GREEN INFRASTRUCTURE

CAPTURE - FILTER - INFILTRATE

Green Infrastructure can both treat and sink runoff, positively impacting water quality, and providing both ecological and social benefits to humans and local wildlife. Exploring green infrastructure design elements around D.W. Field Park could have positive implications for those who enjoy the park and its waterbodies, as well as those in the broader Taunton Watershed.

What is Green Infrastructure?

Green infrastructure (GI) is a collective term for strategies and designs that use plants, soils, and permeable materials to increase evapotranspiration and slow and sink stormwater. GI can capture and treat runoff close to where it falls, reducing the flow of untreated stormwater into sewers and surface water supplies.

What are the unique maintenance needs of Green Infrastructure?

Maintenance of GI features often differs from more traditional park and road maintenance and may require additional training. GI strategies that include plantings, such as rain gardens and vegetated swales, entail regular horticultural maintenance, such as weeding and seasonal pruning and cut backs of herbaceous vegetation. Over time, GI designs, especially permeable pavement and bioretention areas, can become clogged with trash and sediment. Soils used in GI designs also need to be replaced approximately every 10 years to maintain their ability to uptake and filter water, as well as hold nutrients for plants. (Boston Water and Sewer Commission)

GREEN INFRASTRUCTURE STRATEGIES FOR D.W. PARK

Conceptual designs presented in this planset explore the following GI strategies for managing stormwater runoff along roads and parking lots, and in key park destinations.

Bioretention/Rain Gardens/Bioswales

Bioretention areas slow, filter, and infiltrate runoff with plants, soils, and microbes. Rain gardens and vegetated bioswales filter pollutants from runoff and either sink the stormwater on site, or move runoff elsewhere with the installation of impermeable liners beneath the soil. The size of a rain garden should be 5-7% of the drainage area. (Mass Structural BMPs Volume 2, Ch 2, p 26).

Pros: High power pollutant removal of 80-90% TSS (total suspended solids) from runoff. Potential aesthetic and ecological benefits of adding plants to a landscape.

Cons: Regular horticultural maintenance required to keep plants healthy and maintain a tidy appearance.

Porous Pavement

Porous, or permeable, pavements are surfaces that include larger air voids. More water is able to infiltrate and reach the subsoils, reducing stormwater runoff from roads. While some porous pavement looks like asphalt, other options include grass and stone pavers. Porous pavement is generally not recommended for high traffic road ways, but can be effectively used for footpaths and parking stalls.

Pros: Can catch 70-80% of rainfall, and be incorporated into retrofits.

Cons: Maintenance is higher for porous pavement than regular asphalt as the material can get clogged and become impermeable. These areas should be regularly inspected, and vacuumed or washed to remove built-up detritus (Mass, Structural BMPs Volume 2, Ch 2, p 118). Sharp plows, salt, and sand can damage porous pavement materials.

Vegetated Buffers

Dense strips of plants and trees placed between waterways and roads or structures can help stablize shorelines and treat runoff. In order for buffers to function effectively, water must enter as sheet flow rather than be directed by channels, spreading out the flow and allowing time for it to more evenly infiltrate.

Pros: Vegetated buffers can treat water before it reaches waterbodies like Upper Porter Pond and Waldo Lake, while also providing habitat for wildlife. Buffers may also deter waterbirds from approaching the shoreline which could have positive implications for water quality within the park.

Cons: Vegetated buffers can be sensitive to trampling, especially while getting established. Vegetated buffers installed in places previously accessible to people may need additional protection (e.g. temporary fencing).