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Scope of Work:
· First time maintenance dredging of the rock cut intake channel constructed with Schoharie Reservoir / Gilboa Dam (circa 1920).
· Approximately 5,000 cubic yards of sediment and debris which accumulated in the channel where removed mechanically through the utilization of a crane mounted on segmental floats.Transport barges shuttled material in containers which were then off-loaded to trucks with a large crane on shore. Dredged material was trucked upland to designated stockpile areas.
· New bar racks were fabricated and installed two weeks after dredging concluded in order to re-open the Shandaken Tunnel sluice gates.
· Up to a 6-person dive team utilized for pre/post dredge surveys, bar rack inspection/replacement, as well as hydraulic dredging in front of the bar rack.
· Installation of a barge-mounted bypass pumping system capable of 60-70 MGD was necessary in order to continue the conveyance of water through the Shandaken Tunnel during dredging operations. This system included over 3,000-feet of 18” HDPE fused pipe, (4) 18” & (4) 12” Dri-Prime Electric Pumps with Variable Frequency Drives (VFD), powered by (1) 1,000-kW & (1) 400-kW 3-phase, diesel gensets.
· Bar rack replacement included the fabrication by D.A. Collins, heavy-lifting of (2) assembled rack sections, each weighing over 16-tons, with underwater diver-assisted anchor drilling and installation.
· Strict DEC permit requirements called for upgrading the existing stormwater system, as well as the installation of an inner and outer turbidity curtain system were required during the dredging operation. Two curtains approximately 700-feet long and up to 70+ feet deep to account for fluctuating reservoir water levels (up to 20-feet).
· Turbidity levels (NTU’s) were monitored by the Owner/Owner’s Representative (DEP/Dvirka & Bartolucci) at the bypass pump system discharge point within the Shandaken Tunnel.
· 2.5-miles of the dredge sediment haul route were resurfaced with approximately 20,000-tons of aggregate.
· Best Available Technology (BAT, Local Law 77) and Ultra-Low Sulfer Diesel (ULSD) Fuel requirements adhered to via retrofitting Diesel Particulate Filters (DPF) and Diesel Oxidation Catalysts (DOC) to equipment to be utilized.
· New technologies used – Sidescan sonar & Clamvision
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