Hamilton Is Building Infrastructure For Growth

Hamilton, Ontario, is preparing for growth with a massive trunk line running 5 miles in length and as deep as 300 feet underground.
Hamilton Is Building Infrastructure For Growth
Susan Jacob, design manager for the City of Hamilton’s Engineering Services Division, stands at the massive drop shaft under construction as part of the Centennial Sewer Project. (Photography by Bruce Bell)

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Hamilton, Ontario, Canada, is building infrastructure for the next 20 years of growth. The city of 500,000 is located on the western tip of Lake Ontario, about 50 miles southwest of Toronto. Known affectionately as The Hammer, the urban center is ripe for development, especially given skyrocketing Toronto real estate prices.

“We have developers waiting for sewer and water infrastructure so they can start building,” says Susan Jacob, manager of the design section in the city’s Engineering Services Division.

Jacob’s group is responsible for taking project concepts from the city’s planning group, designing the job, permitting, tendering and awarding contracts. She’s been involved with the Centennial Sewer Project, one of the largest infrastructure projects in the city’s history, since its inception.

A right-of-way along arterial road Centennial Parkway was an obvious choice for locating the sewer trunk and an associated water main, but the city’s topography and geology still provide challenges.

Built on a mountain

Hamilton is a city built on a mountain, so the tunnel must conform to a drop of more than 350 feet. Phase 1 of the project, valued at $14.5 million, runs along the lower elevation for almost 1.5 miles to depths reaching 300 feet. Phase II, the Upper Centennial, is valued at $51 million and runs along the upper elevation for more than 3.5 miles at a more modest 65 feet. The two phases of construction will be joined in the middle by a 250-foot drop shaft.

“The sewer is gravity-fed, so we had a choice of using 72-inch pipe or using 60-inch pipe and increasing the slope to increase capacity,” Jacob says. “We’re not yet certain about the intensity of development in this area of the city, so we wanted to get the size of the pipe right.”

Ultimately, a 72-inch form factor was chosen. Hamilton construction firm McNally International was awarded the contract on both phases of the project.

Tim Cleary, general manager with McNally, notes that the biggest challenge of the project has been piercing the hard Queenston limestone that makes up the Niagara Escarpment, the dominant geological formation that underpins the city. The company is using tunnel boring machines purchased from The Robbins Company.

“On the first phase of the project, we used a cast-in-place concrete liner,” Cleary says. “We had a telescopic form that moved along at night, while during the day they pumped concrete into the tunnel behind the forms.”

On the second phase, the contractor found it more economical to import more than 3 miles of 72-inch precast concrete pipe manufactured by HOBAS in Texas and shipped to the site.

A century-old system

The sewer line will ultimately tie in to a utility with a long history. The first length of Hamilton sewer was constructed in 1859. Its first sewage disposal plant was built in 1896 — the first facility of its kind in Canada. By 1960, the city operated five sewage disposal facilities; however, the needs of the population soon outstripped plant capacity. In 1964, the city commissioned the modern Woodward Wastewater Treatment Centre (WWTC), still in operation today but heavily upgraded to treat an average of 75 million gallons of wastewater per day.

About 15 percent of the sewer system is older than 100 years, 14 percent is from 60 to 100 years, 51 percent is from 20 to 60 years, and 20 percent is 20 years and newer. Slightly more than half the pipe — 52 percent — is concrete. About 15 percent is clay, 11 percent is PVC, and the rest is a mixture of polyethylene, brick and ductile iron, with 9 percent composed of unclassified material. Most of the pipes measure about 40 inches in diameter, with a few as large as 18 feet.

Harry Krinas, acting senior project manager with the asset management section of the Hamilton Public Works Department, oversees maintenance of the city’s sewer system.

“Although it’s a system made of a wide variety of materials over a long range of time, it’s structurally solid,” he says. “Much of that can be attributed to continuous inspection and rehabilitation through CIPP. We currently have about 200 miles of sewer lines rehabilitated by CIPP.”

The greatest challenge to the system is its age and the original construction methodology used to build the infrastructure.

“We’ve changed the loading on the roads, and traffic patterns have changed,” Krinas says. “You start to get minor corrosion, infiltration and loose soil around the pipes, and a series of smaller problems leads to pipe breakage. The more fragile clay pipes are particularly susceptible.”

All of the major contracts for the sewer system, from construction to inspection to mapping, are outsourced.

The big drop

Strategically, some lengths of sewer are difficult to access. Because the city is built on a mountain, it contains seven drop structures of at least 150 feet.

“Those areas are not easy to inspect, and it’s difficult to divert flows,” Krinas says. “They’re also not as easy to engineer for odor control.”

Inspection covers 90 percent of the system on a five-year cycle, with two active programs: one for trunk sewers and another for smaller pipes.

“We use regular CCTV inspection for smaller pipes, and we then zoom in on potential problem sections flagged by the cameras,” Krinas says. “For the trunks and interceptors, we have an engineering consultant design more specialized inspection programs that range from laser profiling to sonar and robotic cameras from such companies as RedZone Robotics.”

The entire system has been GIS mapped by GeoMedia from Hexagon Geospatial.

A harbor city with a busy port, Hamilton has long battled combined sewer overflows. Much of the early system is combined, and the city’s strategy toward eliminating CSOs has involved a complex system of diversion and containment structures. Large tanks have been built to contain sewage during storms for later treatment at the WWTC. A sophisticated SCADA system manipulates a series of gates and diversion controls to channel sewage to the pipes most available to accommodate it.

“We’re currently looking at building another in-line storage facility or a sewer pipe with enough capacity to store a large quantity of combined sewage, so it can be treated later,” Krinas says.

Designed for the future

The Centennial Sewer Project is being designed for longevity, incorporating lessons learned from the existing system. Shafts are being drilled into the tunnel every 500 feet for the purposes of rock removal. These shafts will act as future manholes and inspection ports.

“We’re also mindful that the pipe has to withstand long-term corrosion from hydrogen sulfide,” Jacob says. “If we relied only on a few new developments coming online, the flow in the Centennial sewer would be slow moving and produce corrosive hydrogen sulfide. To solve that problem and any odor problems that result from low flow, we’ll be diverting flow from the nearby Binbrook sewer interceptor into the Centennial to provide enough initial volume to keep everything moving until we reach full development.”

While Phase 1 of the Centennial Sewer Project is already in operation, the Upper Centennial is scheduled to be commissioned in 2017.

“We’re determined to finish on schedule,” says Jacob. “There’s quite a bit of development waiting.”


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