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Grass Swales

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  1. Grass Swales Grass swales or channels are adaptable to a variety of site conditions, are flexible in design and layout, and are relatively inexpensive (USDOT, 1996). Generally open channel systems are most appropriate for smaller drainage areas with mildly sloping topography (Center for Watershed Protection, 1998). Their application is primarily along residential streets and highways. They function as a mechanism to reduce runoff velocity and as filtration/infiltration devices. Sedimentation is the primary pollutant removal mechanism, with additional secondary mechanisms of infiltration and adsorption. In general grass channels are most effective when the flow depth is minimized and detention time is maximized. The stability of the channel or overland flow is dependant on the erodibility of the soils in which the channel is constructed (USDOT, 1996). Decreasing the slope or providing dense cover will aid in both stability and pollutant removal effectiveness.

  2. Vegetated Roof Covers Vegetative roof covers or green roofs are an effective means of reducing urban stormwater runoff by reducing the percentage of impervious surfaces in urban areas. They are especially effective in older urban areas with chronic combined sewer overflow (CSO) problems, due to the high level of imperviousness. The green roof is a multilayered constructed material consisting of a vegetative layer, media, a geotextile layer and a synthetic drain layer. Vegetated roof covers in urban areas offer a variety of benefits, such as extending the life of roofs, reducing energy costs and conserving valuable land that would otherwise be required for stormwater runoff controls.

  3. CONSIDERATIONS

  4. LID BENEFITS • Minimizes land clearing and grading costs • Reduces infrastructure costs (streets, curbs, gutters, sidewalk) • Reduces storm water management costs (reduces or eliminates storm sewers and ponds) • Increases lot sale yields and reduces permit fees • Increases lot and community marketability • Protects site and regional water quality by reducing sediment, nutrient, and toxic loads to waterbodies • Balances growth needs with natural resource protection • Reduces municipal infrastructure and utility maintenance costs (streets, curbs, gutters, sidewalks, storm sewers and ponds) • Fosters public/private partnerships • Provides local accessibility to open spaces, recreation and wildlife areas • Preserves and protects amenities that can translate into more saleable homes and communities • Provides shading for homes and properly orients homes to help decrease monthly utility bills • Preserves integrity of ecological and biological systems • Protects site and regional water quality by reducing sediment, nutrient, and toxic loads to water bodies • Reduces impacts to local terrestrial and aquatic plants and animals • Preserves trees and natural vegetation • Creates connected corridors of wildlife habitat

  5. ECONOMICS • Compared to conventional subdivisions, environmentally-sensitive development can lower capital costs by 10 to 33 percent, due to fewer infrastructure costs. To illustrate, siting a house closer to the road reduces the length of its driveway, which lowers paving costs and adds the environmental benefit of creating less impermeable surface area. • Preserving land for open space in a cluster scenario also reduces costs for clearing and grading land by 35 to 60 percent, while it achieves reductions in total impervious cover by 10 to 50 percent. A report by the Center for • Watershed Protection on the redesign of two conventional subdivisions into open space subdivisions indicated a significant reduction – 45 to 60 percent – in the amount of nutrients carried in runoff leaving the site. From an economic perspective, studies show that homes in a cluster development setting consistently sell for a higher value than homes in conventional subdivisions.

  6. Youngstown, an urban area in central New Brunswick has been awarded the Canada Summer Games 2016. After much discussion, the old landfi ll area has come to the top of the list of proposed sites for the Games. The large landfi ll site was closed and remediated 15 years ago. The land being discussed has, in the last 5 years, started to attract populations of birds and other wildlife, and there is a large group of vocal citizens that have advised this sucessful conversion of landfi ll to natural area should be protected from the impacts of development. Youngstown offi cials have indicated that reuse of the previously developed areas is desired, but must meet current environmental standards. Soils at the site are classifi ed as “urban complex” indicating the severe alterations from a natural state. Soil samples were completed (Appendix A). For a number of years the landfi ll leachate had drained directly into the Morgan-Lee and Reeder Creeks, without pre-treatment in holding ponds, this changed in the last 10 years of the landfi ll’s existence and just now, evidence is being recorded of fi sh being seen. The Creeks are part of a recreation corridor, and popularity for canoeing, rowing and kayaking is growing. The Reeder Creek (southern creek on map) fl ows into the Morgan-Lee Creek (northern creek on map) and they enter the DeJong River, just upstream of the new drinking water intake for Youngstown. The area is surrounded by the Wildlife Refuge to the North, the light industrial park to the East, the high to moderate density residential housing and light commercial development to the South, and DeJong River to the West. Nearby land use also includes major highways. At outreach meetings, public comments have been expressed concerning the added traffi c that could be expected; noise; potential contamination of surface and ground water; and fl ooding in major storm events. The North Mound has 95 hectares, is the same elevation as the majority of St Stephen and has a slight south-facing slope, the East Mound - 195 hectares, is just slightly above sea level and at the base of a west facing slope, the South Mound 172 hectares, slopes toward the Reeder Creek and the West Mound 220 hectares, has a slight depression in the middle. One proposal for redevelopment has suggested seeking certifi cation under the Leadership in Energy and Environmental Design (LEED) program, as an indication of lowimpact design. You and your team have been asked to explain and provide examples of how the use of low-impact design can mitigate or greatly reduce the public’s concerns about environmental impacts. As well, it is very important to indicate how the site will be protected from Non Point Source Pollution from the surrounding areas. Because a development plan hasn’t been submitted yet, you will be talking in general terms but may include should suggestions of where to site a: 1. Sports arena with appropriate parking areas (1200 vehicles = approx 3.5 hectares). One concept already submitted has planned 10 hectares of the site for these uses. 2. 3 seperate areas with 500 residential units each as well as light commercial development which will each encompass approximately 15 - 20 hectares (parking will encompass approx 2 hectares at each site). Other elements of the plan should include suggestions for 1. Road Development 2. Forest areas and riparian plantings within the site 3. Storm water management facilities 4. Travel corridors for wildlife 5. Best Management Practises to continue improvements to quality of water in the Creeks and River As part of your presentation, you should explain: What is meant by “Low-impact design” (LID)? What options are possible to control the volume of storm water leaving the site? How will the heavily compacted soil affect this? What options exist for pre-treating storm water run-off before it reaches the Creek? How can thermal (heat-island) effects be avoided? How does the long-term costs compare between traditional development and low-impact? http://www.sustainablecommunities.fcm.ca/fi les/Movies/Webinar_Podcasts/2009-Webinar-Podcasts/February18-2009/Webinar_FEB1809.mov http://www.epa.gov/owow/NPS/lid/ http://www.lid-stormwater.net/background.htm http://www.lowimpactdevelopment.org/ http://www.pca.state.mn.us/index.php/water/water-types-and-programs/stormwater/stormwatermanagement/low-impact-development-stormwater-management.html http://www.cwp.org/ http://www.psp.wa.gov/stormwater.php http://www.bae.ncsu.edu/stormwater/2011lid/program.html http://www3.villanova.edu/vusp/about_us/lid-marc.htm http://www.unh.edu/unhsc/