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WORK PLAN FOR GROUNDWATER INVESTIGATION Chevron Service Station # 94054 Stockton, CA October 26, 2016 equipment will be decontaminated with high pressure steam following the completion of each soil boring. Down-hole sampling equipment will be decontaminated between samples using an Alconox detergent solution and a tap water rinse. 3.4.2 Well Installation Following completion of each well boring, a groundwater monitoring well will be installed within the drill casing. Well materials will be placed through the drill casing using tremie pipe (where applicable) and the well casing will be raised out of the boring during well construction to ensure the integrity of the well. The table above summarized the anticipated well construction details for proposed monitoring wells 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 feet 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. 3.4.3 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 pumping (using a submersible pump)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 10% 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). 3.4.4 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). 3.5 SOIL SAMPLE COLLECTION AND ANALYSIS Selected soil samples from the well installation borings will be submitted for chemical analyses and will be based on visual observations, soil type, and VOC measurements as determined by a Stantec 5