Archived News Release: August 12, 2015 - At approximately 12:30 a.m. on Wednesday, August 12, 2015, an underground plant effluent water (PEW) pipe located in a recently excavated hole broke at the City of Ann Arbor Wastewater Treatment Plant. PEW is treated wastewater except for disinfection, which is the last treatment step before discharge to the Huron River. PEW leaked out of the pipe for approximately one hour, filling the excavated hole until an estimated 3,000 gallons overflowed and entered the plant's stormwater sewer system that discharges directly to the Huron River. Within 20 minutes of locating the leak, plant staff had completely shut off the portion of the PEW piping system that had broken.
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 hour over which the discharge occurred was approximately 8,000,000 gallons; consequently the estimated 3,000 gallons of PEW was diluted by a factor of 2,700. There are no communities downstream of the plant that withdraws water from the Huron River for drinking purposes. In addition, there is no direct-contact hazard for recreational river users, due to the dilution effects.
In accordance with regulatory protocols, the City of Ann Arbor Wastewater Treatment Plant 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, which prevented this situation from becoming any worse. Additionally, actions to avoid similar circumstances are being evaluated by plant staff.
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