Bayou Bonfouca is a 54-acre former creosote plant in Slidell, Louisiana that operated from 1882 to 1972. It was added to the EPA's National Priorities List in September 1983. About 750 residents live within a mile of the site. A fire in the early 1970s ruptured storage tanks and sent creosote directly into the bayou, sterilizing more than a mile of it. Former site owners later donated the waterfront property to the City of Slidell.
EPA identified 26 contaminants of concern across soil, sediment, sludge, solid waste, and groundwater. These include polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene and naphthalene, along with benzene, toluene, xylene, ethylbenzene, styrene, and tributyl(chloro)stannane. In the early 1980s, creosote-contaminated sediments and water caused second-degree chemical burns to divers and injured or killed aquatic animals and waterfowl.
EPA excavated and incinerated over 170,000 cubic yards of contaminated sediment and creosote waste between 1993 and 1995. Contaminated soils and ash were placed in an on-site landfill capped to block exposure. A groundwater treatment system has run since 1991 and has treated nearly 12.7 million gallons of contaminated groundwater. Soil and sediment cleanup finished in 1997. The State of Louisiana has managed site operation and maintenance since 2001.
The sixth five-year review, completed in July 2021, found the current remedy only short-term protective. EPA must still evaluate institutional controls, collect more soil contaminant data, work with St. Tammany Parish on groundwater use restrictions, and investigate possible upgrades to capture dense non-aqueous phase liquid (DNAPL), a form of contaminant that sinks in groundwater. A new groundwater remedial investigation and feasibility study began in April 2020. An Explanation of Significant Differences for groundwater was issued in March 2026.
Human exposure is currently under control, but groundwater migration control is insufficient due to uncertainty about contaminated groundwater movement. The site has not been deleted from the National Priorities List. However, the site has been partly redeveloped into Heritage Park, a public marina, and commercial space, with four businesses employing 108 people as of December 2024.
The seventh five-year review will begin in late 2025 and conclude by September 30, 2026. A public comment period was held from September to October 2025. The five-year review will evaluate the current protectiveness of the remedy and will make any recommendations needed to ensure the remedy is protective over the long term. For questions, contact the EPA Community Involvement Coordinator or Remedial Project Manager.
