001-40_WC_144_SEPT-OCT25_PT - Flipbook - Page 22
April. Workers used a floating ‘amphibious’ excavator equipped with pontoons
and leg-like stabilizers to dig a shallow
trench into the St. Lawrence and remove
a 180-metre-long portion of buried pipe
that bypasses the beach, a boardwalk
and multiple sand dunes on its trek into
deeper water, and replace it with a newly
built section.
While the pipe sits underneath the
ocean floor, with two upright risers at the
far end to diffuse the treated effluent into
the St. Lawrence, its burial was shallow
enough to warrant trenching rather than
tunnelling. “There’s about a metre and a
half of material over the pipe,” says Sean
MacDonald, who oversaw the outfall
work as the county’s director of capital
construction. The process of trenching
and installing the pipe took just three
days. MacDonald says the excavator was
equipped with GPS positioning software,
and the operator could see the alignment
of the pipe on a screen and know factors
such as depth at all times. On dry land
behind the beach and dunes, meanwhile,
the new 400 millimetre high-density
Inverness County, Nova Scotia.
polyethylene pipe was attached to older
pipe that has remained in good condition over the years, and the two sections
were made watertight with a sealant near
the last on-shore manhole.
“Continuous昀氀owinstallationshaveuntreatedin昀氀uentwastewater
While the outfall component was
completed quickly enough, there were
enteringthetankduringall昀椀vestepsofthetreatmentcycle,with
constraints. “We had a pretty tight
ba昀툀estocontrolthe昀氀owinordertoreduceshort-circuiting.”
weather window,” Lauren MacDonnell
says, noting a few brief postponements
due to high winds and wavy conditions.
“The offshore work is very dependent
on the wave conditions, but the next window we would have
installations have untreated influent wastewater entering the tank
had to do that work would have been in the fall, and by that
during all five steps of the treatment cycle, with baffles to control
point you’re into hurricane season. So it was definitely tight, but
the flow in order to reduce short-circuiting.
everything worked out.”
Crews have also started masonry work on a new process buildCrews also had to protect wildlife. The piping plover is protecting, installed roofing, and begun placing working components
ed in Nova Scotia, and its nesting season begins in mid-April and
and equipment inside. “Currently, the UV disinfection system is
lasts well into August, so most of the heavy lifting was done in the
outside in an enclosed structure, but it is susceptible to freezing,”
first half of April. “Everything was carefully planned,” MacDonMacDonnell explains. “The new system will be inside the process
nell says, noting extensive consultations and planning with the
building to mitigate against that.”
project engineering and environmental consultant, CBCL. “The
While the project is largely in its initial stages, the outfall that
permit we received from DFO (Fisheries and Oceans Canada)
conveys treated wastewater into the Gulf of St. Lawrence was very
included mitigation methods used during construction to protect
quickly repaired during a three-week construction spree in early
22
WATER C AN ADA • SEP TEMBER/OCTOBER 2025
WAT E R C A N A D A . N E T
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