Water Treatment

Chromium Spill in Huron River Update

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Frequently Asked Questio​ns

1. What happe​​​ned?

​​​​Michigan Department of Environment, Great Lakes, and Energy (EGLE) was notified at 3:21 p.m. August 1 by Tribar that it had released several thousand gallons of a liquid containing 5% hexavalent chromium into the sewer system. The company says it discovered the release Monday but indicated it may have started as early as Saturday morning according to Wixom city officials. 

Testing of the Huron River has been ongoing and of more than 145 water samples collected throughout 42 river miles since the release, three came back with detections of hexavalent chromium – two detections in Milford’s Hubbell Pond and one in the middle of Kent Lake. The Kent Lake detection, completed by lab analysis – was 5 parts per billion (ppb) – just at the detectable limit of 5 ppb. The two Hubbell Pond detections were 11 and 9 parts per billion. All three were at or below values to protect aquatic life.​

View EGLE's Surface Water Sampling Results Map​

​​​2. What is ch​​romium?

Hexavalent chromium, or Chromium VI, is a carcinogen if inhaled and can result in an increased risk of lung cancer. Total chromium is regulated by the Safe Drinking Water Act and has a Maximum Contaminant Level in drinking water of 0.1 micrograms per liter (mg/l) or 100 parts per billion (ppb)​.

3. What about Ann Arbor's drin​​​king water?

The city’s water remains safe for all uses. Safety is our number one priority.

EGLE continues to collect and analyze samples from specific locations along the Huron River between the confluence of Norton Creek, the source of the spill, and Barton Pond.  EGLE News Release: Additional tests don't detect hexavalent chromium in Huron River​ System ​

4. What is the city doing to protect our drinking water? ​

City staff are doing the following:  ​

  1. ​We are continuing to sample our intake in Barton Pond.  Samples from this location have all been non detect for Chromium to date. Daily test results are posted at the top of this webpage. 
  2. We are evaluating treatment modifications to our treatment process to remove any chromium found in our water supply to safe levels that meet all Safe Drinking Water Act regulatory requirements. We also have the ability to optimize the use of our groundwater supply as source water for the water treatment plant which is not impacted by the Chromium spill. ​

​5. What agencies ​are involved in response efforts? 

The Michigan departments of Health and Human Services (MDHHS) and Environment, Great Lakes, and Energy (EGLE), and local health and government officials are working together in Monroe, Oakland, Livingston, Wayne and Washtenaw counties to address the situation.  

6. What is the​​ impact?

Currently, there are no recreational limitations in the Huron River for canoe liveries or recreation. On August 12, ​​​​​MDHHS lifted its recommendation for no contact with Huron River water after reviewing data related to Tribar toxic chemical release

Residents with questions about hexavalent chromium, potential health effects or exposures can call the MI Toxic Hotline at 800-648-6942, 8 a.m. to 5 p.m. Monday through Friday. ​​ ​

7. How will the city keep the public ​informed?

In order to keep our community informed, the city will post all information, agency news releases and analytical test data related to this spill on this webpage and promote updates via city communication channels. ​You may also subscribe to water quality email updates from the city​. ​

8. Is it possible to clean up or stop the flow of chromium before it could reach Ann Arbor? 

No. EGLE has not identified a means to stop the flow or migration of the contaminant.

9. If chromium is detected in the Ann Arbor water supply, what action will the city take? 

City staff have materials and are evaluating treatment process modifications that could be implemented to remove chromium.

10. Is it possible to remove Chromium with filtration, and if so, are filters installed in the City water treatment facility? 

Filtration is not the process that would remove chromium. Metal precipitation and settling would be the most effective treatment.​

11. Is there an alternative source of water identified that can be used instead of the Huron River? ​

The city has two water sources, the Huron River and wells at Steere Farm. The Steere Farm wells are not impacted by this event and can be used if the Huron River source were to be compromised.​

12. Should residents be stockpiling water?

No. The city's water is safe for all purposes.​  

13. Does the Water Treatment Plant observe a standard of 100 parts per billion (ppb) of overall chromium? 

Hexavalent chromium is not currently regulated at the state or federal level. The drinking water standard for total chromium is 100 ppb.

14. What is your sampling strategy for the Barton intake? 

Staff have been collecting samples daily at our intake in Barton Pond. Sample test results are posted on this webpage. 

15. What are the range of possible scenarios from best to worst case regarding this spill in the Huron River? 

The best-case scenario is that the chromium released never reaches the city's intake in Barton Pond at detectable levels. The detection levels for total chromium and hexavalent chromium are below health-based criteria, so non-detects would be protective of public health. The worst-case scenario is the chromium released reaches the city's intake at concentrations above the Safe Drinking Water Act maximum contaminant limit of 100 ppb. This scenario would require treatment. If it is determined that the city is not able to treat the surface water and meet Federal health-based regulatory limits, then we would rely on our well water sources until the plume passes the intake.

Supporting Documents

Upda​ted 8/​​16​/22​