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' a'q KLEINFELDER 6 The additional geotechnical considerations for the proposed project are detailed in a separate report ' Based on the conclusions noted above the following recommendations are being made A It is anticipated that dewatering in the Franklin Area will require treatment of groundwater prior to discharge to the sanitary sewer It is estimated remedial efforts will ' take approximately two to six weeks for set up prior to discharging water B As part of the remedial effort dewatering rates are critical to the design of a remedial system Dewatering rates in the Shell site area may give indications of potential dewatering rates assuming similar dewatering methods ' C Removal of sediment and fines within the trench (assuming a trench dewatering system) is essential in the remedial design to limit costs Above ground filter control can be costly and contaminants typically absorb to suspended sediment and fines, which may be more difficult to effectively remove in an above ground filtration system (especially at high flow rates) The signatories of this report should be consulted as part of planning the dewatering sediment control methodology ' D Permitting issues for dewatering discharge should be conducted well in advance of dewatering operations and can be commenced by Kleinfelder based on your authorization E Periodic groundwater testing is recommended during dewatering operations in ' groundwater contamination areas including monitoring of perimeter monitoring wells from adjacent sites of concern noted north of Country Club ' F Although no significant soil contamination was detected at depths above first encountered groundwater, the excess soils should not be reused on residential properties or at a location adjacent to, or in contact with, surface waters (e g levees) Soil ' excavated at or below groundwater contaminant zones should be considered contaminated and handled as such The soil should be stockpiled on visqueen and subsequently tested for disposal purposes ' G As previously noted in the Shell Area, efforts should be made to reduce the amount of dewatering so as to reduce or eliminate the risk of impacting several plumes noted north of Country Club in proximity to the Franklin Site Area As a precaution, discharge should not be made to a surface water body or the storm drain system ' H Additional research is being conducted on properties in this area to potentially supplement Kleinfelder's investigation If that research warrants, an addendum to this report will be issued 1 ' 28699 E01 /STO3R759 Page 14 of 17 Copyright 2003,K[emfelder,Inc May 20,2003