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The spillway approach channel at the Garrison Dam near Riverdale, ND is filling in with sediment and needs the situation to be addressed so spillway operations are not greatly affected. The purpose of this project is to reduce one of the primary source of sediment entering the approach channel by repairing and armoring a portion of the east channel bank. In addition, sediment will be removed from in front of the spillway gates through dredging. This will allow the spillway de-icing bubbler system to operate and prevent ice from forming against the upstream side of the Tainter gates thereby permitting emergency wintertime gate operations. Originally the east channel bank below the berm at elevation 1865 was protected with 2 feet of riprap placed over 1 foot of spalls that was underlain by 1 foot of gravel filter blanket.

The slope protection, as originally designed, extended from the spillway structure upstream a distance of approximately 1,400 feet. All but 300 feet of the slope protection was removed in 1975 for repairs on the Snake Creek embankment. Since removal of the slope protection in 1975, high water events and wave action have eroded and steepened a significant portion of the east bank cut slope, depositing close to 1,000,000 cubic yards of sediment within the base of the approach channel. This sedimentation has reduced the capacity of the approach channel and interfered with the operation of the spillway gate bubbler system.

This rehabilitation project consists of three (3) main features of work:

1. The first feature is repairing and armoring a portion of the eastern channel bank. This involves dredging material in the spillway in front of the bank, sloping the embankment, placing bedding, fabric, aggregate, mesh, post and riprap needed to build the slope to the design provided by the government.

2. The second feature of work is performing further dredging on the upstream side of the tainter gates. This will allow for free gate operation and allow the bubbler system to perform as designed keeping the front of the gates free of ice in the winter.

3. The third feature of work is building a retention sediment ponding facility at a location below the dam between the spillway and the fish hatchery. The dredged material will be piped over to this facility where the sediment will settle out per the government design.

For purpose of understanding the size of this scope the project is expected to involve the following orders of magnitude: The riprap placement order of magnitude is 80,000 tons, the dredge material order of magnitude is 200,000 cubic yards. The contractor will excavate and backfill an order of magnitude of 120,000 cubic yards material between the work on the slope and in the settlement pond.

In accordance with DFARS 236.204, the magnitude of this project is expected to range between $10,000,000 and $25,000,000.

Estimated Project Solicitation Issue Date: 5 June 2024

Small Businesses are reminded under FAR 52.219-14(e)(3), Limitations on Subcontracting Services, General construction, at the contractor agrees it will not pay more than 85% of the amount paid by the Government for contract performance, excluding the cost of materials, to subcontractors that are not similarly situated entities. Any work that is a similarly situated entity further subcontracts will count toward the prime contractor’s 85% subcontract amount that cannot exceeded.

Prior Government contract work is not required for submitting a response to this Sources Sought synopsis.

Project Period of Performance: 890 calendar days from construction NTP.

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