Sequoia was awarded the contract to excavate and process coal ash from three inactive ash basins that were in service from the 1950s to the early 1980s. Sequoia previously fortified and rebuilt the dam structures at this site to control the risk of overtopping from severe storm events. This project supports a coal ash recycling operation onsite which determines the rate of excavation for these ponds. Given the protracted 6 year schedule for this work, Sequoia was challenged with managing the excavation over several hurricane seasons and were required to develop detailed water management, storm and evacuation plans in addition to covering exposed ash during flood events.
The inactive ash basins contain approximately 1.2 million cubic yards of coal ash located in a heavily vegetation coastal flood plain. Sequoia was challenged with clearing the basins, segregating the excavated ash into salable and waste fractions. Useable ash was segregated, screened, and hauled to a stockpile at an adjacent site for re-processing. Vegetative waste and soil impacted ash was hauled to a commercial landfill offsite. Detailed water management plans, excavation plan, stability engineering and flooding evacuation plans were developed to support the work.