Green Stormwater Infrastructure - Volume 1: Primer (2017)

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26 GSI strategies can provide effective stormwater management and deliver a variety of aesthetic and economic benefits to airports, including the following: • Environmental—water quality, aquifer recharge, landscape aesthetics, streambank protection, flood mitigation, and successful compliance with the federal Clean Water Act • Economic—potentially lower capital and operation and maintenance costs for stormwater infrastructure, and reduction in facility energy and other operation costs • Social—demonstration of stewardship to communities and stakeholders • Land use—efficient use valuable property by replacing conventional landscapings Potential Cost Savings GSI can reduce operating costs if the stormwater is collected and reused, and may be more cost effective than conventional infrastructure over the long term. Case studies, such as the following, have shown that the cost of construction and installation of GSI may be 15 to 45 percent less than the cost of conventional stormwater infrastructure (U.S. EPA 2007): • Runoff treatment: The GSI installed at a New Hampshire shopping center, which can be compared to GSI landside applications at airports, saved an estimated 26 percent of the total cost for stormwater management. The $930,000 savings resulted from avoidance of the costs of piping and earthwork associated with the installation of a conventional infra- structure stormwater management system [University of New Hampshire Stormwater Center (UNHSC) 2012]. • Flood control: Better management of peak runoff during extreme weather events can reduce property damage incurred by floods (Minkel 2009; Francis 2010). Compared to traditional road and drainage design, swales along roads can attain the same runoff volume reduction goals more cost effectively (City of Seattle, n.d.). According to U.S. EPA, “these savings derive from lower costs for site grading, paving, and landscaping, and smaller or eliminated piping and detention facilities” (U.S. EPA 2012). Additional Resources • The Center for Neighborhood Technology (http://www.cnt.org/) provides guidance on mea- suring and valuing the benefits of GSI for estimating annual monetary savings. • The Green Values® National Stormwater Management Calculator (http://greenvalues.cnt. org/national/calculator.php) compares performance, costs, and benefits of GSI with conven- tional BMPs. Benefits of Green Stormwater Infrastructure

Benefits of Green Stormwater Infrastructure 27 • Post-Project Monitoring of BMPs/SUDS to Determine Performance and Whole-Life Costs. 2004. L. Lampe. Final report prepared for the Water Environment Research Foundation. WERF Report 01-CTS-21T. London, UK: IWA Publishing: http://www.iwapublishing.com/ books/9781843397168/post-project-monitoring-bmpssuds-determine-performance-and- whole-life-costs. Operation and Maintenance Costs GSI strategies for stormwater management are expected to entail lower capital and operation and maintenance costs for the airport [City of Chicago and Chicago Department of Aviation (CDA) 2012, City of Chicago 2014]. As explained in Banking on Green, “Properly functioning green infrastructure practices are premised on using natural processes rather than built systems, which requires a shift away from capital-intensive, infrequent maintenance to less-invasive tasks that may be more frequent but less expensive overall” (American Rivers et al. 2012). The cost of the operation and maintenance of GSI BMPs can be estimated using a variety of tools as noted in the Additional Resources section below. These estimates are often based on a combination of data from actual operations and standard cost-estimating tools (e.g., RS Means), and are, by their nature, dependent on regional labor and material rates. For example, Table 8 shows unit costs for estimating BMP maintenance costs developed by the Urban Drain- age and Flood Control District (UDFCD) in Denver, Colorado (costs shown are for illustrative purposes only). Additional Resources • 2012 Biennial Report, pp. 28–29. 2012. UNHSC. http://www.unh.edu/unhsc/sites/unh.edu. unhsc/files/docs/UNHSC.2012Report.10.10.12.pdf. • Best Management Practices and Low Impact Development Whole Life Cost Models: Version 2.0. 2009. Water Environment & Reuse Foundation. http://www.werf.org/bmpcost. • BMP sizing tool and BMP-REALCOST (Rational Estimation of Actual Likely Costs of Storm- water Treatment) software. 2013. UDFCD. http://udfcd.org/software. Source: UDFCD (2013). Table 8. Example table of BMP maintenance unit costs developed for an effectiveness and cost analysis model.

28 Green Stormwater Infrastructure Volume Reduction Reducing the volume of runoff using the GSI approach potentially reduces the costs associ- ated with a completely conventional infrastructure approach by minimizing the construction, installation, and maintenance of stormwater pipes and outfalls, as well as the energy costs associ- ated with pumping the runoff to the discharge location or a treatment plant. Reduction of Energy Costs By promoting infiltration of stormwater on-site, GSI reduces the amount of water that needs to be conveyed off-site. This, in turn, minimizes the energy costs associated with transporting stormwater via piping and pumps to a discharge location. Further, reusing collected stormwater on-site can yield significant savings in water use and associated energy consumption (Natural Resources Defense Council 2009). Green roofs may further reduce heating and cooling costs by providing added insulation in the summer and winter. At a larger scale, GSI appears to signifi- cantly reduce the urban heat island effect (Clark et al. 2010). Green roofs and other vegetated land covers can absorb heat and mitigate the heat island effect at airports (Velazquez 2005, Center for Neighborhood Technology 2010). As such, green roofs can provide an estimated 10 percent reduction in air conditioning costs. Because they protect the roof from mechanical damage, ultraviolet rays, and hail/extreme temperatures, green roofs can also increase the life of a standard roof two- or three-fold (City of Chicago 2003). Reduction of Flooding Damage GSI reduces the volume of stormwater runoff by reusing, infiltrating, and retaining storm- water where precipitation accumulates. The result is reduced peak runoff flow, thereby mini- mizing flood damage (such as in Figure 18) due to swollen downstream rivers and streams. Conventional retention/detention basins, though not considered GSI, also reduce peak flows and prevent downstream flooding. When applied at the scale of an entire community, imple- mentation of GSI can substantially reduce the risk of flooding. Source: Michael Baker International. Figure 18. Damage from flooding.

Benefits of Green Stormwater Infrastructure 29 Better management of peak runoff during extreme weather events can reduce property dam- age incurred by flooding. Protection of Water Quality GSI reduces pollutant loads in stormwater runoff through natural filtration by ground vegeta- tion and other natural mechanisms. This reduction in pollutants benefits downstream receiving waters, nearby residential communities, and the environment. The reduction in thermal loads, nutrients, and suspended solids entering local streams, ponds, and wetlands can be significant. Preservation of local water bodies provides increased habitat for aquatic species. Specifically, GSI protects water quality in the following ways: • Runoff from impervious surfaces (e.g., streets, roofs, and parking lots) is a major source of water pollution. GSI practices that replicate natural hydrology, such as wetland treatment systems, bioswales, and bioretention basins, serve as filtration systems that treat stormwater before discharging to nearby surface waters or eliminate stormwater by discharging to ground- water systems (Oregon State University et al. 2006, Taylor et al. 2014). • Plants and soils provide biofiltration of pollutants from impervious surfaces without the need for costly pipe maintenance and wastewater treatment (City of Seattle, n.d.). • Reducing runoff helps to maintain more consistent stream flows and to minimize tempera- ture fluctuations that can threaten aquatic habitats (Francis 2010). • Permeable pavement at a New Hampshire shopping center parking lot resulted in a 60 percent reduction in total suspended solids and an 84 percent reduction in total phosphorus found in runoff (UNHSC 2012). • In contrast to gray infrastructure, GSI is designed such that water can infiltrate into soils and percolate to the water table, providing recharge for surficial aquifers (Center for Neighbor- hood Technology 2010). The indirect benefits of clean water for public health can be difficult to quantify—particularly the mental health benefits of access to recreational opportunities and open spaces—but they are substantial and observable. Studies by the University of Illinois Landscape and Human Health Laboratory (http://lhhl.illinois.edu/all.scientific.articles.htm; accessed January 2015) have shown that trees and other types of vegetation positively impact well-being and mental health. Stewardship and Aesthetics Airports implementing GSI exhibit stewardship in their communities. Research indicates that communities and other stakeholders look favorably on the forward-thinking approach to GSI (American Rivers et al. 2012). The Chicago Department of Aviation considers the vegetated green roofs installed on top of 12 facilities at O’Hare International Airport an initiative that makes their “commitment to the environment very visible” (CDA 2015). Installing GSI typically yields the non-monetized benefit of goodwill from the nearby com- munity as well as from regulators. The aesthetics of “green” fields and plant growth offer pleasant views for neighbors and recreational opportunities for hikers and strollers. Further, GSI offers a natural aesthetic by minimizing the use of outfall structures. Conventional infrastructure collects and discharges stormwater via an outfall structure, which conspicuously discharges stormwater into the local water body. The GSI approach naturally filters runoff (by removing certain pollutants and dispersing stormwater).