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Congressional District # 06


EPA ID# WIN000509947
Last Updated: March, 2015

Site Description

The WPSC Oshkosh former MGP site is located north of the Upper Fox River, about 0.2 miles downstream of Lake Winnebago, in Oshkosh, Wisconsin.  The Oshkosh MGP site totals about 12 acres in size, with about 7.6 acres on land and about 4.3 acres of potentially contaminated sediment found in an adjacent stretch of the river.

The Oshkosh MGP site is located in a historically industrial, commercial, and residential area of the city.  The city has owned the site since 2003 and has redeveloped it into a public park that includes an amphitheater and river walk.  Boat docking is desired along the shoreline to enable boaters to visit the park. 

Manufactured gas plants (MGPs) were industrial facilities that produced gas from coal, oil, and other feedstocks.  MGPs started operating in the U.S. in the early 1800s, typically in urban areas where gas was needed for lighting, cooking, and heating.  The Oshkosh gas plant operated from 1869 to 1946.  Two gas production methods were used at the MGP facilities: coal carbonization and carbureted water gas.  Both processes produced waste and by-products such as tars, purifier waste, oils, sludges, and acidic waste. Disposal of these wastes and spills and leaks often resulted in contaminated soil and groundwater.  MGPs were often located near waterbodies and sediment contamination is common.

Wisconsin Public Service Corporation (WPSC) is a potentially responsible party for several former MGPs located throughout Wisconsin including the Oshkosh site.  WPSC is addressing six former MGP sites under EPA's Superfund Alternative site program.

Site Responsibility

The WPSC Oshkosh former MGP site is being addressed through potentially responsible party (PRP) actions under state and federal oversight.

Threats and Contaminants

Soil, groundwater, and sediment at former MGPs are often contaminated with variable amounts of tarry compounds called polynuclear aromatic hydrocarbons (PAHs), a group of volatile organic compounds (VOCs) called benzene, toluene, ethylbenzene, and xylene (BTEX), the heavy metal, lead, and with cyanide.

WPSC had conducted a soil cleanup action on the most highly-contaminated areas at the Oshkosh MGP site; however, soil at the site still contains residuals of PAH, BTEX, lead, and cyanide.  Shallow groundwater in the area flows south from the site toward the Upper Fox River while bedrock groundwater appears to flow north away from the river.  Groundwater contamination includes PAHs, cyanide, and BTEX.  Sediment in the nearby Upper Fox River contains PAHs.

People could be exposed to residual MGP-derived contaminants at the Oshkosh site by dermal contact with contaminated soil or river sediment or by drinking contaminated groundwater.  Benthic (bottom-dwelling) organisms could be exposed to sediment contaminants in the river.  Exposure to the MGP contaminants could cause toxic health effects.

Because residents and nearby businesses use the Oshkosh city water supply for drinking, no one is drinking contaminated groundwater from the site.  Exposure to contaminated soil is now limited because of the previous soil cleanup action.  However, EPA is working to determine if additional remedial action is necessary to further reduce or eliminate exposure to residual MGP wastes.

Cleanup Progress

WPSC and EPA entered into a settlement agreement in May 2006 to address site conditions at six former MGP sites in Wisconsin including the Oshkosh site.  Under the enforcement agreement, WPSC has agreed to conduct remedial investigations and feasibility studies at the six former MGP sites. Because the six sites have similar conditions and contaminants, and WPSC is a potentially responsible party (PRP) for each, the agreement allows a streamlined approach to site investigation and remedy development.  Some benefits of the agreement include the use of multi-site documents, a mechanism to review the adequacy of past work, and scheduling flexibility to address the "worst problems first."

WPSC has conducted various investigations of the Oshkosh site under the state voluntary cleanup program since the 1990s.  In 2002, WPSC conducted cleanup actions that included source area excavation and thermal treatment of about 23,500 tons of contaminated soil; installation of a sheet pile containment barrier wall along the shoreline of the Upper Fox River; groundwater treatment and gradient control; and capping the site.  Routine groundwater monitoring occurs annually.

EPA plans to have WPSC begin a remedial investigation at the Oshkosh site in 2016 in accordance with the 2006 enforcement agreement, with the goal of selecting a final cleanup remedy for the site by 2018 or 2019.

Community Involvement

The city of Oshkosh has developed the former MGP site into a public park.


Remedial Project Manager, U.S. EPA
margaret gielniewski (gielniewski.margaret@epa.gov)
(312) 886-6244



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