ASK THE EXPERTS

Franco Montalto, PhD, PE

Assistant Professor, Civil, Architectural, and Environmental Engineering Department, Drexel University

Franco Montalto is a licensed civil/environmental engineer and hydrologist with 20 years of experience working in urban and urbanizing ecosystems as a practitioner, designer, and researcher. This experience includes planning, design, implementation, and analysis of natural area restoration and green infrastructure (GI) projects, featuring natural treatment systems for wastewater and stormwater management as well as water harvesting and reuse systems. In addition to serving as the president and principal engineer of eDesign Dynamics LLC (EDD), Franco directs the Sustainable Water Resource Engineering Laboratory at Drexel University, where he was appointed as an assistant professor in the Department of Civil, Architectural, and Environmental Engineering in 2007. He is a member of the advisory board of the New York City (NYC) Natural Areas Conservancy, among other organizations, and serves as co-chair of the American Society of Civil Engineers’ Technical Committee on Low-Impact Development Computational Methods. Prior to founding EDD and joining academia, Franco served as the wetlands engineer at the New Jersey Meadowlands Commission, where he was responsible for large urban wetland restoration projects, such as the engineering design of the 139-acre Mill Creek Marsh in Secaucus, New Jersey. Franco has also worked in Europe, Africa, the Caribbean, and Latin America. In addition, he was formerly a fellow at the Earth Institute at Columbia University, a Fulbright Scholar, and an adjunct professor at Cooper Union for the Advancement of Science and Art.

Q: Please tell us a bit about the watersheds where you have worked (geographical location).

A: My interest is in heavily urbanized watersheds. I work principally in the regions in which I live or have lived in NYC, Northern New Jersey, and Philadelphia, though I have also worked internationally in places like Italy, Ethiopia, Denmark, and Haiti. Work in urban and urbanizing watersheds is extremely important because the world’s population continues to urbanize and the shortcomings of traditional end-of-pipe water management strategies are now widely recognized. Innovations in urban watershed management are urgently needed.

Q: How do you define GI?

A: I define GI broadly as decentralized engineering, enhancement, or protection of multifunctional landscape features. Although the principal driver for, and characteristics of, each GI project will differ based on local conditions, all GI projects provide multiple benefits.

I wear three hats that include practitioner, researcher, and community stakeholder. As a practitioner at EDD, I am typically tasked with developing GI designs that reduce the rate and volume of runoff generated on urban catchments. However, these same designs can also provide new urban microhabitats; become a source of nonpotable water; remove pollutants; or aesthetically enhance a streetscape, alley, courtyard, playground, or park. As a researcher, I quantify how much water directed to specific GI facilities evaporates, replenishes the soil moisture, or infiltrates. These hydrologic processes underlie many important ecosystem services. Urban evapotranspiration, for example, wicks heat away from the city, mitigating the urban heat island effect. By replenishing soil moisture, GI practices can enhance the ability of urban vegetation to sustain prolonged droughts, though they can also create waterlogged conditions that are detrimental to certain types of vegetation. Infiltration can recharge local aquifers but, if promoted in the wrong places, can also create basement flooding problems or otherwise interfere with the functioning of underground infrastructure, such as buried utilities or subway tunnels.

Q: What is your experience with GI, and what reasons or decision-making processes were behind the adoption of this approach to address combined sewer overflows, whether throughout the region/area or for a specific project?

A: I have been a consultant and scientific advisor to the NYC Department of Parks and Recreation, the NYC Department of Environmental Protection (DEP), and the NYC Mayor’s Office of Long-Term Planning and Sustainability, among other organizations. All of these government divisions were interested in GI, both as a cost-effective combined sewer overflow (CSO) control strategy and to promote various urban sustainability goals. One of the most interesting periods of my career was between 2005 and 2007, when decision makers in New York began to seriously consider GI at a large scale. The case for GI was made, initially during the advisory board meetings that led to PlaNYC, the City’s blueprint for sustainability and climate change adaptation. Stakeholder input was a key part of this process. The case for GI was built further during intense debates that occurred during the Citizen’s Advisory Committee meetings held during the development of the City’s long-term control plans for CSOs and during public hearings organized by City Councilman James Gennaro, chair of the council’s Environmental Committee. Around this same time, GI was also discussed extensively in public comments associated with a variety of large redevelopment projects then underway across the city, such as the World Trade Center site, Hudson Yards in Manhattan, and Atlantic Yards in Brooklyn.

Q: What were the reasons behind your research focus in this area? Why is GI a good solution for CSOs?

A: I first became interested in GI as a CSO abatement strategy while teaching a class in 2004. I gave students in my class at Cooper Union a typical knee-of-the-curve chart that displayed how much CSOs into Brooklyn’s Gowanus Canal could be reduced using detention tanks of different sizes. I asked them to develop a similar set of curves associated with decentralized stormwater control measures. After 16 weeks of analysis, the students produced results showing GI systems to be cost-competitive with the centralized approach. After further scrutinizing the findings myself, we published it in the Journal of Landscape and Urban Planning. The publication was immediately posted on the website of the Mayor’s Office in NYC and on US Environmental Protection Agency websites. I became interested in how individual types of GI work, how their performance compares to one another, and how their benefits scale as more and more decentralized practices become installed in urban watersheds. Nine years later, my Drexel research team is studying more than 15 GI practices in NYC, New Jersey, and Philadelphia. Currently, we are also conducting paired urban catchment studies that monitor flow at the manholes, catch basins, and at the “downstream” city block for catchments that will be greened (test sites) and those that will not be greened (control sites). Using GI to reduce CSOs is wise because of all of the other ancillary benefits that GI provides, and this enhances the argument for its cost-effectiveness.

Q: Does the adoption of a GI approach to address CSOs result in regulatory issues that differ from those associated with more conventional or traditional engineering solutions to address CSOs?

A: Now that cities like NYC have committed to GI, regulators are expecting it to reliably reduce CSOs. Because GI is implemented gradually over time, I believe that cities committed to the GI approach will more easily meet regulators’ expectations than those that have elected to take a grey infrastructure approach. Since GI is implemented gradually over time, the design of specific practices can be improved as more is learned about what does and does not work. The ability for urban watershed managers to gradually refine GI system designs as successive waves of GI are built and tested is a great advantage over centralized grey approaches that are designed, built, and then subsequently not easily modified.

Q: Can you identify a few key challenges that you have encountered in implementing GI?

A: Early on, GI implementation was hindered by a lack of governmental leadership. However, the current NYC DEP Commissioner, Carter Strickland, joined the agency already with a deep interest in GI. Thanks to his leadership, the City has formally committed to GI, and implementation challenges today are largely associated with physical constraints posed by the urban environment. The siting of GI systems is constrained by mandatory setbacks from foundations, property lines, and underground utilities, as well as by the presence of high bedrock and shallow groundwater. Other considerations include on-street parking, driveways, contaminated soils, and the root systems of mature existing street trees, all of which are common in the postindustrial landscape of NYC. After all these factors are considered, the area that is actually available for GI on a typical NYC block may be very limited, and this is a key challenge. For GI to get approved and built in these kinds of environments, creative and innovative design strategies are needed. For example, on some of our most challenging projects, my firm has designed shallow, lined constructed wetlands on brownfields adjacent to building foundations. We have even used solar and human-powered pumps, float valves, and other advanced control systems to enhance and dynamically manage retention capacity. Currently, we are working on the design of a lined curbside bioswale for detention of the water quality volume in areas with high bedrock.

Another key challenge to GI implementation is the push toward standardization, which can hinder design innovation. Local officials need to standardize GI design practices to streamline the siting, design, and approval of GI systems. But if the codes become overly prescriptive, it will become very difficult to achieve the level of GI penetration needed to significantly reduce CSOs. The local officials that permit GI practices need to find ways to simplify the design and permitting process while simultaneously allowing for the development of site-specific design innovations.

Q: Beyond the goal of using GI to address pollutant loadings in receiving waters, in your experience, what other community/social or economic benefits resulted from using GI?

A: The more we can engage urban stakeholders in GI siting and design decisions, the more successful urban GI programs will be, and the more benefits this unprecedented investment in urban neighborhoods will engender. Without public support, it will be difficult and costly to maintain a decentralized network of GI facilities. On the other hand, if local residents are engaged throughout the greening process underway in their communities, they are more likely to become GI stewards. There are many ways to do this. GI systems can be incorporated into urban agriculture facilities, for example, and can become visually engaging amenities to otherwise sterile or barren urban landscapes. These projects can also motivate urban residents to attend public meetings and to participate in local government. Community-based organizations can be employed in the ongoing operation, maintenance, and monitoring of GI systems. All of this is only possible if government agencies commit to involving the public in GI decisions.

Q: What programs or assistance are available to advance the use of GI, and what criteria are used to determine what type of solution is most appropriate? Which assistance needs are being met, and which are not? Is the information getting to the practitioners?

A: In NYC, there have been multiple grant programs that have created opportunities for many designers, property owners, and other watershed stakeholders to participate in the design, construction, maintenance, and monitoring of specific GI projects. These programs have been effective at engaging and educating individuals and firms about GI. Practitioners in NYC now also have available to them the recently issued GI Design Standards released by NYC DEP’s Office of Green Infrastructure. I believe we still need to improve the baseline assessment protocol used to determine which types of GI facilities are most appropriate for specific sites. This will happen naturally as we learn more from implementation and monitoring studies.

Q: Can you share a “success story”? If so, who was involved (e.g., organizations, volunteers, or researchers)?

A: A very rewarding project for me has been helping the NYC Department of Parks and Recreation (Parks) to monitor and to build stormwater capture capabilities into their Greenstreets Program. In the past four years, we installed sensors in five different Greenstreets built in traffic islands and bumpouts. We have also established an ecological reference site, an old growth forest in Alley Pond Park in Queens. The monitored Greenstreets are hydraulically connected to impervious catchment areas in different ratios, have different inlet designs, and different stormwater storage capacities. The instrumentation, funded by the National Science Foundation, New York State Department of Environmental Conservation, and New York State Department of State, now provides real-time, continuous monitoring of climatic, hydrologic, and groundwater conditions at all the sites, which we use to help Parks improve their GI design strategies. The collaborative research effort involves both undergraduate and graduate students from Drexel, as well as a variety of engineers, landscape architects, and designers from Parks. Starting this year, the monitoring will also involve a troop of Citizen Scientists who live near the sites.

Q: Based on your experience with GI, what research or other work (e.g., coordination or programs) is still needed for its effective watershed management application?

A: We need site-specific studies that document how the GI facilities’ performance changes over time and also how the GI practices perform when subjected to extreme climatic events, such as Hurricane Irene in 2011 and Superstorm Sandy in 2012. We need to better understand the fate of infiltrated water in heavily urbanized watersheds. We need to be able to predict the GI facility density required for measurable CSO reductions. Finally, I believe we need to find efficient, constructive ways to engage urban residents in GI practice decisions in their neighborhoods.

Suggested Resources

eDesign Dynamics www.edesigndynamics.com

Sustainable Water Resource Engineering Laboratory at Drexel University website—see the Greenstreets video http://www.cae.drexel.edu/swre/home.html

Standards for Green Infrastructure (right-of-way bioswale standards for NYC) http://www.nyc.gov/html/dep/pdf/green_infrastructure/bioswales-standard-designs.pdf