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Groundwater Investigation,Monitor Well Destruction and Installation,and Interim Remediation Pump Test Report Boyett Petroleum,419 S.Main St.,Manteca,CA ' January 30,2004 Page 12 . Table 4 Monitoring Well Construction Details ' Monitoring Well MW-411 MW-10 MW-11 EW-1 Date Installed 10/30/2003 10/30/2003 10/30/2003 10/30/2003 Well Depth(ft.) 25 25 39 39 Well Casing Diameter(in.) 4 4 4 4 ' Borehole Diameter(in.) 10 10 10 10 Well Screen Interval(ft.) 10 -25 10 -25 29-39 29-39 Filter Pack Interval(ft.) 7-25 7-25 26-39 26-39 ' Bentonite Seal Interval(ft.) 3 -7 3 -7 23 -26 22.5-26 Grout Seal Interval(ft.) 0-3 0-3 0-23 0-2.2.5 Monitoring wells MWAR and MW-10 were constructed with 15 feet of four-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.010); both wells were completed to ' a depth of 25 feet bgs. Wells MW-11 and EW-1 were constructed with ten feet of four-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.010); both wells were completed to a depth of 39 feet bgs. A flush-threaded PVC bottom cap was placed at the bottom of each ' screen section and blank FVC casing was installed above the screen to the ground surface. MW-4R and MW-10 were screened above and MW-11 and EW-1 were screened below the clay horizon separating the upper and lower soil horizons (previously described in Section 3.6). ' . A filter pack of#2416 Monterey sand was placed in the annular space to approximately three 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 was gradually retracted to avoid bridging. To form a protective seal, approximately three feet of bentonite pellets was installed above the sand as the augers were retracted. The bentonite was hydrated using potable water. A surface seal of neat cement was poured into the annulus and extended from the bentonite to the ground surface. The augers ' were removed before emplacement of the grout. Each well was completed with a flush mounted traffic- rated vault box. ' 4.2.3 Soil Sampling Soil grab samples were collected from the drill cuttings during the installation of each well boring for site waste characterization. All soil samples were logged according to the Unified Soil Classification System ' (USCS). Geologic logs were prepared containing field observations including soil type, photoionization 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). Drill cuttings from the well borings were placed in polyethylene bags and checked with a PID meter for ' the presence of volatile hydrocarbons. PID measurements were recorded for soil samples collected over five-foot intervals above the water table and ranged from 0.8 to 6.9 parts per million (ppm). Soil discoloration and petroleum hydrocarbon odors were not noted during monitoring well installation activities. Two soil samples from the drill cuttings from each boring were collected for laboratory analyses as they were advanced to characterize the soil for disposal. The soil samples were collected in clean brass tubes CONDOR