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utilized to compensate for any settlement prior to placement of the bentonite seal. A three-foot layer of bentonite chips will be placed on top of the upper filter pack and hydrated to form a transition seal. Each well will be sealed with bentonite slurry from the top of the chip seal to approximately 3 feet bgs and completed from 3 feet bgs to the ground surface with a watertight, flush-mounted, traffic-rated vault and set in a 3-foot concrete perimeter seal. Proposed well construction details for the three B zone monitoring wells are illustrated on Figure 11, Proposed Monitoring Well Construction Details (MW-15B, MW-17B and MW-19B). Following completion of the proposed C zone well borings MW-16C, MW-18C and MW-20C to an estimated depth of 85 feet bgs, they will be completed as a groundwater monitoring wells. The construction of the proposed wells will consist of blank 2-inch diameter Schedule 40 polyvinyl chloride (PVC) casing from the surface to an approximate depth of 65 feet bgs and attached beneath with 20 feet of slotted (0.010-inch slots) 2-inch diameter Schedule 40 PVC well screen. The annulus of the screened portion of the monitoring well will be backfilled with a #212 Monterey sand (or equivalent) filter pack from the bottom of each borehole to approximately 3 feet above the top of the screen interval which will then be settled by surging and adding more sand prior to placement of the bentonite seal, if necessary. A three-foot layer of bentonite chips will be placed on top of the upper filter pack and hydrated to form a transition seal. Each well will be sealed with bentonite slurry from the top of the chip seal to approximately 3 feet bgs and completed from 3 feet bgs to the ground surface with a watertight, flush- mounted, traffic-rated vault and set in a 3-foot concrete perimeter seal. Proposed well construction details for the three C zone monitoring wells are illustrated on Figure 12, Proposed Monitoring Well Construction Details (MW-16C, MW-18C and MW-20C). Following well completions, the newly installed groundwater monitoring wells will be developed by manually removing groundwater from the well with the use of a pre-cleaned, 2-inch diameter Teflon- lined PVC bailer attached to new, 3/8 —inch nylon rope. Groundwater removed during well development will be contained in 55-gallon drums pending treatment and disposal. The groundwater monitoring wells will be installed and developed in accordance with IES's Standard Operating Procedures - Soil Sampling and Drilling(Includes Well Installation,Development,and Surveying). All drilling and sampling equipment will be thoroughly decontaminated between sample intervals and between borings to minimize the possibility of cross contamination. All drill cuttings will be collected in Department of Transportation (DOT)-approved 55-gallon drums and will remain on-site pending proper disposition. Soil cuttings will be managed in accordance with SJCEHD guidelines. If a well boring is not completed as a well (for example, if unable to advance boring to groundwater), it will be backfilled through the hollow stem auger with bentonite grout from total depth to approximately 3 feet bgs, and capped with concrete to the surface. An IES staff scientist will complete lithologic logs for each boring in general accordance with ASTM Method D 2488-90. California Tank Lines Innovative Environmental Solutions Addendum to Work Plan -6- Encinitas,California