...Drilling down to bedrock is a fairly standard and, based on modern geology and construction technology, a fairly mundane and predictable process. It is, however, an expensive process, and the deeper you need to go to reach that bedrock, the more expensive it is.Building on a less-than-solid bedrock, one that's "crumbling," "fractured" and "unstable," resulting in a long, messy expensive process: You don't suppose somebody was trying to send mausoleum-enthusiasts a message, do you?
For this project, it was very expensive. Consider that the caissons for this project varied in price between $40,000 and $400,000 apiece. That variance in price is the result of a Manitoba geology that is diabolically unpredictable. The flood plain is very flat, but the bedrock underneath is quite undulating. That means you can reach bedrock very easily in places such as Winnipeg's northwest quadrant, but in other areas, the bedrock is elusive, if it is there at all.
PCL [the construction company] found this out when the coring barrels bored deeper and deeper into the ooze which surrounds The Forks. The soil is silty and even when the coring barrel reached rock, it was not stable.
"We usually find bedrock in Winnipeg about 17 metres below the surface," said Craigen. "In this instance, the bedrock was much, much deeper. And even when we did hit rock, it was fractured or crumbling. Or it had clay or sand seams running through it and was unstable."
PCL and its foundation contractor, Subterranean Manitoba Ltd., eventually hit solid bedrock at 38 metres, more than twice the typical depth.
But that was not the only problem. Albuquerque-based architect Antoine Predock's design called for the building to start below grade so that visitors would have to descend into the entrance between the giant concrete roots. This was a major design element, and the architect insisted it be part of the final design. The big problem is that once excavated, this brought the foundation level to the same level as the Red River, which runs along the site's eastern edge. The depth of the foundation and its proximity to the river mean the site's natural water table is very high. Thousands of litres of water were pumped out of the excavation hole to allow the foundation work to proceed. It was a long, messy, muddy process.
The foundation took 11 weeks longer than expected to complete.
"We did start off in a bit of a hole with that part of the project," Craigen said. "But we're making it up in other areas."
Total cost for the museum foundation, including all piles and caissons, was $15.1 million...
Monday, October 18, 2010
Construction Woes at the 'Human Rights' Mausoleum a Metaphor for the Entire Project?
The Winnipeg Free Press reports on the, er, progress of the "human rights" white elephant (the one that's costing us an arm and a trunk):