Fitting stormwater design into the landscape
By Maureen Kelly
STORMWATER RUN-OFF is a major contributor to water quality problems in the Gulf of Maine region. Rain sends pollutants - from oily car drippings to pet droppings to fertilizer and more - pouring off roads, parking lots, and lawns directly into waterways. In early April, town planners, engineers and residents gathered at a conference in Mashpee on Cape Cod to share information about how communities can use LID to meet new federal stormwater regulations and reduce stormwater pollution. The conference was spearheaded by the Cape Cod Commission and sponsored by a number of partners including Horsley Witten Group, the Massachusetts Bays Program and the Massachusetts Office of Coastal Zone Management. LID stormwater systems are built into the landscape to capture rainwater close to where it falls, slowing the gush of water, and allowing it to seep back into the ground. Permeable paving is one tool. Other techniques use vegetation to absorb and filter run-off though plant roots, which remove nutrients and contaminants. These can be built on the roadside as grass swales or on rooftops to direct rainwater into a vegetated layer, or as in-ground bioretention areas - shallow vegetated depressions where rainwater gathers and percolates through mulch, soil, roots and gravel. The Barnstable Municipal Airport in Hyannis is another location where bioretention will be put into place. As part of major upgrades to the airport, there will be bioretention islands dotting the parking lot and grassed overflow parking areas to cut down on impervious surfaces. LID systems also function at the house level, but whether in a parking lot or someone's backyard, they require regular maintenance to remove sediment build-up and landscaping for plants. While LID systems can handle normal rainfall, watershed planning still is necessary for managing the infrequent large storms, according to Rich Claytor of Horsley Witten Group, a Cape Cod-based firm that is designing the Barnstable airport improvements. “Planning for floods is a community effort,” Claytor said, which calls for an understanding of flood-prone areas and for communities to make choices about whether to develop in flood zones or build structures for flood control or water detention. © 2006 The Gulf of Maine Times
Increasingly, communities in Massachusetts are tackling the problem by using Low Impact Development (LID). LID works with the natural landscape, conserving open space, reducing the footprint of structures by clustering buildings, minimizing paved surfaces and preserving natural hydrology.
The town of Cohassett chose LID to reduce nutrient-loading in Lily Pond, the town's drinking water supply, which has suffered from excessive algae and weed growth. A bioretention area, or “rain garden,” was planted on the shore of the pond to soak up stormwater streaming off a parking lot. The town plans to install 50 more gardens, which are expected to reduce the flow of pollutants into the pond by half.