Рецепт Report seems to counter Halifax Water on ‘daylighting’ Sawmill River

• An engineering report on replacing an aging Dartmouth culvert appears to challenge claims by Halifax Water and the municipality that unearthing the buried Sawmill River is too costly and complicated.
• The CBCL Ltd. report, obtained by The Chronicle Herald under a freedom of information request, examines options for replacing a half-kilometre long storm sewer that runs from Sullivans Pond to Dartmouth Cove.
• The 2.7-metre corrugated steel pipe was installed in the 1970s to bury the Sawmill River, the watershed of four Dartmouth lakes, after torrential rains caused the river to breach its banks and flood a large swath of the city.
• With the rusting underground tunnel in need of replacement, calls for “daylighting” the river — uncovering the underground river — have grown louder.
• CSP culvert
• corrugated steel pipe
• structural plate
• The 361-page CBCL report delves into multiple options for replacing the pipe and settles on both a box culvert and an open channel.
• This is recommended as the “lower-cost, least-risk and most technically viable solution,” the report said, adding that it also has “a lower project life-cycle cost and the shortest construction schedule.”
• The old steel pipe would be replaced with a roughly four metre-by-four metre box culvert — significantly larger than the existing steel pipe to accommodate increasing storm surges and sea-level rise — and include a fish passage from the harbour to Irishtown Road.
• From there, the Sawmill River would once again become an open “daylighted” channel to Sullivans Pond, with needed bridges along the way.
• The total project would come with a price tag just under million.
• Although the 0,000 CBCL report was finalized in July, Halifax Water has had a draft copy of the CBCL findings since last April.
• Yet the utility has repeatedly dismissed daylighting Sawmill River as too costly and fraught with challenges.
• “The most cost-effective solution for conveying the stormwater remains that oversized culvert,” Halifax Water engineer Jamie Hannam said in March.
• Hannam admitted that “open streams do have some benefit to fish passage,” but he said the utility was working on other “engineered solutions” to provide fish passage within the culvert.
• Halifax Water spokeswoman James Campbell clarified Friday that the utility has always been on board with an open channel.
• “I think there seems to be some confusion with daylighting,” Campbell said. “There is a distinction between a naturalized daylighted channel and an engineered open channel.
• “What we’re proposing is an engineered open channel, which is also what CBCL is recommending.”
• Indeed, the consultant’s report delves into the various degrees of daylighting.
• “Creating an open channel to convey a previously buried watercourse is commonly referred to as ‘daylighting,’” the report said. “Daylighted streams have varying characteristics that depend on the site and can range from a fully naturalized waterway that allows for a wide range of restored ecosystem functions to a pipe or box culvert with its top removed.”
• Campbell said the problem with fully restoring Sawmill River is that it would require a 34-metre span for trees and proper sloping. Halifax Water only has a 15-metre easement.
• “It would basically be a three-sided concrete structure with an open top that may or may not have some sort of fence or grated structure over the top for safety reasons,” Campbell said.
• He said the utility’s mandate is to provide water, waste-water and stormwater service at the best cost to ratepayers and that anything above and beyond that — such as bankrolling the creation of a naturalized daylighted river — wouldn’t get a stamp of approval from the regulator.
• Efforts by The Chronicle Herald to obtain internal emails and documents from Halifax Water related to the CBCL report and replacing the storm sewer hit a roadblock.
• In response to a freedom of information request, Carl Yates, the utility’s general manager, said compiling the large volume of records would cost about ,550 — an hour for 44 hours of work, plus {cbq:ncontent}.20 each for 1,000 photocopies.
• Proponents say restoring Sawmill River to its natural state would offer local residents an urban oasis in a rapidly growing area of Dartmouth, improving quality of life and creating recreational opportunities.
• Although an engineered open channel would fall short of these ambitions, it would still give fish a better chance of surviving the trip from the ocean to the lakes.
• Unlike in the 1970s, when the underground pipe was first installed, Fisheries and Oceans Canada requires passage for migratory fish that go between salt water and fresh water. In Sawmill River, that once included Atlantic salmon, gaspereau, American eel and sea-run trout.
• The CBCL report said the option of a mix between a box culvert with fish passage and an open channel “was the most favoured” by Fisheries and Oceans.
• Jocelyne Rankin, Ecology Action Centre’s water co-ordinator and an advocate for daylighting Sawmill River, said the CBCL report is extremely detailed and thorough.
• She said it covered off many questions related to unearthing Sawmill River, including costs, design, engineering, geology, fish passage, archeology and history.
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