(Adapted from an article in the Fall 2008 "Great Bay Matters" by Steve Miller, CTP Coordinator, GBNERR)
At a conference in June, 2008, titled "Weathering the Storm: Managing Stormwater with Low Impact Development (LID) in Northern NE," one of the conclusions reached was that "more demonstration projects and case studies of successful LID" were needed. The Great Bay Discovery Center Campus is now such a demonstration site. The UNH Stormwater Center designed an integrated storm water management strategy for the Discovery Center as part of a parking lot improvement project. The LID strategy includes a porous asphalt parking lot, porous concrete parking and walkways, and an area of green auxiliary parking. Low Impact Development refers to stormwater management approaches that emphasize conservation and use of existing natural site features integrated with stormwater controls to more closely mimic natural hydrologic patterns. As such, the management plan utilizes the natural features of our site including the soil types, and mimics the natural hydrology by getting runoff into the ground rather than shipping it off to the surface waters of Great Bay.
 Porous asphalt is not new technology, having been used on highways for decades to improve driving visibility by reducing road spray after a rain, and to reduce road noise in areas where residential development is close to highways. The porous asphalt surface allows water to flow through it into the stone base and then infiltrate into the native soils below. Among other benefits, it has been found that porous asphalt requires 0-25 percent of the salt routinely applied to impervious asphalt to achieve equivalent or better winter de-icing and traction. This is great news, since road salt contamination of surface and sub-surface waters is a major environmental issue yet to be solved.
The Great Bay Discovery Center demonstration site will also include two parking spaces and walkways paved with porous concrete. Porous concrete functions the same as porous asphalt, in that water passes through it into the base and then into the native soils. But porous concrete has other characteristics that may make it a desired choice in some locations: The surface reflects more light and stays cooler, which is helpful in areas where heat from a dark surface is a problem, or where lighter colors will have greater visual appeal.
Another area of the Campus will be "paved" with a heavy-gauge plastic grate over a prepared gravel surface. The grate will be filled with soil and planted with grasses. This type of surface is perfect for areas that are not used for parking every day: When not in use for parking, the area looks like a lawn, allows water to pass through, provides biological filtration, and gives off oxygen.
The Coastal Training Program will be holding demonstration/workshops at the Discovery Center, and interpretive exhibits should be installed by the spring of 2009. All are welcome at any time to stop by and view the project.
(Jan. '09 update) Lou Iuliano of Ideal Concrete Block Company in Westford, MA wanted to introduce the Discovery Center staff to another alternative to porous asphalt and concrete. After some discussion, he offered to install samples of two different kinds of permeable pavers in the outdoor exhibit area: Eco-Stone and Aqua-Bric. Both feature a unique design and installation process that allows water to infiltrate into the ground, reducing storm water run-off and recharging groundwater suppli es. The Aqua-Bric is an ADA-compliant paver which looks much like antique Beacon Hill bricks, many of which were made with Great Bay clay! The Eco-Stone is a granite-like paver, which now surrounds the demo plots in the exhibit area.
The Rye Driftwood Garden Club has donated $500 to be used for plantings in and around the Porous Pavement exhibit area and the entrance to the Discovery Center. The funds will be used to purchase a maple tree and blueberry bushes for planting in the Spring of 2009.
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