By now, you’ve probably heard of triple bottom line accounting, a full cost accounting approach considering the economic, environmental and social impacts of a decision or more poetically, the three P’s:people,planetandprofit. In the stormwater infrastructure planning world, as in many other urban planning arenas, this approach is gaining popularity. This is an encouraging trend as it provides a framework for capturing the multiple benefits of infrastructure improvement projects.
The relationship between the three P’s is dynamic. In most cases, increasing the benefit for one factor will increase the cost of another. The most common trade off is the additional project cost associated with enhancing social or environmental benefits. For example, project costs generally increase as more water is treated or as infrastructure for public use is added such as benches, walkways and signage.
In the regulatory world, I see a similar triad of interrelated factors affecting outcomes. A policy proposal must be scientifically based, politically achievable and economically viable to stand a chance of making it to policy. It’s interesting to view recent policy shifts toward a Green Infrastructure based approach through this lens. There is obvious political appeal.
Sustainability, low impact development and green infrastructure are near universal goals at a broad level. There is also compelling evidence that the kinds of multiple benefit, runoff reducing technologies that are the building blocks of such approaches can provide superior protection to downstream environments at lower costs. So, everybody wins!
Well not exactly, or at least not all the time. There are tradeoffs. On the Science front, there is still a lot of work to do. We seem to take it for granted that matching pre-development runoff hydrology mainly by relying on infiltration BMPs is the way to go. But, is there a danger of over infiltrating if most rainfall is evapotranspired in the natural condition? Will we be able to recover pollutants we’re accumulating in our groundwater and soils? Can landscape based BMPs effectively control pollutants like nutrients, bacteria, pesticides and herbicides? The answers to many of these questions will be locally specific.
在政策方面,我们必须确保我们不是creating unwanted side effects like urban sprawl and avoidable new potable water demand. We must ensure that the maintenance, funding, expertise and authority exists to care for distributed landscape based BMPs and that proper material procurement and construction practices can be assured. Policies and design standards must be simple and prescriptive so that plan checkers can efficiently review plans.
In an era of $500k per block green street demonstration projects, it’s helpful to remember that we have an obligation to protect the beneficial uses of receiving waters, not of project sites under the Clean Water Act. It’s a nice bonus if a project provides recreation, habitat, or aesthetic benefits at the project level, but these things cost money. If we are going to have any chance of meeting our receiving water quality goals we need to spend every dollar judiciously.
As we balance these often competing interests, concessions will be made and the political, scientific and fiscal purists will be disappointed. Those able to wear all three hats simultaneously stand the best chance of emerging satisfied.
