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Additional Groundwater and Agriculture Drain Monitoring Work Plan Residential Neighborhood G April 18,2005 Page 4 Six boreholes will be drilled at the locations indicated on Figures 2 and 3 and wells will be constructed in each borehole.Boreholes will be a minimum diameter of eight inches. Wells will be completed in three of the boreholes to a total maximum depth of 25 feet or less and three wells will be completed to a depth of 12 feet regardless of soil types encountered. Each well will be constructed according to attached Figures 5 and 6. The casings will be of two-inch diameter PVC, 0.010-inch slotted screen, threaded bottom cap, #2/12 sand filter pack, and a two-foot bentonite pellet seal. The slot size and sand pack are designed to exclude fine soils observed to be present at the site. The sand filter will extend at least 12 inches above the top of the screen openings. The filter pack of newly installed wells will be surged prior to installation of the transition seal if field conditions allow. The annular space from the top of the bentonite to the existing grade will be filled with neat cement containing three to five percent bentonite by weight. The surface completions will consist of locking monuments set in 3-foot diameter concrete pads, or equivalent rectangular pads at least four inches thick containing concrete reinforcing wire to prevent cracking. Fluorescent yellow bollards will be installed protect the pedestals. The wells will be fitted with stovepipe well monuments with maximum stick-up heights of approximately four feet (depending on location). Each well will be equipped with a watertight expansion cap to protect against flooding. In the three deep wells (25 feet deep), 10 feet of screen will be placed at the bottom of the well. The remainder of the well will be completed with blank casing. The three shallow wells (12 feet deep) will contain five feet of screen. Soil cuttings from the six boreholes will be disposed of on site. 4.4 MONITORING WELL SURVEYING,DEVELOPMENT,AND SAMPLING Following installation of the monitoring wells, the wells will be surveyed to determine the location and elevation of the well collar relative to a common datum. The well collars will be surveyed with a vertical accuracy of 0.01 foot and horizontal accuracy of 1.0 foot. The measuring point for water-level measurements will be marked on the well collars. The groundwater gradient will be estimated using the survey information and depth-to-water measurements collected from these wells, and correlated with data associated with existing on-site monitoring wells. After at least 48 hours following construction, the monitor wells will be developed by surging and bailing the groundwater in the well until the discharge water is relatively free of sediment (clear to the unaided eye) or until the wells are dry (and recharge is very slow). The monitoring wells will be bailed until the temperature, electrical conductivity, and pH of the water has stabilized. All well-development equipment will be cleaned prior to use by washing in a solution of laboratory-grade, non-phosphate detergent and deionized water,wiping with isopropyl alcohol, and double rinsing with deionized water.The purge water removed from the wells during development will be discharged to ground surface. Groundwater samples will be collected at least 48 hours following development of the monitor wells. Prior to sample collection, the static water level in the wells will be measured to the nearest 0.01-foot with a battery-operated, water level meter. The monitor wells will be purged using a clean, disposable bailer until the temperature, electrical conductivity, and pH of the water has stabilized. At least three casing volumes of water will be purged from the deep monitor wells.Recharge capability will be assessed in the shallow wells at the time of well development. If there is insufficient recharge (insufficient volume for sampling within 4 hours of purging dry) the wells will be sampled without purging, as is conducted on existing shallow wells. The purged water from the wells will be discharged to ground surface. i«1 CONDOR