Green Stormwater Infrastructure - Volume 2: Guidebook (2017) / Chapter Skim
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Pages 33-59
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33 Follow-up information for each BMP type is provided in this section. The nine types of GSI BMPs are as follows: • BMP 1: Bioretention (bioretention cells, rain gardens)
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34 Green Stormwater Infrastructure BMP 1: Bioretention (Bioretention Cells, Rain Gardens) Bioretention BMPs function as soil-and-plant-based filtration devices that remove pollutants through physical, biological, and chemical interactions between the pollutants in the runoff and the plants and organic media in the BMP.
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Understanding GSI Best Management practices 35 of the planting media can also be adjusted as needed. In areas with a shallow water table or low permeability soil, bioretention can be implemented with an underdrain.
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36 Green Stormwater Infrastructure areas to minimize wildlife attraction. Martin State Airport considered bioretention during hangar development, but because of hazardous wildlife use concerns, runoff from the hangar area is directed to the drainage system.
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Understanding GSI Best Management practices 37 BMP 2: Green Roofs (Vegetated Roofs, Rooftop Gardens) A green roof is a vegetative layer grown on a rooftop.
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38 Green Stormwater Infrastructure Green roofs are typically designed and installed by specialist companies. Each company tends to have proprietary aspects to their designs, with components that can be customized for a particular installation.
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Understanding GSI Best Management practices 39 Potential Issues and Constraints The main concern regarding the use of green roofs is hot and/or dry climates. Several airports, including Los Angeles International Airport, San Diego International Airport, Dallas/Fort Worth International Airport, Southwest Florida International Airport, and Naples Municipal Airport, expressed concerns about the use of green roofs due to low rainfall conditions.
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40 Green Stormwater Infrastructure BMP 3: Harvesting and Reuse (Rain Barrels, Cisterns) Rainwater can be harvested from rooftops, stored using rain barrels and cisterns, and later reused in a variety of ways, e.g., landscape irrigation.
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Understanding GSI Best Management practices 41 Runoff Volume Control Harvesting and reuse allows for up to 100 percent reduction in the volume of runoff from the design storm event. This can be a very important consideration in locations where combined sewer overflows occur.
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42 Green Stormwater Infrastructure BMP 4: Infiltration Galleries (Infiltration Trenches, Infiltration Basins) An infiltration gallery is a stone-filled trench with no outlet that receives stormwater runoff (see Figure 11)
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Understanding GSI Best Management practices 43 shallow infiltration galleries, where nearly one-third of the 30 acres of the new runway has been designed to drain into a 1.75 acre infiltration gallery covered with artificial turf. The infiltration gallery is composed of 3 to 4 inches of crushed rock that captures and infiltrates approximately 18,000 cubic feet of stormwater runoff.
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44 Green Stormwater Infrastructure Maintenance Requirements and Indications of the Need for Maintenance The primary maintenance activity for infiltration galleries is the removal of any trash or debris from the surface of the infiltration gallery. This activity is critical in the airside areas to prevent the generation of FOD.
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Understanding GSI Best Management practices 45 BMP 5: Porous Pavement (Permeable Pavement, Porous Asphalt, Pervious Concrete, Pavers) Porous pavement is a type of pavement that allows rain to pass through the surface.
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46 Green Stormwater Infrastructure does not need to be permeable. Consequently, designs often vary in the amount and location of the permeable sections, as shown in the two examples in Figures 14 and 15.
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Understanding GSI Best Management practices 47 Runoff Volume Control The volume of runoff is expected to be reduced up to 100 percent when the pavement is located on permeable soils. Potential Issues and Constraints The primary constraints of porous pavement are load-bearing capacity, damage from spills, and vegetation growth.
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48 Green Stormwater Infrastructure BMP 6: Sand Filters (Media Filters) Sand filters consist of basins that capture stormwater runoff and then filter the runoff through a bed of sand in the floor of the facility.
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Understanding GSI Best Management practices 49 Design Features that May Be Customized Several components of a sand filter can be customized. Depending on the hydraulic head at the site, the ponded water depth may range from less than 1 foot to more than 5 feet, with the largest depths resulting in smaller facility footprint.
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50 Green Stormwater Infrastructure Maintenance of the filter media is necessary when the draw-down time exceeds 48 hours. When this occurs, the upper layer of sand should be removed and replaced with new material meeting the original media specifications.
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Understanding GSI Best Management practices 51 BMP 7: Filter Strips (Vegetated Filter Strips) Filter strips, also known as vegetated filter strips, are vegetated areas with shallow slopes.
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52 Green Stormwater Infrastructure Source: Seattle–Tacoma International Airport. Figure 18.
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Understanding GSI Best Management practices 53 would have to be mowed regardless of whether they were considered filter strips; therefore, there would be no additional O&M costs for this GSI practice. Replacement Needs A filter strip is expected to have an unlimited life span.
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54 Green Stormwater Infrastructure BMP 8: Bioswales (Vegetated Swales, Grassy Swales) Bioswales are vegetated channels that convey stormwater and remove pollutants by sedimentation and infiltration.
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Understanding GSI Best Management practices 55 structures, such as bioretention cells. Enhanced bioswales have engineered soils and an underdrain to provide filtration of pollutants.
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56 Green Stormwater Infrastructure include weed control practices, although herbicide use should be kept to a minimum. An integrated pest management approach can help reduce chemical use.
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Understanding GSI Best Management practices 57 BMP 9: Wetland Treatment Systems (Constructed Wetlands, Conventional Stormwater Wetlands) Constructed wetlands are facilities that create growing conditions suitable for marsh and wetland plants, which may be designed as either surface or subsurface systems (Figure 21)
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58 Green Stormwater Infrastructure Design Features that May Be Customized The primary design consideration is to ensure that there is sufficient residence time of the runoff within the wetland to allow biological processes to operate effectively. Consequently, the size of the facility will vary substantially depending on the rainfall characteristics of the area.
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Understanding GSI Best Management practices 59 Potential Issues and Constraints The main issue with wetlands is their potential to attract wildlife, primarily birds. Seattle– Tacoma International Airport and Minneapolis–St.
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