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--- green_infrastructure [2022/08/19 11:30] – admin
+++ green_infrastructure [2024/05/07 15:04] (current) – admin
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 ====== Green Infrastructure ======
-Green infrastructure is any stormwater practice that infiltrates, evapotranspirates or reuses stormwater to reduce flows to sewer systems or surface waters. Practices that meet this requirement include, but are not limited to, the following: [[rain garden]], [[bioretention device]], [[infiltration basin]], [[grassed swale]], [[permeable pavement]], [[green roof]], planter connected to roof drainage, rain barrel and rainwater harvesting/reuse.
+Green infrastructure is any stormwater practice that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters. Practices that meet this requirement include, but are not limited to, the following: [[rain garden]], [[bioretention device]], [[infiltration basin]], [[vegetated swale]], [[permeable pavement]], [[green roof]], planter connected to roof drainage, rain barrel and rainwater harvesting/reuse.
-Dane County requires that for redevelopment with proposed impervious surface area greater than 80% of existing, the first 0.5 inches of runoff from impervious surfaces must be captured using green infrastructure.
+Dane County requires that for redevelopment with proposed impervious surface area greater than 80% of existing, the first 0.5 inches of runoff from impervious surfaces must be captured using green infrastructure. Surfaces designed to generate no runoff from a 0.5 rainfall and are approved by the local approval authority may be considered pervious when determining if this requirement applies to the site.
 =====Modeling Guidance=====
-Depending on the chosen practice, there are different ways to model that the first 0.5 inch of runoff is being treated. For simple systems that store the full volume of runoff, the calculation is a simple volume check. For more complex systems that have water being actively routed through them, some additional modeling is required. Details on how different practices must be modeled is described below.
+Depending on the chosen practice, there are different ways to model that the first 0.5 inches of runoff is being treated. For simple systems that store the full volume of runoff, the calculation is a simple volume check. For more complex systems that have water being actively routed through them, some additional modeling is required. Details on how different practices must be modeled is described below.
 ====Cisterns and rain barrels====
@@ Line 13: / Line 13: @@
 ====Rain Gardens / Bioretention Basins / Infiltration Basins / Planters====
-**Volume Method**
-Demonstrate that the ponding volume in the device (above the soil surface and below the lowest outflow device) is at least the treatment volume. This approach is conservative because it ensures that if there is suddenly 0.5 inches of runoff and there is no time for the water to infiltrate, it will be captured.
+**1. Volume Method**
+Show that the ponding volume in the device (above the soil surface and below the lowest outflow device) is at least the treatment volume. This approach is conservative because it ensures that if there is suddenly 0.5 inches of runoff and there is no time for the water to infiltrate, it will be captured.
 {{ :wiki:images:green_infrastructure_volume.png?600 |}}
-**HydroCAD**
-Using TR-55, a 0.7-inch rainfall produces 0.5-inch of runoff from an impervious surface (CN=98), as seen in Figure 1. To show that the green infrastructure practice is able to capture this runoff, a 0.7-inch 24-hour MSE4 design storm (Figure 2) must be modeled to show that no surface discharges occur (Figure 3). Due to the slow rate at which water flows through engineered soil, underground storage should not be incorporated into the model.
+**2. HydroCAD**
-[{{ :wiki:images:hydrocad_0.7_to_0.5.png?600 |Figure 1: 0.7-inch of rainfall to 0.5-inch of runoff}}]
+Using TR-55, a 0.7-inch rainfall produces 0.5 inches of runoff from an impervious surface (CN=98), as seen in Figure 1. To show that the green infrastructure is able to capture this runoff, a 0.7-inch 24-hour MSE4 design storm (Figure 2) must be modeled with no surface discharges from the practice (Figure 3). For the most common green infrastructure practices, such as bioretention and permeable pavement, this means all captured water must leave via the underdrain and/or by infiltrating into the native soils. For practices using engineered soil, underground storage should not be incorporated into the model, because of the relatively slow rate at which water flows through the soil.
-[{{ :wiki:images:hydrocad_.5_storm.png?600 |Figure 2: 0.5-inch 24-hour design storm}}]
-[{{ :wiki:images:hydrocad_no_overflow.png?600 |Figure 3: Output showing no surface overflow}}]
-{{ :wiki:images:green_infrastructure_hydrocad.png?600 |}}
+[{{ :wiki:images:hydrocad_0.7_to_0.5.png?200 |Figure 1: 0.7-inch rainfall to 0.5 inches of runoff}}]
+[{{ :wiki:images:hydrocad_.5_storm.png?400 |Figure 2: 0.5-inch 24-hour design storm}}]
+[{{ :wiki:images:hydrocad_no_overflow.png?400 |Figure 3: Output showing no surface overflow}}]
+\\
-**WinSLAMM**
+**3. WinSLAMM**
 Run the WinSLAMM model from 4/6/81 to 4/7/81 (Figure 1) and show that no surface discharges occur from the green infrastructure practice (Figure 2). A 0.7-inch storm occurs during this period, resulting in 0.5 inches of runoff.
-[{{ :wiki:images:winslamm_.5_storm.png?400 |Figure 1: Dates for modeling 0.5 of runoff}}]
+[{{ :wiki:images:winslamm_.5_storm.png?400 |Figure 1: Dates for modeling 0.5 inches of runoff}}]
 [{{ :wiki:images:winslamm_.5_overflow.png?400 |Figure 2: Output showing no surface runoff}}]
+\\
 ====Green Roofs====
-It must be shown that the volume of voids within the green roof’s growth media is equal to 0.5 inches over the contributing area.
+It must be shown that the volume of voids within the [[green roof|Green Roof’s]] growth media is equal to 0.5 inches over the contributing area.
 ====Permeable Pavement====
-It must be shown that the volume of voids in the pavement system is equal to 0.5 inches over the contributing area. The permeable pavement must be designed per the DNR technical standard and specified run-on ratio maximums.
+It must be shown that the volume of voids in the pavement system is equal to 0.5 inches over the contributing area. The [[permeable pavement]] must be designed per the DNR technical standard and specified run-on ratio maximums.
 =====Additional Guidance=====
@@ Line 50: / Line 55: @@
 For sites that are a mix of new development and redevelopment, treating the full site to new development standards is acceptable. If this approach is used,  an infiltration exemption cannot be claimed.
+====References====
+[[https://pubs.usgs.gov/circ/1496/cir1496.pdf|Green Infrastructure in the Great Lakes]]
+[[https://www.epa.gov/green-infrastructure|EPA Green Infrastructure Homepage]]