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FIELD INVESTIGATION: SSI - PHASE TWO As previously discussed,the objective of the SSI— with a Mobile B53 drilling rig using 8-inch Phase Two scope of work was to confirm or refute diameter hollow-stem augers operated by Central the existence of a deep groundwater plume at the Valley Drilling, a licensed well driller from Site In addition PHS/EHD requested collection Rancho Cordova, California As required, and analyses of two additional soil samples The PHS/EHD was notified in writing of the scheduled SSI—Phase Two scope of work performed drilling(HLA, 1998c)and a PHS/EHD included the following representative was present onsite to observe ' ♦ Drill, log, and sample a soil boring to a depth drilling and sampling activities during the field of approximately 40 feet bgs near the location investigation of HP-2 Monitoring well boring MW-7 was advanced to a • Collect soil samples at 5-foot minimum depth of 415 feet bgs in the center of the former intervals in each boring UST excavation Soil samples were collected, the • Analyze soil samples from approximately boring was logged, cuttings were handled, and ' 25 and 30 feet bgs TPHg with EPA decontamination procedures were performed as Method 8015M and for BTEX with EPA described in the section above The soil samples Method 8020A were analyzed in accordance with the analytical ' ♦ Construct monitoring well MW-7 in the soil program described above boring with a screened interval between 30 and 40 feet bgs MONITORING WELL CONSTRUCTION ♦ Develop monitoring well MW-7 after 48 hours On April 30, 1999,monitoring well MW-7 was ♦ Purge and sample monitoring well MW-7 after constructed using flush-threaded, 2-mch diameter, 72 hours Schedule-40 polyvinyl chloride(PVC)casing and w Analyze the groundwater sample for screen The bottom of the well was fitted with a TPHg with EPA Method 8015M, for threaded PVC end cap The screened portion of BTEX with EPA Method 8020,and for each well consists of 0 020-inch wide factory-slots TBA, MTBE, DIPS, ETBE, TAME,and that extend from approximately 30 to 40 feet bgs 1,2-DCA with EPA Method 8260B A sand pack of Lonestar No 3 sand extends from In addition, one complete sampling of all wells the bottom of the well to two feet above the top of was performed and samples were analyzed in the screened interval corresponding to a depth of accordance with the approved analytical program 28 feet bgs A two-foot-thick bentonite chip seal (28 feet bgs to 26 feet bgs)was placed above the Prior to the initiation of any onsite sampling sand pack and hydrated for at least 30 minutes activities, Underground Service Alert(USA)was prior to backfilling the remaining annular space notified to trace existing public utilities present at with a slurry of neat cement and powdered ' the site A site specific Health and Safety Plan, bentonite to a depth of one foot bgs The well was prepared consistent with the requirements of Title completed with a locking expansion cap, a traffic- 8 CCR 5192 was present onsite and all field work rated well box with a rubber seal, and with the was conducted in accordance with the plan well box set slightly above grade to prevent ponding of surface water over the well The MONITORING WELL BORING AND SOIL construction details for well MW-7 are SAMPLING documented on the boring log(Appendix A) Monitoring well boring MW-7 was drilled on April 30, 1999 at the same location as boring HP- 2, as shown on Plate 3 The boring was advanced ' L U00001387371wP\38737N19 Harding Lawson Associates 14