Salem Living Shoreline Project Report - July 2016 Salem Living Shoreline Project-
Conceptual Designs
CZM Green Infrastructure for Coastal Resilience Grant
City of Salem
May 25, 2016
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Introduction
Chester Engineers participated with Salem Sound Coastwatch and Jeff Elie of the City of Salem in the
criteria development for a site selection decision matrix and then participated in using the matrix to
prioritize approximately ten sites down to the three sites that would be evaluated further in the
Feasibility and Conceptual Design task. The Site selection process is described separately in materials
submitted to CZM. As part of that process descriptive profile were developed for each of the possible
candidate locations (also submitted to CZM separately). Data in the profiles were used in the site
evaluation process.
As part of the site selection and conceptual design process, a number of factors were considered in the
site selection and evaluation process. They included:
• Erosion rates and trends,
• Aerial photography,
• Topographic information
• Sea level rise projections
• FEMA Flood Mapping
• Nearshore geology and seafloor mapping
• Sediment and sediment transport
• Marine resources
• Current usage by the public
• Tidal Datums
Factors Entering into the Design
Erosion rates and trends
Shoreline changes maps that have been compiled in MassGIS were used to identify shoreline change in
the Salem area. A map is included as Figure 1. Details of the Shoreline Mapping Project are found in
Thieler et al, 2013.
The coast of Salem is generally rocky with interspersed coves and pocket beaches. The shoreline change
map shows that the shoreline has generally been fairly stable of the times period on the maps (going
back to the 1800’s). There are numerous sections of the coast that appear to have had accretion. In
reality these are areas that have been filled. They are low-lying and are shown to be more vulnerable to
flooding in FEMA flood maps and inundation mapping to project potential sea level rise.
Aerial photography
To assist to the review of site, aerial photography was consulted from various sources, including
MassGIS and Goggle Earth. Google Earth has historical imagery going back to about 1995. Review of
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historic photographs confirmed what was seen on the shoreline change maps, that is that the coast and
shoreline have been generally stable.
Topographic information
Detailed and accurate topographic information is critical is designing shoreline green infrastructure
projects. To assist in the interpretation of other data e.g. inundation mapping and in the formulation of
designs, detailed LIDAR mapping was downloaded and process from MassGIS. One-foot contours
referenced to NAVD88 were used in our analyses. An overview map of the Collins Cove area is included
in Figure 2. Detailed topographic information is included with the conceptual design for each of the
three candidate sites.
Sea level rise projections
An implicit objective in the conceptual designs is to make the make the specific locations more resilient
to rising sea levels. While no claim can be made in regard that the designs will be resilient to a specific
large elevation due to limitations in the low elevations of adjacent land areas, the objective is to make
the areas more resilient. For example, studies have shown that waves traveling over marsh areas can
have wave height reduced by as much as 70%.
Sea level rise projections in MA CZM document have been adopted for use in this study,
Sea Level Rise: Understanding and Applying Trends and Future Scenarios for Analysis and Planning,
Massachusetts Office of Coastal Zone Management (CZM), December 2013.
This report indicates a potential intermediate high se level rise in the Boston area of 4 feet by the year
2100.
FEMA Flood Mapping
Flood Insurance Rate Maps (FIRMs) for Salem were consulted to help identify low areas susceptible to
flooding. This was a major consideration in site selection.
Nearshore geology and seafloor mapping,
Limited information is available on the nearshore marine geology in the Salem area. One
comprehensive study by USGS (Barnhardt et al, 2005) describes the general nature of the areas but does
not have data in the immediate nearshore areas of our candidate sites. The general environment in
Salem Sound as a nearshore basis is described as follows:
The Nahant-Gloucester study area lies in the western Gulf of Maine, where the coast and inner
continental shelf are bedrock framed with numerous rocky islands and rugged headlands.
Bedrock in the region consists of complexly faulted and deformed intrusive rocks that range in
age from Precambrian (> 540 million years) to Paleozoic (250-540 million years) (Zen and others,
1983). Bedrock is widely exposed along the shoreline and is a primary control on the shape of
the coast. Rocky headlands provide shelter for small harbors and pocket beaches. The rugged
topography of the seafloor is presumably due to these same rocks cropping out offshore…
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The coastal landscape has been sculpted by multiple glaciations. During the last Ice Age, glaciers
reached their maximum extent south of Cape Cod about 21,000 calendar years ago. As climate
warmed, the glaciers retreated northward across the study area, passing the present coast
about 14,500 years ago (Kaye and Barghoorn, 1964). Numerous moraines, outwash plains,
drumlins, kettle lakes, and other features record the glacial history of the region. Glacial-marine
sediment was deposited contemporaneously with ice retreat, blanketing wide areas of the coast
and inner shelf from northeastern Massachusetts (the "Boston blue clay" - Kaye and Barghoorn,
1964) to eastern Maine (the Presumpscot Formation - Bloom, 1963). This sediment
unconformably overlies older glacial deposits and bedrock, and typically consists of well
stratified sand and mud with scattered dropstones of ice-rafted material. Thick sequences of
glacial-marine sediment are best preserved in bedrock valleys and deep basins in the western
Gulf of Maine (Belknap and Shipp, 1991). The relatively thin glacial deposits in the Cape Ann
region are discontinuous and only partly mantle the underlying bedrock (Shaler, 1889).
Nearshore Basins (NB) are areas of shallow, low-relief seafloor adjacent to the mainland and
separated from offshore areas by islands and shoals. Along its landward margin, the basin
sediment merges with the intertidal zone in a gradational contact. One large Nearshore Basin is
recognized in the study area, located inside Salem Sound and Marblehead Harbor. It is sheltered
from the open ocean by small islands and shoals. The basin is bordered by the mainland coast
on its landward side and terminates against Rocky Zone, Shelf Valley, and Bay-Mouth Shoal on
its seaward side. The inner-most part of the basin is the Danvers River estuary. Although
exposures of bedrock and coarse-grained sediment locally occur within the basins, the generally
smooth seafloor primarily consists of sandy and muddy sediment. Nearshore Basins comprise
22.4 km² or 13.1% of the mapped area (table 4.1). Water depths range from 0 to 19 m.
Sediment and Sediment Transport
As with nearshore sea floor mapping, limited information on nearshore sediments in the Salem area is
available. A MA Division of Marine Fisheries report (Ford et al, 2010) describes sediments in the Salem
Sound area as mostly muddy, but sandy, gravelly, and hard are also common.
In our shorelines surveys done for this project, (submitted separately to CZM) intertidal sediment varies
greatly by location, ranging from sand, to gravel, to rock.
There appears to be relatively little longshore sediment transport along the coast in Salem. This is a
function of the rocky nature of the coast, with no long stretches of coast uninterrupted by rocky
headlands. Pocket beaches may have limited transport along the beach, as well as onshore-offshore
transport, depending on wave conditions.
Marine Resources
A summary of marine resources in Salem Sound is found in a 1997 report by MA Division of Marine
Fisheries (Chase et al, 1997). The report focuses on biological resources including shellfish, and finfish.
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This report will be a resource during future permitting of the project. It is anticipated that detailed
studies and surveys will be required during the permitting phase of the project.
Current usage by the public
Usage of coastal areas considered is discussed in previous sections and was a major factor in the site
selection process. City interests were a major consideration into what areas might be most important
for application of coastal green infrastructure.
Tidal Datums
Understanding local tides is critically important is the design of living shoreline projects such as this. In
particular, marsh grasses e.g. Spartina species can live in a narrow tide of tide, and if incorrectly planted
relative to tide, will not survive.
The following table summarizes tidal datums for Boston. Tides referenced to NAVD88 are not available
for Salem, but could be established with local surveys. As can be seen below the mean range of tide is
almost 9.5 feet. The mean range of tide in Salem at Station ID: 8442645 is 8.93 feet.
Tide Datums Boston
Station
8443970
NAVD88 (feet)
Datum Description
MHHW Mean Higher-High Water 4.77
MHW Mean High Water 4.33
MTL Mean Tide Level -0.42
MSL Mean Sea Level -0.3
DTL Mean Diurnal Tide Level -0.37
MLW Mean Low Water -5.16
MLLW Mean Lower-Low Water -5.51
NAVD88 North American Vertical Datum of 1988 0
STND Station Datum -9.03
MN Mean Range of Tide 9.49
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Conceptual Design Considerations
MAPTITE
MAPTITE (Marsh Analysis and Planning Tool Incorporating Tides and Elevations) is a ZGIS add-in that was
used in the initial planning stage of the project to help establish vegetation planting zones relative to
tidal datums. It was developed by National Oceanic and Atmospheric Administration (NOAA) as a tool
to aid in the selection of vegetation types for different restoration elevations based on a combination of
a digital elevation model (DEM) derived from GPS observations, local tidal datums, and grass type
information. See https://tidesandcurrents.noaa.gov/maptite.html .
MAPTITE was used in conjunction with our understanding of local tides and detailed topographical
information derived from the LIDAR data. A GIS MAPTITE output for the Collins Cove area is included in
Figure 3.
Conceptual Design Considerations
As discussed earlier, three sites were selected for development of conceptual design of living shorelines:
Collins Cove, Furlong Park, and Juniper Cove. At the onset of the project several living shoreline
techniques were anticipated to be considered for implementation. Selection would be based upon
evaluation of site information. The green infrastructure alternatives mentioned at the project proposal
stage included:
• Beach, berm, and dune building, enhancement, or restoration with compatible sediment and
native vegetation
• Bioengineering with coir rolls (on coastal banks or for salt marsh restoration/creation), natural
fiber blankets, and other organic, biodegradable materials combined with planting/revegetation
• Shellfish (mussel or oyster) reef creation, enhancement, or restoration
• Fringing salt marsh creation or restoration
• Natural enhancement of existing coastal structures
• A combination of alternatives.
Beach, berm, and dune building in itself was not considered appropriate for Salem given the nature of
the rocky coast with limited sediment supply, and few beaches in the areas considered most vulnerable.
Shellfish (mussel or oyster) reef creation, enhancement, or restoration was considered but is not
recommended for implementation at this time. Shellfish beds in Salem are closed due to contamination
concerns. Creation of reefs with edible shellfish such as oysters might be a desirable technique but since
oysters might be illegally harvested that might potentially be contaminated, this technique was not
pursued.
Marsh augmentation with ribbed mussels was given serious consideration. Unlike the the blue mussel,
ribbed mussels are not commonly eaten by people. They have been used as a component of marsh
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restoration projects in Delaware Bay and elsewhere. They live in low, regularly flooded marshes and
mud flats. They attach themselves to marsh grass roots and other surfaces with strong, thread-like
strands secreted from the byssus gland. Particles of organic nutrients are processed into inorganic
matter by the ribbed mussel which is recycled back into the mud. This concentrated inorganic material
helps to enrich the surrounding mud and contributes to salt marsh growth. See
http://www.edc.uri.edu/restoration/html/gallery/invert/ribbed.htm .
Ribbed mussel production and use in marsh restoration was the topic of a CZM grant report by Martha’s
Vineyard Shellfish Group in 2015. As part of the current project we talked with Rick Karney of Martha’s
Vineyard Shellfish Group. It appears that much was learned about growing ribbed mussels but they
have not been yet to produce the mussels in quantities that would be needed for a marsh restoration
project. Therefore the use of ribbed mussels in conjunction with Salem project is not recommended as
this time.
The living shoreline technique considered most appropriate for the three candidate sites is to fringing
salt marsh creation/restoration using bioengineered techniques with coir logs, natural fiber blankets,
with plantings of Spartina patens and Spartina alternaflora. In each of the three sites, existing site
features were incorporated into the design (e.g. a rock sill at Collins Cove).
A literature review was conducted to help identify viable techniques and build upon previous
experiences applying these techniques. Discussion was held with some experts in the field including Dr.
David Buskek of Rutgers University and Dr. David Burdick of University of New Hampshire (see
Acknowledgements).
Conceptual Designs
After the literature review, a basic design was created that is similar to what is known as the DELSI
Tactic, after research and implementation in many locations in Delaware Bay. Figure 4 show the basic
concept, (from LIVING SHORELINES IN THE DELAWARE ESTUARY, 2013).
At each location a basic design was implemented. Figure 5 shows the basic design concept. Two rows
of core logs are positioned on an arcuate pattern in the area of marsh establishment (or restoration).
Each arcuate section is approximately 75 feet in length. Premium coir logs of 12 foot length are
recommended. There is overlap from log to log.
Coir fiber mat may be used to provide foundation in soft substrate (if necessary) and to provide further
support for new plantings of Spartina patens and Spartina alternaflora. Each species is planted at
appropriate tidal elevation for optimal growth. Target range for Spartina alternaflora is mean sea level
(MSL) to mean high water (MHW), and Spartina patens is targeted MSL to Mean Higher High Water
(MHHW). The section in Figure 5 shows the planting zones. A mix Spartina alternaflora and Spartina
patens is planted in a zone near the MHW mark. As mentioned earlier, the GIS tool MAPTITE was used
to assist in establishing the planting zones.
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In some locations it may be necessary to add sand to provide adequate substrate for growing the plants.
Sections are laid out to increase to size of the marsh establishment area. A small gap is left between
sections to allow draining. The sections may have some preferred orientation to the shore, depending
on prevalent wave direction.
Collins Cove
Conceptual designs for Collins Cove are shown in Figures 6 to 8. The approximate 700 foot section of the
cove selected is parallel to Webb Street. There is some sparse marsh grass present particularly near the
high tide mark. This is a low-lying area, vulnerable to flooding. There is an existing, somewhat irregular
rock sill in this location. The proposed design will be implemented landward of the sill to take advantage
of the wave buffering by the rocks. There is a break in the eastern portion to allow access for kayakers
and others to the water.
Furlong Park
Furlong Park is another low lying area of Salem selected to consideration of implementation of a living
shoreline. The conceptual design is shown in Figures 9 to 11 for this approximate 800 foot area. Furlong
Park is somewhat exposed to waves with a fetch from the northeast. The design sections are slightly
overlapped to allow some buffering of waves from sections to section.
The park has a shoreline bordering rock sill or low revetment. There is a single sill in the northern
portion and a double sill in the southern portion. The design sections would be placed in front of the
sills/revetment, due to tide elevation considerations. Figure 10 show typical sections for both areas
with a single sill and with a double sill.
The extreme southern portion of the area (near the ball field) is quite low, and it may be desirable to
slightly increase the height of the sill/revetment and add fill behind it as shown on Figure 10.
Juniper Cove
Juniper Cove is the third area selected for possible implementation of living shoreline as shown in
Figures 12 to 15. The area is subject to flooding through an opening in the wall along Columbus Ave.
There is existing marsh in this area but it does not appear to be thriving. It is partly desiccated with
voids in the marsh surface. There is also a rock groin that is partially surrounded by marsh. The
proposed design is intended to help expand the marsh and make the area more resilient.
The design section would be placed seaward of the existing marsh as shown in Figure 14. Due to the
elevation of the marsh, the coir logs would be placed at a lower elevation than the other two areas, and
would serve to provide some buffering while the marsh gets restored.
Figure 15 shows a before and after rendition of what the Juniper Cove area may look like after
implementation.
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Cost Estimate
The approximate materials cost for a typical design section is included in the table below.
Salem Living Shoreline Costs, per
typical 75 foot section Source
Pinelands Nursery, NJ)
Item Quantity Unit Cost Total Cost
12" Coir Log 14 $ 93.00 $ 1,302.00
6.5' x 165' Coir Fiber Mat 1 $ 248.00 $ 248.00
2"x2"x4' Hardwood Stakes (12 per log) 168 $ 2.25 $ 378.00
1/8" Duckbill Earth Anchors (2 per log) 28 $ 13.00 $ 364.00
Spartina Alternaflora Plugs (12" O.C.) 635 $ 0.70 $ 444.50
Spartina Patens Plugs (18" O.C.) 236 $ 0.70 $ 165.20
Total $ 2,901.70
It is not known at this time how the project might be implemented in regard to contracting or a possible
community volunteer project. It is also not known if any or all three areas are implemented, or
complete designs are implemented or just portions of an area. This will obviously affect costs. Detailed
cost estimate will be developed at the detailed design and construction stage.
The following are rough cost estimates for installed costs, on unit cost basis:
• Coir logs (12" diameter)—including purchase & delivery, duckbill anchors, wood stakes and
labor—$50.00 / LF.
• Coir Fiber Matting—all-in cost as well—$5.00 / SY.
• Salt Marsh Plugs—all-in—$4.00 / Each, inclusive of warranty.
• Fill Material—furnished and placed—can vary quite a bit depending on composition, quantity
and access. Given the anticipated small quantities for these locations, approximately $80 - $100
/ CY. If the quantity gets bigger, unit price could come down.
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Permitting
Permitting would be conducted at the next project phase after a specific project is defined and designs
are further developed. A number of permits are potentially applicable.
It is recommended that as project specifics are being developed that a meeting be held with CZM staff
(starting with Kathyrn Glenn, North Shore Regional Coordinator) to discuss permitting needs and to get
guidance on the most efficient route to permitting.
The following are some of the permits and regulatory considerations potentially applicable to this
project.
• Wetland Protection Act—Notice of Intent (City of Salem Conservation Commission)
• Section 401 Water Quality Certification
• Section 404 of the Clean Water Act for dredge of fill (Army Corps of Engineers)
• CZM Federal Consistency
• Chapter 91 Public Waterfront Act MA Environmental Policy Act Filing
• Massachusetts Endangered Species Act
• DMF Resource Survey (100 foot minimum from project location (sea grass, lobster, winter
flounder, cod, and horseshoe crabs) NMFS Essential Fish Habitat (multiple species).
Acknowledgements
Dr. David Buskek of Rutgers University, Haskin Shellfish Research Laboratory, was very helpful in
discussing design concepts. He reviewed draft conceptual designs and offered beneficial comments.
Dr. David Burdick of University of New Hampshire also reviewed the initial designs and provided helpful
comments.
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REFERENCES
Demonstration of living shoreline technology and development of ribbed mussel seed production to
protect and restore salt marsh in coastal Massachusetts, Martha’s Vineyard Shellfish Group, Inc., July 31,
2015.
High-Resolution Geologic Mapping of the Inner Continental Shelf: Nahant to Gloucester, Massachusetts,
By Walter Barnhardt, Brian Andrews, and Brad Butman, USGS Open-File Report 2005-1293.
LIVING SHORELINES IN THE DELAWARE ESTUARY: Best Practices from Lessons Learned and Information,
Collected by the Partnership for the Delaware Estuary and the Rutgers Haskin Shellfish Research
Laboratory, 2008 – 2012, June 2013, PDE Report Number 13—04).
MARINE RESOURCES OF SALEM SOUND, Massachusetts Division of Marine Fisheries, Technical Report
TR-6, 1997, Bradford C. Chase, Jeffrey H. Plouff, and Wayne M. Castonguay.
Seafloor Sediment Composition in Massachusetts Determined Using Point Data, Massachusetts Division
of Marine Fisheries Technical Report TR-45 by K. H. Ford and S. Voss, December 2010.
Sea Level Rise: Understanding and Applying Trends and Future Scenarios for Analysis and Planning,
Massachusetts Office of Coastal Zone Management (CZM), December 2013.
User Guide for Marsh Analysis and Planning Tool Incorporating Tides and Elevations MAPTITE- A GIS
Application for Marsh Restoration, National Oceanic and Atmospheric Administration, May 2014
Thieler, E.R., Smith, T.L., Knisel, J.M., and Sampson, D.W., 2013. Massachusetts Shoreline Change
Mapping and Analysis Project, 2013 Update: U.S. Geological Survey Open-File Report 2012–1189, 42 p.,
http://pubs.usgs.gov/of/2012/1189/.
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FIGURES
Figure 1: Shoreline Change Map
Figure 2: Collins Cove LiDar
Figure 3: MAPTITE Output Collins Cove Area
Figure 4: DELSI Tactic
Figure 5: Typical Living Shoreline Concept Plan
Figure 6: Collins Cove Design Layout Concept
Figure 7: Collins Cove Living Shoreline Concept Section
Figure 8: Collins Cove Typical Living Shoreline Concept Plan
Figure 9: Furlong Park Design Layout Concept
Figure 10: Furlong Park Living Shoreline Concept Sections
Figure 11: Furlong Park Typical Living Shoreline Concept Plan
Figure 12: Juniper Cove Design Layout Concept
Figure 13: Juniper Cove Living Shoreline Concept Section
Figure 14: Juniper Cove Typical Living Shoreline Concept Plan
Figure 15: Juniper Cove Living Shoreline Rendering