Project Detail – Florida

Feasibility Study, Major Utility Company

Power plant

Services Provided:
  • Conceptual design analysis
  • Regulatory liaison
  • Detailed financial analysis
Project Objective:

The purpose of the feasibility report was to present the results of additional airspace and site life analyses performed by AWT and Geosyntec of nine conceptual vertical expansion options using AWT’s and traditional MSE technologies. Additionally the purpose of the economic feasibility was to provide the permitting and economic evaluation components of the vertical expansion options using AWT’s and traditional MSE technologies. Additionally the purpose of the economic feasibility was to provide the permitting and economic evaluation components of the vertical expansion feasibility study as well as the regulatory permitting framework and likelihood of success for the expansion. A number of physical design requirements were considered as part of the initial feasibility study including lateral limits, berm height, CCP fill slope, top deck elevation, and CCP disposal rate. Along with the design parameters outlined above, three wall height options were considered including 30, 40, and 50 feet. For each wall height, the increase in storage capacity and associated service life was calculated for both AWT technology and traditional MSE wall construction options.

AWT, LLC & Geosyntec Scope of Services

The focus of the evaluation was on the use mechanically stabilized earth (MSE) technologies, primarily Advanced Wall Technology, LLC’s (AWT) patented approaches, for vertically expanding the landfill. Specifically, review of existing physical geometry of the facility; development of one or more typical MSE wall cross sections; development of one or more scenarios of increased storage capacity; calculations of increased storage capacity in terms of volume and site life and estimates of costs to implement one or more scenarios. AWT & Geosyntec conducted informal discussions with Tallahassee representatives of the Florida Department of Environmental Protection (FDEP) as well as permitting engineering staff of the Southwest District of FDEP. These discussions were generic and in a format to gauge FDEP’s understanding of MSE wall technology and the level of acceptance to this approach in concept. The team prepared an economic evaluation for each scenario based on projected costs to construct the MSE walls. The costs were presented in terms of dollars per ton of gained CCP storage capacity. The project team prepared a report containing a discussion of the vertical expansion scenarios, related capacity gains and economic evaluations, and permitting considerations.

Notable Accomplishments

The facility’s need for additional CCP landfill airspace is pressing and vertical expansion of the CREC facility using MSE berms provides a cost-effective expansion and more streamlined permitting option compared to a new disposal site. The AWT MSE berm system provided the most cost effective MSE berm design, and additionally it creates a beneficial use of all of the CCP generation concurrent with construction of the berm and prior to actual development of disposal capacity. The results included:

  • An increase of 7,252,800 cubic yards of additional airspace, the most of any option.
  • A very low cost per cubic yard cost for airspace of the expansion methods while maximizing the volume of CCPs utilized in berm construction (2.7 years of plant output).
  • A full encapsulation of the CCP’s utilized in construction of AWT walls by a Subtitle D equivalent liner section.
  • Significantly delay large capital expenditures that would be required for design, permitting and construction of an entirely new CCP disposal facility.