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The proposed excavation depth should remove the majority of the identified saturated and vadose zone soil contamination, and enable removal of a significant amount of contaminated groundwater. Residual soil impacts previously identified deeper than 22 feet bgs should be addressed by backfilling with ORC. The proposed excavation area is underlain by approximately 4-feet of sand to silt fill, followed by silt layer down to approximately 19 to 21 feet bgs. The silt is underlain by saturated sand. Boring 1613-7b was advanced to 18.5 feet bgs, did not penetrate the sand layer, and no groundwater entered the hole after allowing it to stabilize over night. The proposed excavation is designed to reach the sand layer and enable removal of groundwater and free product that may be present in the sand below the silt layer. Excavation below 22 feet bgs will not be attempted because recent sampling has not encountered soil contamination below this depth, ORC backfill can address residual groundwater contamination, and because the shored excavation will be engineered for a set depth. 6.2 Excavation Volumes The proposed excavation will generate approximately 684 cubic yards or 1,100 tons of soil. It is estimated that 2 to 5 excavation volumes of water(one volume is 28' x 30'x 4') will be removed after soil excavation, or approximately 12,000 to 30,000 gallons of water. The soil will stockpiled and characterized for offsite disposal. Clean, shallow soil may be re-used on site. Clean import material will be used as backfill. While backfilling procedures will be determined by the project geotechnical engineer,we anticipate that the bottom 4 to 5-feet of excavation will be backfilled with pea gravel backfill and ORC compound. 7.0 REMEDIATION SCHEDULE We can begin the excavation as soon as this workplan is approved by the SJCEHD. The excavation would take approximately one week to shore and another 3-4 days to excavate. The excavation will likely remain open 3 to 7 days to complete the de-watering, which may include setting up a skimming pump if free product is present. Backfilling,recompaction and shoring removal will take an additional 4 to 7 days. 10 25971014.DGD 7 April 2004