Lee Hall Dam

With a storage capacity of 960 million gallons, the Lee Hall Reservoir is a key part of a water supply system that serves 400,000 people on the Virginia Peninsula. A change in the regulatory requirements applicable to the reservoir’s lower impoundment dam meant that its spillway needed to be upgraded to handle the maximum amount of rain that could fall in a given time period for the area. As well, the upper impoundment dam needed significant rehabilitation to comply with the requirements. To ensure safe dam operations and extend the facility’s service life, Newport News Waterworks embarked on an ambitious dam rehabilitation effort.

GFT provided design and construction services for the project. The work involved decommissioning the upper dam, raising the main portion of the lower dam embankment, and installing a two-stage labyrinth spillway, allowing the facility to maintain a higher water level. A new auxiliary spillway created by armoring part of the embankment with articulated concrete blocks further increased spillway discharge capacity. Now complete, the upgraded dam enables Newport News Waterworks to maintain reliable water service while protecting the surrounding community.

Our firm provided alternatives analysis of possible solutions during the project’s first phase and preliminary and final design as well as bidding assistance for the second. Because the Lee Hall Reservoir is the terminal reservoir in the area’s water-supply system, maintaining near-full water levels throughout design and construction was critical for system operation. Our firm developed a construction sequencing plan so the water could be diverted during the work without interrupting water supply to Waterworks customers, and without affecting the adjacent municipal park.

GFT completed hydrologic and hydraulic modeling to develop inundation mapping required to update the facility’s emergency action plan for a dam break scenario. Our firm also provided geotechnical services, including subsurface exploration to assess underlying conditions and soil testing to confirm suitability for construction. Detailed analyses of embankment overtopping, slope stability, and potential seepage, as well as the abandonment or relocation of a number of utility pipelines from the embankment, ensured that the rehabilitated dam was safe and stable.