This spring, USA Member Monticello Nuclear Generating Plant began an External Flooding Barrier Project to enhance flood protection strategy by installing permanent infrastructure. This infrastructure will decrease the time required to install temporary flood protection in the event of the design-basis probable maximum flood.

The installation of a bin wall along the north side of plant property and the east and west of the intake structure are part of this permanent infrastructure. In addition, steel plate walls and extensions on the top of the intake structure itself are being installed.

These structures will create a barrier that rises to a height of approximately 12 feet above plant grade, or two feet above the probable maximum flood. In the event a flood is predicted, a levee system will attach to the bin walls and encircle the power block.

The intake structure modifications
• A box extension to the exhaust hood that raises the structure 4 feet. Approximately 18,000 pounds of steel plate and structural steel were used to construct the box.
• Plate wall sections that consist of 1/2 inch steel plate supported by structural steel bracing that is Hilti-bolted into the intake structure walls and roof and sealed

The east bin wall
• Measures 140 feet long, 12 feet above grade and 9 feet deep,
• Consists of 14 bins with 460 stringers, spacers, verticals and top caps bolted together,
• Is filled with 40 cubic yards of compacted sand per bin, for a total of 560 cubic yards of fill in the east bin wall.

The west bin wall
• Measures 140 feet long, 12 feet high above grade and 12 feet deep,
• Consists of 14 bins with approximately 1140 discrete parts
• Is filled with an average of 106 cubic yards of compacted sand per bin, for a total of 1484 cubic yards of fill in the west bin wall

In the event of a flood, additional bins would be added to close the gap between the east bin wall and the intake structure. Several temporary bins also would be added on each end of the east and west bin walls to connect them to a temporary levee that will be built when the probable maximum flood is predicted.

The completed project will be a major enhancement to Monticello’s flooding plan. It will decrease risk to plant personnel and provide additional time margin when implementing the flood plan. The External Flooding Barrier Project is a key component of Monticello’s commitment to protect the health and safety of the public by increasing safety margins.

Monticello Nuclear Generating Plant installs permanent bin walls to enhance their flooding protection strategies.