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4"' � Revised Additional Vapor and Groundwater Monitoring Well Work Plan Raymond Investment Corporation October 30,2009 Page 6 V 14 feet below the water table to 6 foot above the water table. A flush-threaded PVC bottom cap will be placed at the bottom of the screen section in the well. Blank PVC casing will be installed above the L. screens to the ground surface. A filter pack of#2112 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 r y the augers are being gradually retracted to avoid bridging. To form a protective seal, approximately five- Zi*nir feet of bentonite chips will be installed. abovethe sand in the well. 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 well and will extend from the bentonite to the ground ,�2�'!2� LAsurface. The monitoring wells will be completed with locking caps and 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. A generalized shallow monitoring well construction diagram is included as Figure 4,Appendix A. +� Table 1.Monitoring Well Construction and Sample Interval Details Well ID MW-4D MW-5 MW-6 MW-7 8 9 Location Near MW4 Northeast from Near SB-9 Near corner of Grant +� and SB-7 MW-4 and Channel St. Sample interval None Every 5 feet - 25, 35, 40 feet None Laboratory analysis None 5, 15, 25, 35,45 feet 25, 35, 40 feet None interval 4ry 5a.13 Neat cement interval 0-5 feet 0-18 feet 0-18 feet 0-18 feet Bentonite interval, 5$ 63 feet 18-23 feet 18.23 feet 18-23 feet LA pellets or chis Sand interval, 2112 feet 23-45 feet 23-45 feet 23-45 feet — _ washed Montere 56 '20 ry Screen interval, 60-70 feet 25-45 feet 25-45 feet - 25-45 feet` 0.010" slotted PVC Total depth 70 feet 45 feet - 45 feet 45 feet 4.2.2 Soil Vapor Monitoring Well Installation Procedures Soil vapor monitoring well installation will be conducted with hand auger borings (SV-4, SV-5 and La SV-6) and expendable soil gas implant probes. The hand auger borings will be advanced to a depth of five feet bgs through holes cored in the concrete surface. The soil encountered in the 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 deionized water and double rinsed with deionized water. L• One expendable soil gas implant probe will be installed in each boring.`Each probe will be connected to '/4-inch Teflon or polyethylene tubing and lowered to th toottom of the boring while the open end of the tubing is held above the ground surface. A filter pack of#3 Monterey sand will be placed in the boring to LM approximately one foot,above the probe. Dry granular bentonite will be placed in the boring from the top of the sand to onfoot 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 tr CONDOR