Attachment_1_-_Drag_Reservoir_Spillway_Cleaning_PWS.pdf

BLM, NCMD, Malta Field Office Drag Reservoir Repair

Performance Work Statement

Drag Reservoir Secondary Spillway Cleaning:

Location:

Drag Reservoir is a reservoir with its embankment located at T19N, R23E, S22, S23 (47.38686, - 108.13235), approximately 38 miles north of Winnett, Montana in Petroleum County. Road access to this site consists of approximately 2 miles of maintained dirt road and approximately 36 miles of graveled county road.

Site Description:

The principal spillway of Drag Reservoir dam consists of a vertical 36-inch outside diameter steel inlet culvert that extends downward 20 feet to a 90-degree transition elbow where it connects to a horizontal 30”-inch inside diameter steel outlet culvert. This outlet culvert discharges downstream with a gradual grade to the toe of the dam at the dam’s lowest downstream point. The distance from the 90-degree elbow to the spillway discharge point is roughly 205 horizontal feet. Both the 36-inch I.D. and 30-inch I.D. steel culverts are smooth walled.

There is a secondary spillway that allows the water in the reservoir to be dropped to below the outlet for maintenance purposes. This is where the obstructed pipe exists. See DWG sheet 2 of the drawing set for details. At the present time the exact diameter of the secondary outlet is believed to be 24” but it is unverifiable. For the purposes of pricing the contractor shall assume a 24” diameter pipe. The secondary spillway is obstructed with finely graded sediment and debris from the slide gate to the inlet in the reservoir. The length of the obstruction extending into the horizontal outlet culvert is around 45 linear feet. (See drawing 2 of 2 of the drawing set)

Description of Work:

1) Sediment should be jetted out of the low water outlet standpipe. Then the sediment should be jetted out of the 24” horizontal outlet pipe. Once water begins to flow it should be run for 20 minutes at ¾ gate opening.

2) Provide video inspection services to verify the condition of the primary spillway structure and secondary spillway structure. Document the physical condition of the full length of horizontal pipe. The final deliverable will be a video of the pipe inspection delivered to the government (by email) in MP4 or WMV format.

Miscellaneous Work Information:

Steel antivortex plate located at top of spillway inlet is bolted in place and may be temporarily removed for better access, as necessary. Replace antivortex plate to original condition at completion of project.

See Detail B4 on Sheet 4.

Rock and debris material that is removed from the obstructed spillway may be disposed of onsite in the scour hole below the primary spillway outlet.

Safety first. Call before digging. To request a locate of underground utilities in your excavation area simply dial 811, or 1-800-424-5555 (Montana811.org).

Timeline:

Work shall be completed prior to September 30, 2024.