June 10, 2008

280 piles were sunk 30 metres deep to support the 60,000-square-foot Grey Bruce Health Unit building.

Excavation wreaks havoc with Owen Sound project’s construction timelines and budgets

MARY BAXTER

correspondent

OWEN SOUND

Paving the way for future development on former harbourfront industrial lands has not been easy for those involved in building new quarters for the Grey Bruce Health Unit.

Problems during the excavation process have wreaked havoc with construction timelines and budgets, says Brian McCormack, who is managing the project for the region’s health unit on behalf of UMA Engineering Ltd.

McCormack says the project was initially built with the best of intentions: to create the city’s first gold LEED (Leadership in Energy and Environmental Design) certified building and initiate brownfield development in the area.

The project was slated to forge ahead after the city completed site remediation in 2005.

The work was needed to remove pockets of high concentration of metals and some hydrocarbons.

The metal concentrations “weren’t particularly high levels but they did exceed the Ministry of Environment tables for that land use,” says McCormack.

Originally plans had called for replacing about two metres of soft soil with engineered fill. But as site preparation began, it was realized that the approach would mean having to drop groundwater levels by at least a metre.

“That’s where it became a problem,” McCormack says. Without the introduction of barriers, dewatering could create movement in water beneath other properties and the possibility of contaminants “moving from one property to the next.”

The MOE would not approve the work being done without the introduction of preventative steps. Work was brought to a standstill while the project’s engineering consultants, locally-based Henderson Paddon & Associates, explored options. A pile foundation became the solution. In total, 280 piles were driven down nearly 30 metres to support the 60,000-square-foot, three-storey building.

In the meantime, however, the project’s earthworks contractor, Quantum Murray LP, had begun some excavation in an area that would eventually become the health unit’s parking lot. That’s when they came across another project-stalling discovery — more contaminated soil.

“This is probably environmentally the most challenging (project) I’ve had to deal with,” admits McCormack, a 29-year veteran of the industry.

The situation has also posed a challenge for the city, which is taking legal action against CH2M HILL, the firm responsible for the initial cleanup.

The second round of remediation added more than $1.5 million in costs to the $500,000 originally budgeted to remove contaminants from the site.

John Johnston, Owen Sound’s operations director, says contaminated soils were also found in the road allowance to the new facility. However, it was the costs of the approach to dewatering that added an extra $300,000 to that project’s original budget of $1.3 million.

“We had to sheet pile the excavation and dewater the excavation primary instead of drawing down the aquifer for some distance aside,” he explains.

At the Grey Bruce Health Unit site the early setbacks pushed work behind nearly a year (it’s now scheduled for completion next month) and $1.8 million over the original budget of $15.4 million.

But things could have been worse if the earthworks hadn’t been split from the main general contract, McCormack says. With the second round of remediation “we would have had a general contractor sitting around not able to work for almost a year.”

He credits the decision to keep the earthworks separate to a hunch.

“From day one, I was nervous about the site and the soils and it proved to be the biggest challenge on the job,” he says.

And as far as the building’s construction is concerned, it’s been relatively smooth sailing since.

Working towards the LEED designation has meant some different approaches to co-ordinating the project’s construction.

Qualifying for the designation not only means achieving energy efficiencies and paying attention to the materials in the building, “it’s how you manage materials and waste during the construction,” he points out.

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