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Mill River Dams Feasibility Study River Restoration and Diadromous Fish Passage
January 31st, 2008 Prepared for: Massachusetts Riverways Program Riverways Program, DFG 251 Causeway St., Suite 400 Boston, MA 02114
3602 Atwood Avenue Suite 3 Madison, WI 53714
2007 Inter-Fluve Inc. Mill River Concept Report 5
1. Executive Summary
This study examined the feasibility of various fish passage and river restoration options for the three
downstream impoundments on the Mill River in Taunton, Massachusetts (Figure 1-1). We conclude that
fish passage and river restoration are feasible, and we offer concept level design options for alternatives at
each dam.
1.1. State Hospital Dam
The State Hospital Dam is an earthen fill dam with a concrete spillway (8 ft head) impounding a pond
area of approximately 5.2 acres. The impoundment contains a maximum of 30,000 cubic yards of
deposited sediment consisting primarily of sand.
No Action Alternative – As part of the study, we examined the implications of no action at each
structure. No action at the State Hospital Dam would result in continued riverine habitat degradation
through sediment deposition, organic material buildup, invasive plant proliferation, thermal pollution, and
concentration of nutrients and pollutants. These negative effects of dams are well documented in
numerous studies (Baxter 1977, Dauta et al. 1999, Petts 1984, Poole and Berman 2001, Schuman 1995,
Stanley et al. 2002, Ward and Stanford 1979, 1987). No action also results in continued selective removal
of fine material from the downstream reach, resulting in over-widening of the channel and
homogenization of in-stream habitats (Gray and Ward 1982, Ligon et al. 1995, Ward and Stanford 1983).
No action with regard to river restoration and fish passage will require continued dam inspection,
maintenance and eventual repair or replacement to keep the dam in compliance with Massachusetts
Department of Dam Safety standards. The cost of these activities is typically borne by the dam owner. All
dams continue to degrade, and without regular maintenance and repair, the risk of flooding due to dam
failure increases. No action results in continued liability risk to the dam owner and continued risk to
public safety (Graber et al. 2001).
Dam Removal Alternative – Removal of the State Hospital Dam is feasible and would fulfill the goals
of the project. Dam removal would result in passage for diadramous fish (alewife, blueback herring) and
other species (eg. American eel, amphibians), free flowing conditions, restored riparian and in-stream
habitat, lower water temperatures, increased dissolved oxygen concentrations and the reestablishment of
river dependent fish and wildlife (Bednarek, A. 2001, Calabro 2007, Maclin and Sicchio 1999). These
include lithophilic or gravel dependent spawning fish, mussels and other macroinvertebrates, as well as
riparian birds, amphibians, reptiles and small mammals. Dam removal would also reconnect the nutrient
flow of upstream and downstream reaches, allowing both fish and nutrients to pass from reach to reach.
Migrating fish, including alewife, blueback herring, eel and other species, would be able to move daily
Figure 1-1. Mill River in Taunton, MA showing the location of the project dams
State Hospital Dam
West Britannia Dam
Whittenton Pond Dam
Morey’s Bridge Dam
2007 Inter-Fluve Inc. Mill River Concept Report 7
and seasonally through the reach to ensure access to optimal feeding and spawning habitat. Removal of
the State Hospital dam would also remove dam owner liability and public safety concerns by eliminating
potential risk of flooding due to dam failure.
Fish Passage Alternatives – Both a fish ladder and a nature-like bypass channel (Figure 1-2) are
feasible at the State Hospital site and both fulfill the fish passage goals of the project. Either approach
does not remove the dam owner’s liability, and does not improve the degraded condition of the upstream
channel. Affordable Denil and prefabricated Alaska steep pass fish ladders have been shown to be
successful in facilitating the migration of
diadramous migratory alosid species (eg. alewife,
blueback herring, American shad) in the northeast
(Haro et al. 1999, Kleinschmidt 2005, Quinn
1994). Such a ladder could be installed at the State
Hospital site, but the degraded raceway would
require stabilization or partial reconstruction to
provide the structural support necessary for a
ladder. At this site, fish may have a tendency to
bypass the fish ladder inlet and occupy the 60 feet
of rock riffle apron. It is possible to limit low flow
over the main spillway and divert or interrupt
higher flows to create more attraction in the
preferred downstream location. Any fish ladder
would require significant concrete work to repair the dam, stabilize the left bank raceway and manipulate
spillway flow patterns to ensure attraction. This concrete work could increase the cost of a ladder project
while not ensuring passage of all Mill River fish species.
Nature-like or natural bypass channels have been successful at allowing passage of a wide variety of
species (Eberstaller et al. 1998, FAO/DVWK 2002, Jungwirth et al 1998, Aerestrup et al 2003, Mader et
al. 1998). A natural bypass channel was deemed feasible given the existence of the left bank historic
sluiceway which would allow for bypass channel construction with minimal excavation. The gentle slope
afforded by this route allows for a cascading riffle and pool design that would mimic natural stream
conditions and allow for passage of both migratory species (eg. alewife, herring, adult American eel) and
resident species (pickerel, darters, elvers).
Figure 1-2 – Example of a nature-like fishway or bypass channel (photo L. Aadland)
2007 Inter-Fluve Inc. Mill River Concept Report 8
1.2. West Britannia Dam
The West Britannia (Reed and Barton) Dam is 85 feet long with a structural height of 8.0 feet and a
hydraulic head of 4.0 feet. The dam is an earthen berm and masonry dam with a concrete cap masonry
spillway formerly impounding a pond area of approximately 8.23 acres. The dam is currently drawn down
and has no significant impounded water area. The impoundment contains a maximum range of 13,000 to
26,000 cubic yards of deposited sediment consisting primarily of sand.
No Action Alternative – Because of the lowered impoundment and current run-of-river condition at
the West Britannia Dam, no action does not have the same type of impacts as predicted for the State
Hospital Dam. No action at West Britannia will maintain the existing condition of the impoundment, and
the river conditions will remain relatively static. The dam will continue to block fish passage and will
continue to present a maintenance cost and liability due to the risk of flooding from dam failure. In
addition, the existing raceway (right bank) is a continued risk to the Reed and Barton mill buildings under
which it flows.
Structural repairs are recommended for the West Britannia Dam. No action will still require some
maintenance and repair to be financed by the dam owner.
Dam Removal Alternative – Removal of the West Britannia Dam would result in free flowing
conditions, restored riparian and in-stream habitat, increased dissolved oxygen concentrations and
reestablishment of riffle and pool dependent fish and wildlife. The reach is currently a deep, rectangular
wetland channel. Removal of the dam would result in a steeper channel slope and more natural
geomorphic function, including sediment movement, bar formation and riffle and pool development. Free
passage of migrating fish and wildlife would be assured. Removal of the West Britannia dam would
remove dam owner liability and public safety concerns by eliminating flooding due to dam failure or
water passing under the mill buildings.
Fish Passage Alternative – Three non-removal fish passage alternatives were considered at the West
Britannia site, rock ramp, fish ladder, and natural bypass channel. A rock ramp was deemed infeasible due
to the filling of the channel downstream of the dam and the potential hydraulic impacts to the downstream
bridge crossing. The flood capacity of the West Britannia Street bridge could potentially be reduced as
filling would need to extend under the bridge.
An Alaska steep-pass or Denil-type fish ladder is feasible at the site, and would accomplish
diadromous fish passage goals. A fish ladder could be installed along the left bank retaining wall. Any
fish ladder would require significant concrete and masonry work to repair the dam, stabilize the left bank
2007 Inter-Fluve Inc. Mill River Concept Report 9
retaining wall and manipulate spillway flow patterns to ensure attraction. We recommend that any fish
ladder design at the West Britannia dam also consider specialized eel and elver passage ramps.
A natural bypass channel was also deemed feasible if it could be constructed on the left bank
floodplain area. With either fish ladder or natural bypass channel, the degraded condition of the upstream
river reach remains, as does the dam owner’s liability risk.
1.3. Whittenton Pond
The Whittenton Pond Dam is a 10 ft high concrete and timber structure temporarily stabilized by a
riprap spillway. The dam currently impounds a pond area of approximately 9.5 acres. The impoundment
is currently partially drawn down as a result of 2005 emergency repairs that lowered the head of the dam
to approximately 8 feet (Belisle 2006). The impoundment contains a maximum range of 1400 to 4,000
cubic yards of deposited sediment consisting primarily of sand.
No Action Alternative – No action at the Whittenton Pond Dam will maintain the existing degraded
river condition of the upstream reach, including continued sedimentation, littoral vegetation accumulation
and expansion, thermal pollution and nutrient loading. The stabilization measures taken in 2005 were
intended to be temporary, and movement of stones and degradation of the structure were noted in our
field effort. The dam will need to either be removed or rebuilt in the near future. In the meantime, the dam
will continue to block fish passage and will continue to present a maintenance cost and liability due to the
risk of downstream flooding from dam failure.
Dam Removal Alternative – Removal of the Whittenton Pond Dam would result in free flowing
conditions, restored fish passage, restored riparian and in-stream habitat, increased dissolved oxygen
concentrations and the reestablishment of riffle and pool dependent fish and wildlife. Removal of the
Whittenton Pond Dam would remove dam owner liability and public safety concerns related to flooding
from dam failure. Removal would result in a conversion of general ecological condition from a lentic or
lake environment to a lotic, or riverine environment. This would include a restored sinuous channel
roughly 50 feet wide with a riparian zone managed with natural and private landowner aesthetics in mind.
Fish Passage Alternative – Three non-removal fish passage alternatives were considered at the
Whittenton Pond site, including rock ramp, fish ladder, and natural bypass channel. A rock ramp was
deemed infeasible given the high cost versus benefit and the potential change in hydraulics at the
downstream bridge crossing. The fish ladder and natural bypass options are feasible at the site, but would
require rebuilding of the dam. Of the two alternatives, a fish ladder would be the most economical, but a
natural bypass channel would ensure passage of a wider variety of fish species. With any of these fish
2007 Inter-Fluve Inc. Mill River Concept Report 10
passage alternatives, the degraded condition of the upstream river reach remains, as does the dam owner’s
liability risk.
Alternatives analysis tables
Full dam removal and alternative fish passage options were both found to be feasible at each of the
three study dams, with a range of associated feasibility level cost estimates. The following tables show the
alternatives considered at the three dams considered in the study, and the advantages and disadvantages of
each option. A more detailed discussion of restoration options is given in subsequent sections of this
document. Detailed cost estimates are included as Appendix A.
Table 1-1. State Hospital Dam – fish passage alternatives
Estimated costs* Advantages Disadvantages
Do Nothing
Repair - $250,000
Long term maintenance costs are variable
• No immediate cost • Maintain pond aesthetic
• Increased cost of repair with time • Persistent long-term risk/liability of
failure and subsequent flooding • Continued riverine habitat degradation • Continued water quality impacts - thermal
pollution, dissolved oxygen • Continued degraded sediment quality
Full Dam Removal
RECOMMENDED
$989,000 – assuming special handling of sediments
$546,000 – assuming no special handling
• Improved fish passage • Restored natural river processes • Reduced or stabilized contaminants • Restored floodplain wetlands • Improved water quality • Increased property value • Reduced public safety risk • Funding available for removal and
sediment management • Improved park land opportunity
• Short term construction disturbance • Cost of contaminated sediment requires
additional grant funding effort • Removal of sediment adds substantial
cost, particularly if special handling is required
Dam repair with fish passage bypass channel
$250,000 – repair
$224,800 – fish bypass
Total $474,000
• Improved fish passage • Maintained impoundment water
levels • Reduced public safety risk
• Cost of repair is generally not funded by outside sources (eg. State or Federal grants)
• Short term construction disturbance • Persistent long-term risk/liability of
failure and subsequent flooding • Continued riverine habitat degradation • Continued water quality impacts - thermal
pollution, dissolved oxygen • Continued degraded sediment quality
*Estimates are rounded to the nearest thousand and include construction, engineering and permitting. Estimates for engineering, permitting, dewatering, site repair and maintenance are shared by both dam repair and fish passage elements.
Estimates are feasibility level. The actual cost of construction may vary depending on final project approach, heavy construction market cost fluctuations and other factors. Estimates do not include construction cost contingency..
2007 Inter-Fluve Inc. Mill River Concept Report 11
Table 1-2. West Britannia Dam – fish passage alternatives
Estimated costs* Advantages Disadvantages
Do Nothing
Repair - $200,000
Long term maintenance costs are variable
• No immediate cost • Maintain pond aesthetic
• Increased cost of repair with time • Persistent long-term risk/liability of failure
and subsequent flooding • Continued riverine habitat degradation • Continued water quality impacts - thermal
pollution, dissolved oxygen • Continued degraded sediment quality
Full Dam Removal
RECOMMENDED
$694,000 – assuming special handling of sediments
$452,000 – assuming no special handling of sediments
• Improved fish passage • Restored natural river processes • Reduced or stabilized contaminants • Restored floodplain wetlands • Improved water quality • Increased property value • Reduced public safety risk • Funding available for removal and
sediment management
• Short term disturbance of the west end of the parking lot area (left bank – Reed and Barton)
• Cost of contaminated sediment remediation requires additional grant funding effort
Dam repair with fish passage bypass channel
$200,000 – repair
$230,000 – fish bypass
Total $430,000
• Improved fish passage • Maintained impoundment water
levels • Reduced public safety risk
• Cost of repair is generally not funded by outside sources (eg. State or Federal grants)
• Short term construction disturbance • Persistent long-term risk/liability of failure
and subsequent flooding • Continued riverine habitat degradation • Continued water quality impacts - thermal
pollution, dissolved oxygen • Continued degraded sediment quality
Dam repair with fish ladder
$200,000 – repair
$61,000 – Alaska steep pass fish ladder
Total $261,000
• Improved fish passage • Maintained impoundment water
levels • Reduced public safety risk • Fish passage funding for ladders is
potentially available
• Cost of repair is generally not funded by outside sources (eg. State or Federal grants)
• Short term construction disturbance • Persistent long-term risk/liability of failure
and subsequent flooding • Continued riverine habitat degradation • Continued water quality impacts - thermal
pollution, dissolved oxygen • Continued degraded sediment quality
*Estimates are rounded to the nearest thousand and include construction, engineering and permitting. Estimates for engineering, permitting, dewatering, site repair and maintenance are shared by both dam repair and fish passage elements.
Estimates are feasibility level. The actual cost of construction may vary depending on final project approach, heavy construction market cost fluctuations and other factors.. Estimates do not include construction cost contingency.
2007 Inter-Fluve Inc. Mill River Concept Report 12
Table 1-3. Whittenton Pond Dam – fish passage alternatives
Advantages Disadvantages
Do Nothing
Rebuild Dam
$1.5 Million
Long-term maintenance costs variable
• No immediate cost • Impoundment maintained at current level
restores some of the riparian zone
• Not a practical option given that repairs must be made to address public safety
• Wetlands filling over time • Short term construction disturbance • Persistent long-term risk/liability of
failure and subsequent flooding • Continued riverine habitat degradation • Continued water quality impacts - thermal
pollution, dissolved oxygen • Continued degraded sediment quality
Full Dam Removal
RECOMMENDED
$927,000 – assuming contaminant removal
$564,000 – assuming no contaminant removal
Includes $50K for fire suppression improvements
• Improved fish passage • Restored natural river processes • Reduced or stabilized contaminants • Restored floodplain wetlands • Improved water quality • Increased property value • Reduced public safety risk • Funding available for removal and
sediment management • Potentially increased property frontage
• Lowered water levels (change in recreational and aesthetic features)
• Requires alternate fire suppression for the Mill area
• Cost of contaminated sediment requires additional grant funding effort
Dam replacement with fish bypass channel
$1,505,000 - dam reconstruction
$203,000 - bypass channel
Total $1,708,000
• Improved fish passage • Maintained impoundment water levels • Reduced public safety risk
• Cost may be prohibitive • May not be permittable • Long-term risk of failure and sudden
flooding remains • Wetlands filling over time • Degraded habitat • Water quality impacts - thermal pollution,
dissolved oxygen • Slow release of contaminants
Dam replacement with fish ladder
$1,505,000 - dam reconstruction
$69,000 - fish ladder installation
Total $1,574,000
• Improved fish passage • Maintained impoundment water levels • Reduced public safety risk
• Cost may be prohibitive • May not be permittable • Short term construction disturbance • Persistent long-term risk/liability of
failure and subsequent flooding
*Estimates are rounded to the nearest thousand and include construction, engineering and permitting. Estimates for engineering, permitting, dewatering, site repair and maintenance are shared by both dam repair and fish passage elements.
Estimates are feasibility level. The actual cost of construction may vary depending on final project approach, heavy construction market cost fluctuations and other factors. Estimates do not include construction cost contingency.
Mill River Dam Removal Photosimulations
State Hospital Dam, West Britannia Dam, and Whittenton Mill Pond Dam
Note: these photosimulations were created to give people an idea of what the Mill River could look like at the dam sites if the dams are removed. These are not designs or engineering plans; they are conceptual only.
State Hospital Dam, State Hospital Dam, Taunton, MATaunton, MA
State Hospital Dam removal State Hospital Dam removal simulation, Taunton, MAsimulation, Taunton, MA
West Britannia Dam, Taunton, MA
West Britannia Dam removal simulation #1, Taunton, MA
West Britannia Dam removal simulation #2, Taunton, MA
WhittentonWhittenton Mill Pond Mill Pond Dam, Taunton, MADam, Taunton, MA
WhittentonWhittenton Mill Pond Mill Pond Dam removal simulation Dam removal simulation #1, Taunton, MA#1, Taunton, MA
WhittentonWhittenton Mill Pond Mill Pond Dam removal simulation Dam removal simulation #2, Taunton, MA#2, Taunton, MA