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' 2.1.3 Monitoring Well Installation and Groundwater Sampling Four groundwater monitoring wells will be installed at approximate locations presented in ' Figure 3. The locations may be moved based on the results of the geoprobe groundwater grab sampling with at least one well (MW-8) located downgradient of the known plume. To install ' the wells, soil borings will be advanced using a truck-mounted drill rig equipped with eight-inch diameter hollow-stem augers. The borings will be drilled to a depth of 20 feet bgs and completed ' as groundwater monitoring wells. Construction of the existing monitoring wells is summarized in Table 6. Screen intervals of the existing monitoring wells (10 to 25 feet bgs) are below the ' current water table. The newly installed wells will be screened from 5 to 20 feet to coincide with the water table. A well construction diagram is included as Figure 4. During drilling, a soil sample will be collected from each boring at a depth of five feet using a ' modified California split-spoon sampler lined with brass tubes. The sample will be used for observation of the soil, field measurement of volatile organic compounds using a PID meter, and possible laboratory analysis. Procedures for drilling, logging, and soil sampling will be in ' accordance with regulatory guidelines and IT technical procedures, and conducted under the direction of a California Registered Geologist The groundwater monitoring wells will be constructed using 15 feet of two-inch diameter, ' 0.020-inch slotted, schedule 40 PVC well screen and 5 feet of blank casing. The screened interval will extend approximately 2.5 feet above the encountered saturated zone to allow for ' seasonal fluctuations of the water table. A filter pack of Monterey#I C sand will be installed to approximately 1 foot above the screened interval. A one-foot bentonite seal will be placed above t the sand, and the remaining annulus will be filled with a 20:1 cement/bentonite grout sanitary seal. The top of the wells will be secured with water-tight locking caps and 8-inch diameter ' utility box, finished approximately 1 inch above grade. ' After the wells are completed and the grout has had sufficient time to set (at least 72 hours),the monitoring wells will be developed to maximize hydraulic yield and minimize turbidity. Development will consist of alternately surging(with a vented surge block), bailing, and/or ' pumping to remove fine-grained materials. Fluid levels in each well will be monitored and pH, electrical conductivity, turbidity, and temperature measurements will be recorded to document ' the development procedure. t7