Concrete tunnel canvas created for Peel museum

The word “tunnel” often conjures up images of dark medieval passageways or hand dug escape routes from jails as portrayed in Hollywood movies.

In the case of the 82-metre-long, 3.5-metre-wide and 3.5-metre-high concrete tunnel at the Peel Art Gallery Museum and Archives (PAMA), nothing could be further from that image.

“It (the tunnel) could have been a bunker, but it isn’t,” says PAMA manager Claire Loughheed.

Highlighted with two 2.5-metre-high glazed skylights that stream sunlight into it, the tunnel will be decorated with art and artifacts when the complex reopens this November after being closed for a major and complicated $16-million renovation and expansion project which has been underway since the spring of 2010.

Designed by Ojdrovic Engineering and built by MJ Dixon Construction Limited, the general contractor on the project, the tunnel provides a controlled environment for the easy movement of people and sensitive museum exhibits between the two main wings of the heritage complex which is located at the juncture of Wellington and Hurontario streets in the historic downtown core of Brampton.

The east wing is comprised of the former 1867 Peel County Jail which is where the museum and archival records are located and a 1890s land registry building which had served as the art gallery before the closure.

Fronting onto Hurontario Street kitty corner from the City of Brampton administration headquarters is the west wing. It consists of the former 1867 Peel County courthouse and an old hydro headquarters building. Constructed in 1958, that building is being transformed into a major art gallery.

While the project had been planned for some time, the tunnel was actually a late addition to the development plans, says Loughheed.

It might be argued that, for the structural consultant and MJ Dixon Construction Limited, the challenges they faced in making the tunnel a reality were comparable to the ones portrayed in the movies.

Even before tunnel work could commence, significant underpinning of the four buildings was necessary because of the impact of the tunnel and related services, says Nebojsa Ojdrovic, principal of the engineering firm.

As just one example, he cites the work required to structurally reinforce the old jail building and the adjacent walled courtyard which served as the prisoners’ exercise area. A concrete consolidation encasement of the courtyard wall footing had to be erected and then both that wall and the jail house building wall had to be supported using helical piles. As the excavation went down in lifts, the soil below the jail building wall had to be tied back using steel panels and helical tiebacks.

With little available information on the original construction of the four buildings, there were unforeseen complications, Ojdrovic says. “In at least two locations, the site locations that we discovered required immediate underpinning or replacement of foundations to stabilize the structures.”

The underpinning was a labour-intensive exercise, as many sections were up to 20 feet deep and all work had to be done by hand, says MJ Dixon Construction Limited vice-president Paul Chiang.

As well, the tunnel footprint was in an area already congested with existing services. Several schedule items in the original base contract, such as a geothermal ground source system, had to be re-sequenced, modified, and postponed until the tunnel was finished in order to avoid undermining the geothermal system, he says.

Additional mechanical site services were also needed to accommodate the tunnel.

Constructing it was also a difficult and time consuming. Due to the restricted access, all the concrete had to be pumped to the site in limited quantise. Approximately 1,000 cubic metres of concrete was used, he says.

Designed by Toronto-based Goldsmith Borgal and Company Ltd. Architects, the overall expansion project has quadruped the facility’s climate-controlled storage areas, doubled its art gallery exhibition space, and almost doubled the its museum exhibition space, says Lougheed.