Due to the landscape of the Red Hill Valley, many considerations had to be made to prevent the roadway from flooding. The following are some of the measures undertaken to deal with flooding and to protect the waters from potential contaminates.
*Based on information from Philips Engineering.
Ancient creek beds provide design for new creek
The route through the valley that the Red Hill Creek followed from the upper escarpment to Lake Ontario changed several times over hundreds of years. One of these ancient creek beds called paleo channels waschosen for the new alignment of the creek. The fill excavated from the paleo channel was used dto fill the pre-2006 creek bed. Management of run off water allows for storing water for irrigation on the King’s Forest Golf Course.
In 2005/06 Red Hill Creek was moved to this ancient creek bed or paleo channel to provide a shaded alignment with stable banks. “Sod Mats” from the flood plain were used to construct the banks and local grasses and shrubs weighing several tons were lifted and placed here. This provided immediate stability to the slopes and minimized the environmental disruption to the valley.
Aesthetic and Functional form of Stormwater Management
Snowmelt and rainfall runoff of the expressway may contain debris and fine particle contaminants from the hard surface. To allow for these to settle out of the runoff, series of small holding basins or ponds were integrated in the valley taking advantage of the natural setting and topography.
The pond at the escarpment bridge is an example of careful placement to protect the valley from flooding, erosion, and water quality impacts.
How to construct a roadway in a valley and protect it from flooding
The large volume of runoff flowing through the valley comes from over 65sq. kilometers which is more than 70% developed with surfaces that shed water rather than absorb it. An innovative engineering solution was called for to manage this water and prevent major flooding and erosion which had been a constant occurrence in the valley. Construction of three strategically located flood control stormwater management systems Dartnall, Greenhill, and Davis, solved the problem by using the natural valley for storage upstream of the QEW.
At the Greenhill flood control site, a low flow channel carries day-to-day water along with small storms and the sediment in the water without any ponding. During bigger storms the “sediment-moving-stream” breaches its banks by using the new expressway embankment as a dam. This reduces the rate of flood that flows downstream and protects the road from flooding.
The Davis Creek Flood Control facility like the Greenhill facility upstream is part of the engineering design to manage the runoff of over 65 sq. kilometers which flow through the Red Hill Valley. The new design uses smaller sized box culverts to control flood water and protect local properties from flooding. It allows for fish and wildlife movement through the valley and moves sediment downstream. In a 100 year storm, a large volume of water equal to … swimming pools is held back reducing downstream flow rates.
Combined Sewer overflow Extension
In the early twentieth century accepted practice had municipal storm and sanitary sewers combined carrying wastes to the sewage treatment plant. During storms, strategically placed relief points called overflows discharged sanitary sewage and stormwater directly to our creek and lakes. The impact of the sewage was diluted by the storm runoff. Over time we have become increasingly aware of the environmental damage of these combined sewer overflows (CSO). The innovative solution used here in the Red Hill Valley collects excess combined sewage in tanks to prevent it from discharging into the creek in all but the worst storms and sends it to the sewage treatment plant after the storm. This solution, while costly to build and maintain, is still more economical than physically separating the sewer network. Before you is the Greenhill CSO-2 tanks serving…homes reducing overflows from 25 per year to 2 per year. The rainfall which used to discharge upstream of this point has been extended under the new channel to its new location.
Before the Red Hill Creek Valley project, there were several major outfalls of combined sewage. As well, a … m diameter sewer flowed along the valley to the treatment plant. Now a … km long and … m diameter pipe extending from King St. to Rennie Street holds overflow during all but the largest storms predicted to be twice a year. In front of you is one of the three outfalls which overflow when the tunnel’s storage capacity is reached.
Unique area combines many functions
This remnant creek area cut off the alignment of the expressway is a vital part of flood management in the valley. It now contains a small stormwater management area for runoff from the expressway and from the surrounding urban area of … homes. It also contains a new stable creek reach to carry controlled floodwaters from upstream.
Retrofit Stormwater Management Facilities provide a zero-net impact to Hamilton Harbour
The current practice of stormwater management design removes 80% of the sediment and contaminants from runoff in urban areas from rainfall and snowmelt. The goal for the Hamilton Harbour and Windermere Basin was to remove 100% of the sediment and contaminants entering from the Red Hill Creek Valley.
The Queenston Road facility receives runoff from … homes. It stores water and removes … kg of sediment each year. The end result is that the Red Hill Valley runoff does not cause any negative impacts to the Harbour and in fact contributes fewer contaminants than before Expressway construction.
The Barton St. Stormwater Management Area Remedial Action Plan developed by the federal and provincial agencies and stakeholders called for 100% effective stormwater management for the Harbour and Windemere Basin. This Barton Street facility is part of engineering design to meet that goal. The … m diameter drain and larger pond remove … kg of sediment per year. The end result is that the harbour contains fewer contaminants than before construction of the expressway.
Rebuilt floodplain enhances watercourse and reduces land fill waste
This area was re-engineered to remove landfill waste dumped here in the flood plain at the turn of the nineteenth century and to prevent flooding of the new expressway. A carefully designed “Landfill Bridge” was built to allow flood water to access the floodplain without flooding the Expressway.
Wetland Enhancement Project
Van Wagner’s marsh north of the QEW and the Red Hill marsh south of the QEW are remnants of the extensive wetlands and marshes that were once found here. Significant amounts of earth fill were needed to construct the QEW Expressway interchange. Collaboration between ecologists and engineers led to this unique solution – the necessary materials were found on site and … truck loads of fill were excavated and were taken for the interchange. The resulting excavated area became a wetland supplied with water from the Red Hill Creek and backwater from Lake Ontario via Hamilton Harbour.