In a Nutshell

• An automotive supplier accidentally released industrial amounts of toxic hexavalent chromium into a sanitary sewer system that ultimately drains to the Huron River.
• Subsequent testing and analysis determined that most of the chromium was prevented from entering the river due to a combination of actions taken by the Wixom wastewater treatment plant and plain old good luck. 
• While this incident appears not to have imposed any significant health or ecological consequences, it is the latest in a series of embarrassing headline-grabbing pollution incidents. Michigan should strengthen its environmental policy to prevent future incidents, protect the health of residents, and support the role of natural resources in Michigan’s economic future.

By Eric Paul Dennis, PE

Like many states with an historical manufacturing economy, Michigan has numerous sites contaminated with legacy pollution that cannot practically be removed. Michigan has been a center of industry and manufacturing since the early 20th century when society knew very little about the environmental and human health implications of various chemicals. It was common for toxic materials to simply be dumped into open pits or waterways.

Today, we have much more knowledge about the consequences of pollution. As we work to remediate legacy pollution and mitigate impacts on human health and the environment, we must also prevent pollution from current activities. 

The August 2022 Hexavalent Chromium Spill

Hexavalent chromium (chromium-6) is the chemical that made Erin Brockcovich famous. It’s nasty stuff. Not only is it carcinogenic, but acute exposure can damage any human organs that it comes into contact with, including skin. Chromium-6 can occur naturally, but the EPA limits its presence in drinking water to only 100 parts per billion (0.1 mg/l, or a 0.00001% solution).

Concentrated chromium-6 is used in a few industrial processes, including the manufacturing of chrome-plated automotive trim. Chromium-6 is so noxious that its use in chrome plating has been banned in Europe. The U.S. Department of Defense has a policy to minimize its use. The Occupational Health and Safety Administration recommends it not be used. Many manufacturers now use low-toxic trivalent chromium and have found it a suitable substitute. 

Considering how dangerous chromium-6 is, the Michigan health and environmental community was alarmed to learn of a discharge of “several thousand gallons of a liquid containing 5% hexavalent chromium (Cr(VI)) into the sewer system.” This sewer system is ultimately discharged into the Huron River.

The Michigan Department of Environment Great Lakes, and Energy (EGLE) and the Michigan Department of Health and Human Service (MDHHS) immediately issued recommendations to avoid all contact with the Huron River downstream of the discharge point. This included ponds and lakes that the river feeds, including Mill Pond in Downtown Milford and Kent Lake in Kensington Metropark – two popular recreation sites in southeast Oakland County.

EGLE then collected water samples from multiple downstream locations. Three samples tested positive for chromium-6:

• Mill Pond: 11 parts per billion (ppb) at surface
• Mill Pond: 9 ppb near the bottom
• Kent Lake: 5 ppb at 9” depth

These positive tests were all taken on August 4th, three days after the initial notification of accidental discharge. While chromium-6 was found in the water, the results were well within the 100 ppb maximum contaminant limit for drinking water, and also within acceptable limits for chronic ecosystem exposure. However, MDHHS and EGLE erred on the side of caution and extended the no-contact advisory while testing continued. No subsequent tests detected the contaminant and the no contact advisory was lifted.

Crisis Averted

The initial information was that up to 10,000 gallons of a 5% chromium-6 solution (4,170 pounds of pure chromium-6) was released into the Huron River. Such an event would have been disastrous for Huron River ecology and the public health of the communities that line its shores. Fortunately, testing and investigation showed the spill to be far less severe. 

Only 3 of dozens of water samples detected any hexavalent chromium, and these were within health and safety thresholds.

Source: EGLE

The spill was largely mitigated by a pre-treatment filter at the manufacturing plant. This filter was installed to mitigate PFAS discharges, but was partially effective at capturing chromium-6. In another stroke of luck, the environmental conditions within the sanitary sewer system worked to naturally convert much of the toxic hexavalent chromium to its non-toxic sibling, trivalent chromium. After being notified of the chromium-6 release by the manufacturer, the Wixom wastewater treatment plant staff quickly acted to divert some of the contaminated water to a temporary holding pond rather than the Huron River. EGLE now estimates that less than 20 pounds of total chromium was released into the Huron River, only a fraction of which was the toxic chromium-6 form.

High Profile Michigan Pollution Stories

While the August 2022 chromium-6 incident concluded without significant harm to the environment or human health, it became an embarrassing headline. This is only the latest in a series of embarrassing headlines regarding pollution in Michigan. Some of the more sensational stories include the following:

Ann Arbor’s Gelman Plume: Dioxane is an industrial solvent and likely carcinogen. Dioxane was used from the mid-1960s to the mid-1980s in the manufacturing processes at a medical equipment manufacturing facility west of Ann Arbor. Wastewater from the plant, containing dioxane, was disposed onsite during that time. The pollution remains and has become a groundwater prohibition zone. The spreading plume of contaminated groundwater increasingly threatens drinking water and the Huron River. Dioxane and dioxin contamination has been an issue in other parts of the state as well. 

Huron River PFAS Dump: The same manufacturer that released chromium-6 into the sewer system was previously found to be discharging PFAS chemicals into the sewer system and Huron River. They were made to install on-site filters, but did not face any consequences for the damage already done. To this day, it is considered unsafe to eat fish from much of the Huron River because of that incident.

Interstate 696 “Green Ooze”: In December 2019, bright greenish yellow liquid was found leaking from a barrier wall of Interstate 696. The ooze was found to contain various toxic chemicals, which had leached into groundwater from the basement of a shuttered manufacturing facility. This site was under active remediation for chromium-6 among other chemicals, but containment measures had failed.

Flat Rock Gasoline Spill: In August 2021, gasoline leaked from a large automotive assembly plant into the City of Flat Rock’s sanitary sewer system. The polluter did not inform regulators of this very serious incident. Officials learned of the leak through an anonymous tip. This incident initially created the risk of explosion. Once that risk was abated, the concern became toxic substances (especially benzene) affecting air quality in homes. Hundreds of residents were subject to a weeks-long evacuation order, during which they had no access to their own homes due to health and safety concerns 

East Side Detroit Automotive Assembly Air Quality Violations: In 2019, the first new automotive final-assembly plant in Detroit city limits in over 30 years. The construction and operation of the plant precipitated dozens of complaints of air quality problems from nearby residents, and accusations of environmental injustice. EGLE has since issued multiple violation notices to the plant, but resident complaints continue.

The “green ooze.” Contaminated groundwater leaks from an I-696 retaining wall in Oakland County.

Image Source: Bridge Michigan.

These headline cases are embarrassing and concerning, but what is more concerning is that they represent only a small fraction of Michigan’s pollution problem. There are thousands of contaminated sites that we know about. About half of these are “orphan sites,” where “there is no connection to a responsible party that can be identified – either it’s unclear who caused the contamination or those responsible are no longer alive.” Given the state’s long industrial history, it is nearly certain that there are thousands more of these contaminated sites we don’t know about. As we continue to discover sites contaminated with industrial chemicals and agricultural effluents, it is becoming increasingly concerning that Michigan is facing a potential “groundwater emergency.”

Need to Strengthen Pollution Control Policy

Michigan has thousands of contaminated sites with no plan for remediation. Ideally, we would now be in the slow, arduous process of cleaning up Michigan’s environment. By some measures this is happening, but in the case of water contamination, it seems to often be a case of ‘one step forward, two steps back.’

Huron River’s “Cascades” in Ann Arbor was one of the sites closed to visitors as EGLE tested the water for chromium-6

Source:  a2gov.org.

Polluters are often allowed to pollute their own property and never clean it up so long as they can argue that the pollution will not make humans sick.

Michigan’s permissive law regarding pollution remediation has not helped. At the core of this issue is the Natural Resources and Environmental Protection Act, Act 451 of 1994. Per this law, when contamination by hazardous substances is discovered on an industrial or commercial parcel, the responsible person can propose to remedy the situation – not by removing the contaminant, but by adopting a restrictive covenant; a legal agreement to limit current and future uses of the property as to reduce human exposure to the hazardous substance.

A covenant typically includes things like access for inspections and limitations on residential use. In extreme cases, the restriction may completely prohibit future access and use of the property. In other words, polluters are often allowed to pollute their own property and never clean it up so long as they can argue that the pollution will not make humans sick. 

EGLE can challenge such plans to leave contaminants in place. However, there is a high burden on EGLE to show that the hazardous material on site poses an “unacceptable … human health risk” via “reasonable and relevant exposure pathways.” To force a polluter to clean up their hazardous materials from the site, EGLE would have to prove in court that not doing so will make people sick. This burden of proof is high, and EGLE’s resources are limited. Ecosystem health does not enter the equation. As a result, it is very common that the solution to pollution is to try to contain it in-place, put a fence around it, and let it be. 

An EGLE database lists over 3,200 individual parcels where soil or water contamination by hazardous materials is intentionally being left in place. These properties now include restrictive covenants that prohibit various uses. So under current Michigan environmental law, any industrial parcel has the potential to legally and formally become a hazardous waste site in perpetuity. This lowers the cost burden on the polluting business but may also prevent parcels from being put into productive use in the future.

Hazardous contaminants spilled on soil or stored in leaky holding ponds can leach to the water table, polluting groundwater and even surface waters via flowing “plumes.”

Image Source: Michigan DEQ

To complicate matters, contamination often doesn’t stay on site. Rain and snow melt leaches contaminants from soil into groundwater and surface waters. Groundwater flows offsite, spreading contamination underground through hidden “plumes.” Floods come and go, spreading hazardous material across the region. Abandoned wells often provide a direct path for contaminants to pollute drinking water aquifers. Even wind-blown dust can distribute pollutants if the site is not properly “capped.” Often, by the time restricted properties become an obvious human health risk that would compel the polluter to remediate the site, that person or business responsible often no longer exists, and the financial burden falls to taxpayers.

Incidents like the Huron River chromium-6 release and Flat Rock gasoline spill made headlines because the spilled contaminants happened to drain into a sanitary sewer and created an emergency situation. But a larger long-term danger is the unknown number of sites that are spilling contaminants onto the ground, slowly and irrevocably polluting soil and water. Overall there are over 24,000 known contaminated sites. Over 300 of these are determined to have “immediate risks” to human health. Contaminated and polluting sites are often clustered together such that the cumulative impact turns entire neighborhoods into “sacrifice zones.” New sites are frequently uncovered by whistleblowers and citizen investigations, and many never will be. It’s impossible to know how widespread and hazardous the problem is.

Strategy: ‘Polluter Pay’ and Increased Resources

Between the overly permissive pollution law and the resource limitations placed on environmental regulators, Michigan has developed a culture where many industrial actors appear unconcerned about their impact on the environment. Short-term business interests take precedence over long-term stewardship of the land and environment. Storage tanks and holding ponds often go uninspected and unmaintained because any leakage is unlikely to require cleanup. Some businesses use their property as informal hazardous waste dumps, trusting that even if they are caught there will not be any substantial consequences.

We cannot reverse time and undo decades of industrial pollution. But we can do better – starting now. It’s much easier to clean up a hazardous waste spill when it’s done immediately. When material is allowed to spread around and percolate into the ground for years, cleanup can become infeasible. We need to adopt a “polluter pay” law that would encourage businesses to refrain from contaminating soil and water, and immediately clean up contaminants that are spilled.

Nobody wants to place regulatory burdens on companies that prevent them from conducting business in Michigan.

Nobody wants to place regulatory burdens on companies that prevent them from conducting business in Michigan. Under any reasonable incarnation of a “polluter pay” provision that requires cleanup of sites, EGLE would have flexibility to work with business owners to balance environmental and human health risks with the cost of remediation. It often truly is the case that the best remedial action plan for hazardous contamination is to cap it and restrict use of the site. But current law makes this the default option and continues to contribute to degradation of Michigan’s environment and quality of life; this has to change.

As it stands, EGLE has very little authority or resources to compel remediation of contaminated sites, even when cleanup would be feasible and not impose excessive financial burden on the polluter. The law effectively grants businesses a de facto license to pollute.

There are two actions policymakers could take that stand out as opportunities to substantially improve pollution control policy in Michigan: 

1. Amend the Natural Resources and Environmental Protection Act to require polluters to clean up hazardous waste spills if it is feasible.
2. Provide EGLE with the resources needed to enforce environmental protection laws, including working with businesses to remediate contaminated sites to the extent feasible.

The scope and scale of Michigan’s environmental problem is enormous. There are thousands of existing contaminated sites and thousands more waiting to be discovered. Many of these will still be contaminated decades from now. We can’t change that, but we can prevent new sites from being created. Reforms made now will yield benefits to Michigan’s residents and communities decades into the future. 

We must reform Michigan’s environmental policy and culture to prevent the continued proliferation of hazardous waste sites and the statewide “groundwater emergency” that environmental advocates fear.

Updated 9/8/2022 to revise number of known restrictive covenants from “over 3,000” to “over 3,200.” Also minor grammar issues were addressed. Updated 10/13/2022 to specify that the filters at Tribar were installed to mitigate PFAS discharges.