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Infrastructure Cost

Another positive benefit of conservation design is the reduced need for infrastructure. In this case infrastructure can be defined as water, sewer, roadways/walkways and electric systems. The typical clustering of homes common in conservation design allows for lower construction and maintenance costs for the public and private sectors resulting from the reduced distance between connections and subsequent reduced need for piping, wiring, paving and fixtures like streetlights. CH2M Hill found that in clustered developments public service costs were 4%-8% lower than in large lot developments (NIPC, 2003).

Stormwater infrastructure (sewer connections) can also be reduced when natural stormwater techniques and natural landscaping are used to create bioswales, rain gardens, rain barrels, filter strips, green roofs, etc. These techniques retain a portion of the stormwater runoff on site or nearby, filtering out many pollutants and reducing the capacity needs for sewer infrastructure. Depending on how these techniques are realized and how much open space is available, conservation design developments can have a construction/infrastructure cost savings between 11% and 66% (Ibid). In more urban environments, conservation design can have a positive effect on existing infrastructure by reducing the amount of stormwater to enter sewer systems through the use of on site stormwater techniques. Local sources emphasize this can be especially important in communities that have a combined sewer system (water and wastewater) in which flooding can cause cross-contamination.

The reduction of impervious surface also supports reduced infrastructure needs. Impervious surface and stormwater runoff are directly related in terms of velocity and quantity. Impervious surface prevents stormwater from infiltrating the ground and carries the stormwater as it picks up speed to the sewer systems increasing the infrastructure capacity needs for that location and/or increasing the likelihood of flooding. Such practices can also reduce roadway/sidewalk infrastructure needs because conservation design calls for shorter driveways and sidewalks and narrower streets. By simply reducing the width of a 300 foot stretch of roadway from 28 feet to 18 feet, imperviousness is reduced by 35% and construction costs are reduced by $5,000(Ibid). As shown above, often conservation design techniques have multiple benefits for a site.

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