Sierra Pacific Industries 8/16/2020

CITY OF EVERETT CHAPLAIN BRIDGE INSTALLATION DETAILS,SPECIFICATIONS,AND REQUIREMENTS Material Quantity(yd3) Sill Foundation 60 Channel Riprap 107 Gravel Filter Layer 18 Roadway Subgrade Backfill 72 Roadway/Bridge Surfacing 31 Streambed Cobble 110 M. Approved fish exclusion and bypass methods shall be in place at all times during installation unless otherwise approved by the Contract Administrator in writing.The water flow rate while pumping around shall be consistent with natural flow rate at the time of bridge installation. N. Water bypass and fish exclusion methods during bridge installation must be preapproved by Contract Administrator. Except by written prior permission by the Contract Administrator, fish exclusion and bypass methods are restricted to one of the following methods: Method 1: Passive bypass using existing 6-barrel crossing In this method the bridge footings and abutments shall be installed in two phases,with one side being installed at a time. A coffer dam shall be built around the west half of the existing six-barrel crossing to prepare the site for installation of the bridge footings and abutments. Seines,minnow traps,dip nets,fish herding,or other approved fish exclusion methods shall be used to safely remove fish from the work area. A pump shall be placed in the work area to remove any water that enters the coffer dam. The sediment- laden water shall be pumped to an upland area where the sediment will settle out before the water re-enters the stream. The site shall be monitored to ensure fish do not re-enter the work area. Stream water shall flow through two or three culverts on the east end of the existing crossing,with the number of culverts depending on flow conditions at time of installation. The west end of the existing crossing shall then be removed,and the west bridge footing and abutment shall be installed. Once this is complete,the coffer dam shall be slowly repositioned on the east end of the six-barrel crossing. Stream flow shall divert to the west end of the crossing adjacent to the new abutment. The east bridge footing and abutment shall then be installed. Once this installation is complete,the bridge shall be set in place and the coffer dam shall be slowly removed to prevent turbidity. Method 2: Passive bypass through coffer dam using flexible pipe In this method a coffer dam is installed around the work site and flexible pipe shall be used to pass water through the work area. This pipe shall be installed within the coffer dam and may pass through two or three of the existing six-barrel culverts,depending on flow conditions at time of installation. Seines, minnow traps,dip nets,fish herding,or other approved fish exclusion methods shall be used to safely remove fish from the work area. A pump shall be placed in the work area to remove any water that enters the coffer dam. The sediment-laden water shall be pumped to an upland area where the sediment will settle out before the water re-enters the stream. The site shall be monitored to ensure fish do not re-enter the work area. One side of the six-barrel crossing shall then be removed and the bridge footing and abutment shall be installed. The flexible pipe shall then be relocated to allow removal of the other side of the existing crossing. After installation of the second bridge footing and abutment,the bridge shall be set in place and the coffer dam shall be slowly removed to prevent turbidity. Method 3: Passive bypass by creating new channel around work site In this method a new channel shall be dug approximately 70'east of the six-barrel crossing to bypass the work site. A coffer dam shall be installed on either side of the existing crossing to restrict water from entering the work site. Seines,minnow traps,dip nets,fish herding,or other approved fish exclusion methods shall be used to safely remove fish from the work area. A pump shall be placed in the work area