Green building-rating systems have been around for well over a decade. The best known in the United States is LEED (Leadership in Energy and Environmental Design), the certification system administered by the U.S. Green Building Council. LEED is for the "horizontal infrastructure" world of buildings. But what about "horizontal infrastructure" -- our roads, bridges, railways, landfills, water and wastewater-treatment plants, power-transmission lines, and public spaces in our cities and towns?

At a recent sustainability conference, I learned about an intriguing effort to bring to infrastructure what LEED brings to buildings. It's called the Envision Rating System, and it's a joint project of the Institute for Sustainable Infrastructure (ISI) and Harvard University's Zofnass Program for Sustainable Infrastructure.

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Envision is just getting out of the starting blocks. Essentially, it's a guide for sustainability decision-making by government. "We now have a way to help government prioritize needs and allocate resources for the physical infrastructure upon which everything else depends," explains William Bertera, ISI's executive director. Ann Radil, an Envision user who is senior scientist for Parametrix, a Portland, Ore., environmental-engineering consulting firm, says that "for infrastructure Envision has done the heavy lifting on sustainability. These tools help you ask the right questions."

As governments make decisions about scarce resources, too often the decision-making process is limited to locally available knowledge or experience and misses the possibilities presented by best practices from other communities. Envision is based on a list of best practices that can be considered as a project is designed and implemented.

What intrigues me most, beyond its sheer scope of application, is the emphasis Envision places on transparent public engagement in the planning, development and implementation process. In challenging financial times, government investment in infrastructure merits particularly intense scrutiny, and any measurement of value must take into account not just the cost of pipes or pavement. "When you look at any community," says Bertera, "there are values held in high regard: voter satisfaction with government, appropriate use of existing resources, an open decision-making process, a well-preserved environment. These can't be directly monetized but add value."

For Bertera, sustainability "is a state of mind," but where this happens in most current planning, it happens by accident. It is much better to include consideration of sustainability issues purposefully throughout the whole of the life of a project. Envision adds structure to the conversation on sustainability.

And we always need to keep in mind that the decisions that come out of that conversation will be with us for generations. "Ultimately we are dealing with broad systems, not single actions," says Bertera. "Sustainability is a judgment of history. Whether we did well or not will be a discussion by our grandchildren, not us." I think Bertera has it right.