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Velsicol Chemical Corp. (formerly Michigan Chemical Corp.) produced various chemical compounds and products at its 54-acre main plant site in St. Louis, Mich., from 1936 to 1978. Products included the fire retardant polybrominated biphenyl (PBB) and the pesticide DDT. To address contamination discovered at the former plant site, Velsicol, EPA and the state of Michigan entered a consent agreement in 1982. Velsicol agreed to construct a slurry wall around the former plant site and put a clay cap over it. The Pine River, which borders the former main plant site on three sides, was significantly contaminated, which caused the state of Michigan to issue a no-consumption advisory for all fish species.

 From 1998 to 2006, actions taken at the site addressed contamination in the Pine River at a cost of over $100 million. From 1998 to 2006, EPA funded a sediment cleanup in the Pine River adjacent to the site. Over 670,000 cubic yards of DDT-contaminated sediment were removed and disposed of off-site in an approved landfill. DDT levels in fish have been reduced by over 98 percent, but the state plans to keep the fish advisory in place until the entire site has been cleaned up.

 In early 2000s, studies showed the slurry wall and clay cap at the main plant site were failing to keep contamination out of the river. In response, EPA and Michigan's Department of Environmental Quality (MDEQ) launched a remedial investigation and feasibility study at the main plant site. The resulting report stated that soil and groundwater were contaminated. The study identified areas with high concentrations of contaminants known as “potential source areas.” EPA evaluated different cleanup alternatives to address contamination at the site and, in June 2006, selected a remedy that included a comprehensive cleanup of the main plant site and a residential soil cleanup. During the residential cleanup, EPA excavated and disposed of 50,000 tons of contaminated soil at an off-site landfill. Currently, EPA and MDEQ are completing what’s called a “Remedial Investigation” in the Pine River downstream of the former chemical plant property.

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What Has Been Done to Clean Up the Site?

Drinking Water Supply

In May 2014, construction began for the replacement of the city of St. Louis drinking water supply. St. Louis and Alma formed a joint water authority called the Gratiot Area Water Authority (GAWA). In October 2015, St. Louis switched to the new GAWA drinking water. A summary of completed construction activities is included below.

  • Expansion of Alma’s water treatment plant.
  • Construction of water mains from Alma water treatment plant to St. Louis.
  • Construction of two booster pump stations for new water mains.
  • Construction of an elevated water tank in St. Louis.
  • Installation of new water wells.

Main Plant Site

The two largest contaminated areas on the site are referred to as Areas 1 and 2. The following is a list of completed cleanup activities.

  • Design and cleanup of residential area.
  • In situ (in-place) thermal treatment design for Area 1.
  • Excavation design for potential source areas.
  • Predesign investigation for additional potential source areas.

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What Is the Current Site Status?

In-Situ Treatment

The Velsicol site received $9.7M of funding for the in-situ thermal treatment system for Area 1 of the main plant in early 2017. In-situ thermal treatment involves removing harmful chemicals from the soil and groundwater, in-place, using heat. EPA completed site preparation activities over the summer, which included the construction of additional service roads, a new entrance from M-46, and a new high-voltage electrical circuit and process pad for the in-situ thermal treatment system.

EPA’s contractor began cleanup activities on the main plant site in fall 2017.  The thermal treatment system was installed and the system began operations in December 2017.

A summary of upcoming and in progress construction activities is listed below.

Drinking Water Supply

In Progress

  • Construction of additional water wells and mains to Alma water treatment plant.
  • Determine necessity of additional raw water supply.

Main Plant Site

The two largest contaminated areas on the site are referred to as Areas 1 and 2.

In Progress

  • In situ thermal treatment of Area 1.
  • In situ thermal treatment design for Area 2.
  • Groundwater modeling for groundwater pump and treatment system.


  • Cleanup design for additional potential source areas.
  • Predesign investigation for groundwater collection trench.
  • Construction design for a vertical barrier wall.
  • Construction design of an engineered cap.

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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.

On-site groundwater is contaminated with DDT, chlorobenzene, carbon tetrachloride, trichloroethylene (TCE), and other chlorinated compounds. Onsite soil samples revealed contamination with PBBs, copper, chromium, zinc, and magnesium. The sediments of the Pine River were also contaminated with similar contaminants through direct discharges from the site; however, surface waters do not show any significant impacts. Potential risks exist for people who eat contaminated fish and wildlife in the vicinity of the site.

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Sampling and Monitoring

Data is available on the in-place thermal treatment system. This system is installed at the site to capture underground contamination by heating the soil and capturing contaminated vapors. An interactive map shows system location and sampling data, including air monitoring data, collected during the operation of the thermal treatment system.

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