Skip to main content

Stormwater pond contaminant litigation

The City of Bloomington has filed a federal lawsuit against seven refiners of coal tar for allegedly contaminating numerous stormwater ponds with chemicals called polycyclic aromatic hydrocarbons (PAHs).

Bloomington is seeking damages to fund proper disposal of PAH contaminates.

PAHs are found in coal tar sealants that were used throughout the region until a 2014 statewide ban on their sale. The manufacturers of these products have traditionally marketed and sold them for use in sealants or coatings for roads and driveways.

Bloomington has already been testing its stormwater pond sediments for contaminants. The City is currently inventorying ponds and collecting information to determine the maintenance priority of the ponds.


What is coal tar sealant?

Coal tar sealant is a thin black coating applied to paved surfaces (typically driveways, parking lots, etc.). It is not commonly used to pave roads.  

What is a polycyclic aromatic hydrocarbon (PAH)?

A polycyclic aromatic hydrocarbon is a class of chemicals that occur naturally in coal, crude oil and gasoline. They are also produced when coal, oil, gas, wood, garbage or tobacco are burned. 

How does coal tar sealant migrate from driveways and parking lots and into stormwater ponds? 

After several years, use and weather exposure can cause fine particles of the sealant to wear off. These particles wash into stormwater ponds.

How did the City discover the presence of PAH in Bloomington stormwater ponds? 

Bloomington participated in the Minnesota Pollution Control Agency's (MPCA) study regarding the contamination of stormwater pond sediments by PAHs.  

Is Bloomington the only city to have discovered PAH in its ponds?

No. The presence of PAH has been detected in ponds all over Minnesota. Several other cities have filed similar lawsuits.

Are there health implications? 

As long as it remains in sediment in stormwater ponds, PAH is not a public health concern. However, once the contamination is dredged it could pose a health risk if the dredged soil is not properly disposed of in an authorized landfill designed to ensure that the waste cannot migrate into the environment – this is why the City is moving forward with a plan to clean up the contamination. 

More information about environmental concerns can be found on MPCA’s website.

Why do cities have stormwater ponds?

Stormwater ponds were built to perform flood control and water quality functions. One purpose of a stormwater pond is to catch contaminants so they don’t go elsewhere.

How many stormwater ponds are in Bloomington?

The city has 300 public stormwater ponds. These ponds are maintained by the City on both public and private property within public easements and are inspected on a rotating basis for functionality.

Does the City know how many ponds contain the contaminant?

Not yet. Limited study and sampling have been done, but recent information from other sources suggests that 20-50 percent of ponds may have some PAH contamination present. 

How will the City remove PAH from ponds? 

To remove the contaminants, crews will dredge the pond and, when required, haul contaminated substances to a landfill for proper disposal. The excavation process is routine, but the size and placement of each pond will affect the removal timeline.

Does the City know how much it will cost to dispose of PAH? 

Based on the project information available, cleanup could cost approximately three to four times as much as common excavation costs. 

Why litigation?

It is very costly to remove PAH contamination from stormwater ponds. The City wants to hold the correct party responsible for the financial burden to correct this issue. This cost should not be funded by taxpayers.

What damages are the cities seeking?

The cities are seeking compensatory damages for past and future costs of testing waste/sediment and past and future costs of removing and disposing of that waste from the stormwater ponds. 

Will residents who used coal tar sealants on their driveways be responsible for damages in this lawsuit?

No, the City is not suing users of the coal tar sealant.

Is there any chance the contaminant would be found in ponds on private property? 

Yes, it is possible the PAH contaminant exists in private ponds. Homeowners are encouraged to visit the MPCA website on PAH to learn more.

How do I know if the pond near me is maintained by the City? 

If there is public roadway drainage directed to the pond, then it is most likely a publicly maintained pond. An exception would be if there were a specific legal agreement that requires the private property owner to perform maintenance.

If you have questions about the ownership of a pond near your property, contact Bloomington’s Water Resources Manager Bryan Gruidl at 952-563-4557.