Progress / Science

The Importance of Learning by Example: Green Infrastructure

This September, the Green Infrastructure Collaborative – the new partnership between the Department of Environmental Conservation and the Lake Champlain Sea Grant Program at the University of Vermont (UVM) – lead a Green Stormwater Infrastructure (GSI) tour of Burlington for a couple dozen Great Lakes researchers and educators visiting for a Sea Grant Network Meeting in Burlington. The group toured installations on private, municipal, and University property. What made this tour different than others of its kind was the focus on problem installations.

Becky Tharp, Green Infrastructure Collaborative program manager explains, “We could have stopped and admired dozens of perfectly functioning and visually appealing Green Infrastructure installations in Burlington. But this tour was an opportunity for scientists and educators to learn from our successes as well as our more challenging projects. It is often when things do not go according to plan that we can learn the most. We visited seven sites in total and looked for those important lessons.”

Burlington’s stormwater coordinator, Megan Moir, met the group at a Cherry Street Silva Cell installation where she discussed the benefits and challenges associated with that project. Silva Cells are supportive frame systems installed under roads and sidewalks for support while providing access to soil for street trees – allowing them to grow larger and healthier.

Silva Cells function as stormwater infrastructure when runoff is directed into the supported soil for filtration, treatment, and uptake by tree roots. The Cherry Street installation coincided with a particularly wet spring, where adjacent property owners experienced wet basements. Although a link between the soggy first floors and the Silva Cell installation hasn’t been made, Burlington disconnected the system to investigate thoroughly. A major takeaway from this project is the importance of educating and involving adjacent property owners early in the process. It also highlights how changing management approaches can be difficult for the public to understand. Champions of new technologies should be aware of the potential public skepticism and be prepared to share information about the technologies, including monitoring data if available.

A second site with learning opportunities is the pervious pavement public parking lot located at the bottom of Burlington’s College Street, right at the shore of Lake Champlain. The lot was installed with pervious concrete over six years ago – a new material at the time. Pervious concrete looks similar to the conventional variety but with a courser surface.

Great Lake scientists and Ian Anderson stand on the Storm Crete parking lot in downtown Burlington. Photo credit: Becky Tharp

Great Lake scientists and Ian Anderson stand on the Storm Crete parking lot in downtown Burlington.
Photo credit: Becky Tharp

A number of factors, including salt application, insufficient maintenance, and possible errors in the mix and installation conditions, have contributed to the concrete “raveling” or breaking apart soon after installation. Raveling clogs the pores in the concrete, making what was intended to be a pervious surface, no longer pervious. Burlington is planning to upgrade that parking lot and is researching improvements that will avoid the problems that they experienced the first time around – such as grass pavers or pervious asphalt. The lessons at this site include the importance of informed project installation and a detailed maintenance plan prior to installation. Tharp explains, “All Infrastructure– from bridges and roads to wastewater systems and stormwater systems including green stormwater infrastructure – require maintenance. New Green Infrastructure technologies often require installation details and a maintenance plan that may be new for municipalities. Training is important to improve the likelihood of success.”

When UVM’s Trinity campus parking lot required an upgrade a few years ago, Dr. Mandar Dewoolkar and his PhD student, Ian Anderson, installed monitoring equipment in dug wells under the Storm Crete® parking surface to investigate performance. Storm Crete® is similar to pour-in-place porous concrete in appearance, but it is manufactured in a factory in 5 by 5 foot panels and delivered on-site for installation. The factory curing eliminates some of the difficult-to-control realities of pouring concrete in the natural elements.

The advertised benefits of Storm Crete® include the ability to replace a single panel in the case of raveling and the accessibility of panels for cleaning (they can be lifted up with a front loader and rinsed to remove embedded particulates when necessary). In practice, this installation has had some problems with extensive raveling, uneven settling, and clogging. Ian investigated the impacts of extreme cold temperatures and salt on the material and found that while cold temperatures and freeze/thaw cycles did not degrade the panels, the addition of salt caused the concrete binding agent to break down, leading to raveling and clogging.

“The research of Dr. Dewoolkar and Ian Anderson demonstrates the benefit of having the University of Vermont investigate the functionality of these new technologies in cold climates,” said Tharp. “Other researchers on UVM campus are investigating green roofs and bioretention cells for pollutant removal and performance under climate change conditions. The University campus is serving as an incubator for Vermont-based scientific investigations to answer questions about GSI applications in our region and are providing detailed information about their performance in cold climates. This research presents an important resource for trial, error, and learning so that, moving forward, Vermont municipalities can employ these technologies with the right management and maintenance plans in place.”

Participants in the tour were impressed and appreciated the opportunity to evaluate the more practical elements of green stormwater infrastructure, such as design, installation and maintenance approaches, and benefited from discussing the lessons learned from Burlington’s experiences. One tour participant from Illinois commented that based on what she saw, Vermont is more advanced in GSI implementation than any of the Great Lakes states.

“Of course we have much to do to reach our water quality goals and achieve broad adoption of green infrastructure to better manage stormwater,” remarks Tharp. “But being out in front of the pack in research and implementation of Green Stormwater Infrastructure means that we may make mistakes. Partnering with UVM and other researchers to capture those lessons will make us more informed and prepared to successfully mitigate the water quality impacts from stormwater runoff.”

Want to take your own GSI Tour of Burlington? Check out this Google Map for some suggested stops in the Queen City: Have some suggestions that you don’t see on this list? Let us know so we can add them to the map:

Scientists get a tour of the a potential Green Roof on UVM campus.

Scientists get a tour of the Green Roof on UVM campus. Photo credit: Becky Tharp