The City of Owen Sound, Ontario, is modernizing its water and wastewater infrastructure at a solid pace. However, on occasion Mother Nature, in the form of an unexpectedly cold winter, can drive the city to move even faster.

Owen Sound is a city of about 22,000 people with a relatively mature and stable population. It’s located about 150 miles north of Toronto, along the shores of Georgian Bay. The city’s first water system, fed by a spring, dates back to 1880 when the local lumber industry drove the town’s growth.

Today, the city is served by a modern water treatment plant, upgraded with UV disinfection.

The city’s water mains are typically cast iron, between 6 and 8 inches in diameter. Local trunks 16 inches in diameter or greater are largely made of ductile iron. The city’s largest main is a 24-inch Hyprescon reinforced concrete pipe (Hanson Pressure Pipe). The age of the system spans the city’s history with about one-third aged 90 to 130 years, one-third aged 60 to 90 years and one-third aged less than 50 years.

In-house audit

A city asset management and infrastructure report was completed in 2013, largely by in-house staff. It reveals that just over 70 percent of the water distribution network is in good to very good condition, 16 percent is fair condition and only 13 percent is poor to very poor condition.

“When water pipes break, statistically it’s mostly caused by corrosion, frost heaves and occasionally even water hammer,” says Matt Prentice, M. Eng., P. Eng., manager of water and wastewater with the City of Owen Sound. “Many of the breaks are circular and fairly easy to deal with using clamps. It’s the longitudinal breaks that cause the most problems.”

The system typically sees between 20 and 40 water main breaks annually, with the exception of the last winter, which was far worse with more than 50 main breaks from November 2014 to May 2015.

The city balances multiple water pressure zones, which create operating challenges.

“We have a large number of control valves to operate to keep that working,” says Prentice. “It also means we have a fair number of dead ends, and we need to continually bleed the system in those locations to keep chlorine residual up.”

Prentice is also overseeing an effort to renew cathodic protection on ductile iron trunk mains.

“We need to replace those anodes in the next two years, since they were originally installed in the early 1990s and are beyond their useful life,” he says.

A newer sewer

A typical sanitary sewer pipe is made of vitrified clay and measures 8 inches in diameter, although the system contains some atypical construction as well. The system also includes small sections of historic 24- by 36-inch brick-lined box sewers. The largest sewer is the city’s east-side interceptor measuring 40 inches in diameter.  

“Generally speaking, the wastewater system is not as old as the water system,” says Prentice. “It began to be constructed in earnest in the early to middle 20th century.”

The condition of the system reflects its newer construction timeline. About two-thirds of the collections is in fair to very good condition, and the older remainder is poor or very poor condition.

“We’ve had some significant sewer main failures over the years, and it’s always been a clay pipe,” says Prentice. “In one case a few years back it was a complete collapse of an entire city block of pipe underneath a roadway.”

On the sanitary sewer side, the city struggles primarily with inflow and infiltration. “Normal flows at the sewage plant go from about 2.6 mgd to well over 10.5 mgd,” says Prentice. “Under extreme storms we go up to 21 mgd. Once flows get in the 13 to 21 mgd range we are pretty much certain to be bypassing at multiple locations on the system. We’ve established a roof drainpipe diversion program and constructed a detention tank on the west side in 2000, but we still have issues on the system.”

Construction of a new $48 million, state-of-the-art wastewater treatment plant with increased capacity will allow the plant to exceed rigorous federal standards for wastewater effluent. The new plant is scheduled to come online in late 2016.

Employing in-house expertise

The city has developed a tremendous capacity for in-house expertise in repairing and replacing both water and sewer mains.

Water main break repairs are handled by city Water Distribution crews, while sanitary sewer break repairs are handled by city Public Works staff. Trenchless technologies are always considered as an option for sewer line repair, although the city isn’t currently engaged in any trenchless or relining programs.

“We only get contractors involved for repair-type work when the problem exceeds our capacity,” says Prentice. “Full road reconstruction projects, including the underground infrastructure, are designed by consultants under direction of the city Engineering Department and put out to tender.”

While the city still favors high-pressure concrete for trunk lines, smaller-diameter sewer and water pipes are almost universally replaced with PVC.

The overall sewer inspection program is carried out by contractors. Cleaning and camera inspection of most of the sewer system and the city-owned portion of sewer laterals are almost complete. However, a city-owned camera truck performs routine lateral inspections and locates. A city Vactor also performs a regular cleaning regimen in parts of the city that demonstrate recurring issues.

“GIS mapping is a work in progress,” says Prentice. “Some of the information related to our water system is already available on GIS — for instance, our hydrants. We’re continuing to make progress on this with in-house staff using Esri ArcGIS and Geocortex Essentials.”

Frozen

There’s still no doubt that cold weather can be the water system’s greatest nemesis. How cold was the winter of 2014-15 in Owen Sound, Ontario? So cold that it threatened to shut down one-third of the city’s residential water distribution system.

“Many of our older water pipes are buried no more than about 4 feet underground,” says Prentice. “Frost was penetrating as far as 8 feet underground. Under those circumstances we instruct many residents to keep running their water to prevent freezing.”

By March, warming normally allows customers to slowly ease back on running their water, but this year the cold continued to expand its grip.

“It soon became abundantly clear that we were down the rabbit hole and had to take it to the next level,” says Prentice. “We were delivering water-run notices door to door and were adding blocks to the ‘run water’ list on a daily basis until we covered about a third of the system.”

As water services froze, city crews fought back using Magikist Pulse Jet deicers to defrost individual services. The department also ordered a pair of low-voltage, high-amperage RIDGID electric water main defrosters to maintain home service.

“All of our efforts were a drop in the bucket,” says Prentice. “Cast iron mains began to split and we had to perform triage, isolating burst mains and cutting and capping them. We then ran temporary surface waterlines, which we covered in straw for insulation. We needed so many hoses to restore service to 300-plus homes that we were cleaning out supplies of garden hose from hardware stores in neighboring cities.”

City crews and local contractors immediately began round-the-clock water main reconstruction, using open-trench methods to construct new PVC water mains. This time, mains were installed at a depth of 6 feet, and where that was not possible, to a 4-foot minimum depth with two sheets of insulation protecting them.

“By midsummer we were still working hard on replacing sections of the water distribution system, with just one project to go in the fall,” says Prentice. “That was the only part of the project where we had the luxury of enough time to send it out to tender.”

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Historic shipwrecks fail to scuttle outfall pipe construction

Divers conducting a pre-construction survey of the area around an effluent pipe project at the City of Owen Sound, Ontario, made a surprising discovery: historic shipwrecks.

The exploratory dive preceded the construction of the upgraded outfall diffuser for the city’s $48 million secondary wastewater treatment facility.

“Provincial regulations required a diffuser to be placed at the end of the pipe to meet mixing criteria for the concentration of effluent leaving the pipe into Georgian Bay,” says Matt Prentice, manager of water and wastewater at the City of Owen Sound. “The marine contractor discovered the ship in 20 feet of water about 650 feet off shore while using side-scanning sonar around the outfall pipe.”

Scarlett Janusas Archaeology identified the ship as the Dan Proctor, a 200-foot, three-masted schooner built in Michigan in 1893. It was originally named the Ed McWilliams, but was later converted to a barge, renamed and eventually scuttled in 1936. Two older unidentified shipwrecks were located farther south.

Prentice notes that construction crews who built the outfall pipe in 1962 were almost certainly aware of the existence of the shipwreck.

“They probably wanted to finish the project without a delay, so they didn’t mention it,” he says. “In order to protect the wrecks, we only had to make minor modifications to the project by slightly shortening the diffuser pipe and directing the effluent away from the Dan Proctor.”