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DATA GAP ASSESSMENT WORK PLAN Stockton Charter Way Commingled Plume July 30, 2014 (TAME), ethanol, 1,2-dichloroethane (1,2-DCA), 1,2-dibromoethane (EDB), and naphthalene using EPA Method 826oB. At the terminal depth of each well boring, a groundwater monitoring well(see Figure 8)will be installed within the drill casing. Table h4&9w)summarizes the anticipated well construction details; however, these details may be modified in the field based upon the actual soil stratigraphy encountered. A sand filter pack will be placed in the annular space surrounding the entire screened interval, and will extend approximately two foot above the top of the screened interval. A bentonite annular seal will be placed and extend approximately two ft above the filter pack and hydrated. The remainder of the annular space will be filled with cement and/or grout from the top of the bentonite seal to within 12 inches of the surface. The wells will be secured with a locking well cap and completed with a watertight traffic-rated well box installed at grade. 4.5 WELL DEVELOPMENT After a minimum of 48 hours following the well construction, the newly constructed wells will be developed to clean and stabilize the filter pack around the slotted well casings. Development will be accomplished by alternately surging each well with a vented surge block followed by bailing to remove accumulated sediment. Final purging will be performed with either a submersible pump or bailer, and pH, temperature, and conductivity will be measured at regular intervals during purging. Development will be considered complete when: 1) eight well volumes have been removed and physical-chemical parameter trends have stabilized over three consecutive measurements (<0.05 pH, 3% conductivity, and 1o%temperature); 2)ten well volumes have been removed;or,3)the well has been purged dry(if the well does not sustain flow or is slow to recover). 4.6 WASTE HANDLING AND DISPOSAL Soil cuttings, drilling fluids, purge water, decontamination water and PPE generated during drilling operations will be containerized in DOT-approved 55-gallon drums and temporarily stored on the subject property pending characterization and disposal. Upon characterization, wastes will be transported by an appropriate disposal contractor to a licensed disposal/treatment facility. 4.7 SURVEYING Following well construction, a licensed land surveyor or registered civil engineer will survey newly installed wells. The tops of casings of wells on and off-site will be surveyed within the California State Plane Coordinate System for horizontal and vertical control to meet the State of California Water Resources Control Board requirements. The coordinates will be referenced to a known benchmark according to the North American Datum of 1983 (NAD83) and the North American Vertical Datum of 1988 (NAVD 88). 9