The first two in a series of planned nature-based stormwater treatment systems were recently completed in the Three Bays watershed in Barnstable. Across Cape Cod many of our coastal waters like the Three Bays are threatened and impaired by excess nutrients and bacteria coming from human activities on land. Bacteria from pet and wildlife waste cause beach and shellfish closures and the nitrogen from septic, fertilizers and stormwater results in coastal algal blooms and fish kills.
The new rain garden at Cordwood Landing in Cotuit captures and treats rain runoff flowing into Cotuit Bay, and the sand filter at Prince Cove Marina removes pollution before entering Prince Cove. Both systems are designed to maximize removal of bacteria and nitrogen to help clean up our waters. These “green infrastructure” systems do this by using native plants, specific soils, and design conditions that filter and break down pollutants from stormwater before it flows into the bays.
The systems were designed and constructed as part of a project managed by the Association to Preserve Cape Cod in partnership with the Town of Barnstable Department of Public Works, Horsley Witten Group, Barnstable Clean Water Coalition and the Barnstable Land Trust.
“The Town of Barnstable is seeking to lead the way in installation of alternative stormwater systems such as these and has worked closely with the team throughout the project on planning, design and oversight of construction,” said Dan Santos, Barnstable Department of Public Works director.
Both sites were designed using native plants reducing maintenance needs, and providing habitat for wildlife and pollinators while addressing the problem unique to each site. The design at Cordwood Landing includes not only the new rain garden but also improvements to an existing system up the road previously installed by the Town.
“Balancing form and function were key when designing these systems,” explained Michelle West, project manager and water resources engineer with Horsley Witten Group. “For example, at Cordwood Landing, we stabilized the water access using porous pavers. The pavers prevent erosion of sediment that carries bacteria and other pollutants, allow rainwater to soak into the ground and stabilize the access for the public. It’s a win, win, win!”
The Barnstable Land Trust, which owns the land, and the Nature Conservancy, which holds the conservation restriction, gave permission to use the space adjacent to Prince Cove Marina for the second of the two new systems. “At the Barnstable Land Trust, our mission is to conserve land to protect and restore Barnstable’s natural resources,” said Janet Milkman, Barnstable Land Trust executive director. “This project amplifies the ability of the Prince Cove conservation parcel to protect and restore the land and water around it.”
“This is engineering with nature,” says April Wobst, Association to Preserve Cape Cod restoration ecologist and overall project manager. “By treating water as a resource and using green designs to help rain water soak in where it falls, we can go beyond traditional stormwater treatment, which focuses more on reducing flooding of roadways than pollution removal. With this new green infrastructure approach we can do both.”
These new systems are part of a five-year project underway in the Three Bays watershed to assess, prioritize, design and install green stormwater solutions to improve water quality and habitat. Planning, design, permitting and construction is currently underway for other priority sites in the watershed, with additional systems anticipated for completion in late 2019 and early 2020.
In addition to creating new stormwater treatment systems, the Association to Preserve Cape Cod and the Town of Barnstable have partnered through Channel 18 to create a series of informational videos. The goal of the series is to educate and inform members of the public about what they can do to help keep our waters clean. The first video in the series, found at https://youtu.be/BBe675pb8A8, provides an introduction to stormwater management.