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1 �raject Deserz�taon <br /> excavated materials associated with pump station constructian would rest�lt in ovex 35 truck trips at <br /> an average of 4 daily truck trips during this phase af the proJect. <br /> The water table in the area has been measured at approximate elevations lietween 2.0 and 4.d feet. <br /> Dewatering would be needed for the wet well excavation and may be teqiured for the storm drain <br /> trenches. Discharges from dewatering would be pumped to the nearest se«'er manhole as <br /> recomtnended by the City. <br /> When excavation is comp�.ete,workers would install tlie concrete support pad for the wet well,the <br /> vault, and the pad for the emexgency genexators. Crews would then install the submersible pumps <br /> and appurtenances including electrical and telepl�ane service connections.TE�e existing pump station <br /> would then be demolished and removed. The pump starion site would be backfilled and graded to <br /> conform to adjacent elevations. Installation of the pump starion and related fac.ilities would not <br /> require any work witl�in Redwood Creek. <br /> US 1 oI Undercrossing Construction <br /> Construction activiries for the joint-use path crossing benearh US 101 would begin with xerouring <br /> the existing utiiities within the�imits 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 appro�mately 8-foot high cofferdam,designed <br /> hy the contractor,would isolate an area appraxirnately 175-feet long and 15-feet wide. The <br /> cofferdam area would be dewatered as needed to inauitain dry conditions for insta]Iation of the <br /> retaining walls and bottom slab of the path. <br /> Dewatering consists of discharging accumulated groundwater, stormwater,or sutface water fram <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 acrive treatrnent system {ATS); 3} directly discharging to neaYby <br /> surface waters;or,4) discharging or trucl�ing the water to a loca.l.publicly-owned treatment system. <br /> Prior to reuse or dischaxge, 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 pxovide details and speci5cations for the <br /> handling and sampling of water from dewatering operarions. The Cantractor would develop work <br /> plans to handle the collection,treatment,and moz�toring for dewatering operarions. An agreement <br /> or permit would be obtained fxom 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 tequite excavarion to a depth of approxirnatel�r 12-1$ <br /> inches. Beneath the US 101 bridge at Redwood Creek,construcrion of the joint-use path would <br /> requixe approximatelp eight feet of excavation for the retaining wall on the north side of the path in <br /> firont of the existing bridge abutment and rhe joint-use path itself. Excavation for the undercrossing <br /> would require removal of approxunately 2,350 cubic yards of material using a small backhoe, <br /> 1-7 US 10� Pede.rtrian U�aderc�ossing rrnd <br /> Bair Island 5tor»a Drairr Pump Stalzon Project <br />