The owner of a power plant in Ohio that generates electricity from two 1,300-MW coal-fired units required an additional 47 million cubic yards of disposal capacity for coal combustion residuals (CCR).
Geosyntec was retained to finalize a siting study, in part due to our experience designing and successfully permitting other such landfills, including one that involved construction over a former fly ash reservoir. Our client's objective for the project was to overcome the numerous technical challenges to enable utilization of the lateral expansion site at a reasonable construction cost. Also, the permit for the work needed to be received within about 18 months from application to ensure that the landfill was available as the existing RWL reached capacity.
Geosyntec's Scope of Services
Based on our siting study, our client selected a site adjacent to an existing residual waste landfill (RWL) and surface impoundment (SI) with over 80 ft of wet-sluiced fly ash undergoing simultaneous closure. The site offered operational advantages owing to its proximity to the existing landfill but also came with significant design and permitting challenges. The areas available for an expansion included artifacts of previous surface and underground coal mining, active oil and gas wells, construction over portions of the former SI and its former spillway channel, complex site topography, existing utility corridors, and a very limited lateral expansion footprint area. Another complicating factor was that there were essentially no on-site sources of clay materials for the bottom liner.
Geosyntec performed a siting feasibility study and detailed engineering and design of the selected site and prepared the four-volume permit-to-install (PTI) application for submittal to the Ohio Environmental Protection Agency (OEPA). We completed a comprehensive subsurface site investigation program that yielded the geologic, hydrogeologic, and geotechnical data necessary for the siting and design of the landfill. Our investigation and design included the sampling and analysis of fly ash and an assessment of static and seismic liquefaction. We finalized the engineering analyses, detailed design drawings, quantity calculations, and supporting plans and report and prepared the permit application. The permit application addressed the siting criteria, subsurface characterization, staged site development sequence, waste haul road design, detailed landfill grading, and design sheets for the liner, leachate management, stormwater management (chutes and ponds), and final cover systems and closure plan. We then modified the permit to include a geosynthetic clay liner (GCL) alternate liner that met the 2015 CCR Rule. Construction documents were prepared for Stages 1, 2, 3 and 4 and we have supported construction activities for several years.
Geosyntec was able to address the significant geometric constraints and geotechnical challenges, including liquefaction and settlement potential of the ash pond areas of the subgrade, to achieve an acceptable disposal capacity for the expansion. The client reported that the estimated initial startup cost ($ per cubic yard in the first five years of development and construction) was one of their lowest over the past 10 years. They also received OEPA verbal approval of the PTI only 14 months after initial submittal, four months sooner than their original goal, with only one comment OEPA letter. In addition, the alternate GCL was the first GCL accepted by OEPA for such a use and it reduced construction costs by avoiding importing clay from off-site borrow areas.
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- Location: Southern Ohio
- Client: American Electric Power
- Project Practice Areas: Waste Management, Environmental Management
- Type of Facility: Coal-fired power plant
- Services Provided: Final siting study, Subsurface site investigation, Landfill engineering analyses and design, Treatment pond design, Liquefaction evaluation, Alternate GCL bottom liner, Landfill permit application preparation, Construction and operations planning, Construction documents
- Type of Work: Coal ash landfill expansion
- Governing Regulation: Federal and state