Due to the new Federal and State CCR regulations, the CCR basins at this retired, coal-fired facility required clean closure. The basin had an active water table which required dredging to predetermined grades at a maximum depth of sixty feet. This large volume, high visibility project had a mandated completion date and almost constant scrutiny by the media and both government and non-government environmental groups.
“Trans Ash utilized GPS guided dredges as well as regular bathometric surveys to confirm that the dam was not compromised and the design grades were being met.”
Project Challenges & Solutions
The schedule and environmental factors created a unique set of challenges:
- There was a variety of material below the water level including, CCR material, sand, miscellaneous debris and a large number of Cypress stumps. The Trans Ash project plan utilized multiple dredges combined with the bridging of the pond surface. This allowed for both hydraulic and mechanical removal of all subsurface materials.
- The basin included a state-regulated dam that could not be compromised. Also, the construction plan involved dredging to design grades including benches and slopes. Trans Ash utilized GPS guided dredges as well as regular bathometric surveys to confirm that the dam was not compromised and the design grades were being met.
- This was a large volume project with a mandated completion date. To ensure that the completion date requirement was met, Trans Ash utilized multiple dredges and employed additional personnel as required.
- The harsh coastal climate and heavy rains, including a Category 1 hurricane/1,000 year rain event created constant weather challenges. Trans Ash’s construction plan
created a project management system that ensured the dredge crews were protected and constantly prepared for extreme weather events.
- Dredging operations occurred in close proximity to the sheet pile lined canal and an existing wetland that could not be disturbed. Trans Ash utilized state of the art GPS guidance systems to maintain proper operating boundaries and protect those areas.
- As dredging and excavation progressed, the area available for material collection and dewatering continued to diminish. Trans Ash utilized a discharge pipe management and control system that allowed for multiple discharge points and quick redirection of the discharge water.