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Flooding Mitigation Projects 

 

Sewer Infiltration and Inflow Reduction

Extraneous water from infiltration and inflow (I/I) sources reduces the capacity and capability of sanitary, combined sewer systems, and treatment facilities to transport and treat domestic and industrial wastewater. I/I occurs when existing sewer lines and manholes undergo material and joint degradation and deterioration. The elimination of infiltration and inflow by sewer rehabilitation, operation and maintenance programs ensures protection in the investment in the sewer system. This initiative will reduce flow to the Wastewater Treatment Plant, combined sewer overflows and loading to the environment. Source control of I/I is the most cost effective method to limit extraneous flows and prolong large sewer replacement and expansion of treatment facilities and it is a key part of the Cornwall Blueprint.

Grand/Miron/Eleventh Street Sewer Project

Chronic flooding in the Grand / Miron / Eleventh area will be mitigated by a project which commenced in 2014 to construct deeper sewers on Eleventh, Grand and Miron and redirect sanitary flow to another drainage area where sufficient capacity can be developed. Specifically this includes: . removal of the old Guy St. sewage pumping station. . constructing a new deeper sanitary sewer on Eleventh St. and parts of Grand Ave. and Miron Ave. . constructing a new pumping station at Eleventh and Marlborough Streets with state-of-the-art monitoring and controls, backup power and a new forcemain on Marlborough St. from Eleventh to Sixth Street. . constructing a new storm sewer on Marlborough from Second to Eighth Street to remove existing storm sewer and catchbasin contributions from the combined sewer on Marlborough and provide capacity to accept the flow from Grand / Miron / Eleventh area.

This project was approved for $2 million in funding from the Provincial Municipal Infrastructure Fund, to assist with the $5 million total project cost, with approximately $1.7 million received to date and the balance expected in early 2016.

Drain and Ditch Maintenance

Sediment and debris removal and bottom reshaping of strategic open overland storm drainage systems; removal of sediment buildup from within box culverts and corrugated steel pipe culverts located within strategic overland storm drainage systems; removal of sediment and debris from large storm water sewers. To date, all overland storm drainage systems have been cleaned and reshaped.

Easton Avenue Sewer Inflow Reduction

As part of the Flood Reduction Initiative developed in response to storms in 2010 and 2013, flooding clusters were identified. Some areas required further investigation to establish appropriate mitigative measures. One such area is south of First St., east of Danis, where the sanitary sewer is prone to backup. Catchbasins in some low areas were found to be connected to the sanitary sewer. The proposed project will redirect these inflows, requiring a storm sewer in Easton Ave from Danis to Anthony, and in parts of Danis and Lefebvre. Approximately 18 catchbasins, along with associated runoff that is collected, will be redirected to the storm network, thus reducing loading in the sanitary network.

Christy/Dunkirk Flood Risk Reduction Project

Some higher risk areas required further investigation to establish appropriate measures to reduce potential for basement flooding. One such area is the vicinity of Christy and Dunkirk. Investigation determined that the sewer from the area to the north (Birmingham/Lascelle alignment) has high flows, exacerbated by stormwater inflow to the sanitary sewer. Storm sewer construction to intercept these flows is proposed for 2015. Future work includes redirecting flow directly to the Northern Trunk sewer (instead of through the Christy/Dunkirk area then to the Northern Trunk) by constructing a relief sewer on Lemay St. when this street is reconstructed.

Sewer Separation Projects

Separation of combined sewers has the objective of reducing wet weather flows in the sewage system and to the Waste Water Treatment Plant. It reduces the potential for basement flooding because flows are lowered in the pipe that houses are connected to. Separation also reduces Combined Sewer Overflow (CSO) volumes and the potential for bypasses from the Wastewater Treatment Plant to the St Lawrence River. It is achieved by constructing new storm sewers so that the combined sewer can be converted to sanitary. Projects are prioritized based on roadway surface condition so that sewer works can be done before resurfacing. Projects proposed for this year are; - Walton St. from McConnell to Guy - Surgenor St. from Boyd to Joyce

Boales Drain Culvert Replacement

The culvert crossing Boales Drain at the intersection of Cumberland Street and Emma Avenue was found to be deteriorated. If not replaced could affect the roadway over it, in addition to possibly obstructing flow in Boales Drain. Cumberland Street and Emma Avenue are both arterial streets and failure would have serious traffic disruption impacts. Boales Drian is a major drainage channel. The existing corrugated steel pipe culvert is to be replaced with a concrete box culvert.

Eamers Corners Stormwater Retention Pond

A stormwater retention pond is to be constructed on the south side of McKenzie Street, between Ross Avenue and Pitt Street, on land the City purchased some years previously. Work includes upgrade of the large culvert crossing Pitt Street at McKenzie. The pond's purpose is to balance runoff from Eamers Corners with the culvert crossing under Hwy 401 and into the South Branch of the Raisin River. Surface flooding at the south end of Eamers Corners is contributing to inflow and infiltration into the sanitary sewer. In past years construction of storm sewers and redirection of about 75% of foundation drains has reduced extraneous water from infiltration and inflow (I/I). This project will reduce potential for both surface flooding and stormwater contribution to the sanitary sewer.

Seventh Street Low Impact Development (LID) Stormwater Management

Reconstruction of Seventh Street East from Sydney Street to east of Amelia Street was identified as an opportunity to initiate a stormwater management demonstration project. Low Impact Development techniques are an effective way to transform the high volume, rapid response of impervious urban watersheds into something that is more consistent with a predevelopment environment. Primarily by means of vegetation topped bioswales that promote infiltration/groundwater recharge, runoff storage, and evapotranspiration, stormwater is attenuated and the total contribution to the sewer outlet is reduced. Because in this case the sewer outlet is a combined sewer, the reduced discharge helps to lower flows to the wastewater treatment plant and reduces risk of sewer overloading and potential for basement flooding. LID techniques can improve a community's visual environment as well, and have been successfully applied throughout North America. For more see http://water.epa.gov/polwaste/green/bbfs.cfm

Plan 240 (Grant's Subdivision) Stormwater Collection Improvements

Replacement/construction of new inlet structures to the Boales Drain within the limits of Plan 240 (west side of Brookdale Avenue, south of Tollgate Road) will enable surface runoff from a 1:100 year storm to enter the Boales Drain box culvert. This major storm drainage system was designed to convey the 1:100 year flood, and improvements in capturing runoff will reduce ponding and localized surface flooding which contributes to sewer inflow/infiltration. In addition, manhole covers deemed susceptible to inflow will be sealed, thus reducing stormwater contribution to the sewer system in an area severely impacted by rain events in 2010 and 2013.

Sewer Network Monitoring

To better understand the baseflow (dry weather) and storm response (wet weather) of sewer collection systems, 16 flow monitors have been installed at various locations within the trunk sewer network. Information on sewer flows is available in realtime, accessible through a web browser. Together with computer modeling, this is an integral component of assessment of future upgrades to infrastructure and understanding of impacts of future growth and development. It will help to identify mechanisms of sewer overloading which affect the various flooding clusters, and in turn permit optimal use of capital and other programs for I/I reduction and flood-proofing, as part of the Cornwall Blueprint. A dedicated weather station with data logger located at the Municipal Works administration building is part of the monitoring effort, to quantify the volume and duration of rainfall, and therefore be able to assess the impact of various rain events on sewer flows.

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