Dam removal: Safety as a priority

Posted in: Energy, Environmental, Water

Dam safety is just as critical during dam commissioning and removal, as it is for construction and maintenance of large infrastructure projects.

After years of project design and permitting, the Mill Pond Dam Removal and Habitat Restoration project is underway in northeast Washington. The project will restore the natural riverine ecosystem structure and functions to this reach of Sullivan Creek and improve habitat availability, connectivity and quality for native fish populations in the watershed. To achieve this, the first step is dam removal.

The concrete dam, built in 1921 of non-reinforced concrete, has experienced numerous modifications. These modifications include removal of the concrete walkway, piers and gates associated with power generation and construction of a reinforced concrete cap on the left and right abutments.

The removal and restoration project also includes surrender of the Federal Energy Regulatory Commission license. Under their authority, FERC required a dam safety analysis and Quality Control Inspection Program as part of the project design approvals. Working closing with the contractor, we developed a dam removal approach to provide for safe, cost effective removal of the dam.

An excavator-mounted hydraulic impact hammer positioned on a barge will remove the dam, while it is under hydrostatic pressure with the reservoir at the spillway crest. The spillway will be removed sequentially by removing about one foot at a time and allowing the reservoir to recede before proceeding with further removals. The stability analysis evaluated the effect of the removal on the dam stability and identified risk-reduction measures for implementation.

With the safe removal of the dam, the restoration of the natural riverine ecosystems in this reach of Sullivan Creek begins.

Jeff Anderson, PE

About the Author

Jeff Anderson, P.E., works closely with clients to help them comply with ever-changing regulatory requirements. “By taking the time to understand each client’s unique needs, we can help them find innovative solutions to their problems.” In his free time, Jeff enjoys the challenges of raising two energetic children.

Read more posts by Jeff Anderson, PE

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