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Projects > Thompson Mill Pond Restoration Opportunity Assessment

Through a grant from the Maine Corporate Wetlands Restoration Partnership grant program, the Spruce Creek Association and the Kittery Land Trust are planning to conduct a study of the Thompson Mill Pond area of Kittery's Spruce Creek. We are hoping to get a better understand the feasibility of restoration and remediation work to one of Kittery's most beautiful, environmentally sensitive, and historic areas. The purpose of this study will be to determine the tidal curves and stormwater influences, as well as historic value and landowner interests in the partially-restricted intertidal area of an old Mill Pond, and to then assess feasibility of restoration and remediation work to the pond and its marsh, dam and stormwater features. Should there be a strong indicated need for any restoration, a procedure for remediation will be proposed for consideration.

The focus of this project is to ultimately enable greater tidal flow and diadromous fish passage in the old Mill Pond area of Spruce Creek and to restore its salt marsh while protecting the significant historical value of the site.

Thompson's Mill Pond in Kittery, METhe dam is purported to be one of Maine’s oldest mill sites. Since 1991, the Kittery Land Trust has had a conservation easement over the 9.5 acres of the dam, pond and marsh, as well as on 8.5 acres of the abutting wooded upland. The Town of Kittery owns land abutting to the East (Eagle Point park).

The site includes an approximately 75-foot long earthen dam that is open in the center (a span of about 20 feet) and allows some tidal exchange. Long-time residents in the area have noted a change in the amount of dirt and salt marsh in the pond, potentially due to silt and stormwater influences at the headwaters of this marsh area. Potential restoration options include reduction of silt loading, deepening of trench, as well as maximization of dam opening, all while preserving historical values. This feasibility work will help with future stormwater work in this area.

This grant includes approximately $11,000 of services to be provided by MCWRP partners for tidal analysis, habitat suitability assessments, topographic analysis and historical research.

UPDATE March, 2008: Based on preliminary findings of a site review conducted by Normandeau Associates, the potential to restore salt marsh on the pond appears sufficient to merit further assessment. The reduced tidal flow at low tide, infilling of sediment behind the dam, unstable marsh conditions, and presence of invasive vegetation all imply a stressed system. Identifying the sources of stress and the constraints on restoration will be important for restoration planning.

In addition to this mill pond area being an important natural resource to the Town, it’s significant value as a unique and important historical site is also in need of protection. The site includes the substantial remains of an approximately 75-foot earthen and rock mill dam dating back to 1693. At it’s center one can still find an old granite millstone and traces of wood pilings from the mill house.

To protect the historical features of this site, all activity has and will be done in consultation with the Maine Historic Preservation Commission and will require their approval. The Commission has already indicated the need for archeological surveys to be performed in conjunction with any disturbances near or at the dam site, and if funding for this cannot be found no mitigation work will be performed on this portion of the property.

The Kittery Land Trust is hopeful that the MCWRP program will now move to the second phase of the project to conduct a more detailed assessment of the status of the marsh and potential restoration options, including a better understanding of the dam’s structure and depth, analysis of the conditions behind the dam, and an exploration with the SHPO and stakeholders of the possibility of removing a portion of the dam to allow tidal flow, while preserving the remainder.

The results of these studies will guide future work and the type of restoration or management to pursue. If improved drainage via further dam removal is a viable alternative then the potential to increase tidal exchange, raise pore water salinities and decrease the groundwater table may reverse the degradation of the salt marsh. If dam removal is not an alternative, control of invasive plants, freshwater flow into the marsh and surrounding land use will be the primary management tools, although the ultimate restoration potential will be less than increased tidal range

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