South Kingstown, RI

Restoring the Green Hill Pond Watershed

Situated at the southeasterly edge of Rhode Island, South Kingstown is home to the state’s most scenic beaches and a 439-acre salt pond. Green Hill Pond is an enclosed lagoon estuary, separated from the Atlantic Ocean by the Green Hill barrier beach, that once served a robust shellfish industry. The area has been closed to shellfish harvesting since 1994, and since 2006, Green Hill Pond has been regulated under the Rhode Island Municipal Separate Storm Sewer System (MS4) General Permit, which created a total daily maximum load (TMDL) for fecal coliform to preserve the saltwater pond’s overall water quality. At the time, the Rhode Island Department of Environmental Management (RIDEM) identified the sources of bacteria were largely from wildlife, as well as humans, and canines.

Green Hill Pond receives fresh water from Teal Pond and Factory Brook, as well as tidal water flows from Ninigret Pond. Green Hill Pond is not directly connected to the Atlantic Ocean, which means it lacks the regular flow of ocean water that could naturally flush out nitrogen and bacteria. More than a decade ago, Woodard & Curran partnered with South Kingstown officials to develop a TMDL Analysis and Compliance Approach to meet the planning provisions that require TMDLs to be addressed in the municipality’s Stormwater Management Program (SWMP) Plan. More recently, the town requested Woodard & Curran’s stormwater expertise to develop a comprehensive stormwater attenuation study of the Green Hill Pond watershed and to complete engineering design plans and specifications.  The plans and specifications will be for the design of structural best management practices (BMPs), which comply with requirements of the TMDL and are designed to help reduce elevated levels of nitrogen and bacteria.

At the municipal level, Woodard & Curran identified town-owned property within the Green Hill and Ninigret Pond watersheds where stormwater filtration sites can be located to mitigate existing stormwater discharges. Woodard & Curran designed a biofiltration basin for one site to filter stormwater runoff from a residential neighborhood, which currently flows untreated to a wetland before discharging directly to the pond. At another site in Green Hill Park, Woodard & Curran identified an undersized infiltration basin and proposed a pretreatment forebay and infiltration basin expansion to improve basin functionality and treat larger runoff volumes. Finally, within municipal rights-of-way throughout the watershed, Woodard & Curran identified existing catch basins to be retrofitted using an innovative and low-cost BMP – a stone backfilled trench to infiltrate runoff from small storm events.

Getting the community involved

In addition to these stormwater filtration sites, and due in large part to the private residential nature of the watershed, South Kingstown asked its residents to help do their part to improve the water quality of Green Hill Pond. Woodard & Curran’s analysis of source pollution identified that, in addition to private septic systems, a major source of runoff comes from rooftops, driveways, and residential roadways. One solution to this problem is innovative, but rather simple to apply – rain gardens. Woodard & Curran provided several design options for area residents to use as a guide, creating gardens in shallow depressions that serve as infiltration systems for rainfall. The designs include suggestions for hardy, native plants that feed off the excess water and require little to no maintenance beyond regular weeding.

In the fall of 2023, Woodard & Curran employees joined South Kingstown Director of Public services Richard Bourbonnais and area residents to help install the first rain garden in Norma Roelke’s yard. Nearly a dozen residents near Green Hill Pond have volunteered to install a rain garden on their property, and this first garden will serve as an example for others to replicate. Working together, the group dug up an area of lawn and planted perennials Roelke had purchased from a recommended list, including milkweed, dogwood, and winterberry for pollinators and birds to reap the benefits too. Roelke told a local reporter she heard Bourbonnais present the rain garden concept at a community meeting. She said, “It was absolutely serendipitous. I never thought about [rain gardens], but as he was talking about it, it made a lot of sense.”

Rain Garden Install

Norma Roelke Breaks Ground on the First South Kingstown Rain Garden

Completed Rain Garden on Norma Roelke's Property

Woodard & Curran Employees Carly Quinn, Greg Betsold, and Danny Lopes

The rain gardens are just one educational piece in helping the community understand the nature of its watershed. However, by talking with neighbors and sharing information about the rain gardens at community events, it helps raise awareness and can drive other changes, like reducing fertilizer applications, cleaning up leaf litter, picking up after pets, and conducting regular septic system maintenance.

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With so much of the work we do being larger municipal projects that are completed by the city or town, this represented a nice change of pace. It felt like this work was more of a grassroots campaign to get the community started with the use of raingardens at a single residential home – with the hopes it spread to other residences within the community.

Brad Hart Project Manager Stormwater

Rallying the community to participate in stormwater management alleviates some pressure on the municipality, especially if there’s a community group or nonprofit, such as Friends of Green Hill Pond, willing to take the lead on educating and assisting residents with creating and maintaining rain gardens. South Kingstown’s effort has already received national recognition with a mention in the Water Environment Federation’s Smart Brief and can serve as an example for other municipalities that want to establish community-based rain garden programs.

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Woodard & Curran has a lot of new regulatory work – a lot of Clean Water Act requirements – that are driving our communities toward installation and retrofitting and stormwater infrastructure to control the quality of water that’s running off the landscape. This is one tiny example of a project we hope blossoms into a much, much bigger effort to help engage citizens to take action on their own property.

– Zach Henderson Senior Technical Leader Stormwater

As rain gardens are established on private properties around Green Hill Pond and municipal stormwater filtration sites are installed, the town hopes the salt pond can once again be safe enough for swimming and fishing.

Tips for Building a Rain Garden

  • Pick a location downslope from hard, impervious surfaces
  • Ensure the garden is far enough away the home’s foundation, septic tank, or other utility lines
  • The size of the garden should be approximately 30 percent the size of the impervious surface
  • Dig approximately 4 to 8 inches below grade to establish the garden bed
  • Add a French drain to gutters that directs roof runoff to the garden
  • Pick native perennial plants that will thrive based on the sun exposure, moisture, and soil type
  • Before mulching, lay sheets of newspaper or cardboard down to deter weed growth

Project Team

Zach Henderson Senior Technical Leader Stormwater & Flood Resiliency
Brad Hart PE Project Manager Stormwater
Greg Betsold Project Engineer Community Development
Janelle Bonn Technical Manager Stormwater
Carly Quinn PE Project Engineer Stormwater
Danny Lopes Engineer Community Development
Doug Tirrell Senior Consultant Stormwater
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