The words “sustainable” and “resilient” have become widespread descriptors for infrastructure: resonating in brochures, ads, logos, business cards, magazines, and college curricula. These two words represent the current Holy Grail of our environmentally conscious society. More and more people want their communities, projects, and methodologies to be sustainable and resilient.
Of all the environmental issues associated with sustainability in North America, climate adaptation and resiliency have emerged with a degree of urgency. In the United States, Hurricane Sandy’s recent impact on the metropolitan and rural coastline in the states of New York and New Jersey raised awareness of the shortfall in funding for public facilities repair. The primary impacts resulted from surface water runoff, rising sea levels (and the resulting wave forces and flooding), and unprecedented wind velocities. The extreme hurricane impacts renewed focus on regulators and the engineering community to design approaches and retrofits that harden infrastructure against these storms.
We can probably all agree that sustainability and resiliency encompass three broad areas of focus—the so-called “three-legged stool” of economic, environmental, and social factors. We can debate the more refined definitions of sustainability and resiliency until we are “green” in the face, but what matters is this: How do we actually achieve sustainable and resilient infrastructure projects as we move forward to improve our communities?
The generally accepted core sustainability considerations or factors are listed in table 1.
Sustainability approach and outcomes
The steps involved in achieving sustainable and resilient projects can be straightforward if you follow the steps below:
1. Start at the concept stage.
2. Answer the question: What elements can I include/modify in my project to make it more sustainable and resilient through each project stage, from design to construction to life cycle?
3. Achieve the optimum balance of sustainability and resiliency at minimum cost (“knee of the curve”).
Step 1: Start at the concept stage. It’s simple. Don’t wait until 30 per cent or 60 per cent design to ask how to incorporate sustainability or resiliency elements. For example, if the goal is to reduce combined sewer overflow (CSO) volume and stormwater separation is identified as the preferred alternative because of estimated positive benefits, ask the question right away: What needs to be done to make the CSO-reduction stormwater separation project sustainable and resilient?
One ready answer is to recognize that separating stormwater may help to reduce CSO, but that separation will also create new stormwater pollution. Therefore, the proposed plan must also account for the costs associated with mitigating the stormwater pollution in a sustainable and resilient manner. For example, can green infrastructure be incorporated into a separation project to manage and treat stormwater to address water quality and water quantity impacts? Another example may be a street reconstruction project. Can the project incorporate complete street elements and manage stormwater to mitigate pollution while at the same time helping to transform a downtown area into an attractive and inviting space?
Numerous checklists and tools are now available to incorporate sustainable and resilient elements into our infrastructure projects, including LEED, ISI Envision, Greenroads, and GreenLITES. These include the classic “people-occupied” building construction approaches like LEED, but also address non-occupied systems, including water and wastewater, transportation, and other infrastructure. In addition to establishing planning and design concepts and principles for sustainability and resiliency in a project, a number of these rating systems also establish sustainability performance monitoring criteria over a project life cycle.
In one example, Hatch Mott MacDonald (HMM) utilized sustainability and resiliency rating tools for the Town of Oakville’s Mid-Halton wastewater treatment plant expansion in the Regional Municipality of Halton, Ontario. HMM’s analysis recommended the following:
• Take advantage of 65 different opportunities to reduce the overall footprint of mechanical, electrical, and lighting design.
• Install high-efficiency blower units for the activated sludge train to significantly reduce energy demand and life-cycle energy costs.
• Reduce offsite power consumption with solar generation of site electricity, plus cogeneration of energy (electricity and heat recovery) from biogas, and heat energy recovery from sanitary effluent.
• Harness the plant’s outfall for micro-hydroelectric power generation.
• To properly manage and treat the stormwater runoff from the plant site, add low-impact development measures throughout the site, including low-flow wetlands, subterranean overflow galleries, and a cooling trench feature to reduce temperature gain into the waterways.
• Plant three trees for every tree removed.
Step 3: Achieve the optimum balance of sustainability and resiliency at minimum cost. Each element on a checklist of sustainable and resilient elements has capital and life-cycle costs associated with it. This ultimately ends up as total cost savings or cost additions to a project. Given the elements that you want to implement and their associated costs, including capital and life-cycle costs, you can then construct a curve similar to the example in Figure 1. The data can then provide the “knee of the curve” point that identifies the optimum balance of sustainability and resiliency goals at the minimum or optimum cost. This analysis makes it easy to compare both upfront capital cost and life-cycle cost to the company’s goals in order to pick the sustainability and resiliency elements that provide the optimum balance for the community and stakeholders.
Achieving sustainable and resilient projects need not be difficult, and defining sustainability and resiliency doesn’t have to be confusing or daunting. A straightforward stepwise process can be followed to achieve your community’s sustainability and resiliency goals and objectives while balancing short- and long-term costs. After all, many of the costs incurred today will be paid by future generations, so we should take care to leave them assets and not liabilities. WC
Don Nusser is the VP of HMM. Mark Stirrup is an associate and principal project manager, and HMM’s practice lead for combined and sanitary sewer overflow abatement. Brandon Vatter is an associate and watershed/wet weather technology expert for HMM. This article appears in Water Canada’s January/February 2015 issue.