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Diffuser ready to be installed Work underway for underwater sewer repairs in Rankin
Darrell Greer
Northern News Services
Published Wednesday, August 21, 2013
RANKIN INLET
A team of divers were preparing to make repairs to the final point of the community's sewage-treatment system in Rankin Inlet this past week.
Boat captain Harry Ittinuar and divers Donnavan Meierhofer and David Black, from left, listen to final instructions on the day's dive before conducting preliminary work to repair the outfall sewer in Rankin Inlet this past week. - Darrell Greer/NNSL photo |
Foreshore Technologies has been retained by the Government of Nunavut to repair Rankin's outfall sewer.
An outfall is the discharge point of a waste stream into a body of water.
The diver trio of Donnavan Meierhofer, Mark Thompson and David Black were out for preliminary dives on the project this past week.
Project manager Dominic Gerelle said the company is replacing the system's waste-water diffuser, which was found torn away from the outfall during an inspection this past year.
He said a new concrete diffuser is being assembled by Inukshuk Contracting Ltd. and will likely be installed in two weeks time.
"Rankin's outfall for its sewage treatment runs about 300 to 400 metres out into the bay," Gerelle said. "A concrete block is normally at the end of the pipe, with three trumpet-like extensions to help spread the effluent coming out of the outfall.
"It's preferable to have it spread out from three different openings, rather than a single opening."
Gerelle said at times there will be two divers in the water at once, while at others one diver will be underwater with a line to the surface.
He said the divers are in the water for a maximum of 35 to 45 minutes at any one time.
"They'll come out then to either change their tanks or go over the next stage of the project," he said. "There's a lot of little stages that make up the entire job, so you're not in the water for three or four hours at a time.
"It would be pretty cold to have to do that here."
Gerelle said in theory, a diffuser should never have to be replaced.
He said the original Rankin diffuser weighed somewhere between 3.6 and 4.1 metric tonnes.
For the diffuser to come lose, Gerelle suspects at some point, a ship dropped anchor near it.
"It would have been a fairly big ship and, in the process of retrieving its anchor, it ripped the diffuser right off the end of the pipe."
A barge has been fabricated to help deploy the diffuser once it is completed.
It will be suspended below a work platform and lowered into place where the new diffuser will be placed.
Gerelle said there will be about 7.5 to 8.5 metres between the existing pipe and the new diffuser.
He said a section of pipe will be added to connect the diffuser to the old pipe with two couplings.
"It's a risky job, but everything's done step-by-step and discussed well in advance," he said. "If anything changes, we stop and reassess the situation so everyone knows exactly what they're going to be doing."
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