Windswept Bog, Nantucket Island MA: Watershed-scale Wetland Restoration and Research

*The Second and Final Phase of the Windswept Bog Restoration will be Completed in late March 2025!*

Introduction

Windswept Bog, initially constructed in the early 1900's and retired from cranberry production in 2018, sits in the northeastern corner of Nantucket Island, MA. The Nantucket Conservation Foundation, Inc. (NCF), a non-profit land conservation group with an established ecological research staff, owns this 231-acres property which contains 111 acres of natural wetlands and 39 acres of retired cranberry bog cells.

Windswept Bog is sited in a significant watershed with some surrounding residential development but primarily undeveloped conservation land. Most of the water of the watershed flows through Windswept and exits out into Polpis Harbor, a small embayment of Nantucket Island's main harbor. This project is ideally located to provide significant ecological benefit through restoration of the retired cranberry bogs to functioning wetlands.

Partners on this project include the Massachusetts Division of Ecological Restoration's Cranberry Bog Program (DER), consulting engineers at Fuss and O'Neill, contractors from SumCo Eco-Contracting and staff from NCF’s Department of Ecological Research, Stewardship and Restoration. The overall goals are restoring wetland flow and connectivity, creating natural gradients between restored wetlands and surrounding uplands, maintaining or establishing valuable plant and wildlife habitats in both wetlands and the surrounding uplands, perpetuating and enhancing public access and maximizing the restored wetland's ability to filter excess nutrients to improve water quality. For more information: https://www.nantucketconservation.org/science-stewardship/research-projects/windswept-bog-wetland-restoration/

Project Details

The project team and other research partners have spent extensive time gaining an understanding of the existing ecology of the site to inform restoration and eventually assess the results of restoration actions. Research has included a variety of topics from native turtles to hydrology and more detailed below:

• Spotted Turtle distribution and habitat use across the Windswept property.
• Wetland bird species diversity across the restoration site.
• Vegetation inventories of the cranberry bog cells and adjacent uplands with attention to documenting rare and threatened species.
• Vegetation Community composition within the bogs for comparison to post-restoration wetland vegetation composition.
• Hydrological modeling across the site using Hobo water level loggers.
• Water quality analysis of water exiting the entire Windswept system.
• Ground Penetrating Radar surveys of the bog surface to locate and document historic wetlands and peat deposits.
• Pilot study of the results of differing mechanical disturbances of the bog surface on vegetation recruitment.

Restoration Design

Using current best management practices for cranberry bog restoration, key components of restoration design include:

• Complete removal of berms to allow natural surface flow across the site and to restore connections between bogs and adjacent wetlands.
• Decommissioning (i.e., removal) of twenty-eight water control structures (WCS) located between the retired cranberry bogs and certain reservoirs. WCS are 24-inch metal culverts with an adjustable weir integrated into the “upstream” end of the culvert. During cranberry production, WCS are used to precisely manage water for draining and irrigation purposes.
• Excavation within bogs cells to lower the ground surface elevation and create semi-permanent and seasonally flooded wetlands. GPR surveys, soil excavations and hydrologic monitoring inform depth and location of sediment excavation, particularly in areas of deep peat.
• Roughening of the soil surface within the bog cells to break up the cranberry bog mat and underlying confining sand layers. This will expose native peat deposits and create microtopography to improve habitat diversity.
• Restoration of external Irrigation/Drainage Ditches to create more naturalized water flow around the bog area.
• Maintaining Stump Pond, an artificial impoundment with significant ecological value and rarity on Nantucket, and creating a new, more naturalized water flow connecting Stump Pond to the restored bog. Constructing a new flow path between Stump Pond and the downstream bog to replace the two WCS proposed for removal.
• Filling or plugging most of the lateral and perimeter ditches located within the 14 retired cranberry bogs. Depending on the location, this will be achieved during roughening of the bog surfaces, by pushing or otherwise transferring material into the selected ditches from bog surfaces, excavated berms, or both.
• Reconfiguration of the trail system and access roads. The site is currently open to the public and contains a popular trail system, which connects to a larger network off-property around Stump Pond. Since many trail segments are located on berms that will be removed, the restoration design proposes a revised trail system that seeks to maintain the same degree of public access to recreational opportunities and scenic areas throughout the site. The revised layout includes the locations of boardwalks, which will be constructed at targeted locations where berm sections are to be removed. To maintain NCF’s site access for its ongoing stewardship, maintenance, and research programs, certain crossing structures proposed are specified as being able to allow for light-duty equipment or maintenance/emergency vehicles to use the crossing.

Project Status and Timeline

The timeline of this project is as follows:

December 2023: completed project permitting and contractor selection (SumCo Eco-Contracting was contracted).
Jan to March 2024: Mobilization and implementation of Phase 1 of the wetland restoration in 7 bog cells, ~10.5 acres.
Nov 2024 to March 2025: Mobilization and implementation of Phases 2 of the wetland restoration in remaining 7 bog cells, ~29.5 acres and restoration construction completion.
Throughout Project and After Completion: Monitoring of restoration response, ongoing outreach and education.

Funding

Special thanks to the Mass. Department of Ecological Restoration, Mass. DER Cranberry Bog Program, the SNEP Watershed Implementation Grants Program of the Southeast New England Program (an initiative of the U.S. E.P.A.), Richard King Mellon Foundation, and the US Fish & Wildlife Service National Coastal Wetlands Conservation Grant Program for funding to support this project.