Low-Impact Development Urged To Limit Water Pollution

By Andrew Gorosko

Through appropriate environmental design and construction, the principles of “low-impact development” (LID) can be employed to limit water pollution, according to a state expert on water resources.

Michael Dietz, PhD, of the University of Connecticut’s Center for Land Use Education and Research (CLEAR), told those attending a land development seminar at Booth Library on March 20 that various methods can be used to counter the water pollution that results from growth.

Dr Dietz was among several environmental experts who spoke at the seminar titled, “Green Development for Blue Water.” The workshop session was sponsored by The Housatonic Valley Association (HVA), The Pomperaug River Watershed Coalition, and the Newtown Planning and Land Use Department.

In the past, water pollution largely was considered to be a “point source” occurrence, through which pollutants entered waterbodies at a specific point, such as a pipe extending outward from a factory to a river.

The US Clean Water Act addressed point-source forms of pollution and such pollution has been cleaned up to an extent, Dr Dietz explained.

The leading cause of contaminated waterbodies is now considered to be “non-point-source” pollution, which occurs when stormwater runoff flows across impervious surfaces, such as paved roads, parking lots, driveways, sidewalks, and rooftops, picking up and carrying various contaminants as it flows across the impervious landscape.

The presence of impervious surfaces results in stormwater quality and stormwater quantity problems, Dr Dietz said.

“Urban [stormwater] runoff is a major problem in this country,” he said.

Dr Dietz used charts and graphs to illustrate the relationship between the percentage of impervious surfaces in a given area and the consequent adverse effects on nearby streams.

Low-impact development techniques are intended to preserve the predevelopment hydrology of a site, he explained.

Such developmental design is intended to fit the natural terrain of a site, he said. Such design seeks to maintain the predevelopment vegetation and provide suitable vegetation buffers. It also limits the physical disturbance of a site, reducing the amount of impervious surfaces that would be created, compared to conventional development. The LID approach would limit the impervious surfaces on a site and provide earthen areas through which stormwater could infiltrate into the soil.

Rain gardens may be used on sites as pollution control devices, Dr Dietz said. Rain gardens are planted earthen depressions that allow flowing stormwater to be absorbed into the soil, thus significantly reducing the amount of pollution reaching streams.

If properly installed, rain gardens will serve as effective pollution control devices throughout the winter, Dr Dietz said. However, rain gardens require suitable maintenance to remain effective, he added.

Also, vegetated roofs may be employed where possible to help maintain the hydrological balance of a site, he said.

Additionally, various permeable paving systems, or those which allow stormwater to enter the soil lying beneath that pavement, help with pollution control, he said.

In a brief talk at the seminar, Rob Sibley, the town’s deputy director of planning and land use, said that low-impact development is not only intended for large-scale projects, but also can be an effective environmental protection mechanism in small projects.

Mr Sibley said various devices can lessen the pollution effects of land development, including the use of reduced curbing or alternative forms of curbing, the reduction of lawn sizes, and the use of grassy swales.

Also, instead of constructing conventional landscaping islands in commercial parking lots, depressed earthen areas, which are planted with native vegetation, can be created to absorb stormwater runoff. The presence of such devices can prevent downstream flooding, he said.

 A local example of such drainage devices can be found at The Shops at Newtown, a shopping center at 5 Queen Street that contains Caraluzzi’s Newtown Food Market, he said.