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sow I.s Additional Vapor ande.tindwater Monitoring Well Work Plan Raymond Investment Corporation August 4,2009 Page 6 Ir The monitoring well will be completed with locking traffic boxes installed flush with the ground surface. Details of the well construction will be noted on the geologic log, including the depth intervals of the screen, sand pack, and seals. Table 1. Monitoring Well Construction and Sample Interval Details Well ID MW-4D MW-5 MW-6 MW-7 MW-8, 9, 10 Location Near Angled Near SB-9 Near SB-5 and Near corner of MW4 northeast from former tank Grant and and SB-7 MW-4 Channel St. Sample interval None Every 5 feet 25, 35,40 feet 10, 25, 35, 40 None feet - Laboratory analysis sis None 5 15, 25 35 25 35 40 feet 10 25 3S 40 None a > interval 45 feet feet ' Neat cement interval 0-58 feet 0-23 feet 0-23 feet 0-23 feet 0-23 feet Bentonite interval, 58-63 23-28 feet 23-28 feet 23-28 feet 23-28 feet pellets or chis feet Sand interval, 2112 63-75 2845 feet 28-40',feet 28- 9eet 28-40 feet LA washed Montereyfeet vl `' Screen interval, 65-75 30-45 feet 30-45 feet 30-45 feet 30-45 feet 0.010" slotted-PVC feet ? Total de th 75 feet 45 feet` feet I kfeet Efeet __1 (fin %'S J/ La 4.2.2 Soil Vapor Monitoring Well Installation Procedures 'Wt� ? Soil vapor monitoring well installation will be conducted with hand auger borings (SV-4, SV-5 and SV-6) and expendable soil gas implant probes. The hand auger borings will be advanced to a depth of L.d five feet bgs through holes cored in the concrete surface. The soil encountered in both hand auger borings will be described and logged. The hand auger will be thoroughly cleaned before each boring is advanced using laboratory-grade, non-phosphate detergent and hydrocarbon-free water and double rinsed with hydrocarbon-free water. One expendable soil gas implant probe will be installed in each boring. Each probe will be connected to '/<-inch Teflon or polyethylene tubing and lowered to the bottom of the boring while the open end of the w tubing is held above the ground surface.A filter pack of#3 Monterey sand will be placed in the boring to approximately one foot above the probe. Dry granular bentonite will be placed in the boring from the top of the sand to one foot above the sand, and then powdered bentonite slurry will be placed to the ground +"'' surface. The purpose of the dry granular bentonite is to protect the sand from being impacted by the wet bentonite slurry above. The purpose of the bentonite slurry is to provide vapor barrier to surface air intrusion, which is also superior to hydrated bentonite chips alone. The bentonite will be hydrated with potable water. A traffic rated vault box will be installed on each boring at the ground surface. 4.3 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 in order to comply with AB2886 (Water Code sections 13195 — 13198). The well collars will be surveyed with a vertical accuracy of 0.01 foot to a NAVD 88 or NGVD 29 datum, and with a horizontal accuracy of 0.03 foot to a NAD 83 datum. The measuring point for water-level 4MA44. to CONDOR La