U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division
British Petroleum Site, Casper, WY
WY Voluntary Cleanup

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2.4-Day Treatment Process
Engineered Wetland System

Cleanup Objectives: Remediate gasoline-contaminated ground water for 50 to 100 years

Green Remediation Strategy: Installed radial-flow engineered wetlands operating in tandem with free-water surface wetlands and a cascading aeration system

  • Employed Smart Growth principles to complement conversion of the site's former refinery to an office park and recreational facilities
  • Designed wetland components for subsurface locations as much as possible to increase operational control and reduce offensive odors or insects
  • Constructed radial-flow treatment beds consisting of crushed concrete previously reclaimed during refinery demolition
  • Insulated wetland treatment beds with a six-inch layer of mulch to accommodate temperatures reaching -35°F
  • Planted emergent wetland plants such as bulrushes, switchgrass, and cordgrass in each of the four wetland areas


  • Treats up to 700,000 gallons of contaminated ground water each day
  • Achieves a 50% reduction in BTEX concentrations when compared to influent of the pre-wetlands aeration process
  • Achieves non-detectable concentrations of benzene and other hydrocarbons in water prior to discharge into a basin created by former refinery effluent discharge
  • Operates year-round despite cold climate
  • Incurred construction cost of $3.4 million, in contrast to projected $15.9 million for alternative pump-and-treat system employing air stripping and catalytic oxidation
  • Found beneficial use for onsite demolition material
  • Uses passive-energy systems to biodegrade contaminants
  • Allowed for office park occupation within 10 months after the aerated/engineered wetland system began operating

Point of Contact: Vickie Meredith, WY Department of Environmental Quality

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