Rawson Pond Dam Spillway Replacement

Description: Complete all clearing/grubbing necessary for the completion of the proposed work; Construct necessary slope improvements to allow equipment access to the shoreline from the left abutment and to facilitate crane access to the right abutment. Mobilize the crane to the site; Dredge the approach to the auxiliary sluiceway. Install the proposed bypass system. Implement the proposed construction drawdown using the existing bypass pipe, proposed bypass siphons, and auxiliary sluiceway; Install the steel sheet piles. Remove and dispose of the existing bypass pipe immediately before driving the sheets at the location of the existing bypass pipe and begin bypassing flows using the proposed siphon system; Install the proposed cofferdam and dewater the section of sheet pile wall at the location of the proposed stoplog bay. Terminate the right end of the cofferdam at a permanent spillway sheet pile with a top elevation of 114.0 or higher; Complete all required excavation and dredging for the installation of the proposed concrete sheet pile cap, stoplog bay, stoplog bay discharge channel, and stoplog bay scour protection; Install the concrete sheet pile cap, stoplog bay, and appurtenances (seal plates, steel angles) within the cofferdammed area; Supplement / reset downstream riprap right of the stoplog discharge channel to provide a contiguous apron downstream of the weir. Install the upstream riprap scour protection and downstream discharge channel at the stoplog bay; Remove the temporary cofferdam and use the new stoplog bay to maintain the construction drawdown; Cut the steel sheet piles to final height. Install the remainder of the concrete sheet pile cap and appurtenances including the weir board pin sleeves, seal plates, FRP grating, stoplog operator lifter pins, guardrails, and all other proposed miscellaneous items associated with the sheet pile cap and stoplog bay; Add item 1: install weir boards and weir board pins. Top elevation of the weir boards shall be coordinated with the town.