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Underground & Tunnels

Project Name

Oroville Dam River Outlet Diversion Tunnel No. 2

Status

Completed

Year Completed

2009, 20142016

Location Information

Lake Oroville – Oroville, California

Project Sum­ma­ry

The Diver­sion Tun­nel No. 2 work con­sist­ed of three sep­a­rate projects: Removal of Baf­fle Ring and Con­crete Repair; Hyatt Pow­er­plant, Oroville Dam Riv­er Valve Out­let Sys­tem Repairs; and Baf­fle Ring Installation.

The Baf­fle Ring removal and Riv­er Out­let Sys­tem repairs were per­formed under emer­gency con­tract. The Riv­er Out­let Sys­tem repairs includ­ed installing mono­rail hoist sys­tems over two 54-inch fixed cone valves, down­stream of two 72-inch spher­i­cal valves, to allow them to be removed and placed on a float­ing barge for extrac­tion from the tun­nel. The valves were then trans­port­ed off-site for refur­bish­ment. While the valves were being over­hauled, Syblon Reid reen­tered the tun­nel to strip down and rebuild the entire con­t­a­m­i­nat­ed hydraulic sys­tem for the two spher­i­cal valves. This includ­ed scrub­bing and recoat­ing the sump and accu­mu­la­tor, and replac­ing the hydraulic sup­ply and return lines. Once com­plet­ed, Syblon Reid set up a new remote sys­tem to allow safer oper­a­tion of the valves via a com­put­er from inside the pow­er­plant, rather than from with­in the valve pit. Fol­low­ing suc­cess­ful test­ing, the refur­bished fixed cone valves were rein­stalled and the whole sys­tem was operated.

The Baf­fle Ring instal­la­tion includ­ed installing a 75-foot long water-filled blad­der tun­nel plug against a bulk­head, dewa­ter­ing the work area upstream of the cofferdam/​bulkhead, and installing twelve new Baf­fle Ring seg­ments around the tun­nel wall just down­stream of the Riv­er Out­let Valve Cham­ber. DWR was able to meet lockout/​tag out require­ments and oper­ate the pow­er plant 247, while Syblon Reid works around the clock with­out inter­rupt­ing the gen­er­a­tion of clean renew­able ener­gy. The project also includ­ed installing two DWR-fur­nished replace­ment fixed cone valves.

Key Chal­lenges

All three projects were con­duct­ed under strict Cal/​OSHA – Title 8, Tun­nel Safe­ty Orders, as well as all nec­es­sary con­fined space require­ments, due to the use of heavy equip­ment work­ing on barges approx­i­mate­ly a half a mile inside the out­let tun­nel under­neath Lake Oroville. Access to the work area required the use of barges and push boats. Syblon Reid was able to sub­stan­tial­ly reduce the size of the required ven­ti­la­tion sys­tem, and the gen­er­a­tor nec­es­sary to run it, by access­ing the work area through the pow­er­house instead of the tun­nel, there­by by avoid­ing dai­ly boat trips into the tun­nel. To fur­ther reduce ven­ti­la­tion require­ments and improve sus­tain­abil­i­ty on the project, we designed, built, and uti­lized a twen­ty-foot long eco-friend­ly’ alu­minum push boat equipped with twin zero emis­sion elec­tric out­board engines to trans­port mate­ri­als and push equip­ment and work barges into the tun­nel, in lieu of using a diesel-pow­ered work boat.

The access improvement project consisted of:

  • All three projects were conducted under strict Cal/OSHA – Title 8, Tunnel Safety Orders, as well as all necessary confined space requirements, due to the use of heavy equipment working on barges approximately a half a mile inside the outlet tunnel underneath Lake Oroville.
  • Access to the work area required the use of barges and push boats.
  • Syblon Reid was able to substantially reduce the size of the required ventilation system, and the generator necessary to run it, by accessing the work area through the powerhouse instead of the tunnel, thereby by avoiding daily boat trips into the tunnel.
  • To further reduce ventilation requirements and improve sustainability on the project, we designed, built, and utilized a twenty-foot long ‘eco-friendly’ aluminum push boat equipped with twin zero emission electric outboard engines to transport materials and push equipment and work barges into the tunnel, in lieu of using a diesel-powered work boat.
  • The Diversion Tunnel No. 2 work consisted of three separate projects: Removal of Baffle Ring and Concrete Repair; Hyatt Powerplant, Oroville Dam River Valve Outlet System Repairs; and Baffle Ring Installation.
  • The Baffle Ring removal and River Outlet System repairs were performed under emergency contract.
  • The River Outlet System repairs included installing monorail hoist systems over two 54-inch fixed cone valves, downstream of two 72-inch spherical valves, to allow them to be removed and placed on a floating barge for extraction from the tunnel.
  • The valves were then transported off-site for refurbishment.
  • While the valves were being overhauled, Syblon Reid reentered the tunnel to strip down and rebuild the entire contaminated hydraulic system for the two spherical valves.
  • This included scrubbing and recoating the sump and accumulator, and replacing the hydraulic supply and return lines.
  • Once completed, Syblon Reid set up a new remote system to allow safer operation of the valves via a computer from inside the powerplant, rather than from within the valve pit.
  • Following successful testing, the refurbished fixed cone valves were reinstalled and the whole system was operated.

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