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• f Monitoring Well installation Work Plan City of Stockton RWCF April 27,2005 Page 3 installed above the screens to the ground surface. No glue or solvents will be used in the construction of the wells. A filter pack of#3 Monterey sand will be placed in the annular space to approximately two feet above the screens while the augers are in place. The depth of the sand in the annulus of the well will be monitored with a weighted tape measure while the sand is being placed and the augers are being gradually retracted to avoid bridging. If conditions allow,the sand pack will be surged prior to placement of the bentonite seal. Approximately two feet of bentonite pellets will be placed above the sand to form a protective seal. The bentonite chips will be installed as the augers are retracted. The bentonite will be hydrated using potable water. A surface seal of neat cement will be tremied into the annulus of the wells and will extend from the bentonite to the ground surface. The augers will be removed before emplacement of the grout. The monitoring wells will be completed with locking traffic boxes installed flush with the ground surface. Details of the well construction will be noted on the geologic logs, including the depth intervals of the screen, sand pack, and seals. All drilling and well completion activities will be completed under the supervision of a Condor geologist in accordance with the provisions of the SJCEHD permits. Condor will prepare geologic and completion logs for each well. Drill cuttings for the monitoring well borings will be logged according to the Unified Soil Classification System (USCS). Descriptions of soil types encountered and any other pertinent field observations will be recorded on boring logs. Completion details recorded on logs will include the type of screen and casing, depth intervals of the screen, blank casing, sand pack, bentonite seals and surface seals,and the quantities of materials added to the annular spaces. 43 MONITORING WELL SURVEYING,DEVELOPMENT,AND SAMPLING Following installation of the monitoring wells, the wells will be surveyed by a licensed land surveyor to determine the location and elevation of the well collars. The well collars will be surveyed with a vertical accuracy of 0.01 foot(referenced to NAVD88 Datum) and horizontal accuracy of 1.0 foot(referenced to NAD83 Datum). The measuring point for water-level measurements will be marked on each well collar. Ground surface elevation at each well will be recorded to the nearest 0.1 foot by measuring down from the measuring point. At least 48 hours following construction, the monitoring wells will be developed by surging and bailing the groundwater in each well until the discharge water is relatively free of sediment and clear. The monitoring wells will be purged until the temperature, electrical conductivity (EC), and pH of the water have stabilized. The volume of water purged from each well during development will be recorded. All development water will be discharged to the ground surface near the wells. Standard decontamination procedures for wastewater sites require that all field equipment will be cleaned prior to use in each well by double rinsing with de-ionized water and shall include alcohol wipes of all field equipment between sample locations to prevent cross contamination. Groundwater samples will be collected at least 48 hours following development of the monitoring wells to allow the static water level to recover from development activities. Prior to sample collection, the static water level in each well will be measured to the nearest 0.01-foot with a battery-operated, water level meter. The water level meter tape will be decontaminated according to standard procedures for wastewater sites'(above section) prior to measuring the water level in each well. The monitoring wells