Overflow from the city’s sanitary sewer system was discharged into the Huron River – the result of a clog in the system caused by tree roots in the Nichols Arboretum, according to a city of Ann Arbor press release. [.pdf of city press release] The situation was reported on Thursday afternoon, Aug. 29, when “a sewer odor and some gray pooled water” was reported to the city, flowing overland into the river. The sewer was unclogged later that evening, and a city crew applied lime – a white powdery substance – to the ground to kill bacteria.
In addition, city of Ann Arbor canoe livery trips between Argo and Gallup were halted on Thursday through Friday. Water samples will be taken to determine water quality, and a decision about whether to re-open canoe livery operations will be made by 8 a.m. on Saturday, Aug. 31, according to the city.
The city also has contacted the Michigan Dept. of Environmental Quality about this situation, in compliance with regulatory requirements.
There is no indication of how much volume was discharged into the river.
The city had reported a previous incident this summer that occurred on June 27, 2013, when heavy rains briefly overwhelmed the city’s sanitary sewage system and resulted in 10,000 gallons of untreated sewage flowing into the Huron River. The city has separate sanitary and stormwater sewer systems, but the sanitary system receives stormwater flow from cracks in the system as well as footing drains that were connected to the sanitary system as part of standard construction techniques in the 1970s. Incidents like the one on June 27 led to the creating of the city’s footing drain disconnection (FDD) program in the early 2000s. Parts of that FDD program are currently suspended as the city is conducting a study of wet weather flows in the sanitary system.
Updated: The liveries were re-opened, as of 8 a.m , Saturday Aug. 31, 2013 according to city of Ann Arbor staff.