Restoring Former Gas Plant Sites
Times change, and knowledge grows. We know now that the way we manufactured gas historically had some unintended consequences for the environment. WPS restores these areas so they can be used by today's communities.
- The History of Manufactured Gas Plants
- Environmental Issues with Manufactured Gas Plants
- How We're Restoring Sheboygan's Camp Marina
The History of Manufactured Gas Plants
From the early 1800s until the 1960s, local plants manufactured gas for heating and lighting. These plants were the pride of many cities, because gas was a better source of energy. Gas lights replaced oil lamps, and gas eliminated the need to cook and heat with wood or coal. The plants prospered until more affordable, cleaner natural gas began to arrive by pipeline. There are about 2,000 to 2,500 gas plant sites in the U.S.
Environmental Issues with Manufactured Gas Plants
The process of manufacturing gas resulted in byproducts. This included tars, oils and wood chips. Many plants sold the byproducts, especially the coal tar, which could be distilled and used in dozens of products, including fuels, fertilizer, creosote, plastics and pharmaceuticals.
Byproducts that could not be sold were sometimes left on-site. At most plants, storage tanks were made of wood or brick, with piping and other equipment that may have leaked. When the plants were demolished, some waste may have been left on-site. At the time, there were no regulations for disposing of such materials, and these practices were common. However, the result is that some byproducts are still present in the soil and river sediments today. At the depths where they typically occur, they don't present a hazard to people on or near the site. But they do need to be cleaned up to protect groundwater beneath the site.
The chemicals in soil and groundwater at the sites fall into three main categories:
- Volatile organic compounds, like those found in gasoline.
- Polynuclear aromatic hydrocarbons, which are present in byproducts of incomplete combustion (such as car exhaust), asphalt roads, roofing tars, grilled food and other common materials.
- Inorganic compounds such as metals, which came from the coal and gas purifying process.
How We're Restoring Sheboygan's Camp Marina
In the early 1990s, the city of Sheboygan, Wisconsin, was installing a dock along the Sheboygan River as part of its Camp Marina Park project. The city discovered coal tar contamination from the former manufactured gas plant at the site. WPS and the city entered into an agreement to investigate and restore, or “remediate,” the site. Extensive environmental studies followed. After the studies were complete, a plan was made to clean up the site in two phases: first upland and then the river sediment.
The upland portion of the site was cleaned up in 2001. This meant excavating and thermally treating about 10,500 tons of contaminated soil. The thermally treated soil was placed back in the excavation as fill material. The property was then redeveloped as a park.
Cleanup of the river sediment began in 2011. Cleanup began by installing a support structure to protect and stabilize the shoreline. A steel sheet-pile wall, known as a cofferdam, installed from the park shoreline to each end of Boat Island, will block off the eastern channel of the river along the Island. This minimizes the chance that contamination will leave the area and relocate to other parts of the river. The contaminated material is being removed from the river with backhoes, is de-watered and then is disposed of in a landfill. The park will be closed to the public throughout the duration of the project.
Odors are expected during the project. The odors are usually similar to the smell of mothballs or sometimes gasoline. Odor-suppressing foam will be used. Air samples collected throughout the project will be analyzed by a laboratory. We do this to confirm that the clean-up is not releasing anything into the air that could be harmful. Noise levels will be measured as well. If any problems occur, we'll correct them immediately.
The cleanup crews began work in June and started removing sediment in early July. We plan to remove approximately 29,000 cubic yards of contaminated sediment at an estimated cost of $10 million. The project should be complete in December 2011. We plan to restore the park by the end of May 2012.