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4.2.2 INSTALLATION A total of two groundwater monitoring wells will be installed outside the western property boundary of the Site, approximately 10 feet from EI Dorado Street (see Figure 2). The first off-site monitoring well, MW-10A, will be located approximately 200 feet north of Duck Creek/Walker Slough. The second off-site monitoring well, MW-11,will be located approximately 100 feet south of the northern boundary of the Site. The off-site groundwater monitoring wells will be installed using hollow stem auger, sonic, or equivalent and will be constructed using 4-inch diameter, flush-threaded, Schedule 40, PVC blank and screened (0.010-inch slot size) casing. Each well will be advance to approximately 70 ft bgs, based on field conditions observed during drilling. Groundwater monitoring wells typically extend up to 10 feet above and at least 15 feet below the groundwater surface, provided that no competent clay layer is penetrated. The annular space surrounding the screened casing intervals will be backfilled with No. 2/16 Monterey Sand (filter pack) to approximately 1 foot above the top of the screened section. During groundwater monitoring well construction, the filter pack will be completed by surging with a rig-mounted surge block. A 3-foot thick bentonite annular seal will be placed above the well filter pack and the remaining annular space will be sealed with a bentonite grout to approximately 3-feet bgs. For each monitoring well, traffic rated utility access boxes will be installed in structural concrete, slightly above grade at the surface, and locking, watertight caps will be installed to prevent unauthorized access to the well and to limit infiltration of surface fluids. A diagram of the proposed construction details for the off-site wells is presented as Figure 3. Boring logs, documenting the soil lithology every 5 feet bgs, will be completed for each monitoring well installation. In addition, once the wells have been completed, Siegfried Engineering, a Licensed Land Surveyor, will survey the newly installed wells. Features to be surveyed include: top of casing, top of utility access box, vertical and horizontal coordinates (with accuracy to at least 0.01 feet). After installation, the monitoring wells are required to stand for approximately 48 hours prior to development. The wells will subsequently be developed by a combination of surging, bailing, and/or pumping. During development activities, temperature, pH, turbidity, dissolved oxygen, salinity, and specific conductance will be measured as discussed in the Sample Collection and Analysis Plan. Development is considered complete when these parameters vary less than 10 percent from previous readings. 6 �'MILLER MODUKr P:\707 Cove Contractors\WDR\Tech Report and WP 2008\Tech Report and WP-FINAL.doc