Work on Avon River's water gate could start this fall as part of 101 twinning

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The province is working on a design for a new causeway and aboiteau for Highway 101 in Windsor, N.S. (Paul Palmeter/CBC - image credit)
The province is working on a design for a new causeway and aboiteau for Highway 101 in Windsor, N.S. (Paul Palmeter/CBC - image credit)

Nova Scotia says it expects to have the Avon River aboiteau project ready for construction this year, though it still hasn't shared details of its plan with the public.

The provincial Transportation Department is working on designs to replace the causeway through the Avon River in Windsor, N.S., as part of its Highway 101 twinning project. The causeway will include a structural element that will allow fish to pass through.

The department submitted its application for the aboiteau — an opening that allows water to flow through the causeway — to the Department of Fisheries and Ocean on Nov. 5, 2020. In March, DFO requested additional work, saying the proposed design did not allow sufficient fish passage.

A spokesperson for the Transportation Department said pending regulatory approval, the project will be ready for construction later this fall, and will take about two years to complete. That will allow the twinned highway to be open to traffic by fall 2023, they said.

Paul Palmeter/CBC
Paul Palmeter/CBC

But the province is tight-lipped about the plans for the aboiteau — an issue of concern to many who rely on the Avon River and nearby water bodies for fishing, farming and recreation.

In March this year, federal Fisheries Minister Bernadette Jordan issued a ministerial order requiring the tidal gates at the existing causeway be operated in a way that improves fish passage. The order says the gates must be fully opened during outgoing and incoming tides to allow a minimum of 10 minutes of salt water from the Bay of Fundy to enter the lake upstream.

For some, the priority is to allow fish to pass through the area easily. Others are concerned that improving fish passage will allow the salty Bay of Fundy water to inundate the freshwater area on the other side of the causeway, increasing salinity levels in water that's used to irrigate crops and feed livestock.

Opening the gates to allow more water flow has also lowered the water level in Lake Pisiquid, which is used by a local paddling club. This summer, the lake dried up entirely, creating dust storms that bother some residents.

How will the aboiteau work?

The Transportation Department has not said much about its plans for the aboiteau.

A spokesperson has told CBC the option put forward to DFO would have multiple fishways to optimize passage, would allow fishways and tidal gates to be closed in the event of extreme tides or storm surges, and also provide flood protection for the twinned highway and the area upstream from the causeway.

Asked for more details, the spokesperson would only say the initial application to Fisheries and Oceans was based on a freshwater operating scenario, but that the federal department requested more information about other options, called the brackish lake option and the dampened tidal exchange options.

Some information about those options is contained in a PowerPoint presentation from October 2020.

Province of Nova Scotia
Province of Nova Scotia

In the document, the freshwater option is described as allowing the lake level to be maintained, eliminating tidal influx, closing the fish passage during high tides and limiting fish passage during dry periods. That option would allow more freshwater habitat and a stable ecology, but would lower water quality during warmer months.

The brackish lake option would maintain the lake level, keep the fishways open almost all the time, allow a tide of about half a metre in the lake, and permit some sediment and salinity into the lake. That option would create a more natural or dynamic ecosystem, with 25 per cent less freshwater habitat, the document says. The gates would allow for control of tidal flow and salinity and sediment in the lake.

The dampened tidal estuary option would keep fishways open almost always, reduce the tidal range in the lake, create a brackish environment with mudflats and salt marsh and allow some sediment and salinity into the lake. That option would allow the gates to be controlled to protect against flooding and adjust the tidal range and salinity and sediment.

The province's latest proposal would allow for all three scenarios, a spokesperson said.

Next steps

DFO says it is waiting for the additional information it requested from the province. Although there is no deadline for the province to submit it, the project cannot proceed until it is submitted.

DFO must ensure the proposal adheres to the Fisheries Act and the Species at Risk Act. Those laws require that, wherever possible, fish are not blocked from accessing their natural habitats by human-made infrastructure.

DFO says in the past few months, gaspereau and other species have returned to their natural habitat on the Avon River.

The province says it will submit the information to DFO once it's ready.

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