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Mr.Mark Clardy <br /> ' Page 6 <br /> April 3, 2006 <br /> • Once the excavation has progressed to the point that visibly impacted soil is not observed in the <br /> ' excavation(as determined through visual and olfactory means), or the target vertical depth has <br /> been achieved,confirmation soil samples will be collected from the sidewalls and excavation <br /> floor. In the event that soil impact is noted extending to and/or below the target depth, final <br /> ' confirmation samples will be collected at the target depth,but the excavation will terminate at <br /> that depth. The lateral extent of the excavation will be determined by the indications of impact <br /> to the soil by petroleum hydrocarbons and by excavation required for equipment access,and <br /> ' excavation beyond that scope(e.g. geotechnical considerations, such as differential settlement) <br /> will not be performed. <br /> ' A temporary fence will be erected around the excavations while they are open to prevent access. <br /> At the end of each day,the fence will be secured to completely surround the excavation. <br /> ' Soil Stockpiles <br /> During excavation, soil will be segregated as it is excavated,as necessary, and placed in different <br /> ' stockpiles. Soil with no visible or olfactory impact will be stockpiled for testing and re-use as <br /> backfill material. The samples will be collected in a grid pattern and composited at a 4:1 ratio. <br /> Each four-point composite sample will represent approximately 1,000 cubic yards of soil. If no <br /> detectable constituents are noted, the sector represented by the grids will be deemed suitable as <br /> t backfill material. If constituents are detected,the magnitude of the concentrations will be <br /> evaluated by Shell and the property owner(s),and the issue will be discussed with the RWQCB <br /> regarding use of the material as backfill and it will be used as such if deemed acceptable by the . <br /> RWQCB. If not acceptable,the soil will be transported for off-site disposal. . <br /> Impacted soil will be loaded directly into trucks for off-site disposal. Soil from the site will be <br /> ' pre-profiled for disposal at a landfill to increase flexibility in handling the soil. A full-time street <br /> sweeper will be employed during periods of soil transport off site to prevent generating dust and <br /> dirt on public roadways. Unpaved haul roads will be sprayed with water as necessary to control <br /> ' dust, and at a minimum twice a day(at the start and end of each workday). <br /> Excavation Backfilling <br /> ' The clean excavated material will be tested for TPH and if not impacted, as discussed above, will <br /> be used as backfill in the excavation. Based on the expected volume of impacted soil, <br /> approximately 12,000 cubic yards of soil will be hauled off site for disposal, and imported <br /> backfill will be needed to replace this volume. Backfill will be placed in the excavation in <br /> '/z-foot lifts,and compacted to 90 percent of American Society for Testing and Materials D1557 <br /> maximum dry density for excavations less than 10 feet in depth, and to 95 percent relative <br /> compaction for excavations greater than 10 feet. This backfill compaction approach will be <br /> followed for all excavated areas, and will not vary based on the location of the excavation(i.e., <br /> within a street, or within the residential development portion of the property or the industrial <br /> ' portion of the property). <br /> Post Remediation Considerations <br /> ' During the site investigation,soil borings were advanced at a 25 foot spacing along the entire <br /> 3,200 foot length of the pipeline alignment within Neighborhood B. Based on the findings from <br />