Landfill Cap Improvements

A confidential industrial client owns a closed landfill in Clinton, Iowa along the Mississippi River shoreline. The industrial landfill was closed in 2000 with the installation of a clay cap, leachate collection system, and storm sewer system, approved as part of the original closure permit. In 2014, the Iowa Department of Natural Resources (IDNR) detected contaminants of concern (COCs) in downgradient monitoring wells during their Annual Water Quality Review. The downstream detections indicated that vertical migration of landfill leachate into groundwater was occurring. The IDNR issued a Closure Permit Amendment (2014) requiring additional leachate control and capture. In 2015, Roux was retained by the client to design a new 9-acre landfill cap and obtain a Closure Permit Amendment for installation. Roux’s design included abandoning the existing damaged storm sewer system, regrading the landfill to provide positive drainage and stormwater conveyance through a new storm sewer system, installation of geosynthetics including a geocomposite gas collection layer, an impermeable high-density polyethylene (HDPE) geomembrane layer, and a geocomposite stormwater drainage layer. In 2016, Roux was retained by the client to complete the construction of the new cap with a total construction cost of $2.9M.

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