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laboratory, located in Sacramento, California. Sample locations are presented in Figure 3 <br /> Appendix C provides the laboratory analytical results <br /> 2.3.3 Vapor Observation Point Installation <br /> A vapor observation point was installed at the bottom of the excavation following excavation <br /> activities This well was installed to provide an opportunity to monitor volatile petroleum <br /> hydrocarbons (if any) emanating from the soil Figure 4 provides a schematic illustration of <br /> the vapor observation point construction The site photographs showing the vapor point <br /> installation are presented in Appendix A <br /> Approximately four inches of pea gravel were initially "tailgated" into the excavation and <br /> leveled using the backhoe bucket. A 4-inch diameter, 0 10-mch Schedule 40 slotted PVC <br /> well screen, capped at one end, was then set on top of the gravel length-wise along the base <br /> of the excavation This well screen was wrapped with a non-woven geotextile fabric to <br /> minimize the tisk of sediment entering the screen. A 90' PVC elbow point was attached to <br /> the open end of the well screen and a 4-mch Schedule 40 PVC riser was attached and <br /> extended to ground surface. Additional pea gravel was tailgated into the excavation to <br /> approximately four inches above the well screen. <br /> A polyethylene geomembrane (6 mil thickness) was then draped on all sides of the excavation <br /> and clean fill material was used to backfill the excavation around the riser pipe to grade, as <br /> described in Section 2.3.4 The annular space around the vapor observation point was sealed <br />' below grade using cement, and the observation point was protected at the surface using a <br /> truck-rated traffic box. <br /> 2.3.4 Backfilling and Site Restoration <br /> Following installation of the vapor observation point, the excavation was backfilled and <br /> compacted Appendix A contains photographs that describe the backfilling operation. The <br /> excavated area above the pea gravel was lined with polyethylene geomembrane to prevent <br /> leakage of vapor from the native formation into the clean backfill material. <br /> Clean backfill material was tailgated into the excavation in six inch loose lifts. The lifts were <br /> compacted using the backhoe bucket to obtain a compaction of approximately 90 percent <br /> Standard Proctor density. A compaction test cell was initially installed at the surface, and the <br /> MZ106-23/95/VDBFR5-0007 5 <br />