HomeMy WebLinkAboutNarrative 2.19.2026Notice of Intent Friends Of Knob Hill Shores,Inc.(Dinah’s Pond),South Yarmouth,MA
Performance Standards Narrative,Alternatives Analysis,and Construction Protocol
Site Description
The project site is located in the channel between Dinah’s Pond and the Bass River (Kelly’s Bay).The main flow of
the Bass River is within Kelly’s Bay,and not Dinah’s Pond,which is a dead ended embayment.There is no work
above the water or landward of MHW,and therefore not in any Riverfront Area.Bass River is a tidal river on
Nantucket sound.The project site is located approximately 4 miles upstream of the river outlet.There is no map or
parcel for the site;since it is entirely underwater,it is located in public tidelands.Abutters were listed as if the project
were to be on the properties directly adjacent to the dredging.No work is in the upland or on any private property.
There is some salt marsh that lines the waterway on the upland on both sides of the project.No work is proposed near
any salt marsh.
The boating access between Dinah’s Pond and Kelly’s Bay is a natural inlet,and to our knowledge has never been
dredged.The access from Kelly’s Bay is at least 3 feet at low tide,and this depth is available from the bay close to
where the access narrows going west into the pond.Over time,the tidal currents have deposited enough sand on the
western edge of the access so that there is only six inches of water at low tide.This process is likely because at some
point the west end of the access got shallower and the incoming tidal action sped up because of less available depth,
then pushing or depositing sand when the edge of the berm was reached on the west side.The outgoing flow is then
restricted,forming a “berm”at the west end that restricts the outgoing tide from washing the incoming sand back out
of the pond.The sand then keeps depositing on the west end and the problem gets worse over time.There is no formal
channel,and boaters must know where and when they can transit the access.The pond itself has seen reduced flushing
over time,with some algae blooms on the north side of the pond.The sediments in the pond are quite muddy,while
the access “channel”is almost entirely sand,likely due to the tidal current,which has increased over the years as the
channel narrows and gets more shallow.
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arrows indicate the area for access and dredging into and out of Dinah’s Pond
Proposed Work -Many people got together to form the neighborhood association “Friends of Knob Hill Shores,Inc.”,an association
with the goal of dredging the access channel to increase flushing in and out of the pond and increase the water depths
for easier boating transit.
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Notice of Intent Friends Of Knob Hill Shores,Inc.(Dinah’s Pond),South Yarmouth,MA
Approximately 99 cubic yards of material is proposed to be removed from the access,creating a channel that will be
25 feet wide,and 3 feet deep at low tide.The channel is proposed to be approximately 270 feet long,to the point
where the depth “daylights”out at -3’MLW at both ends.All of the work is within Land Under Ocean.
The dredged material is proposed to be placed on a barge and offloaded at one or more locations.One configuration
(contractor dependent)puts 6-8 wooden boxes on a barge,with bags inside each box.The material is placed into the
bags and dewatered on the barge through the bags.The bags have straps where a crane can lift the bags out of the box
and then into a truck.New bags are placed into the boxes and the process repeats.For offloading of the material,one
location would be the public boat ramp in Follins Pond.Another option is the potential to use the bulkhead with a
crane to offload at the Mayfair Marina.Permission to do that has not been sought from the owner yet.Another option
is to use a crane and offload the dredged material at the west end of the pond.There is a public access leading down
to the water.This is the closest access for disposal.There is beach grass and salt marsh at the end of the access,
between pavement and gravel and the water.A crane could be positioned in the access to lift the soil bags from the
barge out in the water to a waiting truck in the access.One of the association members has given permission to deposit
the dredged material on their property for use in the cranberry bogs.
Re
Pictures showing alternate dredge spoil offloading area on west end of pond
Tidal Range
Kelly’s Bay is a wide,almost circular embayment,with narrow waterways leading into and out of this area.Past
projects in the area (circa 2008)yielded a tidal range of approximately 1.7 feet,where MHW was 2.1’and MLW was
0.4’(NGVD 29).This translates to approximately MHW at 1.3’NAVD88,and MLW at approximately -0.4’
NAVD88.Dinah’s Pond is located right off of Kelly’s Bay,so the tidal ranges should be quite similar.
Recently,the railroad bridge to the south was removed and the channel widened.This changes the tidal flow by
allowing more water to pass through this restricted area of the river.Potentially,there is more water to be able to
come in at high tide,so the MHW elevation should increase.However,the river south of this restriction is shallow.
Therefore,low tide might not change that much because there may not be an increase in the amount of water that can
leave the embayment because of the shallow bottom,and maynotbe affected as a result in the channel widening.
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Notice of Intent Friends Of Knob Hill Shores,Inc.(Dinah’s Pond),South Yarmouth,MA
To determine the new MHW and MLW elevations,a tide gauge was deployed at the adjacent site for one week in
2019.The tide gauge directly measured the water elevation in NAVD88 Datum at 5-minute intervals for an entire
week.The elevations were compared to the tide charts,and corrected for the plus and minus tides.The resulting tide
elevations were MHW =1.9’(.6 feet higher),and MLW =-0.3’(.1’higher)NAVD88.This would indicate an
increased tidal range from 1.7’to 2.2 feet;an increase of .5 feet.The results indicate that the increased tidal flow is
mainly from the influx of more water into the bay,but does not allow more water to leave than previously.The
increase in the elevations could be due to increased tidal flow,sea level rise,and increased outgoing restrictions due
to fluctuating depths and bottom topography in the narrow area of the river to the south.
If there is a buildup of sediments either on the north or south of the bridge from increased flows,then low tide could
rise further because the water can come in,but can’t get out.Furthermore,these conditions will likely continue to
change as the river re-naturalizes to the new conditions,moving sediments north and south of the railroad/bike path
bridge,etc.
Shorefront Consulting re-deployed its tidal gauge in the spring of 2021,and found the depths for MHW and
MLW had not significantly changed.MLW may have actually risen by about an inch,but this may be due to
the repositioning of the sediments at the bridges.Therefore,the original,conservative data was used for this
design.
Shellfish Survey
A shellfish survey was performed by John Lowell of East Dennis Oysters on 10/21/2025 to indicate the species,sizes,
and densities of any existing shellfish in the area.A copy of the survey report is included with this filing.
Approximately 135 plots were surveyed,with shellfish found in 93 plots (69%).There were approximately 37
shellfish found in transect A,35 in transect B,45 in transect C,41 in transect D,and 52 in transect E,for a total of
210 shellfish found in approximately 2’x2’x135 (540)square feet of plots;a density of approximately 1.56 shellfish
per plot,and 0.39 shellfish per square foot (of the plots).Refer to the report for more specific information.Overall,a
robust and diverse shellfish population exists in the proposed dredge area.
Navigation
Kelly’Bay is approximately 1,700 feet wide at the entrance to Dinah’s Pond,with a well-marked channel.The river
is also a “no wake”zone in this location,limiting the speed of all boats to 6 mph or less.The entrance to Dinah’s
Pond is located over 2,000 feet west from the main channel,at an southwest angle from the marina to the pond,and
access to the pond is only through a narrow inlet.There is no transiting boat traffic in the pond (dead end);only to
transit to and from the Bass River.Because of the bridge restrictions on the river,the size of boat that can transit this
far upriver is limited.Dinah’s Pond is small and used mostly by the residents.The increased channel depth might
invite more transient boat traffic into and out of the pond,which is in improvement to navigation.There will be no
negative impacts to the navigation in Kelly’s Bay or Bass River from this project.Navigation into and out of Dinah’s
Pond will be improved.
Shellfish Mitigation
There are several options for shellfish mitigation for this project.Generally,for dredging projects,shellfish are
relocated from within the dredge area to outside of the dredge area.They are not removed;only moved off to the side.
This has been the general protocol for residential dredging projects in the past.In some cases,the shellfish can be
replaced or re-seeded after the dredging is complete.This option depends on whether the dredge area will be re-
dredged in the future.Since this area has never been dredged before,it can’t be determined how long it may take for
the area to fill in and require re-dredging.Further,the tidal current may prevent successful attachment of spat;
however,the shellfish seem quite robust in this location and will likely rebound on their own in a short time.
Maintenance dredging is allowed for a period of 5-10 years from DEP.In the past,private dredging projects have
only been required to relocate the shellfish.The shellfish mitigation will be conducted per the procedures mandated
by the shellfish warden and the conservation commission.We are open for discussion on this.
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Notice of Intent Friends Of Knob Hill Shores,Inc.(Dinah’s Pond),South Yarmouth,MA
Alternatives Analysis (Discussion of Options)
Option 1-Do nothing
If nothing is done at this site,the entrance to Dinah’s Pond will get more shallow,limiting flushing and continue to
decrease and negatively affect water quality.Boating traffic will continue to be limited,with the possibility of
groundings and inadvertent prop scour.Fish spawning could be limited.Therefore,this is not a desired option for the
association or the environment.
Option 2 —Dredge wider and/or deeper.
This option was discussed.Any dredging of over 100 cubic yards requires a water quality certificate and additional
testing.The boats in Dinah’s Pond are not large;the bridges limit the size of boats anyway,and traffic into and out of
the pond is not sufficient to require a channel where two boats can pass.The channel area is visible from both ends.
If there are two boats requiring access at the same time,they simply can see each other and work it out.A deeper
channel would have to be wider and would likely fill in more quickly.A wider channel could encroach on the 25-foot
setback from the salt marsh.This setback requirement is only for projects requiring a water quality certificate.While
this requirement does not apply to the current project,dredging more than 100 cubic yards would require this setback.
There is limited additional area between the proposed dredged area and the 25-foot setback.The cost of additional
dredging and the increased permitting versus the benefit of a deeper or wider channel is not beneficial to the applicants,
and therefore this option was not chosen.
Option 3 —wait until the dredging can be performed by the town.
This option was discussed.While we believe the dredging of the upper Bass River permitting is underway,the
association is not aware that dredging into and out of Dinah’s Pond is within the scope of that permit or future permits.
The situation requires correction now,and waiting for the town to dredge the area will only make the conditions for
water quality in the Pond worse until (when and if)the town can dredge the area.Therefore,this option was not
chosen.
Option 4 —-Preferred Alternative,Project as proposed
The proposed dredging will provide increased flushing into and out of the pond,benefiting water quality.The
increased depth may benefit fish spawning.The increased depth will also allow normal boat traffic to transit at any
tide and avoid groundings,and inadvertent prop scour.The design and protocols allow the dredging to occur while
protecting the resource areas and shellfish resource.Therefore,the project as proposed meets the objectives of the
applicants and serves to benefit the resource areas and environment,and therefore option #4 is the preferred option.
Performance Standards
The project proposes the dredging of a waterway into and out of Dinah’s Pond by a private organization.
The work is only within Land Under Ocean and Land Containing Shellfish.The proposed project will not have any
significant adverse effects to the surrounding resource areas.
Land Under the Ocean —The dredging,as designed,can be performed without significant negative impacts to the
surrounding area.The dredging process will incorporate a silt curtain to contain turbidity.There will likely be a time-
of year (TOY)restriction to avoid dredging during potential spawning times.The spoils will be dredged and dewatered
on site,so that no other material is transported out of the area until it is contained.The construction protocol prohibits
bottoming of the working barge to avoid negative impacts to the bottom substrate.
Projects not included in 310 CMR 10.25(3)which affect land under the ocean shall if water-dependent,be designed
and constructed,using best available measures,so as to minimize adverse effects,and if non-water-dependent,have
no adverse effects,on marine fisheries habitat or wildlife habitat caused by alterations in water circulation,destruction
of eelgrass (Zostera marina)or widgeon grass (Rupia maritina)beds,distribution of grain size,changes in water
quality,including,but not limited to,other than natural fluctuations in the level of dissolved oxygen,temperature or
turbidity,or the addition of pollutants;or alterations of shallow submerged lands with high densities of polychaetes,
mollusks or macrophytic algae.The project,as proposed,is water-dependent and has no significant adverse effects,
and will in fact improve flushing and water quality for the Pond,and therefore can be conducted and permitted to
minimize adverse effects to the listed interests in accordance with 310 CMR 10.25 (6).
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Notice of Intent Friends Of Knob Hill Shores,Inc.(Dinah’s Pond),South Yarmouth,MA
Land Containing Shellfish —The design of the dredging reduces the potential impacts to shellfish for the surrounding
area by relocating the shellfish resource,either temporarily or permanently off to the side so that there is no loss of
the existing shellfish.Given the density of available shellfish in the area,the shellfish should re-colonize quickly,
with no net loss of habitat or shellfish.The dredging will not change the soil characteristics because the soil
composition is consistently sand throughout the dredge area.No change to the sediment characteristics will occur.
The proposed project minimizes any impacts to this resource.If proper construction protocols are followed,the project
can be permitted as proposed without negative impacts to the shellfish resource or surrounding resource areas.
Therefore,the project can be permitted under 310 CMR 10.34 (4)through (8).
CONSTRUCTION PROTOCOL
The shellfish relocation or any other shellfish mitigation will be accomplished as directed by the Shellfish Warden,
Natural Resources Department,and the conservation commission.All shellfish relocation shall be accomplished
before the start of any dredging.The dredging shall be conducted outside of any TOY restrictions.A silt curtain shall
be in place during all dredging operations.The staging area for materials will be on the working barge or the
association access at the west end of the pond,within the paved/gravel areas,and upland of any resource area.The
dredge material shall be de-watered on the barge before transit and offloading.All equipment shall be stored on the
working barge or the association access when not in use.The working barge may only be used during periods of high
tide and shall not be positioned to ground on the bottom.When not in use,the working barge shall be anchored in
deep water in Dinah’s Pond,not in the dredging area,and in an area that doesn’t restrict boat traffic.
If the association access is used for offloading,the crane must be positioned only on firm ground,and not on the
marsh.The crane must be able to span the marsh and collect the bags with the working barge in deep enough water
to prevent grounding.This option may only be available at high tide,but allows the quick transport of the material to
the property for use in the cranberry bogs.It also leaves public boat ramp areas available.
Pre-Construction Meeting
Prior to construction,a pre-construction meeting shall be held on-site with the Contractor,Property Owner,
Conservation Commission and/or agent,and the Project Manager (Shorefront Consulting).The purpose of the meeting
is to clearly delineate the limits of work and access,as well as the staging area.The Contractor will describe the
proposed means and methods for performing the work within the requirements of the plans,order of conditions and
construction protocol.The Contractor will comply with mitigation measures as established by the Conservation
Commission.
To be discussed at this meeting:
Existing property conditions,necessary precautions to be taken by the Contractor;
Means and methods for construction;
Necessary post-construction reparations and conditions;
Procedure for post-construction inspection;
Shorefront Consulting’s responsibilities for inspection and project coordination
During Construction,the site shall be accessible for inspection during reasonable hours by all parties,members of the
conservation commission and their agents,and the Project Manager.
Post-construction meeting
Upon completion of construction,a post-construction meeting shall be held on-site with the Contractor,Property
Owner,Conservation Commission and/or agent,and the Project Manager (Shorefront Consulting).The purpose of
this meeting is to determine that the project has been satisfactorily completed in accordance with all permits,and that
no additional work or mitigation is required by the Contractor.
Restoration of project area
Upon completion of construction,the buffer zone,lawn,association access,offloading area,staging areas and any
other areas disturbed by the dredging effort shall be returned as much as practical to their pre-construction conditions
to the satisfaction of the property owner and conservation agent.All disturbed vegetated areas shall be re-vegetated
with native vegetation to match pre-construction conditions for the surrounding areas,or as determined during the
pre-construction meeting.
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