The upfront cost to demolish the Calgary Saddledome has been projected at $13.8 million. The environmental repercussions of dismantling and discarding a 474,000-square-foot concrete and steel structure are more difficult to peg.
Life cycle assessment (LCA) — which can help to gauge a building’s environmental footprint from construction through to its end of life — accounts for four distinct sources of embodied carbon as a building is taken out of useful service: deconstruction/demolition; transporting debris; processing waste; and final disposal. In this case, abandonment of the now 36-year-old facility ahead of its designed lifespan will trigger those impacts.
“From a structural perspective, it probably is premature. The question is, is it premature from an economic perspective? The decision whether a building is deconstructed, demolished or preserved is almost always going to be economic,” muses Jamie Meil, research principal with the Athena Institute, a not-for-profit provider of life cycle assessment resources, including free software for estimating the environmental footprint of building materials and pavement. “The number one reason buildings get torn down is economic versus whether they have outlived their usefulness.”
The city of Calgary’s communications around a proposed new event centre — envisioned as a $550-million joint development with private sector partner, Calgary Sport and Entertainment Corporation (CSEC) — aligns with that observation. A list of 27 presumed questions of interest posted on the city’s website begins with the statement: “The City of Calgary remains committed to the economic recovery of our city on behalf of citizens, communities, businesses and customers.”
“The Event Centre is more than an arena,” it asserts. “The Event Centre is a catalyst for attracting private sector investment into the area and the development of under-utilized lands.”
Meanwhile, three references to the Saddledome farther down the list in questions number eight, 10 and 22, repeat the same message: “It has served Calgary well, but is aging.” In other documentation, the city manager’s July 22 summary of the details of the development partnership includes a section with the heading, “Social, Environmental, Economic”. Yet, only the potential economic and social spinoffs are itemized.
“I wouldn’t say: Don’t redevelop the site. But I’m all for being open about the impacts. If they quantify it, maybe they’ll be able to offset it to a certain extent,” urges Ryan Zizzo, an LCA practitioner who is founder and chief operating officer of the climate impact consulting firm, Mantle. “There needs to be transparency.”
Embodied versus operational carbon
The oversight is not the city of Calgary’s alone. Efforts to measure and reduce greenhouse gas (GHG) emissions in the buildings sector have been largely focused on operational emissions from energy consumption and waste production directly within buildings. Whereas, embodied carbon is the tally of indirect GHG emissions tied to the extraction, manufacturing and transportation of building materials and to construction, renovation or demolition processes.
It’s generally estimated that embodied carbon will account for 80 per cent of the environmental footprint of new construction for 10 years after completion, but proportions will vary at the individual building level depending on operational performance and the carbon intensity of the power supply. Heavy reliance on fossil-fuel-fired electricity generation tends to skew the split.
“In Alberta, embodied carbon may not be as big a percentage of the impact, but that doesn’t mean it couldn’t be lower,” Zizzo says.
Under the terms of the deal, the city of Calgary will cover 90 per cent of Saddledome demolition costs, a share currently estimated at $12.4 million. Although CSEC is allocated the remaining 10 per cent, the agreement also caps the company’s contribution at $1.5 million. The Saddledome’s parkade will be left in place and eventually transferred to the Calgary Stampede’s ownership.
A May 2017 consultants’ report — released later in the year to the filers of a Freedom of Information submission — calculates that demolition costs could be kept in the range of $23 to $27 per square foot if 90 per cent of recyclable metals are recovered, and if all concrete is crushed and stored on the Stampede grounds for later use. “Note that repurposing of concrete would provide for cost savings in the millions and, in general, would show a strong commitment to sustainability by the City and Stampede,” it recommends.
Since diesel-powered demolition equipment typically expends 45 to 50 megajoules (MJ) of energy per square metre (m2), Meil estimates that component, alone, would produce about 12 tonnes of carbon dioxide equivalent (CO2e) for a building the Saddledome’s size. Emissions from transporting recovered materials or debris offsite, and the embodied carbon in materials destined for landfill, would also have to be factored into the tally.
While the suggested target for recapturing metals may be realistic, Meil notes that typically only about 50 per cent of concrete is recovered from a deconstruction project and it’s generally then “downcycled” to a lower form of use, such as for roadbed.
“Canada is still at a point where almost 20 per cent of landfill deposit is comprised of used construction materials. It was worse, at almost one third,” observes Marc Denhez, a lawyer, heritage building advocate and former Ontario Municipal Board adjudicator. “You won’t find any recognition of that in public policy. We have policies to reuse items as small as pop bottles, but when it comes to reusing items as large as buildings, or even neighbourhoods, the public record is essentially dead silent.”
Design considerations and accountability
Vancouver is now at the vanguard of addressing embodied carbon at the construction stage. It was identified as one of six “big moves” in the Climate Emergency Response actions City Council endorsed in the spring of 2019. That sets a target for a 40 per cent reduction in the embodied emissions from new buildings and construction projects, compared to 2018 levels, by 2030.
Looking to the United States, the Buy Clean California Act will enforce standards for acceptable global warming potential (GWP) for structural steel, carbon steel rebar, flat glass and mineral wool board insulation used in that state’s public construction projects, beginning in 2021. Building proponents everywhere can also take up the voluntary options in programs like LEED, Living Building Challenge and Carbon Smart Building.
The latter organization sets a goal for the lifespan of existing buildings to reach at least 100 years — a notion that is wildly incongruous with the recent history of venues for professional sports teams. In the past 25 years, 17 cities have built new facilities for their National Hockey League teams and 14 have then demolished vacated arena complexes. Meil cites the example of the Seattle Kingdome, former home to the city’s professional football team, which was demolished, via implosion, just 24 years after it opened and 15 years before the bond used to finance it was repaid.
Many of those venues were consigned to destruction because of their purportedly unworkable suburban locations, but that’s not the issue in Calgary. “The Saddledome is already downtown,” Meil reiterates. The proposed replacement is also expected to have approximately the same 19,000-seat capacity.
Given the ample past evidence, Meil suggests new venues could at least be developed with an eye to possible early obsolescence. Criteria for design competitions and requests for proposals could prioritize materials and structural components that could be disassembled and recovered. Meanwhile, a life cycle assessment of the Saddledome demolition footprint could give Calgary taxpayers better insight into the impacts.
“That might add to the demolition costs, but there are also costs attached to not addressing it,” Zizzo maintains. “The question is: what numbers are they including and what numbers are they just ignoring?”
Barbara Carss is editor-in-chief of Canadian Property Management.