
September 1, 2017 · 0 Comments
Written by Tom Claridge
In the wake of serious flooding of streets earlier this summer, Orangeville’s Public Works director says his staff will look at the potential need for upgrades aimed at reducing infiltration of sanitary sewer lines and increasing the carrying capacity of at least two culverts.
Doug Jones told the Citizen Monday that rainfall from multiple thunderstorms on June 23 caused so much infiltration of sewer lines that the town’s sewage treatment plant couldn’t cope with the flow and raw sewage flowed into the Credit River for eight hours.
During the same storm, culverts on Centre Street and Dawson Road couldn’t handle the flow from Mill Creek and at times the water was over the railway tracks as well as the two streets.
Mr. Jones said the June 23 storm and a shorter one on August 1 also caused major flooding on East Broadway and Townline but he doubted that was because of the lack of bridges similar to those at John, Mill and Wellington streets.
Although the culvert under Townline didn’t have the carrying capacity of the bridges, he said a similar bridge at Townline wouldn’t have helped, because “the whole area there is a flood plain.”
The Public Works director said nothing currently planned will have any immediate impact on the Town’s budget, but his staff will be working with conservation authorities and provincial officials to determine what, if anything, should be done.
He explained that while Orangeville, unlike Toronto, has no combined sewers (designed to carry both storm and waste water), infiltration can become a serious problem.
Other factors he said will have to be taken into consideration are climate change, which could cause more frequent major storms, and the impact of urbanization. It is well known that new housing subdivisions with their sidewalks, asphalt streets and high population densities will not absorb rain as well as open fields.
Mr. Jones said the two storms were quite different, in that the rainfall on June 23 continued so long that the entire local watershed was affected, while the August 1 deluge was comparatively short-lived, with most of the flooding on East Broadway.
He said bridges and culverts in town are designed to cope with the worst storms expected within 10 to 20 years, whereas provincial highways have bridge designs that should prevent any risk of flooding.
“In my 15 years here we’ve had no previous flooding on Dawson or Centre.”
He said it also should be realized that 2017 has been anomalous, with more than the usual rainfall all spring and summer. The two flooding incidents came at a time when the ground was already saturated.
“I think that what we’ll need to do now is look at more risk management.”
“In my 15 years here we’ve had no previous flooding on Dawson or Centre.”
He said it also should be realized that 2017 has been anomalous, with more than the usual rainfall all spring and summer. The two flooding incidents came at a time when the ground was already saturated. “I think that what we’ll need to do now is look at more risk management.”
Mr. Jones said the infiltration of the town’s sewer lines occurs from a combination of circumstances, including leakage in manhole covers, leaky pipes and in the case of some older homes, diversion of water by sump pumps. In the 48 hours between June 22 and 24 the flow of waste water into the treatment plant was about 70,000 cubic metres, compared with an average daily intake of 11,000 to 12,000 cubic metres.
While the treatment plant has a nominal capacity of 40,000 cubic metres a day, the June storm occurred when construction work had left some of its facilities unavailable. The planned infiltration study will include checking out more than 1,000 manholes involved in the town’s 150 kilometres of sanitary sewer pipes.