Water Quality

Every building site is part of a watershed. Water that falls onto a development's roof, parking lot, and landscaping eventually flows into adjacent low-lying areas, creeks, rivers, lakes, or oceans. Disturbing topsoil, removing permeable surfaces, and introducing chemical fertilizers and pesticides, motor oil, vehicle coolant, and pet waste all have negative impacts on water quality and the vitality of the local watershed. Chemical pollutants, increased sediment, and altered water temperature can disrupt water ecosystems and lead to unhealthy conditions for fish, animals, and humans. Increased stormwater volume, created by paving over permeable surfaces, can overwhelm the capacity of the storm drainage system (causing flooding) or water treatment infrastructure (resulting in the release of polluted water).

Stormwater infrastructure varies from region to region and from city to city. Many East Coast cities have combined stormwater and sanitary sewer systems. The benefit of combined systems is that stormwater goes to a treatment facility prior to being released into nearby rivers, lakes, or the ocean. During periods of intense rainfall, however, the treatment facility may be overloaded, resulting in the release of both stormwater and partially treated sewage. In combined-system locations, the most critical strategies are to reduce the volume of water and to slow the rate at which water enters the storm sewer to prevent overloading.

Most West Coast cities—San Francisco being one exception—have separate sewer and stormwater systems. The separation usually prevents system overloading, although some rainwater can still enter the sewer system through cracks in underground pipes. However, stormwater is usually not filtered or treated before it flows into the nearest body of water. In locations with separate systems, the most critical strategy is to remove contaminants from stormwater, either naturally or mechanically, before the water leaves the development site. The first half inch of water from each storm event—the first flush—is the most important to address, as this water contains the greatest number of pollutants from roofs, paved areas, and landscaping. In locations where the storm drain system is outdated or underdimensioned, it is also important to reduce the volume of water leaving the development site to prevent neighborhood flooding.

Practices to improve water quality include:

• During construction use U.S. Environmental Protection Agency (EPA) or local best management practices such as minimizing the area of soil disruption, preserving top-soil, installing silt fences, and providing traps or filters on adjacent storm drain inlets.

• Maintain the permeability of unbuilt portions of the site. Permeable surfaces such as gravel, decomposed granite, mulched landscape beds, and turf areas let rainwater percolate into the soil. Microorganisms in the soil then filter water as it moves slowly down to the water table.

In parking areas, pave only the drive aisles with hard surfaces, using gravel or turf for the parking spaces. For areas that require a hard surface, consider using pavers, porous asphalt, or porous concrete instead of conventional asphalt or concrete. Pave little-used vehicular areas, such as overflow parking and emergency access lanes with porous surfaces. Slope parking areas to drain toward landscaped areas, or provide grease traps and filters at drainage collection areas. For pedestrian surfaces such as walkways and patios, use pavers, gravel or other aggregate, decomposed granite, or wooden planks.

Direct stormwater runoff into recessed areas and vegetated swales for percolation and biofiltration. Route down spouts into gravel pits or other natural infiltration areas. When integrated into the site and landscape design, these systems reduce the need for conventional curb openings, pipes, and filters, thus lowering overall project costs.

Capture a portion of stormwater to reduce the flow rate during storm events and to reduce the use of potable water for irrigation. Cisterns and rain barrels are common approaches for water storage. Green roofs also store and filter water via the soil medium and allow excess water to be released slowly over several days. A green roof can capture and retain up to 75 percent of a 1-inch rainfall in the plants and growing medium.1

Plant trees to reduce peak stormwater flow by capturing water in the leaf canopy, branches, and trunk. One hundred trees can retain about 100,000 gallons of rainfall annually that would otherwise run off into the drainage system.2 Design irrigation to avoid overspray onto paved areas by using drip emitters, bubblers, or microspray sprinkler heads. Irrigation systems that spray onto sidewalks and roads can carry high concentrations of fertilizer, pesticides, pet droppings, and other pollutants into the storm drainage system. In many locations, dry-weather runoff is more contaminated than wet-weather flows.

Homeowners Guide To Landscaping

Homeowners Guide To Landscaping

How would you like to save a ton of money and increase the value of your home by as much as thirty percent! If your homes landscape is designed properly it will be a source of enjoyment for your entire family, it will enhance your community and add to the resale value of your property. Landscape design involves much more than placing trees, shrubs and other plants on the property. It is an art which deals with conscious arrangement or organization of outdoor space for human satisfaction and enjoyment.

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