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MLEEOSHILL•HERKENHOFF, INC. <br /> Monitoring Wells <br /> -f <br /> Three groundwater monitoring wells will be installed in the Lincoln Village <br /> Center. These proposed wells were located to establish the direction of <br /> groundwater flow and gradient across the Lincoln Village Center and to <br /> confirm the presence and aerial extent of suspected shallow groundwater <br /> contamination both upgradient and downgradient from Lincoln Village Cen- <br /> ter. The wells will be generally located in accessible areas near the <br /> perimeter of the Lincoln Village Center as shown on Figure 1 . The wells <br /> will be approximately 65 feet deep and designed to monitor water levels and <br /> water quality in the shallow aquifer. The wells will be constructed with <br /> 4-1/2-inch diameter Schedule 40 PVC well casing with flush joint threads. <br /> No glue or solvent will be used in the construction of these wells. The <br /> annulus of the well will be gravel packed to above the perforated zone using <br /> an engineered sand gravel pack, and then sealed with a bentonite pellet cap <br /> prior to placement of the cement grout sanitary seal . Each monitoring well <br /> will be equipped with a locking cover and grouted to the surface. Locations <br /> and reference point elevations (to 0.01 feet) of the wells will be deter- <br /> mined by surveying. To account for seasonal and annual water level varia- <br /> tions, the perforated interval will extend from approximately 5 feet above <br /> the water table to 10 feet below the water table. A typical monitoring well <br /> design is presented on Figure 2. <br /> The wells will be drilled using direct rotary equipment by a California <br /> /licensed C-57 water well contractor who is experienced in monitoring well <br /> installations. An alternative would be to use 12-inch OD continuous flight, <br /> hollow stem auger drilling equipment; however, the integrity and placement <br /> of the gravel pack and sanitary seal may be difficult to control below the <br /> water table. Rotary drilling will be conducted without the use of lubrica- <br /> tion on the drilling equipment. All drilling equipment and casing materials <br /> will be high pressure stem cleaned prior to initiating drilling operations <br /> at each of the monitoring well sites. All drilling will be done under the <br /> supervision of a professional engineer or certified engineering geologist. <br /> A detailed boring log will be prepared, noting soil types (Unified Soil <br /> Classification System) , moisture conditions, and drilling penetration <br /> rates. <br /> -3- <br />