At the community level, the engineer can test soil absorption on different parts of the site and then do some computer modeling to determine what techniques to use where.

Choices include:

Bio-retention cells. These consist of planted buffer areas, sand beds, and small ponding areas.

Vegetated swales are usually placed along residential streets or highways. They are shallow channels with grass or other plants that reduce runoff velocity.

Filter strips. Also called buffer strips, they can be planted along a community natural water feature like a stream or pond The strip is supposed to catch polluted runoff from roads before it can enter the water. Filter strips can also be placed within parking lots to collect and absorb flow from large expanses of concrete or asphalt.

Cistern collection systems. If codes allow, these can be used to store rainwater for dry-period irrigation, rather than channeling it to streams.

Permeable pavers are most common on individual homes but have also been used for parking areas. Proponents say that costs be can offset by the fact that the pavers reduce the need for storm drains.

Underground chambers consist of large, buried half-pipes over a bed of gravel. They can be used in place of conventional storm drains to manage runoff from large storms and are appropriate for large and small projects. For instance, DS Martin, an excavation contractor in Wrightsville, Pa, was called in to solve flooding problems in a three-house subdivision a few years ago. The contractor used underground chambers to catch and absorb excess runoff before it reached the homes.

Note that local codes may limit chamber placement. Joe Miskovich, president of Triton Stormwater Solutions, a chamber manufacturer in Brighton, Mich., recalls working on a property where the town demanded that the chambers be placed 50 feet from the septic system’s leach field. “They were afraid that the leach field might get saturated and back up the septic,” he says.

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