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ter.-- Monitonng Well Installation Report 730 E Channel Street,Stockton,CA ' December 15,2044 Page 3 California The monitoring well borings were drilled using 8-inch outside diameter, continuous-flight, ' hollow-stem auger The hollow-stem auger and other down-hole equipment were decontaminated between borings by steam cleaning to prevent cross-contamination Steam cleaning rinsate was placed in 55-gallon drums, sealed, labeled, and left on Site pending laboratory analyses ' Drill cuttings from the borings were logged according to the Unified Soil Classification System (USCS) Geologic logs were prepared containing field observations including soil type, photoiomzathon detector (PID) measurements, and the presence of staining or odor Field observations consisting of well-boring - observations, PID screening results, detection of sample odors, and visual observations of the Site geology are included on the geologic logs prepared for all of the well borings (Appendix B) ' 33 SOIL SAMPLING One soil sample was collected from each 55-gallon drum of drill cuttings from the borings for MW-1, ' MW-2, and MW-3 to characterize the soil for disposal The soil samples were collected in clean brass tubes that were sealed at the ends with Teflon® sheeting, capped, and labeled The samples were stored in r a cooler chilled with Blue Ice® and delivered under chain-of-custody procedures to Argon Laboratories (Argon) in Ceres, California, for analyses The samples were composited three-to-one by the laboratory prior to analysis 34 MONITORING WELL CONSTRUCTION The monitoring wells were constructed with 15 feet of 2-inch outside diameter, Schedule 40, flush- threaded, machine-slotted PVC screen (slot size 0 020) A flush-threaded PVC bottom cap was placed at . the bottom of the screen sections Blank PVC casing was installed above the screens to the ground surface The monitoring wells were constructed within the hollow-stem auger Therefore, the auger itself acted as a tremae for the annular seal materials Monitoring wells MW-1, MW-2, MW-3, and MW-3R were all installed to a total depth of 47 feet bgs For monitoring wells MWA, MW-2, and MW-3, a filter pack of #2/12 sand was placed in the annular space to approximately two feet above the screen while the auger _ T was in place For monitoring well MW-3R, a filter pack of#3 Monterey sand was placed in the annular W space to approximately two feet above the screen while the auger was in place The depth of the sand in the well annulus was monitored with a weighted tape measure while the sand was being placed and the auger gradually retracted to avoid bridging To form a protective seal, approximately two feet of bentonite pellets were installed above the sand as the augers were retracted The bentonite was hydrated using r potable water A surface seal of neat cement was then tremied into the annulus extending from the ' bentonite to the ground surface Each monitoring well was completed with a flush mounted traffic-rated vault box A well construction graphic is included as part of the geologic log for each well (Appendix B) Construction details for the monitoring wells are included in Table 1, on the next page I I i I401b CONDOR