Flue Gas Desulphurization (FGD)
Scrubbers are used in U.S. power plants to meet emissions standards set by the U.S. Environmental Protection Agency (EPA). New regulatory programs call for further reduction of sulfur dioxide (SO2) emissions from coal-burning power plants. Flue gas systems frequently use limestone-forced-oxidation scrubbers to convert SO2 in the flue gas to gypsum, which can be sold for wallboard manufacturing, cement additive, or agricultural applications, thus turning a waste stream into a usable resource. Landfills are necessary for the disposal of the gypsum byproduct when demand for the gypsum falls short of the production.
Garrett & Moore, Inc. has provided engineering services to power companies for critical environmental control facilities associated with the FGD scrubber waste. Projects include new gypsum/ash lined landfills and new FGD scrubber blowdown ponds.
Garrett & Moore, Inc. continues to provide consulting and engineering services for landfill operations and overall environmental compliance. The services include preparing groundwater and surface water monitoring plans, detailed operations and maintenance manuals, fill sequence plans, environmental permit tracking, Solid Waste Acceptance and Implementation Plan (SWAIP), borrow area management plan, Storm Water Pollution Prevention Plan (SWPPP), and airspace utilization studies.
FGD Scrubber Blowdown Wastewater Pond Design and Permitting
Garrett & Moore provided engineering services in support of this scrubber project including the design, permitting, and construction quality assurance for the FGD scrubber blowdown wastewater pond. Project highlights included a multi-bay, composite-lined treatment facility, which was designed and constructed within the plant’s existing wastewater treatment pond system.
Duties included coordination with concurrent scrubber project construction, facility layout, wastewater treatment modeling, wastewater permitting, construction bid documents, and construction quality assurance testing.
The project was constructed within the limits of the plants existing NPDES wastewater treatment pond system. Construction within the existing pond system added a very challenging level of complexity for the project. Garrett & Moore, Inc. was responsible for conducting a geotechnical assessment of the existing pond system, including an evaluation of the existing pond embankments, which were constructed about 50 years ago.
The first phase of the project, illustrated in Figure 1, required dewatering, excavation of the accumulated sludge, reinforcing the subgrade with geo-grid, and then installing backfill to provide adequate separation from groundwater.
The second phase of the project, illustrated in Figure 2, included construction of a low permeability clay liner and a 60 mil HDPE liner. Finally, as shown in Figure 3, the liner was overlain with a fabric cushion and fabric-formed concrete.
Garrett & Moore, Inc. was responsible for construction certification and the wastewater permit to operate.