A growing number of projects are using new techniques to control storm water close to the source.
Many environmental problems are caused by attempts to overpower natural cycles, especially the water cycle. In a natural ecosystem, the ground soaks up rainwater, which then makes its way to the water table and eventually to wetlands, streams, and rivers.
In a modern community, by contrast, much rain falls on impermeable surfaces—roofs, streets, and parking lots—and then flows into storm sewers. Because little water gets absorbed by the ground, the results are lowered water tables, dried out wetlands, and streams reduced to a trickle. That is unless it rains really hard, when the ground’s inability to absorb water increases the chance of flooding.
There’s a better way. A growing movement known as Low Impact Development, or LID, is built around practices that attempt to preserve natural cycles. Done right, these practices help restore ecosystems, decrease erosion, and reduce pollution.
LID is a blend of products and design approaches, and dealers should know something about both. As LID moves into the mainstream, dealers will see more demand for products like permeable pavers, underground cisterns, and rain catchment systems. By understanding how the technology works, dealers can better advise customers on the best product for a particular application. For instance, knowing that permeable pavers aren’t recommended on slopes or areas with shallow groundwater is as basic as understanding that 2x3 SPF is used for framing and not finish work.
More information about LID is available at the Low Impact Development Center. The following is a brief overview of this burgeoning environmental movement.
The first thing to understand is that LID is poised for rapid growth, with motivation to adopt it coming from state and local codes and regulations. On the East Coast, New Jersey now requires that sites be constructed to maintain the same average pre-construction groundwater recharge, while the Maryland Storm water Act of 2007 identifies LID as the preferred storm water control method in the state. In California, regional water-quality control boards can fine developers thousands of dollars per day for exceeding runoff limits. Other states have similar rules.
Developers have long used retention ponds to hold storm runoff until it can be absorbed by the ground, but retention ponds have their own problems. For instance, many aren’t maintained. “It’s common to see ponds full of debris, with oil floating on the surface,” says Jeff Benty, sales and marketing manager with Environment 21, a storm water engineering and equipment company in Buffalo, N.Y. And a pond that’s not properly maintained can be a breeding ground for mosquitoes.
A good LID strategy replaces big ponds with smaller features spread throughout the community. They generally don’t announce themselves as LID features—most look like standard green areas—but they’re deliberately placed and contoured to let as much water as possible filter into the ground close to where it falls but away from homes and buildings. They can be implemented at the home and community level.
LID for Homes
A landscape architect decides which water management techniques to use on a particular project by observing how the site naturally handles water. A sample design might include permeable pavers in the driveway and a couple of shallow, excavated garden areas.
Because the permeable pavers soak up water before it can freeze, they have the added advantage of reducing the chance of ice in winter. The base should be a coarse material, recycled gravel mix from highway projects works well. Sand, which is often used as a base for standard pavers, eventually clogs, preventing water from seeping into the ground.
Excavated gardens could be placed in the backyard and along the edge of the property. If properly done—for instance, vegetated areas near the house should be sloped away from the foundation—they can also reduce local flooding and standing water around the house.
A number of early adopter communities have had success implementing low impact development principles and their success will make it easier for others to follow.