Sustainable Building Technical Manual - Etn-presco.net

Sustainable development can solve watershed problems at the source. Its purpose is to (1)restore the infiltrating, cleansing, and storing functions of soils, plants, and groundwaterby preserving natural systems; (2) restore the permeability of constructed pavements; and(3) capture and treat excess runoff by means of natural soil and biological processes.Water conservation, efficiency, and management arise from preserving, restoring, takingadvantage of, and working with the site’s natural systems.. ☛ SUGGESTED PRACTICES AND CHECKLISTIPreservation of Soils and Drainage Ways❑ Emphasize preservation of mature vegetated soils and lowland areas.These natural systems make the watershed work by allowing rainwater and runoff toinfiltrate the soil. In lowland areas, groundwater discharges into surface drainage ways,streams, and wetlands. 2 Stable vegetation around drainage ways and streams filtersinflowing runoff, prevents channel erosion, and creates habitats for functioning aquaticecosystems. Siting construction and earthwork away from drainage courses preservesvegetated buffers and protects stream quality.❑ Minimize pavement area.Minimizing pavement affords some preservation of mature native soils. Also, preservingexisting vegetation generates less runoff. Good practices include:– Concentrate and cluster development to reduce road paving.– Double-load parking lots to share traveling and turning lanes.– Minimize widths of road pavements.❑ Install silt fences to hold sediment on-site during construction.Silt fences should be installed before construction begins and should be maintaineduntil construction is complete and all soil surfaces are vegetated.❑ Minimize use of landscape irrigation, herbicides, pesticides, and fertilizers.In disturbed and landscaped areas, lawn and landscape maintenance can generate ahigh concentration of pesticides, nutrients, and other pollutants. 3Porous Paving Materials❑ Consider use of permeable paving materials (subject to existing codes or obtainedvariances).Permeable paving materials, such as porous asphalt (Figure 1) or porous cement concrete,are some of the most powerful tools available for maintaining and restoring naturalcycles on development sites by allowing for water infiltration close to the source.Most of the impervious portion of a typical development is in pavements for cars, notbuildings for people. In the United States we are paving or repaving a half millionacres per year. A variety of permeable paving materials, available since 1970, can beused for the vast majority of paved surfaces. Impervious pavements can be reserved forspecial situations, responding to specific on-site hazards such as swelling soils, highlyplastic soils, or steep slopes (see Chapter 7, “Site Materials and Equipment”).❑ Use permeable vegetated surfaces for occasionally used vehicular surfaces such asoverflow parking and emergency-access lanes.Permeable vegetated surfaces can be designed with reinforced turf and open-celledpavers, concrete or plastic grids with voids that are filled with topsoil or aggregate. 4❑ Build pedestrian surfaces, such as walkways and patios, with loose aggregate,wooden decks, or well-spaced paving stones. 5