This press release from the City of Ann Arbor was sent to news media on June 28, 2013. As far as I can tell, AnnArbor.com did not run a story. The Ann Arbor Chronicle did publish information about this discharge as part of its meeting reporting for the July 15, 2013 city council meeting.
UPDATE: AnnArbor.com story of July 19, 2013 is up now.
ANN ARBOR, Mich., June 28, 2013 — On Thursday, June 27, 2013, the Ann Arbor area was deluged with intense rainfall that caused flooding conditions and significantly increased the flow of wastewater to the City of Ann Arbor Wastewater Treatment Plant (WWTP) over a short period of time. Plant flows more than tripled within a half hour. As a result of this unprecedented increase in plant flow, approximately 10,000 gallons of untreated wastewater was discharged to the Huron River from 5:20 to 5:30 p.m. By comparison, the WWTP fully treated approximately 350,000 gallons of wastewater during the 10-minute period over which this incident occurred.
Fortunately, due to a number of factors, the impact of this incident on human health and the environment is minimal. The flow within the Huron River for the 10 minutes over which the discharge occurred was approximately 11,000,000 gallons, consequently the estimated 10,000 gallons of untreated wastewater was diluted by a factor of 1,000. Further, mesh filters were already in place over the storm sewer inlets as part of the ongoing major construction project at the plant, which prevented solid material from entering the Huron River. There are no communities downstream of the plant that withdraw water from the Huron River for drinking purposes. In addition, the fact that the discharges occurred during extreme rain conditions makes it very unlikely that direct human contact would have occurred, particularly with the significant and immediate dilution of the discharge by the relatively high river flow.
In accordance with regulatory protocols, the City of Ann Arbor WWTP contacted the Michigan Department of Environmental Quality and the Washtenaw County Health Department to inform them of this unfortunate incident. Plant staff is commended for demonstrating clear thinking and fast action under extreme conditions, which prevented this situation from being much worse. Additionally, actions to avoid similar circumstances are being evaluated by plant staff.
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