Green Stormwater Infrastructure - Volume 1: Primer (2017)

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9 Descriptions of GSI Best Management Practices Bioretention Bioretention (e.g., bioretention cells, rain gardens) normally consists of a filtration bed, pond- ing area, organic or mulch layer, and plants. Bioretention BMPs function as soil-and-plant-based filtration and infiltration devices that remove pollutants through a variety of physical, biological, and chemical treatment processes. Bioretention systems can have a bottom liner where infiltra- tion into the underlying soil is undesirable and may include underdrain pipes. Performance • Bioretention facilities generally have high pollutant removal. When selecting a media mix, be aware that nutrients can leach from compost. • Depending on the permeability of the underlying soil, 30 to 100 percent of runoff volume can be infiltrated in an unlined bioretention system. Potential Issues • High sediment loads can lead to clogging of media, leading to ponding that could attract hazardous wildlife. • Vegetation can provide food, water, and shelter for hazardous wildlife. • Areas with contaminant spill potential should avoid unlined systems to prevent groundwater contamination. Maintenance Requirements • Remove trash and debris; replace mulch; prune or replace vegetation; maintain inflows, under- drains, and outflow. • Inspect after storms to ensure no standing water remains after 48 hours. Replace top mulch layer and/or media as needed to fix ponding. • Monitor wildlife use. • Haze hazardous wildlife as needed. Install netting if hazardous wildlife use persists. Airport Examples • San Diego International Airport (SAN), Minneapolis–Saint Paul International Airport (MSP), Cleveland Hopkins International Airport (CLE), SEA, and Austin–Bergstrom International Airport (AUS) use bioretention systems. GSI Best Management Practices

10 Green Stormwater Infrastructure • AUS installed bioretention systems in the access road medians (Figure 8). They are attractive to the public and are indistinguishable from conventional landscaping in both aesthetics and general maintenance requirements. • SEA uses a combination of bioretention/media filters outside of the airport operations area (AOA) to treat discharge from upstream detention ponds. Additional Resources • Massachusetts Low Impact Development Toolkit: Fact Sheet 4: Bioretention Areas. Metropol- itan Area Planning Council. 2016. http://www.mapc.org/resources/low-impact-dev-toolkit/ bioretention-areas. • Rain Gardens and Bioretention – What’s the Difference? Cascadia Consulting Group on behalf of the Washington Department of Ecology. (Additional resources are included in this white paper.) http://www.ecy.wa.gov/programs/wq/stormwater/municipal/LID/Resources/ LandscapersLIDarticle3.pdf. • Stormwater Technology Fact Sheet: Bioretention. 1999. U.S. EPA. EPA 832-F-99-012. http:// nacto.org/wp-content/uploads/2012/06/US-EPA-1999.pdf. Green Roofs Green roof design consists of a waterproof membrane supporting drainage and vegetated soil layers as shown in Figure 9. Green roofs primarily provide volume reduction through absorption and evapotranspiration of runoff. Green roofs also provide shade, increase insulation, absorb airborne contaminants, and buffer noise. Performance • Green roofs are very effective volume control measures and can retain 25 to 90 percent of precipitation. • Green roofs exhibit limited pollutant removal via filtration; however, nutrients in soil may leach back into the stormwater, resulting in a net decrease in water quality. Source: M. Barrett (© 2015). Figure 8. Bioretention at Austin–Bergstrom International Airport.

GSI Best Management Practices 11 Potential Issues • Green roofs may not be suitable in hot and/or dry climates. • Green roofs can attract hazardous wildlife or cause damage to aircraft from windblown plant matter, both of which can be mitigated through careful design. Maintenance Requirements • Visually inspect and remove weeds every 2 to 4 weeks during the growing season. • Fertilize annually for first 3 to 5 years, then as needed. • Monitor wildlife use. • Apply insecticide or vermicide as needed to decrease food source (worms and insects) for wildlife. • Trim vegetation every 2 to 3 years. • Replace when underlying roof replaced (up to 40 years). Airport Examples • Chicago O’Hare International Airport: – Green roofs on top of 12 buildings (over 300,000 ft2) – Runoff volume retention of 25 to 90 percent depending on the season • Others: MSP, CLE, Frankfurt International Airport (Germany), Airport Schiphol (Amster- dam), and Airport Ibiza (Spain) Additional Resources • Stormwater Management: Green Roofs. Website. State University of New York (SUNY) Col- lege of Environmental Science and Forestry. http://www.esf.edu/ere/endreny/GICalculator/ GreenRoofsIntro.html. Source: Pennsylvania Department of Environmental Quality. Growth Media SW Storage Media Insulation (optional) Water Proofing Membranes Figure 9. Typical green roof design.

12 Green Stormwater Infrastructure • Pennsylvania Stormwater Best Management Practices Manual. Chapter 6: Structural BMPs, BMP 6.5.1: Vegetated Roof. 2006. Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. http://pecpa.org/wp-content/uploads/Stormwater-BMP- Manual.pdf. • Minnesota Stormwater Manual: Green Roofs. Website. Minnesota Pollution Control Agency. http://stormwater.pca.state.mn.us/index.php/Green_roofs. Harvesting and Reuse Rainwater harvesting and reuse BMPs collect rainwater that can be recycled, decreasing stormwater volume and providing an irrigation water supply. These BMPs typically do not pro- vide treatment. Rather, they consist of a collection system draining to a cistern (Figure 10) or underground detention facility where water is stored before use. Performance • Pollutant removal is minimal, as rainwater does not have high levels of pollutants. • Rainwater harvesting systems have high volume reduction and reuse capacities. Volume is lost via evapotranspiration when harvested water is used for irrigation or reused within buildings for toilet flushing, cooling water, and other uses. Potential Issues • The harvesting system must not be accessible or serve as a water source to hazardous wildlife. • In many areas, collection of rainwater may be prohibited by water rights laws. Local plumbing codes may also prohibit reuse or require pretreatment of harvested water. Maintenance Requirements • Periodically monitor to ensure that captured rainwater does not become anaerobic. • If harvested water is treated prior to reuse, maintain the water quality treatment system. • Clean gutters and downspouts. Source: M. Barrett (© 2015). Figure 10. Rainwater harvesting at AUS taxi waiting area.

GSI Best Management Practices 13 • Clean reservoir annually. • Inspect and maintain to ensure system does not overflow, creating water pools. Airport Examples • Airports that have implemented or plan to implement rainwater harvesting systems include AUS, Hartsfield–Jackson Atlanta International Airport (ATL), CLE, MSP, and Gulfport– Biloxi International Airport. • AUS’s Ground Transportation Staging Area achieved LEED (Leadership in Energy and Envi- ronmental Design) Gold status in part by installing a rainwater harvesting collection system. • ATL has implemented multiple 2,500-gallon cisterns to supply water to planters on airport property and one 25,000-gallon water reservoir at the international terminal to collect and store roof runoff. Additional Resources • Rainwater Harvesting: Conservation, Credit, Codes, and Cost Literature Review and Case Studies. 2013. U.S. EPA, EPA-841-R-13-002. https://www.epa.gov/npdes/rainwater-harvesting- conservation-credit-codes-and-cost-literature-review-and-case-studies. • Rainwater Harvesting: System Planning. J. Mechell, B. Kniffen, B. Lesikar, D. Kingman, F. Jaber, R. Alexander, and B. Clayton. 2009. Texas AgriLife Extension Service, Texas A&M University System. http://greywateraction.org/wp-content/uploads/2014/11/Rainwater- Harvesting-System-Practitioner-Manual.pdf. Case Study: Oakland International Airport Oakland International Airport (OAK) is vulnerable to flooding and inundation or liquefaction due to its location on a bay fill, partially surrounded by San Francisco Bay. Controlling runoff, as well as achieving adequate water quality in water discharged into the San Francisco Bay, has therefore become a major priority for the airport. OAK has an advanced stormwater treatment system that diverts runoff from parking lots, roadways, and airport buildings to grassy swales, detention basins, and landscape areas, allowing for increased infiltration and treatment before the water is discharged. As part of a new roadway and civil work project, the airport installed bioswales and a detention basin. Stormwater runoff from approximately 90 acres of impervious land is captured and diverted to the bioswales. Almost 5 million gallons of water are treated during an average rainfall before being channeled into San Francisco Bay. In March 2010, Terminal 2 at OAK became the first passenger terminal in the United States to receive LEED Silver certification, achieved in part due to the airport’s system of bioswales. Additional Information • “OAK’s Terminal 2 Awarded LEED® Green Building Silver Certification.” Press release. http://www. portofoakland.com/press-releases/press-release-194/. • Adapting to Rising Tides: Vulnerability & Risk Assessment Report, Chapter 9: Airport. 2012. San Francisco Bay Conservation and Development Commission. http://www.adaptingtorisingtides.org/wp-content/ uploads/2014/12/Airport_VR.pdf • Going Greener: Minimizing Airport Environmental Impacts. Airports Council International–North America. http://aci-na.org/static/entransit/enviro_brochure.pdf. • “Oakland International Airport Stormwater Management Plan.” Project description. Gresham Smith and Partners. http://www.greshamsmith.com/projects/oakland-international-airport-stormwater-managemen. • “The Future of Mobility: Greening the Airport.” C. Lyster. 2013. Places Journal. https://placesjournal.org/ article/the-future-of-mobility-greening-the-airport/.

14 Green Stormwater Infrastructure Infiltration Galleries Infiltration galleries are facilities that remove stormwater pollutants and decrease stormwater volume via infiltration into the soil. There are multiple variations of these systems, including shallow basins, rock-filled trenches, and underground end-of-pipe treatment. Performance • Infiltration systems may provide up to 100 percent reduction of pollutant discharge to surface waters by infiltrating the entire design storm, filtering out contaminants. • Infiltration galleries provide up to 100 percent reduction in the volume of runoff from the design storm event, often about 1 inch of rainfall. Potential Issues • A high water table and low permeability soils can preclude the use of infiltration galleries. They should also be avoided in areas with existing groundwater contamination. • The infiltration of glycol is typically not allowed. • Pretreatment is recommended to prevent clogging and resultant ponding. Maintenance Requirements • Routine maintenance includes removal of trash and debris on the surface. Airport Examples • Infiltration galleries are common at airports and can be found in SEA, LAX, SAN (Figure 11), and many others. • LAX is implementing a $30 million infiltration project that will help remove bacteria from the runoff to protect nearby beaches. • SAN implemented an artificial turf infiltration area to treat nearly 10 acres of paved area and a design volume of approximately 18,000 cubic feet. Additional Resources • Minnesota Stormwater Manual: Types of Infiltration Trenches. Website. Minnesota Pollution Control Agency. http://stormwater.pca.state.mn.us/index.php/Types_of_Infiltration_trench. Source: J. Jolley (© 2015). Figure 11. Artificial turf infiltration system at San Diego International Airport.

GSI Best Management Practices 15 • Stormwater Management: Infiltration Trenches. Website. SUNY College of Environmental Science and Forestry. http://www.esf.edu/ere/endreny/GICalculator/InfiltrationIntro.html. • Pennsylvania Stormwater Best Management Practices Manual, Chapter 6: Structural BMPs, BMP 6.4.4: Infiltration Trench. 2006. Pennsylvania Department of Environmental Protec- tion, Bureau of Watershed Management. http://www.elibrary.dep.state.pa.us/dsweb/Get/ Document-67992/6.4.4%20BMP%20Infiltration%20Trench.pdf. • Stormwater Management Fact Sheet: Infiltration Trench. Stormwater Manager’s Resource Center. http://www.stormwatercenter.net/Assorted%20Fact%20Sheets/Tool6_Stormwater_ Practices/Infiltration%20Practice/Infiltration%20Trench.htm. Porous Pavement Porous pavement consists of an asphalt or concrete surface containing voids that allow storm- water to pass through to an underlying gravel base before infiltrating into the soil (Figure 12). Treatment and volume reduction are provided via filtration and infiltration mechanisms. Performance • Limited data is available on pollutant concentration reduction. • Up to 100 percent volume reduction is possible when located on permeable soils. Potential Issues • Load bearing capacity is a concern. Conventional porous pavement is not suitable for runways or other surfaces with heavy vehicle or commercial airplane traffic. • Contaminant spills (e.g., fuel or oils) may damage porous pavement and cause groundwater contamination via infiltration. Do not use where spills can occur, such as loading docks, fuel- ing areas (equipment and aircraft), and maintenance areas. • Porous pavement is not suitable for deicing areas due to the potential for groundwater contamination. • Weeds can grow through the porous pavement. Source: J. Jolley (© 2015). Figure 12. Porous pavement at Los Angeles International Airport.

16 Green Stormwater Infrastructure Maintenance Requirements • Perform periodic maintenance, such as sweeping, vacuum sweeping, and/or high-pressure washing. • Inspect for clogging annually and after large storms. Airport Examples • Porous pavement has been used at a many airports across the country, including LAX (largest porous parking lot on the West Coast), SAN, Denver International Airport (DEN), ATL, and Pittsburgh International Airport (PIT). It is typically well suited to use in parking lots and service roads on both the land and airside. Additional Resources • Stormwater Management: Permeable Pavement. Website. SUNY College of Environmen- tal Science and Forestry. http://www.esf.edu/ere/endreny/GICalculator/PermaPaveIntro. html. • Pennsylvania Stormwater Best Management Practices Manual, Chapter 6: Structural BMPs, BMP 6.4.1: Pervious Pavement with Infiltration Bed. 2006. Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. http://pecpa.org/wp-content/ uploads/Stormwater-BMP-Manual.pdf. • Minnesota Stormwater Manual: Permeable Pavement. Website. Minnesota Pollution Control Agency. http://stormwater.pca.state.mn.us/index.php/Permeable_pavement. Sand Filters Sand filters consist of basins that capture stormwater runoff and then filter the runoff through a bed of sand. These BMPs can be configured as either a single basin or separate sedimentation and filtration basins. Sand filters are very adaptable and can be used in areas with thin soils, high evaporation rates, and low-soil infiltration. They can also be used in limited-space areas and in places where groundwater requires protection. Case Study: Stewart International Airport Stewart International Airport (SWF) installed a 6-acre pervious asphalt pavement parking lot in 2010. The intent of this project was to expand airport parking and increase stormwater infiltration. The project cost was $9 million, and the project was designed by the Port Authority of New York and New Jersey Engineering Department. SWF staff currently maintains the parking lot by periodic vacuuming. Additional stormwater BMPs used at this site include bioswales, infiltration trenches, a large void sub-base, and rain tanks. Additional Information • Stewart Airport Pervious Asphalt Pavement. New York State Department of Environmental Conservation. http://www.dec.ny.gov/lands/73105.html. • Case Study of the Sustainable Parking Facility at Stewart International Airport. D. W. Louie, J. A. Calautti, and S. D. Murrell. 2011. First Congress of Transportation and Development Institute. ASCE Library. http://ascelibrary.org/doi/abs/10.1061/ 41167(398)33.

GSI Best Management Practices 17 Performance • Sand filters remove particles and associated pollutants very well. Dissolved constituents are not removed well. Nitrate can be present in the filter effluent. • Volume removal is very high where underlying soils are very permeable. Potential Issues • Basins may not be used in the runway safety areas where they would be a hazard for aircraft. • Sand filters are easily clogged by high sediment loads. Maintenance Requirements • Perform routine maintenance, including inspections, every quarter and after large storms for the first year of operation and typically semi-annually thereafter to ensure water does not pond for more than 48 hours. • Remove trash and debris. • Replace media (at the end of the 50-year filter life). • Monitor the facility for vegetation growth and any hazardous wildlife. Airport Examples • AUS has numerous sand filters in active and non-active airport areas (Figure 13). • SAN has constructed a number of high-rate media filters, which are similar to sand filters but are augmented with compost, zeolite, and other materials to improve removal of dissolved constituents. Additional Resources • New Jersey Stormwater Best Management Practices Manual, Chapter 9: Structural Stormwater Management Measures, 9.9: Sand Filters. 2014. New Jersey Department of Environmental Protection. http://www.njstormwater.org/bmp_manual/NJ_SWBMP_9.9.pdf. • Stormwater Management: Sand Filters Basins. Website. SUNY College of Environmental Science and Forestry. http://www.esf.edu/ere/endreny/GICalculator/SandFilterIntro.html. Source: M. Barrett (© 2015). Figure 13. Airside sand filter at Austin–Bergstrom International Airport.

18 Green Stormwater Infrastructure • Stormwater Management Fact Sheet: Sand and Organic Filter. Stormwater Manager’s Resource Center. Website. http://www.stormwatercenter.net/. Filter Strips Filter strips, also known as vegetated filter strips, are mildly sloped vegetated surfaces that treat runoff from adjacent impervious areas. These BMPs slow runoff velocities and remove pollut- ants via filtration and infiltration. Performance • Filter strip systems perform well for solids and dissolved constituent removal. Bacteria removal is typically small due to bacteria in the soil. • Runoff volume retention depends on the underlying soil. Volume reduction can range from 50 percent to almost all runoff. Potential Issues Hazardous wildlife attraction to the strip vegetation is a concern. This issue can be minimized by regular mowing to keep the grass short and using grass species, such as Zoysiagrass, centipede grass, St. Augustine grass, and tall fescue, that are the least attractive to grass-eating wildlife (Washburn and Seamans 2013). Maintenance Requirements • Mow as needed for safety and to reduce hazardous wildlife use. • Remove any sediment buildup along the pavement edge that may channelize flow into the strip. Airport Examples • SEA and AUS use filter strips in the runways and taxiways to meet runoff permit requirements (Figure 14). • Runway safety areas (RSAs) naturally create the topography needed for a filter strip. RSA requirements specify a stable, compacted, and graded area with a 3 to 5 percent traverse slope. Source: M. Barrett (© 2015). Figure 14. Filter strip at Austin–Bergstrom International Airport.

GSI Best Management Practices 19 RSAs range from 120 to 500 feet in width and 240 to 1,000 feet in length beyond the end of the runway. Additional Resources • Minnesota Stormwater Manual: Vegetated Filter Strips. Website. Minnesota Pollution Con- trol Agency. http://stormwater.pca.state.mn.us/index.php/Vegetated_filter_strips. • Pennsylvania Stormwater Best Management Practices Manual, Chapter 6: Structural BMPs, BMP 6.4.9 Vegetated Filter Strip. 2006. Pennsylvania Department of Environmental Protec- tion, Bureau of Watershed Management. http://www.elibrary.dep.state.pa.us/dsweb/View/ Collection-8305. • Low Impact Development Fact Sheet: Vegetated Filter Strips. M. Cahill, D. Godwin, and M. Sowles. 2011. Oregon State University. ORESU-G-11-003. http://extension.oregonstate. edu/stormwater/sites/default/files/VegetatedFilterStrips.pdf. Bioswales A bioswale, or vegetated swale, is a shallow, open earthen channel with a vegetated base and sides. Bioswales treat stormwater through filtration and infiltration. Performance • Bioswales exhibit moderate pollutant removal related to channel dimensions and vegetation. Bacteria removal is typically small due to bacteria in the soil. • Runoff volume retention depends on the underlying soil. Volume reduction can be substan- tial for permeable soils. Potential Issues • Sediment accumulation can cause standing water. Bioswales must be properly maintained to avoid the creation of a wildlife attractant. • A moderate slope is required to convey runoff and prevent ponding. Maintenance Requirements • Remove trash, debris, and accumulated sediment. • Mow regularly and maintain vegetation health. • Monitor wildlife use. • Maintain outfall wildlife exclusion devices. Airport Examples • Bioswales are widely used at airports including LAX, SEA (Figure 15), SAN, ATL, DEN, CLE, and Baltimore/Washington International Thurgood Marshall Airport. • Bioswales are used along parts of the taxiway at LAX. • SAN implemented bioswales near the car rental center. They infiltrate runoff from roof- top and roadway surfaces. Vegetation consists of native, drought-tolerant vegetation that is watered by the runoff. Additional Resources • Pennsylvania Stormwater Best Management Practices Manual. Chapter 6: Structural BMPs, BMP 6.4.8: Vegetated Swale. 2006. Pennsylvania Department of Environmental Protection, Bureau of Watershed Management. http://www.elibrary.dep.state.pa.us/dsweb/View/ Collection-8305.

20 Green Stormwater Infrastructure • Minnesota Stormwater Manual: Permeable Pavement. Website. Minnesota Pollution Control Agency. http://stormwater.pca.state.mn.us/index.php/Permeable_pavement. • Urban Street Design Guide. Bioswales. National Association of City Transportation Officials. http://nacto.org/publication/urban-street-design-guide/street-design-elements/stormwater- management/bioswales/. Wetland Treatment Systems Wetland treatment systems, or engineered wetlands, are typically shallow basins that treat stormwater through settling and biological processes (Figure 16). Multiple variations of this BMP include wet detention ponds, wet retention ponds, and reticulated wetland treatment sys- tems that have steep bank slopes and deep open water features. Performance Wetland treatment systems provide excellent nutrient removal through physical, chemical, and biological water quality treatment of stormwater runoff. The example wetland system dia- grammed in Figure 17 has a pool near the inlet to allow particulates to settle. The water then follows a meandering path through the main wetland, promoting pollutant removal by keeping water velocity slow and the residence time long. Potential Issues • Hazardous wildlife attraction is a concern and can be minimized by – Designing steep banks and deep open water features without littoral zones. – Covering open water with netting (SEA and MSP) or bird balls. Source: J. Jolley (© 2015). Figure 15. Bioswale at Seattle– Tacoma International Airport.

GSI Best Management Practices 21 Source: Michael Baker International. Figure 16. Full-scale treatment wetland. Source: Pennsylvania Department of Environmental Protection. Figure 17. Constructed wetland.

22 Green Stormwater Infrastructure – Constructing subsurface wetlands with no accessible standing water. – Covering with netting or wildlife fencing. Maintenance Requirements • Inspect before and after the wet season at a minimum. Inspect during a storm event if possible to check proper function. • Monitor wildlife use. • Inspect and maintain wildlife exclusion devices. • Haze hazardous wildlife that try to use the wetland treatment system. • Rejuvenate system every 20 to 30 years by dredging and revegetating the cells (Miller et al. 2003). Airport Examples • Buffalo Niagara International Airport completed four discrete subsurface wetland cells in 2011. During the 2010/2011 deicing season, the treatment system removed an average of 98.3 percent of 5-day biochemical oxygen demand at a loading rate of up to 44,000 lb/day (Wallace and Liner 2011). Additional Resources • Pennsylvania Stormwater Best Management Practices Manual, Chapter 6: Structural BMPs, BMP 6.6.1: Constructed Wetland. 2006. Pennsylvania Department of Environmental Protec- tion, Bureau of Watershed Management. http://www.elibrary.dep.state.pa.us/dsweb/View/ Collection-8305. • Minnesota Stormwater Manual: Stormwater wetlands. Website. Minnesota Pollution Control Agency. http://stormwater.pca.state.mn.us/index.php/Stormwater_wetlands. • Stormwater Management Fact Sheet: Stormwater Wetland. Stormwater Manager’s Resource Center. http://www.stormwatercenter.net/Assorted%20Fact%20Sheets/Tool6_Stormwater_ Practices/Wetland/Wetland.htm. • Urban Small Sites Best Management Practice Manual. Constructed Wetlands: Stormwater Wet- lands. (Saint Paul, Minnesota) Metropolitan Council. http://www.sswm.info/sites/default/ files/reference_attachments/METROCOUNCIL%20ny%20Stormwater%20Wetlands.pdf. Hybrid Stormwater Management Hybrid stormwater management is the mix of conventional stormwater infrastructure and green stormwater infrastructure. Hybrid management may benefit airports by removing pol- lutants from water while providing conveyance and flood protection. Potential benefits include reduced infrastructure costs, reduced runoff volume, and groundwater recharge via infiltration. Airport Examples • SEA uses conventional detention basins to reduce flows followed by end-of-pipe enhanced bioswales that remove nutrients. • End-of-pipe GSI allows stormwater treatment in non-active areas of the airport, decreasing hazardous wildlife attractant issues in the active area. Selection of GSI Best Management Practices GSI BMP selection depends on numerous factors, including land use, required level of pollutant removal, maintenance access requirements, and potential safety constraints. The following selec- tion matrices present BMPs recommended for landside (Table 5), airside (Table 6), and either landside or airside (Table 7) airport land use. Each BMP was described in the previous section.

Airport Area Climate Potentially Suitable GSI Hydrology and Other Site Considerations Effort Required for Maintenance Expected Maintenance Activities Regulatory Issues to Address During Design Commercial Buildings (Landside) All climates Bioretention Sediment loads not excessive Moderate T, M, V, St Potential wildlife attractant Infiltration Galleries Water table not too shallow, permeable soils, no underlying groundwater or soil contamination Low to moderate T None Sand Filters Sediment loads that are not excessive Low to moderate T, M Potential wildlife attractant if standing water persists More than 12 inches of rain/year Bioswales Slope adequate to avoid standing water Low T, Sed, V Potential wildlife attractant when there is standing water Wet climates Wetland Treatment Systems High water table or wet climate Low to moderate V Potential wildlife attractant Parking Lot (Landside) All climates Bioretention Sediment loads not excessive Moderate T, M, V, St Potential wildlife attractant Infiltration Galleries Water table not too shallow, permeable soils, no underlying groundwater or soil contamination Low to moderate T None Porous Pavement Sediment loads not excessive Moderate to high Sed, St, V Load capacity Sand Filters Sediment loads not excessive Low to moderate T, M Potential wildlife attractant if standing water persists More than 12 inches of rain/year Bioswales Slope adequate to avoid standing water Low T, Sed, V Acceptable within runway safety and taxiway safety areas if slope meets FAA safety area requirements, potential wildlife attractant when there is standing water Wet climates Wetland Treatment Systems High water table or wet climate Low to moderate V Potential wildlife attractant Terminals (Landside portion) All climates Bioretention Sediment loads not excessive Moderate T, M, V, St Potential wildlife attractant Harvesting and Reuse None Moderate to high Sed, St, V Potential wildlife attractant, local plumbing codes, and water rights laws Infiltration Galleries Water table not too shallow, permeable soils, no underlying groundwater or soil contamination Low to moderate T None Sand Filters Sediment loads not excessive Low to moderate T, M Potential wildlife attractant if standing water persists Not arid or excessively hot Green Roofs Relatively flat roof Moderate V Potential wildlife attractant More than 12 inches of Bioswales Slope adequate to avoid standing water Low T, Sed, V Acceptable within runway safety and taxiway safety areas if slope rain/year meets FAA safety area requirements, potential wildlife attractant when there is standing water Wet climates Wetland Treatment Systems High water table or wet climate Low to moderate V Potential creation of a wildlife attractant V = Vegetation – all forms of vegetation maintenance, including replacement, pruning, and mowing M = Media – replacement or other maintenance of media such as mulch, soil, and sand T = Trash – removal of trash St = Structural – maintenance of inflows, drains, outlets, and gutters Sed = Sediment – management of sediment via vacuuming or sweeping, or removal of accumulated sediment Table 5. Landside GSI BMP selection matrix.

24 Green Stormwater Infrastructure Airport Area Climate Potentially Suitable GSI Hydrology and Other Site Considerations Effort Required for Maintenance Expected Maintenance Activities Regulatory Issues to Address During Design Parking Areas (Airside) All climates Infiltration Galleries Water table not too shallow, permeable soils, no underlying groundwater or soil contamination Low to moderate T None Sand Filters Sediment loads not excessive Low to moderate T, M Potential wildlife attractant if standing water persists More than 12 inches of rain/year Bioswales Slope adequate to avoid standing water Low T, Sed, V Acceptable within runway safety and taxiway safety areas if slope meets FAA safety area requirements, potential wildlife attractant when there is standing water All but the driest climates Filter Strips None Low V Potential wildlife attractant, mowing height dictated by FAA regulations Ramp/Apron (Airside) All climates Infiltration Galleries Water table not too shallow, permeable soils, no underlying groundwater or soil contamination Low to moderate T None All but the driest climates Filter Strips None Low V Potential wildlife attractant, mowing height dictated by FAA regulations Runways (Airside) More than 12 inches of rain/year Bioswales Slope adequate to avoid standing water Low T, Sed, V Acceptable within runway safety and taxiway safety areas if slope meets FAA safety area requirements. Potential wildlife attractant when there is standing water. All but the driest climates Filter Strips None Low V Potential wildlife attractant, mowing height dictated by FAA regulations Taxiways (Airside) More than 12 inches of rain/year Bioswales Slope adequate to avoid standing water Low T, Sed, V Acceptable within runway safety and taxiway safety areas if slope meets FAA safety area requirements, potential wildlife attractant when there is standing water All but the driest climates Filter Strips None Low V Potential wildlife attractant, mowing height dictated by FAA regulations V = Vegetation – all forms of vegetation maintenance, including replacement, pruning, and mowing M = Media – replacement or other maintenance of media such as mulch, soil, and sand T = Trash – removal of trash Sed = Sediment – management of sediment via vacuuming or sweeping, or removal of accumulated sediment Table 6. Airside GSI BMP selection matrix.

GSI Best Management Practices 25 Airport Area Climate Potentially Suitable GSI Hydrology and Other Site Considerations Effort Required for Maintenance Expected Maintenance Activities Regulatory Issues to Address During Design Facility Buildings (Landside or airside) Not arid or excessively hot Green Roofs Relatively flat roof Moderate V Potential wildlife attractant All climates Harvesting and Reuse None Moderate to high Sed, St, V Potential wildlife attractant, local plumbing codes, water rights laws Roadways (Landside or airside) All climates Bioretention Sediment loads not excessive Moderate T, M, V, St Potential wildlife attractant Infiltration Galleries Water table not too shallow, permeable soils, no underlying groundwater or soil contamination Low to moderate T None Porous Pavement Sediment loads not excessive Moderate to high Sed, St, V Load capacity Sand Filters Sediment loads not excessive Low to moderate T, M Potential wildlife attractant if standing water persists More than 12 inches of rain/year Bioswales Slope adequate to avoid standing water Low T, Sed, V Acceptable within runway safety and taxiway safety areas if slope meets FAA safety area requirements, potential wildlife attractant when there is standing water All but the driest climates Filter Strips None Low V Potential wildlife attractant, mowing height dictated by FAA regulations Wet climates Wetland Treatment Systems High water table or wet climate Low to moderate V Potential wildlife attractant V = Vegetation – all forms of vegetation maintenance, including replacement, pruning, and mowing M = Media – replacement or other maintenance of media such as mulch, soil, and sand T = Trash – removal of trash St = Structural – maintenance of inflows, drains, outlets, and gutters Sed = Sediment – management of sediment via vacuuming or sweeping, or removal of accumulated sediment Table 7. Airside or landside GSI BMP selection matrix.