Since 2019, NCF's Department of Ecological Research, Stewardship and Restoration has been working with the Massachusetts Division of Ecological Restoration’s Cranberry Bog Program (DER) to plan a watershed-level wetland restoration project for its Windswept Bog property, located off Polpis Road in the northeastern portion of the island. Years of research, monitoring, engineering plan development, permitting, and grant writing will all be coming together in January 2024 when the project is scheduled to go to construction. NCF is extremely grateful to our project team members who worked so hard to get us to this stage: Jessica Cohn from DER and Michael Soares and Dr. Julianne Busa from Fuss & O’Neill, Inc. engineers. This project is being funded by DER and generous grants from the Southern New England Estuary Program (SNEP) Watershed Implementation Program and a private family foundation.
NCF has contracted with SumCo Eco-Contracting, a firm that specializes in ecological and environmental improvement projects with experience restoring wetlands at other retired cranberry bogs elsewhere in Massachusetts. The restoration work at Windswept is scheduled to take place over 2-3 years, with construction activities happening only during the winter dormant season (from November to mid-March) to avoid impacting rare plants, nesting birds and breeding wildlife on the property. Construction this winter will be taking place in the southwestern and northeastern portions of the property and will then proceed to the center and property entrance areas in subsequent years. Although the site will need to be closed to the public during construction for safety reasons, access will be reopened when the work is completed. Visitors will be able to view the restored wetlands as they become re-vegetated over the coming growing season via walking trails and boardwalks that will be installed across the property.
Windswept Bog, owned by Nantucket Conservation Foundation, Inc. (NCF), is located on Polpis Road in the northeastern portion of Nantucket Island, Massachusetts. Constructed and cultivated as a cranberry bog in the 1920’s, NCF acquired the property in 1980 and continued to operate the cranberry farm until 2018, with organic certification received in 2004.
In 2019, NCF’s Board of Trustees decided to retire cranberry cultivation at Windswept Bog in order to pursue a watershed level wetland restoration project. The 231-acre property, which is contiguous with several thousand acres of protected conservation land in the Middle and Eastern Moors, contains 39 acres of former cranberry bog and 111 acres of natural wetlands. The site currently contains a popular trail system, which connects to a larger network around Stump Pond and into the Middle Moors.
The decision to abandon cranberry cultivation was based on two important factors: the many economic and climate-change related challenges facing this industry across the northeast and concerns about downstream water quality and nutrient loading within Polpis and Nantucket Harbor from the bogs and larger surrounding neighborhood. This restoration project does not include the Foundation’s Milestone Cranberry Bog operation, which is still being actively farmed for cranberries.
The Foundation’s Department of Ecological Research, Stewardship and Restoration worked with staff from the DER and Fuss & O’Neill to develop wetland restoration plans for the former bogs and surrounding areas at Windswept. Through its Cranberry Bog Program, MassDER works with local, state, and federal partners to provide technical services (such as engineering, design work, permitting and construction assistance), small grants, and project management and fundraising help to landowners interested in restoring wetlands on retired cranberry bogs. The Windswept Bog Wetland Restoration was selected as a Priority Project in 2020 by DER’s Cranberry Bog Program.
The former cranberry farm at Windswept Bog is divided into fourteen discrete bogs ranging in size from 0.7 to 8.4 acres. Each bog is separated by a 2- to 6-foot-high berm with water control structures built in to manage water levels for cranberry production. Primary legacy impacts on former cranberry farms such as Windswept include: (1) a sand fill layer placed over native wetland soils, (2) lateral and perimeter ditching, berms, and water control structures, and (3) physical simplification including channel straightening. The cumulative effect of these alterations is altered hydrology, dry soils in the upper bog platform, and a trajectory toward more upland plant species over time.
The overall goals for this project include restoring wetland flow and connectivity, creating natural gradients between restored wetlands and surrounding uplands, maintaining or establishing valuable plant and wildlife habitats, perpetuating and enhancing public access, use and enjoyment of the Windswept Bog property, educating the public about the importance of restoration work, maintaining Stump Pond (a unique but human-made wetland created to serve as a reservoir for the cranberry operation back in the early 1900’s), and maximizing the restored wetland’s ability to filter excess nutrients to improve water quality in Polpis and Nantucket Harbors.
Since the early stages of this project, the Foundation’s ecology staff have been collecting information on pre-restoration site conditions. This includes capturing and tagging spotted turtles on the property and tracking their movement patterns via radio telemetry, conducting preliminary water quality monitoring at multiple sites around the wetland, creating a comprehensive species list of plants on the property to document native, rare, unusual or invasive species to be considered in the restoration process, conducting wetland bird surveys, and conducting vegetation monitoring along transects and within plots to document the pre-restoration plant communities present.
Data loggers installed at numerous locations across the property have given us understanding of how surface water and groundwater flows through the site to inform these plans. We have also surveyed nearby wetlands on Nantucket to serve as reference sites - areas of comparable size, structure, and function to what Windswept likely supported before it was altered by cranberry farming. Working with DER and Fuss & O'Neill, all this information has been incorporated into the project's restoration design plans to minimize environmental and rare species impacts to the greatest extent possible. The permitting process for the project has been completed.
Summary of the Proposed Restoration Design
Key features of the proposed restoration design for Windswept Bog involve the following:
- Complete or partial removal of most berms to allow natural surface flow across the site and to restore and establish hydrologic connections between bogs and adjacent wetlands to the greatest extent possible.
- Removal of water control structures located between the retired cranberry bogs. During cranberry production, water control structures were used to precisely manage water for draining and irrigation purposes.
- Excavation in select areas of bog cells to lower the ground surface elevation and establish areas that are expected to form semi-permanent and seasonally flooded wetlands that support wetland and/or aquatic vegetation.
- “Roughening” the surface of selected sections of bog. For retired cranberry bogs, roughening is the physical action that breaks apart the existing mat of cranberry plants and the underlying sanded surface. The goal is to expose native seed bank and peat deposits, as well as create microtopography to improve habitat diversity.
- Modification of drainage ditches located between the retired cranberry bogs or water reservoirs. These artificial, incised channels were constructed to convey water between bogs and reservoirs for cranberry farming and are not representative of natural flow paths found on the island. Drainage ditches will be restored as diffuse, vegetated flow paths that mimic the natural surface flow conditions typical on Nantucket.
- Filling or plugging the lateral and perimeter ditches located within the retired cranberry bogs to create diffuse, vegetated flow paths.
- Construction of a new flow path between Stump Pond and the downstream bog on the eastern side of the property to replace the water control structures proposed for removal. A permanent spillway transition will be constructed to maintain an adequate water level in Stump Pond.
- Reconfiguration of the trail system and access roads to allow for continued public use and provide land management equipment and emergency vehicle access. Since portions of existing trails are currently located on berms that will be removed, the restoration design proposes a revised trail system that seeks to maintain public access for passive recreational opportunities throughout the site. The revised layout includes crossing structures, such as bog bridges or boardwalks, to be constructed at key locations where berm sections will be removed.
What Will It Look Like?
Based on post-restoration vegetation response observed at similar completed cranberry bog wetland restoration projects in southeastern Massachusetts, the initial vegetation communities that rapidly establish from the seed bank are dominated by graminoids (grass-like vegetation including grasses, sedges, and rushes). Over a longer time period, shrubs and small trees may become established. There will be small pools of open water and slow flow paths that increase the amount of time that water moves from the east side of the property to the west, allowing wetland plants to uptake excess nutrients prior to existing the property at Polpis Road and heading downstream to Polpis Harbor.
If this project proceeds as planned, the first phase of construction will take place during early 2024.
We are extremely grateful to our partners at Mass DER for technical expertise and funding provided to support this project since its inception. Generous funding has also been provided by the Southern New England Estuary Program (SNEP) Watershed Implementation Program and a private family foundation.