Hydrologic Modeling Associated with Permitting an Expansion of a Coal Combustion Products Landfill

摘要

Construction of Coal Combustion Products landfills often impact streams and wetlands that are protected by Federal and State Regulations requiring permitting. In addition, landfills require the installation of a liner system over relatively large areas which reduces groundwater recharge causing potential secondary impacts to streams and wetlands in the form of reduced flow. This paper provides an analytical approach to determine potential stream/wetlands impacts by performing a field evaluation of downgradient streams/wetlands to determine the source of hydrology. The method then calculated the existing, and post-development, surface water flows to downgradient streams and wetlands for both short-term storm-events and long-term (annual) conditions. Using this information the design for a landfill expansion included engineering controls so that stormwater could be captured and then discharged either directly or indirectly to the streams and wetlands depending on the existing source of water. Engineering controls included locating sediment basins upstream of the streams/wetlands to store surface water which could then be discharged directly to the stream or discharged to infiltration trenches to provide a groundwater recharge component. A hydrologic budget analysis was performed to demonstrate that the amount of water received by the streams and wetlands after landfill construction is equivalent to the volume of water received prior to construction on both a short-term and long-term basis.