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Project L7.B. - Page 33 <br /> excavated materials associated with pump station construction would result in over 35 truck trips at <br /> an average of 4 daily truck trips during this phase of the project. <br /> The water table in the area has been measured at approximate elevations between 2.0 and 4.0 feet. <br /> Dewatering would be needed for the wet well excavation and may be required for the storm drain <br /> trenches. Discharges from dewatering would be pumped to the nearest sewer manhole as <br /> recommended by the City. <br /> When excavation is complete,workers would install the concrete support pad for the wet well,the <br /> vault,and the pad for the emergency generators. Crews would then install the submersible pumps <br /> and appurtenances including electrical and telephone service connections. The existing pump station <br /> would then be demolished and removed. The pump station site would be backfilled and graded to <br /> conform to adjacent elevations. Installation of the pump station and related facilities would not <br /> require any work within Redwood Creek. <br /> US 101 Undercrossing Construction <br /> Construction activities for the joint-use path crossing beneath US 101 would begin with rerouting <br /> the existing utilities within the limits of the proposed path. <br /> The contractor would install a cofferdam along the first row of piers under the US 101 bridge before <br /> excavating for the tieback and creek-side walls. The approximately 8-foot high cofferdam,designed <br /> by the contractor,would isolate an area approximately 175-feet long and 15-feet wide. The <br /> cofferdam area would be dewatered as needed to maintain dry conditions for installation of the <br /> retaining walls and bottom slab of the path. <br /> Dewatering consists of discharging accumulated groundwater, stormwater, or surface water from <br /> excavations or temporary containment facilities. Dewatering can be handled in four ways, <br /> depending on the quality and quantity of discharge. These options include: 1) on-site reuse; 2) <br /> treatment through the use of an active treatment system (ATS);3) directly discharging to nearby <br /> surface waters; or, 4) discharging or trucking the water to a local publicly-owned treatment system. <br /> Prior to reuse or discharge,the water must be sampled to determine the types and levels of <br /> contaminants present,per applicable regulatory requirements. The contract documents would <br /> include dewatering best management practices and provide details and specifications for the <br /> handling and sampling of water from dewatering operations. The Contractor would develop work <br /> plans to handle the collection, treatment,and monitoring for dewatering operations. An agreement <br /> or permit would be obtained from the South Bayside System Authority if the water is discharged to <br /> the publicly-owned treatment system. <br /> Most elements of the joint-use path would require excavation to a depth of approximately 12-18 <br /> inches. Beneath the US 101 bridge at Redwood Creek, construction of the joint-use path would <br /> require approximately eight feet of excavation for the retaining wall on the north side of the path in <br /> front of the existing bridge abutment and the joint-use path itself. Excavation for the undercrossing <br /> would require removal of approximately 2,350 cubic yards of material using a small backhoe, <br /> 1-7 US 101 Pedestrian Undercrossing and <br /> Bair Island Storm Drain Pump Station Project <br />