Green stormwater infrastructure technologies outpace local codes

Posted in: Highways, Municipal, Water

Stormwater, storm water, green, sustainable, LID, low impact developmentYour whole project team, including the local regulatory agency, wants to use sustainable “green” stormwater management. However, the design codes are still framed to use “gray” infrastructure with traditional pavements, concrete curb and gutter, and solid pipes as the collection and conveyance components. What can be done? Face-to-face discussions with the local agency can find common progressive ground for moving forward with green infrastructure design.

We used this approach with local municipal staff to design grant-eligible, low-impact development (LID) street retrofit projects. The city was open to green stormwater technologies, having allowed bioretention and permeable pavements on local projects. However, there were still some challenges with obtaining approvals for LID technologies within public right-of-way. Working together, we achieved city staff’s forward-thinking goals and excelled at meeting state grant guidelines. As a team we selected site-specific LID combinations of customized street swales, tree well cells, and other filtration and infiltration technologies.

As part of the process, we were cognizant of localized infiltration and maintenance limitations. We listened carefully to city staff’s understanding of the constraints. Infiltration could not be performed near steep slopes with landslide potential. We mixed in gray infrastructure conveyance components as needed to relocate infiltration facilities further from steep slopes. Also, there were existing policy limitations for certain maintenance activities. We borrowed some treatment concepts from other regional entities that better aligned with the current maintenance framework.

Green infrastructure or LID stormwater management practices rely on the use of vegetation and infiltration. These green systems better mimic a natural water cycle. They promote infiltration, biologic uptake of pollutants, and natural dispersion and detention. This in turn yields less runoff that is both slower and cleaner.

Many local and regional governing agencies recognize these benefits and are steering toward more natural approaches to managing runoff. However, existing codes and standards may lag behind emerging and available stormwater management technologies. Smaller communities may not have enough staff or resources to consistently update their codes and standards. They also don’t typically have the project volume or high level of external pressures to move those changes forward in a timely fashion.

When a project has an opportunity to introduce new green infrastructure options in a community, talk to the regulatory agency to better understand its stance and goals. The agency may be looking for the right showcase project to come along. Key agency staff may have specific stormwater management goals. Some agencies may have a vision for sustainability that is still forming, and they are eager to test new ways to navigate the regulatory framework or local construction practice constraints. Sit down with agency staff members and discuss their goals and concerns. This can reveal shared goals and help overcome technical roadblocks.


Having started experimental work in stream hydraulics and coastal erosion at the age of 10, Bob Thayne now tackles his client’s stormwater and flood control needs with high-tech computational modeling. “I love to figure out what the water is going to do,” says Bob. “I use that information to provide water resources solutions.” And he still likes to play with water.

Other blog articles by Bob include: Roughened channel fish passage design addresses problematic streambed materials

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