A tunnel is being drilled seven metres below Sixth Avenue W. (Alison Sandstrom/paNOW Staff)

By Alison Sandstrom

New Sewer

Key section of $3.8 million infrastructure project nearly complete

Jul 30, 2020 | 8:00 AM

The most complex piece of Prince Albert’s largest summer construction project this year is expected to be complete by the end of next week.

Until then, the intersection of 18^th Street W. and Sixth Avenue W. is a hive of activity, with a dozen workers and around $2 million worth of machines, including three excavators, a wheel loader and a remote-controlled trench packer.

While most of the $3.8 million West Hill trunk sewer main can be installed by digging a trench and placing the pipe inside, a different approach is needed for this 70-metre section.

Stage one of the new sewer trunk main is essential for future growth in both the West Hill and West Flat. (Agenda Package/City of P.A.)

“This intersection is congested with water mains, gas mains, sewer, storm trunk infrastructure,” capital projects manager for the City of Prince Albert, Nykol Miller, told paNOW.

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She explained in order to avoid the web of existing pipes, crews with Kelsey Pipeline Ltd. are tunneling below them, digging seven metres under Sixth Avenue W.

Steel casings (4 ft 6 inches in diameter) and augers waiting to be used for the tunnel. (Alison Sandstrom/paNOW Staff)

Using directional drilling, A 54-inch steel casing is pushed through the earth with a large auger. Bedrock, not spotted by geotechnical analysis during the project’s design, has slowed the process down.

“They’ve had to be blasting the bedrock and then hand removing pieces of rock to move the directional drill forward,” Miller said.

Some days they’re only able to make one metre of progress, she said.

Directional drilling is a precise science, just a few millimeters of error can throw off the grade of the whole project. (Alison Sandstrom/paNOW Staff)

Work on the tunnel began in mid-June. Although having to adapt to the bedrock has delayed the completion of this key section by over a month, the entire 1.4 km sewer main is on course to be finished at the end of November Miller explained.

After the casing is in place, a 900mm sanitary sewer line is fed through the tunnel. (Alison Sandstrom/paNOW Staff)

Once complete, the West Hill trunk sewer main will take pressure off a nearby line currently at 96 per cent capacity and make room for future growth in the West Hill and West Flat.

Miller anticipates Sixth Avenue W. should reopen to traffic within 10 days. Next, construction will continue working it’s way west to tie-in with an existing sewer line at 10th Avenue W.

A 6,000 lb remote-controlled trench packer prepares a section of Sixth Ave. W. for repaving. (Alison Sandstrom/paNOW Staff)

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alison.sandstrom@jpbg.ca

On Twitter: @alisandstrom