YEAR IN REVIEW – MARCH 2024
Mark Buckshon
Ontario Development Information
William Coleman had a contractors’ nightmare.
He was a development supervisor liable for tunnels and shafts of the primary part of Ottawa’s Mild Rail Transit (LRT) venture – and main leaks had been plaguing the underground tunnel in Ottawa’s core earlier than its completion in 2019.
Soil situations and the working surroundings had been difficult: At one level in 2016, a sinkhole opened up on Rideau Avenue, sucking in a parked locksmith’s truck, flooding 300 metres of tunnel.
The leaks, some modest, and a few that at instances had been torrential downpours, wanted to be solved, however how?
Ultimately, after making an attempt seven choices in a seemingly futile – and costly – seek for solutions Coleman says he discovered an answer that has confirmed to be cheap, easy-to-implement and sustainable – and is now offering the framework for waterproofing the huge Parliament Hill renovation venture.
Coleman, presently the structural lead for the Ellis-Don/PCL consortium working on the Centre Block, informed his story of trials, tribulations and supreme salvation at Constructing Envelope Council Ottawa Area assembly final Wednesday (March 20).
William Coleman (Picture from Entrance Web page Media Group offered by Coleman to OCN)
Issues started going improper when contractors began boring tunnels and digging shafts for the LRT’s underground line, he stated. Work wanted to be accomplished in a downtown surroundings with many underground utilities, providers, and neighbouring buildings. The stable mattress rock situations made for gradual tedious excavation work and floor water was being managed by typical development pumping.
Underground stations and tunnels alongside the LRT line represented what had been the deepest below-ground structural work within the metropolis’s historical past – and water began pouring into the tunnel close to venture completion; creating an important downside that wanted to be solved, completely.
Coleman says his crew started casting for options. Numerous distributors supply a range of waterproofing options, and he tried them one, by one. Every concerned numerous contractors and materials suppliers.
In his presentation, Coleman averted naming the eight numerous model methods or techniques, however a lot of them are well-known proprietary commercially accessible merchandise. Coleman clarified that there are a lot of merchandise accessible to the market however from hands-on sensible discovery all aren’t appropriate for each water leaking situation. He describes the problem as discovering the suitable instrument from the instrument field for the precise activity.
First strive: Polyurethane 2-part injection
This didn’t work in any respect. It stopped the leaks for a short while, if in any respect. A part of the issue was the “high wick effect” – the sealant would merely take up the water and as extra water poured in and the leak finally overloaded it.
Second strive – Polyurethane two-part injection with components
On this case, the provider supplied an acrylic additive to be pumped in after the polyurethane to fill capillaries and cease the wicking impact.
“This stopped the water instantly, but it cracked over a few weeks with no additional water-stopping ability,” Coleman stated. And the second, ineffective resolution, was extra pricey.
Third strive – Increased density two-part polyurethane
This appeared considerably profitable at grades lower than 4 metres or 13 toes deep. However the resolution didn’t final. The sealant cracked and leaks resumed, and this was once more comparatively pricey.
Fourth strive – Cement base crystalline
Coleman stated this low-cost floor utility merely didn’t cease the leaks. A floor constructive web site utility was no problem for these beneath grade constructions and merely served as a brief time period band assist holding water within the construction earlier than permitting it to bleed.
Fifth strive – Hybrid polyurethane/cement
“It worked in the tunnel, for about 30 days,” Coleman stated. As a result of the sealant was very inflexible, it finally debonded and cracked on account of shrinkage by “head pressure and movement,” thus failing to cease the leaks. It was reasonably costly.
Sixth strive – Acrylic gel
This feature resisted the wick impact, however grew to become “very dense and brittle over time” and will solely be counted on holding for 15 to twenty days.
Seventh strive – Friction activated latex rubber
By this level, Coleman described a way of desperation after the a number of failures. He was able to strive a product developed in South Africa that had been modestly used earlier than in Canada. And it labored – lastly stopping water on smaller cracks for at the least a 12 months or two.
Sadly, the answer didn’t achieve stopping leaks from bigger cracks. “The sample in the office became very stiff and is no longer elastic,” he stated. “The product did not work on larger non-localized leaks.” Extra painfully, it was messy. The sealant unfold in every single place, together with into underground areas of neighbouring buildings.
Lastly, Coleman realized of one other resolution that additionally used rubber, however mixed totally different compounds right into a single part gel, delivered in blocks to the development web site, after which melted quickly with specialised heating gear. As soon as injected, the compound crammed the cracks, then cooled right into a everlasting however versatile non-curing rubber seal.
“This stopped water in all the areas, including small and large cracks long-term,” he stated. “The first injection was in March 2020 and is still holding.” There’s little to no cleanup, and the low-cost resolution remains to be holding up nicely a number of years later.
Coleman stated he took these classes and realized ideas when he moved with EllisDon to work on the Parliament Hill renovation.
With expertise, the contractor didn’t must undergo the identical studying curve to create a watertight basis design suited to the particular situations and challenges of the Parliament Hill restoration.
“The new waterproofing design will integrate a non-curing self healing rubber gel that is heated and then sprayed onto the foundation walls. known as poly rubber gel,” he stated in follow-up notes to Ontario Development Information.
Because it doesn’t want any curing, work could be achieved shortly in all climate situations, and there’s no must gradual the venture.
The product is sustainable, as it’s largely constituted of recycled tires and isn’t a byproduct of the oil and gasoline trade. It’s designed with waterproofing in thoughts.
Coleman signifies that the blame for the LRT basis leak issues might be attributed to a number of causes; together with the final contractor’s failure to make sure correct trades steerage and high quality assurance; designers in failing to specify appropriate merchandise for the location situations, suppliers in asserting their product is appropriate for “all conditions” and sub-trades who might have taken short-cuts or did not observe the processes required to observe advanced provider set up directions.
Ultimately, after eight tries, the poly rubber gel has succeeded as a result of it’s a easy one-part injection expertise, non-curing (thus sustaining flexibility and elasticity), has a medium viscosity (so didn’t run everywhere), totally bonds to moist or dry concrete, really dams the water even in areas the place it’s troublesome to see or entry the leak, and the place there isn’t any materials waste, Coleman stated.
