To take the first step toward its goal of clean energy at its Chesterfield plant, Dominion Energy needed to install a new flue gas desulfurization device (scrubber) at three power units that would remove up to 95% of sulfur dioxide and 90% of mercury emissions. Dominion engaged Schnabel to design the retrofit, which was complicated by extremely restrictive site conditions and challenging project requirements.

We needed to design new pile foundations and earth anchors between existing utilities, pipelines, and foundations that couldn’t be disturbed. Low headroom and confined areas were additional complicating factors. The site conditions, as well as substantial vertical, lateral, and uplift loading requirements, dictated that no fewer than five foundation types be used: micropiles, auger cast piles, drilled shafts, H-piles, and the repurposing of concrete mat foundations.

A secant augercast pile wall was also designed to brace an excavation adjacent to an existing 10-ft diameter circulation water line, which was critical to keeping the power units on line. Since driving of steel H-piles was required within three feet of existing foundations, retaining walls, and utilities, including the aforementioned waterline that had to remain in service during construction, we conducted a full vibration study. This evaluation proved that the vibration impacts of pile driving on adjacent structures could be tolerated.

We also provided third-party construction materials testing and quality assurance services for construction of the new induced draft fans, absorber building, and scrubber for all three units.