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Scope of Work:
¨ DAC provided design and constructability assistance to the Owner and Engineer in developing the remedial approach to this project. DAC’s experience with environmental dredging techniques and in marine construction on Upstate NY rivers contributed significantly in finalizing the remedy with the USACE and NYS DEC.
¨ Dredging objectives required the removal of 4,725 cubic yards of clean sediment deposited near the northern shoreline by uncontrolled erosion and sedimentation resulting from upland development activities. River conditions and depths ranged from shoreline shallows to 15' in the navigational channel.
¨ Turbidity control was maintained utilizing an adjustable curtain system (10' depth) that ran from the shoreline to the downstream side of the dredge floats. The curtain system was designed to be easily adjusted and relocated as work proceeded downstream along the shoreline. Due to dense, compacted sediments, an excavation clamshell (aggressive digging bucket) had to be utilized in lieu of a flat cut environmental bucket.
¨ Dredging tolerances were limited to a 6” overdredge depth. Tolerance and quality control was confirmed using a proprietary dredge positioning system based on the Hypack model. The coordinates (x,y,z) for each bite were reported daily and utilized to monitor and direct the dredging progress.
¨ Dredge spoils were placed into eight (8) roll-offs staged on two separate transfer barges which floated the roll-offs downstream to the material handling area. Roll-offs were then offloaded by a 200-ton crane at a temporary bulkhead and transferred by the roll-off carriage to an upland disposal area. All dredge spoils were placed in an earthen basin in an upland location and allowed to dewater prior to final grading and burial.
¨ At the completion of the dredging phase, medium stone rip-rap was placed along the shoreline for erosion control and shoreline stabilization.
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