WIN000509983, Superfund Alternative Approach Agreements Site | Region 5 Superfund

U.S. EPA REGION 5
PORTAGE COUNTY
STEVENS POINT

Congressional District # 07

WPSC STEVENS POINT

EPA ID# WIN000509983
Last Updated: March, 2015

Site Description

The 3-acre WPSC Stevens Point MGP site is located next to Pioneer Park and near the Wisconsin River in a historically industrial area of Stevens Point, Wisconsin. The site is currently open space owned by the Wisconsin Public Service Corporation (WPSC), an operating utility company. The gas plant was operated from about the 1890s to the late 1940s. During operations, a former slough ran adjacent to the site and carried gas plant waste into what is now Pioneer Park and toward the river, contaminating sediment in a small pond in the park and in the river.

Manufactured Gas Plants (MGPs) were industrial facilities that produced gas from coal, oil, and other feedstocks. MGPs began operating in the U.S. in the early 1800s, typically in urban areas where gas was needed for lighting, cooking, and heating. Two gas production methods were used at the WPSC MGP facility: coal carbonization and carbureted water gas. Both processes produced waste and by-products such as tars, purifier waste, oils, sludges, and acidic waste. On-site disposal of waste and spills and leaks often resulted in contaminated soil and groundwater. MGPs were often located near waterbodies and thus sediment contamination is also common.

WPSC is addressing the Stevens Point MGP site under EPA's Superfund Alternative Sites program.

Site Responsibility

The Stevens Point MGP site is being addressed by the potentially responsible party (PRP) under state and federal oversight.

Threats and Contaminants

WPSC conducted a soil cleanup action at the site in 1998 that concentrated on the more highly contaminated areas. However, soil at the site still contains residual amounts of polynuclear aromatic hydrocarbons (PAHs); volatile organic compounds (VOCs), including a group of VOCs called benzene, toluene, ethylbenzene, and xylene (BTEX); lead; and cyanide.

Groundwater at the site generally flows west, away from the Wisconsin River, because the site is upstream of the Main Street Dam. Groundwater contamination includes PAHs, cyanide, BTEX, and lead.

Sediment in the small pond in Pioneer Park contains PAHs and the nearby Wisconsin River sediment, particularly near the slough, contains PAHs and BTEX, and shows evidence of odor, sheen or tar associated with MGP waste.

Humans could be exposed to site contaminants through dermal contact with soil or sediment or by drinking contaminated groundwater. If people were exposed to site contaminants over time, carcinogenic (cancer-causing) and/or non-carcinogenic health effects could occur.

Cleanup Progress

WPSC and EPA entered into a settlement agreement called an Administrative Order on Consent (AOC) to address the Stevens Point MGP site in May 2006. Under this agreement, WPSC agreed to conduct a remedial investigation and feasibility study (RI/FS) at Stevens Point and five other former MGP sites located throughout Wisconsin. Because the six sites have similar conditions and contaminants, and WPSC is responsible 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 allow the investigative progress to address the "worst problems first."

Under the state cleanup program various investigations and cleanups of the Stevens Point site have occurred since the 1990s. In 1998, an upland cleanup occurred including the excavation and thermal treatment of about 16,400 tons of highly-contaminated soil and placement of a clean soil cover over excavated areas. Routine groundwater monitoring occurred quarterly for some wells and semi-annually for others.

After signing the 2006 AOC, WPSC completed additional investigations of residual site contaminant levels in 2011. EPA approved the RI/FS report in May 2012 and, in June 2012, EPA announced a proposed cleanup plan and opened a public comment period. The proposal called for the placement of institutional controls on contaminated soil and groundwater areas, monitoring the natural attenuation of the groundwater contaminant plume, dredging the contaminated sediment from the river, and covering the contaminated sediment in the pond. EPA signed a Record of Decision selecting this remedy in September 2012.

In May 2013, EPA issued a second AOC to WPSC that compelled WPSC to complete the remedial design. EPA approved the final design on October 22, 2014. Later that year EPA, the State of Wisconsin, and WPSC entered into a Consent Decree under which WPSC would conduct the remedial action once the design was completed. The Consent Decree was entered in November 2014.

WPSC plans to begin active cleanup work at the Stevens Point site in fall 2015 and complete construction work by the following spring.

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