Growing role of green infrastructure

November 2011 » Departments » COMMENT
Bob Drake

Reviewing a list of major wastewater, stormwater, and drinking water system projects (see "Water Projects Pipeline" on page 38), the growing role of green infrastructure and low-impact development (LID) is quickly evident.

As part of consent decrees with the U.S. Environmental Protection (EPA) agency to reduce or eliminate combined sewer overflows and sanitary sewer overflows, cities, counties, and regional utility districts are pursuing more integrated approaches to managing stormwater that include infiltrating and retaining more stormwater onsite to help moderate the costs of improvements to stormwater infrastructure and wastewater treatment plants, as well as to better protect rivers and lakes from runoff pollution and increased erosion.

For example, the Metropolitan St. Louis Sewer District recently agreed to a $4.7 billion consent decree that includes a requirement to spend at least $100 million on green infrastructure such as green roofs, bioretention, green streets, and permeable pavement. As part of a Municipal Separate Storm Sewer System (MS4) permit for Washinton, D.C., the EPA is requiring the following "green performance measures":

  • installing a minimum of 350,000 square feet of green roofs on District properties;
  • planting at least 4,150 trees annually and developing a green landscaping incentives program;
  • retaining 1.2 inches of stormwater onsite from a 24-hour storm for all development projects of at least 5,000 square feet; and
  • developing a stormwater retrofit strategy and implementing retrofits of impervious surfaces draining more than 18 million square feet.

But for such efforts to become "mainstream" across the country, green infrastructure needs to provide some incentive to developers and owners. A recent research report by economic consulting firm ECONorthwest ( – "Managing Stormwater in Redevelopment and Greenfield Development Projects Using Green Infrastructure" – offers some broad conclusions on the economic factors that influence developers' decisions in this arena. Here are some interesting statements from the report:

  • [Developers] emphasized that pursuing [green infrastructure] projects was not without challenge, but they will continue developing in places that require strong stormwater controls and LID.
  • Many developers described the cost of implementing stormwater controls as minor compared to the other economic factors they considered in deciding whether or not to pursue a project.
  • Using LID controls has helped offset some of the increased cost [of stronger stormwater standards.]
  • The costs of stormwater controls in general, and LID controls in particular, tend to be more variable and site-specific for redevelopment versus greefield development.
  • Market demand for projects that include LID stormwater controls have not yet expanded beyond niche markets.
  • [Developers] in redevelopment projects emphasize the importance of considering stormwater management at the earliest stages of development, and of integrating professionals' expertise throughout the project.
  • Market adjustments that have the potential to lower costs include more widespread availability of materials (such as porous pavers), better technologies that reduce the time and/or expense of installation (such as modular green roof systems), and improved design and engineering expertise.

Demand for green infrastructure may currently predominate in niche markets, but an increasing number of regulatory mandates, technologies, and economic benefits could expand the market significantly. Are you prepared to provide owners and developers with the engineering expertise to implement it successfully?

Bob Drake

Upcoming Events

See All Upcoming Events