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10, MEMO F 2021899-7004 - Lammersville School District 9 July 16; 1990 observations,one sample from each boring was selected for laboratory analysis. Samples were preserved manifest to GTE C L Environmental Laboratories, on ice and delivered with the appropriate Chain-of-Custody Inc. (GTEL),a State-certified laboratory,in Concord,California. The soil samples obtained from the three borings (MW-6, MW-7 and MVv8) were analyzed for TAH-G and BTEX using U. S. Environmental Protection Agency (EPA) Methods 50301801518020. 5.5 MONITORING WELL INSTALLATION MW-7, and MW-8}to provide -- The three soil borings were completed as monitoring wells(MW-6, groundwater sampling points east of the site. The wells were installed to a total depth of 20 feet and were _ constructed of 15 fret of 0.020-inch, machine-slotted PVC screen threaded to blank PVC; casing to the surface. The annular space from the bottom of the wells to approximately 1 foot above the slotted interval was filled with number 2112 grain-size sand. The wells were then sealad with approximately 2 feet of bentonite,overlain by sand-cement grout to the surface. The drilling and construction of the yells, and placement of the annular seals,was inspected by Mr.Gregory Lyon of the SJCPHS-END. re installed to provide access to all the wells. Lacking caps and traffic-rated street boxes we Specific well construction details,which are shown on the drill logs, are included in Appendix ll. 5.6 GROUNDWATER MONITORING On June 19, 1990,the wells were dEvelcped 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 �ocarbons[Table 4). Prior to monitoring,all eight and the presence of any separate-phase petroleum hyd levation control. An arbitrary datum of 100 feet was use wells were surveyed to grade level for ed far elevation control, using MWA as a benchmark. The depth to water was measured using an interface at uishes between _ probe, consisting of a dual optical sensor and electrical conductivity probe,witthe s iveysr results lts to determine water and petroleum products. The monitoring data was combs the water table elevation in each of the monitoring wells. Figura 3 presents a Potentiometric Surface Map drocarbons of the water tableelevationsmeasured on June 21,-1990--.-Noseparate-please petroleum y were measured on the groundwater surface, �- GROUNDWATER TECHNOLOGY.INC.