF.0 INGLOC),I\C. '� AN