Green infrastructure can be a resilient, multi-benefit approach to address issues such as urban runoff pollution and climate change adaptation. A substantial number of stormwater green infrastructure projects have been built in the Bay Area over the last two decades with many lessons learned. While we have made substantial progress, there are still many more productive opportunities, asserts Keith Lichten, Associate Engineer at San Francisco Bay Regional Water Quality Control Board. In this presentation from the 2019 State of the Estuary conference, Mr. Lichten discusses the implementation challenges and opportunities of green infrastructure implementation.
He began by acknowledging the work that has already been done. The Bay Area has seen a lot of success with the substantial implementation of green stormwater infrastructure that was driven in part by development and redevelopment through first the dot com boom and now the tech boom. Substantial work has also been done through the Bay Area’s municipal stormwater programs, with most having submitted green infrastructure plans that set targets for the future.
However, there is still a ways to go. “There is a growing range of goals we want to consider attributed with green stormwater infrastructure,” he said. “Chief among these are addressing climate change related impacts, increases in peak flows and durations or rather mitigating those increases, helping to extend the life of the existing underground storm drains and delaying substantial expenditures, improving water supply resilience, reducing the number of high heat hazard days, and so forth. And of course, funding remains a challenge.”
Mr. Lichten said that the landscape scale at which green infrastructure can be most effective needs to be considered. A lot of it has already been built on the site or parcel scale, but there are opportunities for district or regional projects, as well as green streets. Green infrastructure has also been used in flood management projects like the Napa River, which improves multi-benefit effectiveness, project resilience, and reduces costs compared to traditional flood channel design.
Green infrastructure isn’t just for water, he pointed out. Urban street trees can provide shade and an inviting city environment.
Mr. Lichten noted the long and storied history to Green Infrastructure. One example is Boston Fens, designed by Frederick Law Olmsted in the late 19th century to provide a buffer for flooding and the mix of water and sewage coming down the muddy river into Boston’s back bay. At the same time, the project provided a multi-benefit venue for recreation and the connection with nature which was thought to have a civilizing influence on the increasing number or urban residents as the industrial revolution progressed.
“This actually was an early engagement with the question of how gray and green infrastructure can be mediated,” Mr. Lichten said. “He also included in this the design of a sewer interceptor.”
Green infrastructure in the Bay Area doesn’t go quite as far back, but there is a good example of early implementation with the Dust Marsh in 1983, which was a 55-acre marsh in the Fremont-Newark area. The marsh was designed to investigate how marshes could treat urban stormwater runoff. In 1996, San Leandro got into the mix in 1996 with lattice pavers, although there were lots of questions about how big they should be or how they should be maintained.
“These projects are emblematic of the municipal champions who led BMP implementation and who are still playing crucial roles,” he said. “Taking some lessons from low impact development in Prince George County in Maryland, in 1997 the Bay Area Stormwater Management Agencies Association put forth the report, ‘Start at the Source’, which helped establish an overarching philosophy or approach to green stormwater infrastructure that was to reduce and disconnect impervious surfaces, and use GSI to slow and filter runoff. This is still our approach, particularly for parcel scale work, and we’re developing broader multi-benefit scale-specific approaches for street level and district or regional-scale BMPs.”
The low impact development philosophy has been broadly implemented nationwide, which means we can now take advantage of technical studies being completed in cities like Philadelphia, New York, of Minneapolis, who are under consent decrees to reduce combined sewer overflows, he pointed out.
There have been a number of regulatory drivers for green infrastructure. In 1994, Water Board released the staff recommendations which pushed the general idea of green infrastructure and describing actions that cities could take which led to those ideas being incorporated into permits in the late 1990s to the maximum extent practicable. In 2000, technical information such as sizing and hydromodification management was gradually incorporated into permits. In 2012, there was the regional municipal stormwater permit which incorporated TMDLs.
The stormwater permits are reissued every five years so in 2020, they anticipate including or formalizing complementarity in multi-benefit planning, aligning with urban forestry plans, climate adaptation plans, and other similar planning efforts.
The slide below left shows the green infrastructure projects in Santa Clara County as of 2003; he noted there wasn’t a lot of green infrastructure at the time and almost all of it being parcel-scale.
By 2019, there was substantial implementation as shown in the slide above on the right side. These are largely private new and redevelopment projects and green street projects, some of which are funded by grants. There are also a few regional projects.
The private projects are an artifact of where redevelopment or development happens, but there are other locations where green infrastructure can be implemented more broadly.
“We know if we want to control some of our TMDL pollutants, PCBs for example, we want these to be located in old industrial or old urban areas of the Bay – places that have higher concentrations of PCBs so they are captured before they get down to the Bay,” said Mr. Lichten. “But maybe we want to have green infrastructure as part of safe routes to schools or maybe in areas with historic flooding, so the green infrastructure plans submitted by the cities are intended to help inform that future location and future design work.”
Mr. Lichten then focused on three topics: Technical and administrative including permitting, funding, and multi-objective planning.
So how do we continue to get better at getting built projects to achieve their water quality goals? While some would say we’re already there, Mr. Lichten said not quite yet, there’s still more work to be done.
“We have work to do in every category: design, construction, operation, maintenance, and especially around climate change,” he said. “There’s a question about if the water is getting from the curb into the bioretention cell? You can see, not all of it. But Philadelphia just did a study on inlet design including quantitative analysis of slopes and distance that can help inform improvements to this and in fact the SFPUC did came back and make those improvements.”
There is also the question of whether it can be built correctly. Does the contractor know what to do, do they understand the objectives, are there city inspectors that have the skills and ability to influence the outcome, and what tools are needed to operate and maintain it over time?
“In our next permit, we’re going to look at asset management as a framework to both know where everything is, create feedback loops, to basically continuously improve the design,” Mr. Lichten said.
There is also the uncertainty with climate change. Are the storms going to get more or less intense or longer or shorter? He noted that a recent study done in New York City looked at that question and found that really the biggest issue was whether there were leaves or other debris in front of the inlet into the bioretention cell, preventing water from getting in there at all.
Funding is another constraint. Mr. Lichten said they are working with MTC on providing more flexibility in transportation grants for green streets, working with cities to develop alternative compliance or trading programs, and allowing funding to be consolidated into larger and possibly more efficient regional projects as opposed to parcel scale work.
He noted that in Basel and in Berlin, they have stormwater utilities with impervious surface-based rates, which means that single family homeowners have the ability to influence what they will pay to be allowed to drain stormwater into the sewer which creates some revenue for maintenance and improvements of the system.
“Those rates also serve as a driver for better design, because even if folks are comfortable paying what they are now, they’re not sure that they’re not going to go up in the future, so there’s a driver to reduce impervious surface and to do green infrastructure,” he said.
FOCUS ON OPPORTUNITIES
Mr. Lichten then turned to future opportunities. “We want to accomplish water quality objectives, including trash control and we want to look at opportunities to manage flood flows,” he said. “Green stormwater infrastructure is not the whole answer but it may be part of the answer, and in certain neighborhoods, it may be a big part of the answer. We know heat island issues are going to become more significant, so that’s a benefit. There’s an opportunity for water supply results, and projects like Orange Memorial Park which is providing a significant water reuse opportunity next to Colma Creek.”
It’s also providing for multi-modal transportation, encouraging people to get out walking and on bikes and creating community placemaking and providing neighborhood resilience, he said. And given the limited space and the multiple goals we need to accomplish, how can we help improve the habitat that is being restored in the bay.
The picture is an example of a district-scale BMP in Minneapolis that was part of a redevelopment project which includes a giant cistern where water soaks in; it’s part of an 8-acre catchment area where a series of property owners got together in a community facilities district and funded this project that was actually less expensive and more of a community amenity then doing controls on each of the individual parcels.
As for the next steps, Mr. Lichten said they would be continuing the technical and funding work and working with the cities on their green infrastructure plans to see how far they go to achieve water quality goals.
“We suspect that many of these plans may have high goals but a certain limited amount of commitment based on the available funding, so we’re going to try and encourage increased commitment, recognizing that brings with it flexibility and self determination for permittees,” he said. “We’re going to try and recognize alternate goals setting, so we’ve seen PCBs TMDLs as drivers, so these numeric requirements, but how can we line these up with some of the other goals, such as the climate change mitigation goals for example, and connecting with those multi-benefit objectives.”
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