The American Council of Engineering Companies (ACEC), the American Public Works Association (APWA), and the American Society of Civil Engineers (ASCE) established the Institute for Sustainable Infrastructure (ISI). ISI adapted sustainability work underway at the Zofnass Program for Sustainable Infrastructure at the Harvard University Graduate School of Design and published the Envision Sustainable Infrastructure Framework (Envision) in 2012.

Envision provides a roadmap to enhance the sustainability of public infrastructure projects. ISI provides a free Excel checklist, a detailed guidance manual, a credentialing program for professionals, a third-party project verification process for projects, and numerous educational resources.

This is Part I of a two part post that will provide an introduction to Envision. Part I defines the triple bottom line (TBL), ecosystem services, and provides a few ways to view sustainability. Part II will provide more details about Envision, and how it is used to enhance infrastructure projects.

So what do we mean when we say “enhance the sustainability of public infrastructure projects?” First, let’s look at a few definitions of sustainability.

Sustainability: Deliver Triple Bottom Line Benefits

ASCE and others define sustainability using the concept of the triple bottom line (TBL). Sustainability is achieved when social, economic, and environmental benefits realized by a project exceed social, economic, and environmental costs.

Most project teams use a standard accounting ledger with only one column of figures and one bottom line. The project team enters anticipated monetized project benefits in the top portion of the ledger, estimated costs in the middle, and the calculated difference at the bottom line of the ledger. Hopefully benefits are greater than costs and the bottom line shows a profit!

Using a TBL approach, project teams enter monetized economic, social, and environmental cost and benefits into three different ledgers and calculate three separate bottom line values. Sustainable projects deliver more economic, social, and environmental benefits than costs, thus they deliver profit in each ledger.

The table below conceptually illustrates a TBL evaluation of a new wastewater treatment plant.

The table shows how the wastewater utility might see economic benefits if customer revenue exceeds the sum of costs for design and construction, debt service, property acquisition, and operations and maintenance.

The table shows how social benefits might accrue. People hired to work at the plant will earn income. Community members who use the more attractive and cleaner creekside or bayou trails will benefit from being outdoors and from additional social interactions. Social costs might include displacement, because people living on the intended plant site property will need to move. People living near the new plant may experience noise pollution and odors. Hopefully social benefits exceed social costs. Notice how social benefits and costs accrue to more than one entity – not just the facility operator.

Lastly, the table shows how environmental benefits might be recognized. Downstream fish and animals will receive environmental benefits from improved stream water quality. Downstream communities will receive environmental benefits from cleaner water for recreation and possibly drinking. People and wildlife will incur environmental costs associated with resource consumption, energy generation, and carbon emissions associated with the project.

Using this definition, sustainability is achieved when social, economic, and environmental benefits realized by a project exceed social, economic, and environmental costs.

Sustainability: Reduce Consumption While Maintaining Quality of Life

Sustainability can also be achieved by reducing consumption while maintaining an adequate quality of life. Quality of life can be characterized using the United Nations’ Human Development Index (HDI). The HDI for a particular area is based on the area’s average life expectancy, per capita income, and educational attainment. HDI values range from 0 to 1, with 1 indicating a long life, high income, and many years of education; a very high quality of life.

Consumption can be characterized using the concept of ecological footprint. The ecological footprint is defined as the area of land needed to support the consumption of food, energy, and other resources by one person in a particular geographic area. A higher area (a higher ecological footprint) is needed to support a higher consumption rate.

The graph below illustrates the current relationship between quality of life and consumption for a selection of countries in different continents. It shows that there is a positive correlation between the two variables; as quality of life increases, consumption increases.

Two thresholds are shown in the graph. The horizontal lines at 3.1 global hectares per person (1961 estimate) and 1.9 global hectare per person (2014 estimate) indicate the land area needed to support a consumption rate that researchers believe could be sustained for thousands of years into the future. Consumption rates should be reduced to below the 2014 threshold, shown in the blue area at the bottom of the graph.

The vertical lines at HDI of 0.70 and 0.80 illustrate thresholds for an appropriate quality of life. Humans would like to maintain a quality of life higher than those values, as shown in the blue area on the right side of the graph.

Using this definition, sustainability is achieved by reducing consumption while still maintaining an adequate quality of life.

Ecosystem Services

Lastly, sustainability can also be viewed as preserving or enhancing the ecosystem services that provide the foundation for human civilization.

The term “ecosystem services” is likely new to many readers. Ecosystem services are benefits provided by the earth to humans. Examples include provision of food, natural pollination of crops by insects or birds, production of oxygen to breath from photosynthesis in green plants, generation of fresh water from ocean water via the hydrologic cycle, decomposition of wastes from soil bacteria, and flood mitigation, to name a few.

Since humans can’t survive without food, oxygen, water, and other ecosystem services, we should acknowledge that ecosystem services provide the foundation for human society, facilitate the realization of all social benefits, and foster economic activity. This foundational view is illustrated in the diagram below.

Sustainability is about preserving and enhancing ecosystem services so all other aspects of our civilization can flourish. It is similar to the medical profession’s duty to do no harm.

This contrasts with our current legal and regulatory approaches, which guides us to build infrastructure projects that seek to avoid or minimize harms to the environment, but allows those harms to occur if they are mitigated or deemed small enough to not matter.

Using this definition, sustainability is achieved when we preserve or enhance ecosystem services that provide the foundation for human civilization.

Part II will provide more details about Envision and how it is used to enhance infrastructure projects.