Canadian Consulting Engineer

Montreal told to use booms to contain sewage on St. Lawrence

November 10, 2015

Federal government's expert panel report recommends mitigation measures for containing sewage release into the St. Lawrence.

Montreal is set to move ahead with releasing large volumes of untreated sewage into the St. Lawrence River on Wednesday. Canada’s new federal government has granted permission to the City of Montreal, but with four main conditions.
The sewage has to be released to allow repairs to a major interceptor and to allow construction work to proceed on the Bonaventure Expressway where a snow chute is located. The interceptor is scheduled to be closed for a week, requiring an estimated 8 billion litres of wastewater to be diverted untreated into the river. The interceptor was due to be closed on October 18,  but in the days just before the election the federal government called a halt and asked an independent panel to report on the situation.
The expert panel consisted of Daniel Cyr, a professor at the Institut National de la Recherche Scientifique (INRS-IAF), Robert Hausler, a professor in the Department of Construction Engineering at the Écoles des Technologies Supérieures (ETS), and Viviane Yargeau, a professor in the Chemical Engineering Department at McGill University.
Based on their report, on November 9 the new Minister of the Environment and Climate Change, Catherine McKenna, issued the conditions for allowing the release.
The city has to do visual surveillance of the effluent plume and if necessary deploy floating booms or other measures to contain sewage matter that has resurfaced and accumulated. The city must then take action to clean up the mess.
In case there are any unanticipated releases into the sewage system from large industrial facilities, or institutional or commercial facilities during the construction period, the city must have a management plan in place.
It also has to monitor and provide data to Environment Canada on the water and effluent quality, and on the sediments and flora at the outfalls and other selected points downstream. This monitoring must continue until next June.
The report  said that the city must take part in a review of the events leading to the need for the release, to ensure that such a discharge does not reoccur in the future. The review will be led by the federal Department of the Environment and Climate Change and will include neighbouring First Nations and the Province of Quebec.
The expert panel report mentions that the city had originally considered 15 different options, but most of these had been dropped. They concluded, however, that there were three measures that the city should make every effort to implement, with the support of all levels of government: “The first measure (No. 14) consists of using a tanker ship with an inverted siphon. The use of that measure for one of the main discharge points should be reconsidered. The second (combination of measures No. 5 and No. 8) consists of a better monitoring of the plume discharged beyond the shores of the Island of Montréal, associated with an emergency plan for cleaning up the matters discharged, particularly near the Sorel islands. The third measure (No. 11) is to use a mobile treatment unit by targeting a potentially toxic discharge into the sewer, such as the McGill University Health Centre, another hospital, or even an industry.”
The report continues: “All suggestions and improvements presented should be seriously considered for longer-term improvements to mitigation measures for future discharges of wastewater during maintenance on interceptors. Moreover, the proposed measures could be tested on overflow (wastewater diluted by rain when the maximum flow at the treatment plant is reached). The information and data acquired would help in documenting the effectiveness of these measures. This information could be distributed around the world and demonstrate leadership as an environmentally responsible city.”
To read the entire expert panel’s report, dated October 30, click here.
To see an article in CTV News, click here.



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