Times change. Knowledge grows. Now, we know that the way we manufactured gas in the past had some unintended consequences for the environment. Today, we restore these areas so they can be used by communities.
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. This was because gas was a better source of energy. Gas lights replaced oil lamps. Gas also eliminated the need to cook and heat with wood or coal. The plants prospered. Then, 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.
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Environmental issues with manufactured gas plants
The process of manufacturing gas caused byproducts. These included tars, oils and wood chips. Many plants sold the byproducts. The most commonly sold was coal tar. It could be distilled and used in dozens of products. Some products include 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. The tanks had piping and other equipment that may have leaked. When the plants were removed, some waste may have been left on-site. At the time, there were no regulations for disposal. These practices were common. As a result, some byproducts are still 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.
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How we restored Sheboygan's Camp Marina
In the early 1990s, the city of Sheboygan was installing a dock as part of its Camp Marina Park project. During installation, the city discovered coal tar contamination. It was left from a former manufactured gas plant at the site. WPS and the city entered into an agreement. We decided to investigate and restore, or "remediate," the site. Extensive environmental studies followed. After the studies were done, we made a plan to clean up the site. The plan had two phases.
In the first phase of the project, the upland portion of the site was cleaned. About 10,500 tons of impacted soil was thermally treated and put back in the ground as fill material. The property became a park.
The second phase of the project was the cleanup of the river sediment. This began in 2011. First, a support structure was installed. It was used to protect and stabilize the shoreline. A steel sheet-pile wall was installed from the park shoreline to each end of Boat Island. The wall is called a cofferdam. It blocked off the eastern channel of the river along the island. The cofferdam minimized the chance for contamination to leave the area. The contaminated material was removed from the river with backhoes. It was de-watered. Then, it was disposed of in a landfill. A total of 24,572 cubic yards of sediment was removed during this phase.
The Environmental Protection Agency (EPA) started a third project phase to promote redevelopment and improve recreational use. They removed contaminated sediment from sources along the Sheboygan River. We partnered with the EPA, the City of Sheboygan, Sheboygan County and the Wisconsin Department of Natural Resources on this phase. By 2013, an additional 147,810 cubic yards of sediment was removed. This included another 18,000 cubic yards from the Camp Marina area.
In total, 190,382 cubic yards of sediment was removed from the Sheboygan River and surrounding area.
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