September 10, 2012

Windsor-Essex Parkway to enhance watercourses

RON STANG

correspondent

It may seem like a mammoth concrete project but water and natural habitat play a significant role in constructing the new $1.4 billion Windsor-Essex Parkway, which will connect Hwy. 401 to a new bridge to Detroit.

The 11 kilometre, mostly sunken six-lane freeway, along with service roads, will interrupt as many as nine legacy drains in west Windsor which flow partly through urban and semi-rural areas.

Some of these will have to be realigned as the highway will replace the existing watercourses.

Exacting attention, however, is being paid to not just protect the plant and fish habitats but to actually increase and enhance them. It’s all part of the state of the art construction guidelines where environmental sensitivity governs virtually all aspects of Parkway planning, to an extent likely not seen to date in highway construction anywhere else in Canada.

In addition to realigned drains the Parkway project requires seven storm water retention ponds and five pump stations, the latter to be constructed in an unobtrusive aesthetic manner.

More than 11,000 square metres of fish habitat are negatively affected by construction. That is due to channels being cut off from their downstream courses because culverts will become submerged, or new and extended culverts will be constructed, or the fact wholesale habitats will simply be displaced.

But this is all very temporary, say construction officials, because after the highway is completed fish habitat will have been expanded as much as threefold.

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Work has already begun on one the most extensive realignments. That’s the Wolfe Drain, located where the end of existing Hwy. 401 meets the start of Parkway construction.

More than 2,400 metres of watercourse are being realigned slightly to the east to make way for the Parkway. Protecting fish habitat is central to diversion construction guidelines.

“At no time will water management measures result in a barrier to fish passage for more than three consecutive days,” Parkway Infrastructure Constructors spokeswoman Cindy Prince says.

First, two fish conservation ponds are being built. As well, intake screens will prevent fish entrainment in areas like pump intakes.

Meanwhile constructing the drain diversions take account of factors like the water’s velocity, the drain gradient, the flow capacity, and erosion and sediment control.

The new drains are constructed in the dry. Flow diversion will take place mainly through berms and channels but also by work staging and temporary bypass measures including pumping so water flow can be maintained at all times.

Diversions are usually constructed open channel and in numerous segments with side slopes, and with culverts where necessary to carry water under temporary road closures.

All water will flow as it had, westerly towards the Detroit River where the Parkway will also end.

The new diversions’ bottom surfaces will be armoured to prevent scour and sediment disruption. As well, “Realigned drains match the existing elevation to keep water flow consistent,” Prince said.

Preparing the new watercourse requires lining with non-eroding geotextile material.

This provides a stable surface for water running in the same direction. Rip rap stone is then placed on top.

Exposed slopes are covered with erosion control blankets. Some are sodded with native species previously harvested from the Parkway’s excavated route, held in place by inert wooden and live stakes.

Besides diversions, an example of where the project will significantly improve a watercourse is Turkey Creek.

Years ago that part of the creek in urban Windsor had an artificial concrete bottom from where it linked to a wider trapezoidal cement flood control basin called the Grand Marais Drain, which the Parkway project will not alter.

Crews, however, are constructing a three box culvert to support the above roadway. (The City of Windsor is considering remaking Grand Marais Drain into a naturalized linear park.)

“What we plan to do is remove this concrete channel,” says Mark Ruthven, senior biologist for AMEC, an infrastructure and environmental design company contracted by Parkway construction management.

About 900 metres of concrete, about a third of a metre thick, will be broken up and removed, resulting in a natural stream which will “meander” from side to side within a wider flood plain, Ruthven said.

The improved watercourse will have alternating shallow and deeper areas and “provide habitat diversity so you can increase the value of that habitat to a variety of species of fish,” he said.

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