News: Sawmill River Daylighting Phase 1

Sawmill River Outfall. Photo: Metro

It’s easy to miss since it’s an Information Item on this week’s Regional Council agenda and not a report that is up for discussion, but there is an update on the Sawmill River project (aka the Sullivan’s Pond Stormwater Renewal). Work will be getting underway this summer! Halifax Water will also be hosting a public meeting in Downtown Dartmouth in the next few weeks to explain the project and answer questions in more detail so stay tuned.

A Primer:

For those who haven’t followed the Sawmill River saga, here’s a quick primer. The Sawmill River flows from Sullivan’s Pond to Dartmouth Cove. The River played a big part in Dartmouth’s development and it’s historically quite important. It was a Mi’kmaq canoe route, a piece of the Shubienacadie Canal, and a source of power for industry, notably the Starr Manufacturing Plant. The Sawmill River was buried undergound in pipes by the City of Dartmouth after Hurricane Beth caused flooding in 1971. Burying urban waterways had been standard practice for decades and Dartmouth’s decision, although coming near the end of the “bury them” era, wasn’t an unusual response.

Since the 1970s we’ve come to recognize that there are better ways to manage stormwater and now cities around the world are daylighting and restoring their forgotten waterways. Daylighting could be a very positive thing for Dartmouth. It could significantly improve the aquatic environment in Lake Banook and Lake MicMac, enhance park space Downtown, and improve our ability to manage stormwater. The time to daylight is now because the 1970s pipes need to be replaced. They are old and are now undersized to handle a Hurricane Beth style event because of all development that has occurred in the watershed since the 1970s. Daylighting would also save money in the long-run because maintaining and eventually replacing underground pipes is expensive.

The Plan:

After some initial reluctance from Halifax Water and HRM, the utility and municipality are now fully engaged in replacing the existing underground pipes with a new system that includes daylighting in several places. The overall project cost for Phase 1 is $9.6 million with $6.3 million coming from the federal governments’s Clean Water and Wastewater Fund. To get the federal funds though, the work must be complete by the end of March 2018. Phase 1 is happening this summer!

Phase 1 will stretch from the bottom of the Lock 4 Condominium by Irishtown Road up to Sullivan’s Pond. Though the pipe route and project construction falls within Halifax Water’s easement, it’s not an easy area to work in. The route is fairly constrained because Halifax Water’s easement crosses private property (Lock 4) and Ochterloney Street. Since the Sawmill River drains a sizable watershed, the daylighted channel needs to be big enough and sturdy enough to carry a large volume of water. So it’s going to be a very engineered environment. Fish passage is mandated by DFO and will be included throughout meaning that when both Phase 1 and 2 are complete, Gasperau (Alewifes), Sea Trout, Eels and, possibly, Atlantic Salmon will be able to once again swim up to Sullivan’s Pond.

Phase 1. Sullivan’s Pond and areas of daylighted water are in blue, Sullivan’s Pond Park and the Canal Greenway in green.

In Sullivan’s Pond Park there will be some significant changes around the existing dam. The dam will be removed and a waterway will take its place extending down towards Ochterloney. A pedestrian bridge will be installed to maintain the existing pathway around the Pond. A significant fish ladder will be built to allow fish to get to the Pond and it will pass under the new bridge. The work at Sullivan’s Pond is the piece I’m most excited about in Phase 1. The new pedestrian bridge will be a scenic addition to the Park. I can imagine too that the stepped fish ladder will be quite a sight whenever it rains hard enough for the water to overtop the fish baffles and create a cascade of whitewater. Good spot also to watch the fish coming up stream once Phase 2 of the project is complete in the years ahead (potentially 100,000s of Gasperau each spring).

The other section of daylighting that will be very publicly visible is in the Canal Greenway Park behind the old houses on Ochterloney Street that are being used as commercial spaces. Daylighting will be integrated into the park by allowing for a natural flood plain on the Park side up to the boundary of the Lock 4 property. When the River isn’t in flood, you’ll be able to walk down to be almost level with the channel.

Through the Lock 4 property, the Sawmill River will be either underground or grated over. It will flow out and rejoin the old pipe below Lock 4 and there will be a small pond at the transition point. The pond and its boundaries are a bit of a temporary feature because what happens in Phase 2 and what water features exist in the lower section is currently unknown.

Phase 2 and Beyond:

Phase 2 of the Sawmill River project will involve replacing the last section of 1970s pipe from Irishtown Road to the Harbour. Planning for Phase 2 hasn’t been completed yet because HRM is currently looking at how traffic flows through the Alderney Drive, Portland Street and Prince Albert Road intersection and how people will in the future access a redeveloped Dartmouth Cove. I believe the existing road network around the intersection is overbuilt given that most of the capacity feeding into it is a single-lane in either direction on Portland Street. If traffic modelling bears this out, there is an opportunity to reclaim space that could be used for further daylighting and to connect the Harbour Trail to Sullivan’s Pond via the Canal Greenway. There is still a fair bit of work needed to determine what is feasible in this space and until HRM determines what its road needs are, Halifax Water can’t proceed with Phase 2.

Once Phase 1 and Phase 2 are complete, a smaller project will also be needed to fix the Hawthorne Street culverts and build a fish passage in the existing overflow spillway at the lock in Findlay Park. Compared to Phase 1 and Phase 2 of Halifax Water’s project, fixing the Lock and Hawthorne Street’s culverts is a small and relatively uncomplicated challenge. It’s still very important though because fish won’t be able to get beyond Sullivan’s Pond without addressing the Lake Banook end of the Pond.

Stay tuned for more information about the upcoming public meeting.

 

3 Comments

  1. Hi Sam:
    I’m concerned that the aquatic environment in Sullivan’s pond may hurt the fish that migrate there. If so, we could stop them temporarily before the pond, until the ladder to Banook is complete allowing full access to the lake.
    Has the condition of the pond been examined relative to this?

    • Hi Mark. It’s something to think about in terms of phasing the project. The last thing I would want would be all those Gasperau coming up an expiring in the Pond because there is no where for them to go. When Phase 1 of the project is done at the end of March, fish won’t be able to get to the Pond. That will only be possible when Phase 2 is complete. Since Phase 2 is likely a few years off yet, there is plenty of time to figure out the Hawthorne end. Ideally, Phase 2 and the connection to Banook would be finished in the same season.

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