Upper Salmon Reject Gate Structure

IN-WATER MARINE WORK, CONCRETE DEMOLITION, STRUCTURAL CONCRETE, RIVER CHANNEL DIVERSION, STEEL FABRICATION AND ERECTION

DIVERSION OF 3,100 CFS CANAL FLOW, INSTALLATION OF 400FT PROPRIETARY PORTABLE FRAME AND TARP SYSTEM, 76’ LONG BY 20’ HIGH STRUCTURAL FRAME

The Upper Salmon River B Power Plant Reject Gates needed replacement. 5.5 million dollar contract. Project duration was June 2020 to April 2021. Concrete surrounding the original gates was failing due to ASR related deterioration. The B canal power plant is a critical power generating plant. Demolition and replacement of the gates required a complete shut down of the facility and the diversion of the inlet canal.

Prior to diverting the 3,100 CFS canal flow over the existing flash board dam 5 acres of abandon riverbed had to be cleared of trees, brush and debris. JC chose an alternate approach to the project by swinging land clearing equipment over the still flowing canal and began clearing the thick underbrush and trees. Once brush was cleared JC installed 400ft of their proprietary portable frame and tarp system to form a channel embankment. The frame and tarp system channeled full flow for several months thru the winter shut down.

While the brush was being cleared JC fabricated and erected a 76’ long by 20’ high structural frame and pate cofferdam adjacent to the canal. Sections of the cofferdam were flown into place and anchored underwater to the concrete canal floor with a modified hydraulic drill by the contractors dive team. A jig bolted to the canal floor ensured exact placement of the 4 ft long anchors at 8” centers. The divers recorded the grouting operation for review by the structural and geotechnical engineers for verification of grout uptake.

Upon installation of the steel cofferdam the channel was drained, heavy equipment was lowered into the dry canal and the demolition of the existing gates began in earnest. Thru the coldest months of the year demolition equipment removed the gate structure and spillway down to bedrock. Tensioned anchors were installed to lock the spillway and gate structure to the underlying basalt.

While construction was proceeding design and fabrication of the two independent reject gates were being fabricated by an outside fabrication facility. The incredibly tight tolerances and AWWS specifications required constant coordination with the fabricators. Specific welding patterns were required to ensure that welding heat did not distort the gate members.

JC fabricated the elevated gate structure and mechanical hoist platform in house. Upon completion of the structural concrete and setting the gates the mechanical hoist structure and cable hoists were installed.

The Project was successfully completed on time and budget allowing Idaho Power to bring the turbines back online for the heavy summer demand period.

JC Constructors has enjoyed many opportunities to work in deep water. Included in its equipment arsenal are barges, work boats, and a full list of diving gear and underwater tools, along with trained manpower to use them.
JC Constructors has completed demolition of environmentally sensitive materials such as concrete, asbestos, and lead paint around clear waters, habitats for threatened and endangered species, and other environmentally sensitive areas.
JC Constructors has constructed structural concrete for transportation structures, water treatment, and wastewater treatment.
JC installed 400ft of their proprietary portable frame and tarp system to form a channel embankment. The frame and tarp system channeled full flow for several months thru the winter shut down.
From pressure piping manifolds to ascending radial stairs to large fabricated lids, the JCC fabrication team has been able to support almost any fabricated project requirement.