Statement of Work - SOW (Draft).pdf

Mud Mountain Dam 9’ Tunnel Steel Liner

DRAFT STATEMENT OF WORK

1. DESCRIPTION OF WORK

Provide all shop drawings, as-built drawings, equipment, supplies, labor, facilities, tools, materials, and supervision and perform all work in strict accordance with this Statement of Work, the contract and specifications, all Federal, State and Local codes and regulations, and all applicable industry standards to:

Restore the steel the liner at the Mud Mountain Dam 9’ tunnel inlet, specifically from the bellmouth to the steel transition ramp in accordance with these specifications.

The 9’ tunnel is accessed from the downstream end of the dam.

USACE will be responsible for placing the upstream stoplogs to close the tunnel for overlay of the plates. USACE will also place the downstream stoplog at the terminus of the 9 ft tunnel and will pump out the water from that location. All other activities will be the responsibilities of the contractor. See Site Plan in Attachment 02 for site location.

1.1. Tunnel Outage Window: The tunnel closure will be limited to a window of 20JUL2026to 30SEP2026. All physical construction activities must be fully completed within this period.

1.2. Hours of Operation: The contractor is responsible for

conducting business, between the hours of 06:30 AM, and 04:00 PM Monday thru Friday except Federal holidays or when the Government facility is closed due to local or national emergencies, administrative closings, or similar Government directed facility closings. The contractor will not be reimbursed when the government facility is closed for the above reasons. The Contractor must always maintain an adequate workforce for the uninterrupted performance of all tasks defined within this SOW when the Government facility is not closed for the above reasons. When hiring personnel, the Contractor shall keep in mind that the stability and continuity of the workforce are essential.

1.3. Project Sequence and Description:

1.3.1. The government will be responsible for the placement of both the upstream and downstream stoplogs to close the tunnel.

However, it will be the responsibility of the contractor to dewater the tunnel and maintain a dry work environment during the performance of the contract. The stoplogs do not provide a fully watertight seal and the contractor must plan for constant dewatering. Water entering tunnel may be pumped back into the White River. Contractor shall expect to be required to install dewatering system with capable of pumping between 50 and 700 gallons per minute due to seepage and may be required to add additional capacity.

1.3.2. After the stoplogs are placed and the tunnel is closed, river sediment material is expected throughout the 9ft tunnel.

Contractor shall clean 9’ tunnel by removing residual water, rocks, cobbles, sediment. Install system for constant dewatering of leakage occurring around the stoplogs. Traditionally, USACE has built a sandbag barrier upstream of the 9’ tunnel bellmouth (895 ft’ invert) and pumped water vertically through hoses into the 23’ tunnel bellmouth (925 ft’ invert). Significant sediment load will be found on the top of the steel liner, the area from the bellmouth to the steel transition ramp. Contractor shall expect to encounter at minimum 25 cubic yards of sediment on top of the steel liner. Image 01 shows a typical sediment condition.

Minimal amount of sediment is typically encountered at the granite block lined portion of the tunnel. Contractor shall dispose of the river sediment material onsite at the disposal site identified in Attachment 2.

1.3.3. Provide lighting system for length of entire tunnel, approximately 1,694 ft., per U.S. Army Corps of Engineers (USACE) EM 385-1-1 Safety and Health Requirements Manual.

1.3.4. Provide ventilation when required for specific work activities that change the working conditions to a confined space (i.e., grouting, welding.), per U.S. Army Corps of Engineers (USACE) EM 385-1-1 Safety and Health Requirements Manual.

1.3.5. Remove any 3/16” steel patching plates that would prevent flush installation of new steel overlay. Fill Damaged Holes with Epoxy: Fill all damaged holes in the existing steel liner with an appropriate two-part epoxy patching compound per specifications, flush with top of existing steel liner.

1.3.6. Line with new Steel Plates: The contractor shall provide and install new steel plates on top of existing steel plates for the total length of the steel liner and weld to existing with knife plates per the drawings and this specification. Existing drain holes shall be maintained and not obstructed by new steel plate installation. To prevent fish injury and avoid detrimental hydraulic flows, no rough or sharp liner surfaces shall be present at completion of work. A definition of what is considered acceptable for the above conditions will be provided.

1.3.7. Weld joints between plates and walls to retain injectable epoxy grout. Inject Epoxy Grout: Inject epoxy grout into pumping port holes to fill all voids. Provide vent holes to ensure epoxy has filled the voids.

1.3.8. Demobilize and remove all debris, waste and construction materials that are not part of the permanent construction.

1.3.9. The contractor shall plan for emergency demobilization to evacuate the tunnel if high river flows overtop the stoplog and flood the tunnel. In case of such unforeseen circumstances, MMD Operations Staff, would notify contractor of potential event 3 to 5 days in advance, allowing for the necessary safety and logistical preparations and the removal of equipment and materials from the tunnel.