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GE®MATRIX American Society of Testing and Materials (ASTM) Standard D 2488-90. At the LP-7 site, a discrete groundwater sample will be collected near the top of the uppermost aquifer. The sample will be field-tested for pH and electrical conductivity (EC) to determine if the water . quality is consistent with regional norms. 5.2 MONITORING WELL INSTALLATION AND DEVELOPMENT Each new well will be cased with 2-inch PVC casing and 2-inch PVC screen with 0.02 inch slots. The screened interval will extend from about 10 to 25 feet bgs (depending partly on the lithology observed during drilling). The filter material is anticipated to be Lonestar Lapis Luster#3 sand or equivalent and will be placed from the bottom of the boring to a depth of about 2 feet above the top of the screen. A bentonite transition seal will be placed to a depth of about 2 feet above the top of the filter material. The remainder of the annulus will be sealed with a cement bentonite grout. Each well will be finished at ground surface with a flush, locking steel cover and concrete pad. Following installation of each well (a minimum of 24 hours to allow grout to set), the well will be developed in preparation for sampling. Development will consist of surging and bailing to remove sediment from the well. Field water-quality parameters (pH, EC, temperature, and turbidity) will be monitored and development will continue until the field water-quality parameters have stabilized. Prior to sampling, dedicated pumps will be installed in each of the new wells. Dedicated pumps will also be installed in the existing monitoring wells (LP-1, LP-2,LP-3, and PW-1-48), which will continue to be monitored until enough quarterly samples have been collected from the DMP wells to perform statistical analysis (at least 6 samples). 5.3 SAMPLE COLLECTION AND ANALYSIS Following well development (a minimum of 24 hours) and dedicated pump installation, the new monitoring wells will be sampled. Geomatrix protocols for groundwater sampling were included in the Sampling and Analysis Plan for the Lathrop Plant (Geomatrix, 2000). Prior to collecting samples, water levels will be measured using an electric sounder, and at least four casing volumes of groundwater will be purged from each well using the dedicated pump. During purging, field water-quality parameters (pH, temperature, dissolved oxygen, EC, and turbidity) will be measured. Groundwater samples will be collected in laboratory-prepared containers, placed in ice-cooled chests, and delivered to the laboratory under chain-of-custody procedures. IAPROJECn6741.00016741-06.dw 4