Plan results may be viewed in tabular form in the Sites Table or in the site-specific web pages (accessed by site markers in the Interactive Map or via the Sites Table links). The Sites Table provides (and can be sorted by) the following information site number, town, site status / priority, whether a rapid technical assessment (RTSA) was conducted, and whether the site is a DER Priority Project. Additional information about each site is available in the site-specific pages, including acreage*, impact type, and narrative site description. Imagery is also available for each site and includes: aerial photographs, USGS topographic maps, historic maps, and photographs. Twenty-four projects also have additional information available in the form of Rapid Technical Site Assessment (RTSA) Reports. RTSA Reports can be accessed from both the Sites Table and site-specific pages. See the Navigation Help section for more information on how to navigate the Plan and access information.
Total number of sites included in the Plan: 121
Completed sites: 14
Potential sites: 107 (5 of which are currently in various
phases of project development)
Prioritization of potential sites: 10 high,
46 medium, and 51 low
Wetland Impact Types
Alterations or impairments to potential wetland restoration sites in the Plan are designated as fill, agriculture, tidal restriction, and/or other. Many sites include more than one type of impact. The "other" designation is used when there is an additional type of impact, which is described in the narrative descriptions of the site-specific pages. The numbers of sites by specific impact type are broken out as follows:
Tidal restriction: 73
Historically, alteration of wetlands was less regulated than it is today and numerous wetlands were filled to expand upland areas and for other purposes. The effects of filling wetlands are drastic and usually result in the complete loss of all wetland functions. The restoration of historically filled wetlands typically involves the excavation, removal, and re-location of fill to restore appropriate wetland soils, elevation, hydrology, and vegetation. A wide range of fill area sizes are identified in the Plan. Larger fill removal restoration projects tend to be very expensive due to the earth-moving, transportation, and disposal costs. Finding a suitable disposal site for clean fill at or near the restoration project can significantly reduce costs.
Undersized culverts constitute the majority of tidal restrictions to salt marshes. By disrupting tidal flow, tidal restrictions can alter water levels and chemistry, diminish sources of ocean nutrients, alter vegetation and habitats for fish and wildlife, reduce the ability of marshes to respond to sea level rise, and impede the flushing of pollutants out of upstream areas. Each culvert restriction site has unique characteristics that are explained in the narrative descriptions found in the site-specific pages. For some restriction sites, the differences in tidal range and salinity between the upstream and downstream openings were measured, along with other restriction-specific characteristics. When applicable, this information is available in the site's Rapid Technical Site Assessment Report (see below). While many factors must be evaluated before addressing an undersized culvert as a tidal restriction, these sites are among the most promising to remediate because the solution -- replacing the existing culvert with a larger one -- is relatively simple, absent complicating factors such as upstream flooding concerns for property and structures.
Several sites identified in the plan exhibit evidence of past and/or current agricultural alterations. These alterations typically consist of coastal wetlands that have been converted to plowed crop fields that may also be blocked from tidal flow by berms or other types of obstructions. Another type of agricultural impact is caused by runoff of potentially polluted water from cropland into adjacent coastal wetlands. Examples of restoration actions for agricultural impacts include removing coastal wetlands from crop cultivation and creating vegetated upland buffer areas between croplands and wetlands to filter runoff pollutants. Cropping of salt marsh hay remains an economically important agricultural use of Great Marsh wetlands and was not identified as an impact type in this Plan.
Several sites exhibit impacts that are designated as "other" because they do not fall within the three primary designations described above. Information about these impacts is provided in the narrative site descriptions. An example "other" impact is the impoundment of freshwater on salt marsh surfaces that may be the result of historic mosquito control ditching of salt marshes. In these situations, shallow ditch spoil berms were left on the marsh surface and impede drainage of freshwater, resulting in saturation and decay of salt marsh peat. In this case, restoration options may include removal of historic spoil berms and cleaning of ditches to enhance drainage of freshwater from the marsh surface.
Mosquito Control Considerations
Rapid technical site assessments (RTSA) Summary
The control of mosquitoes throughout the Great Marsh region is an important, ongoing activity to protect public health and reduce public nuisance. Wetland restoration projects must be carefully evaluated and designed to prevent increases in mosquito breeding habitat. These projects can often reduce mosquito populations by improving marsh conditions, for example by improving the hydrologic flushing of marsh surfaces and by increasing habitats for fish that eat mosquito larvae. To ensure that restoration projects properly incorporate mosquito control considerations, WRP and other restoration partners coordinate closely with the Northeast Massachusetts Mosquito Control and Wetlands Management District.
To collect additional technical information on a subset of potential restoration sites, WRP hired a consultant to conduct Rapid Technical Site Assessments at 24 locations (see the Methodology page for more information on the RTSA work). The purpose of the RTSAs was to produce site information to aid in the evaluation of restoration potential, including field surveys, hydrologic surveys, and cost estimates. Twenty-one sites were assessed for tidal restriction impacts, and three sites were assessed for fill removal potential. Initial investigations at two sites determined that they did not offer significant restoration potential and they are not included in the RTSA reports. Individual site RTSA Reports may be accessed from individual site pages in the Plan or from the Interactive Map.
The restoration potential of 21 sites was evaluated using the standard protocol described in the RTSA Report. An additional three sites were partially evaluated after two of the original sites selected proved not to have tidal restrictions. Of the total evaluated, 18 were found to be primarily impaired by a tidal restriction, four were primarily imared by existing fill, and two were significantly impaired by both types of impacts. The affected wetland area for the sites included in the RTSAs ranges from 0.2 to 407 acres. Estimated construction costs for recommended restoration actions ranged from $25,000 to $900,000. Further details on the assessment results and restoration potential are provided in the individual RTSA Reports. While the RTSAs provide valuable planning-level information to help assess existing conditions and restoration potential, additional technical work would be needed at any of the RTSA sites to confirm restoration potential and to develop a restoration project.
*acerage - For potential projects it refers to the estimated potentially restoreable acerage. For compeleted projects it is the restored acerage.