Shared Use Path Grade Separation Feasibility Study
RIVER STREET BRIDGE B-16-006=C-01-005 (4F3)
over Charles River
Prepared For
Prepared By
60 K Street
Boston MA, 02127
December 2010
Rehabilitation of the River Street Bridge
MassDOT Project Number 605527
Bike & Pedestrian Underpass Feasibility Study
TABLE OF CONTENTS
1.0
Introduction
1
1.1.
General
1
1.2.
Scope of Study
2
1.3.
Existing Conditions
2
1.3.1
3
2.0
2.1
Existing Volumes
Feasibility Assessment
6
Design Parameters [for Underpass Options]
6
3.0
Description of Alternative Approaches to Underpass Features
9
3.1.
Alternative #1 –Tunnel Through Abutment
9
3.1.1.
Tunnel: Structural Impacts
9
3.1.2.
Tunnel: Geotechnical Considerations
10
3.1.3.
Tunnel: Utility Impacts
11
3.1.4.
Tunnel: Environmental Permitting Considerations
12
3.1.5.
Tunnel: Architectural/Cultural Impacts
15
3.1.6.
Tunnel: Cost Impacts
15
3.1.7.
Tunnel: Schedule Impacts
16
3.1.8.
Tunnel: Traffic Impacts
17
3.1.9.
Tunnel: Recreational Considerations
17
3.2.
3.1.10. Tunnel: Safety Considerations
17
Alternative #2 – Boardwalk Beneath Arch
18
3.2.1.
Boardwalk: Structural Impacts
18
3.2.2.
Boardwalk: Geotechnical Considerations
18
3.2.3.
Boardwalk: Utility Impacts
19
3.2.4.
Boardwalk: Environmental Permitting Impacts
19
3.2.5.
Boardwalk: Architectural/Cultural Impacts
21
3.2.6.
Boardwalk: Cost Impacts
21
3.2.7.
Boardwalk: Schedule Impacts
22
3.2.8.
Boardwalk: Traffic Impacts
23
3.2.9.
Boardwalk: Recreational Considerations
23
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Rehabilitation of the River Street Bridge
MassDOT Project Number 605527
Bike & Pedestrian Underpass Feasibility Study
3.2.10. Boardwalk: Safety Considerations
23
3.3.
Alternative #3 – At Grade Enhancements
23
4.0
Summary of Findings
25
4.1.
Alternative #1
25
4.2.
Alternative #2
25
4.3.
Alternative #3
25
Appendix A – Exhibits A-1
Appendix B – Cost Estimates B-1
Appendix C – Evaluation of Alternatives
ii
C-1
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
1.0 Introduction
1.1.
General
The River Street and Western Avenue bridges over the Charles River are
scheduled for major rehabilitation work in 2011 under MassDOT‘s Accelerated
Bridge Program (“the Project”). The bridges provide major connections between
Cambridge and Boston over the Charles River. In addition to the roadway
network connectivity for motorized vehicles, pedestrians and bicyclists enjoy a
network of paths and sidewalks around the Charles River Basin alongside the
roadways and bridges.
In the fall of 2009, a pedestrian and bike usage study was completed to measure
the patterns and volumes of the bike path around the Charles River. Appreciable
volumes of non-motorized users were observed using the various paths and
bridges around the river. While there are no established "volume warrants" or
"accident warrants" for pedestrian and bike crossings at major roadways where
underpass/overpass should be considered, MassDOT’s Project Development &
Design Guide has written design guidance that discusses in general terms how
to design and scope non-motorized transportation facilities (Shared Use Paths
and Greenways, 2006). The policy guidance indicates consideration should be
given to separating motorized and non-motorized users at intersections, where
feasible, in the interest of safety and capacity. Further, comments received at
public meetings concerning the Project indicate that a number of stakeholders
are interested in exploring potential options for developing grade separated
crossings at Western Avenue and River Street. This report specifically
addresses the possibility of creating grade separated crossings at River Street in
accordance with MassDOT policy guidelines and in
response to public comments. A separate report
has been prepared to address the feasibility of
grade-separated motorized & non-motorized traffic
in the vicinity of the River Street Bridge.
MassDOT recognizes that the pending
major rehabilitation Project may provide optimal
circumstances to consider grade separation
between vehicles, pedestrians and bicyclists, and
directed its design consultant, Hardesty & Hanover,
to study the benefits and issues associated with
developing grade separation prior to design work
for the rehabilitation project getting substantially
underway.
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
1.2.
Scope of Study
The scope of this assessment is to determine how the bridge approaches can be
designed to accommodate a shared use grade separated crossing that improves
intersection capacity and safety for all users at each end of the bridge and the
implications associated with accommodating the grade separation.
The feasibility assessment follows the guidelines located in the Shared Use
Paths and Greenways section of the 2006 MassDOT's Project Development &
Design Guide (PD&DG) and the American Association of State Highway and
Transportation Officials' 1999 Guide to Development of Bicycle Facilities.
According to MassDOT's PD&DG, overpass and underpass options should be
considered for highly volume path and roadway crossings. Due to the existing
topography along the Charles River and the proposed bridge structures, it is
more cost effective to provide underpasses than overpasses. Therefore, this
feasibility study only discusses the feasibility of providing grade separation by
underpass.
The assessment initially presents the structural considerations associated with
incorporating underpass features as part of the rehabilitation Project, and then
addresses other factors that influence the overall feasibility of including
underpasses in the current design effort, including environmental considerations,
utility infrastructure, historical context sensitivity, effects on traffic and
recreational uses, schedule, and cost considerations. Two conceptual
approaches to accommodating underpasses are considered; a tunnel through
the bridge approaches and a boardwalk style path through the bridge arch. As
noted previously, this report focuses on the River Street Bridge, while a
companion report addresses the feasibility of incorporating underpasses into the
rehabilitation of the Western Avenue Bridge.
1.3.
Existing Conditions
Originally constructed in 1925, the River Street Bridge is a three span concrete
arch structure founded on mass concrete and spread footings which bear on
natural granular soils and clay, located below existing fill and organics or river
bed sediments. The River Street Bridge carries vehicular and non-motorized
traffic across the Charles River over a distance of 329 feet. The bridge is a
“contributing element” associated with the Charles River Basin National Historic
District; its intrinsic form and architectural features are an integral part of the
larger historic setting in which it is located. Due to its deteriorating condition, it is
currently under design for major rehabilitation work, with the express
understanding that such rehabilitation be undertaken in a manner that respects
the historic “character-defining features” of the bridge and its immediate environs.
This report does not detail existing conditions concerning the bridge structure
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
itself, but rather focuses on the physical characteristics of the shared path
system as it approaches the bridge.
The paths around the Charles River Basin are used by pedestrians, bicyclists,
runners, skaters, and various other users as an alternative of commuting and for
recreation. The paths meet River Street at Memorial Drive in Cambridge and
Soldier’s Field Road in Boston at signalized intersections. Where the paths cross
River Street, typical sidewalk ramps are provided to accommodate bicycles and
persons with disabilities, and marked crosswalks demarcate the shared use path
zone as it traverses the roadway. Pedestrian indications with push buttons are
provided for shared use path users to obey to cross the roadway on the
Cambridge Side of the bridge. However, on the Boston Side, at the intersection
of River Street and Soldiers Field Road, the intersection is not marked or
signalized for pedestrians. Further, in some locations there are “pinch points” in
which sidewalks or paths are undersized relative to demand for pedestrian and
bicycle access, and unsafe conditions exist in particular areas. In particular, the
southern corner of the intersection of River Street and Soldiers Field Road is of
significant concern and is regularly referred to as “the narrows”, indicative of the
major pinching of pedestrian traffic between the Soldiers Field Road access ramp
and the Charles River seawall.
Due to the proximity of the Charles River and heavily-used roadways, there is
limited land area available to provide enhanced pedestrian and bicycle facilities.
On the Cambridge side of the river, the existing shared use pathway is directly
supported by a granite block retaining wall north of the bridge, while the path is
supported by an earthen embankment to the south of the bridge. The existing
path is 11’ wide on the Cambridge side of the river. On the Boston side of the
river, this condition is reversed, with the shared use path supported by a granite
block wall to the south of the bridge, and by an earthen embankment to the north.
The existing path is between 8’ and 9’, with a pinch point as narrow as 7’ near
“the narrows”, mentioned above, on the Boston side of the river. Some additional
land area is available on the Cambridge side of the river. However this
“available” land supports grass and street trees, providing a desirable buffer
between motorized and non-motorized travel ways.
1.3.1 Existing Volumes
The River Street Bridge provides three travel lanes for motorists and carries
approximately 20,700 vehicles per day (March 2010). Non-motorist counts were
conducted in September 2009 and May 2010 as part of the Charles River Basin
Pedestrian and Bicycle Study for Pathways and Bridges. Two-hour counts were
conducted on a typical weekday evening peak and weekend midday peak.
Counts were conducted from 4:30-6:30 pm on Wednesday, Sept. 23, 2009 and
Tuesday, May 11, 2010 and from 12:00-2:00 pm on Saturday, Sept. 26, 2009
and Sunday, May 16, 2010. Non-motorist users were counted crossing the River
Street Bridge and along the adjacent shared use path system. The count results
are provided in the table below.
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
Table 1.3.1 Overview of Non-Motorized Vehicle Usage
Fall 2009 Counts
Spring 2010 Counts
Weekday
PM Counts
Weekend
Midday
Counts
Weekday PM
Counts
Weekend
Midday Counts
River Street
Bridge
289 users
217 users
244 users
331 users
Path on
Cambridge side
377 users
466 users
383 users
1367 users
Path on Boston
side
247 users
348 users
248 users
769 users
During the Spring 2010 counts, Memorial Drive was closed to motor vehicle
traffic. Additionally, according to the Charles River Basin Pedestrian and Bicycle
Study for Pathways and Bridges, "because of the varying nature of large-scale
events and fundraisers that occur during the spring and summer weekends in the
Basin, count figures from some bridge and path locations changed dramatically
from September to May."
As part of the count program, the non-motorist users were categorized into 4
categories: bicyclists, pedestrians, runners, and others. The following table
provides the breakdown of the counts by users and location within the path
system.
Table 1.3.2 Breakdown of Non-Motorized Vehicle Usage
Fall 2009 Counts
Weekday PM
Counts
Saturday Midday
Counts
Spring 2010 Counts
Weekday PM
Counts
Saturday Midday
Counts
River Street Bridge
Bicyclists
96 (33%)
74 (34%)
107 (44%)
135 (41%)
Pedestrians
96 (33%)
80 (37%)
49 (20%)
99 (30%)
Runners
95 (33%)
62 (28%)
85 (35%)
87 (26%)
2 (1%)
1 (1%)
3 (1%)
10 (3%)
Other
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
Path on Cambridge side
Bicyclists
105 (28%)
148 (32%)
148 (38%)
630 (46%)
Pedestrians
58 (15%)
144 (31%)
64 (17%)
493 (36%)
Runners
213 (56%)
171 (36%)
170 (44%)
149 (11%)
1 (1%)
3 (1%)
1 (1%)
95 (7%)
Other
Path on Boston side
Bicyclists
159 (64%)
171 (49%)
138 (55%)
202 (26%)
Pedestrians
22 (9%)
88 (25%)
39 (16%)
498 (65%)
Runners
63 (26%)
80 (23%)
64 (26%)
51 (7%)
3 (1%)
9 (3%)
7 (3%)
18 (2%)
Other
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
2.0 Feasibility Assessment
As described in the subsequent sections, Hardesty & Hanover explored several
alternative approaches to enhancing pedestrian and bicycle facilities. These
include two underpass options (a tunnel and a boardwalk that passes under the
roadway via one of the bridge arches) and an at-grade option that would involve
modifications to existing crossings including shared use path improvements,
reduction of crossing distance and conflicts and other safety enhancements
aimed specifically at benefiting non-motorized users of the local transportation
network. Due to demands of path connectivity, it should be noted that all feasible
improvements to the at-grade shared use path crossings of River Street will be
considered as part of the rehabilitation project whether or not grade separation is
ultimately determined to be a feasible option.
While it is desirable on shared use path networks to provide separation from
motor vehicle traffic and minimize the number of street crossings, providing
grade-separation may not be appropriate or desirable. The Shared Use Paths
and Greenways section of the 2006 MassDOT's PD&DG provides a set of factors
for the designer to consider when determining whether grade separation is an
appropriate option at a given location. The factors to consider for all alternatives
are:
•
2.1
The suitability of the existing topography for grade separation;
•
The effectiveness of signage of traffic signal control as an alternative
for the crossing given the context of the location;
•
Any changes in alignment that may be necessary to achieve the grade
separation;
•
The opportunities of limitations placed on path connectivity to the
surrounding area by the grade separation;
•
The context in which the path is set, in consideration of safety and
security issues;
•
The volume, mix of vehicles, and speed of cross-traffic on the
roadway; and
•
The volume and mix of path users.
Design Parameters [for Underpass Options]
Certain parameters were observed to develop conceptual designs for providing
underpass features. These are based on the Shared Use Paths and Greenways
section of the 2006 MassDOT's PD&DG.
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
The conceptual alternatives presented in this feasibility analysis adhere to the
following parameters governing design and anticipated use of a path system that
introduces an underpass feature to allow non-motorized traffic to cross River
Street in the vicinity of both of its abutments (i.e., on the Boston side and on the
Cambridge side):
ƒ
Joint use of the path by all users. Separating such uses would take up
additional space within a constrained footprint, and may be interpreted as
‘favoring’ one mode over another relative to the water and buffering from
traffic;
ƒ
Two-way travel, to accommodate any combination of turning movements
and links to adjacent pedestrian/bicycle facilities;
ƒ
Maximum grades less than or equal to 5% to comply with Americans with
Disabilities Acts (ADA) and the Massachusetts Architectural Access Board
(AAB) standards
ƒ
Design speed of no more than 20 mph by bicyclists. Average walking
speeds are 3.5 feet per second, and for safety reasons, it is desirable to
discourage higher speed bicycling on congested shared paths. Due to the
increased speeds associated with the down slope and the limited sight lines
at the entrances to proposed tunnel sections of the underpass, a 20 mph
design speed is used on the approaches to the tunnel sections. The design
speed used where the underpass joins the existing path is 15 mph
ƒ
Minimum radius for horizontal curves of 100-feet to accommodate a
reasonable bicycle design speed (no maximum is established; larger radii
would only serve to encourage bicycles to go faster and would take up more
space
ƒ
Minimum desirable vertical clearance of 10-feet for underpasses. Lower
heights have been determined to discourage pedestrian and bicycle use.
ƒ
Minimum tunnel width (horizontal clearance) of 16-feet to accommodate
shared use and two way travel with some buffer between the travel way and
vertical walls. Narrower widths would discourage pedestrian and bicycle use,
and create more conflicts between users.
ƒ
Minimum path width of 10-feet to accommodate shared use and two way
travel. Ideally shared paths should be designed to be 12-16 feet in width, but
in an effort to reduce the overall footprint, a narrower path was assumed.
ƒ
Recognition of the design flood elevation of the Charles River of 108.5
feet (MDC Vert. Datum). Conceptual designs remain above this elevation to
ensure that the path is accessible (i.e., not flooded) under ordinary
circumstances, and to reduce the need for pumping systems.
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
While a number of variations on these parameters could be considered, each
deviation would have a negative impact on providing an equivalent level of
accessibility to all users, or would result in a larger footprint and correspondingly
greater environmental impacts.
8
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
3.0
Description of Alternative Approaches to Underpass Features
As noted above, Hardesty and Hanover considered three fundamentally different
approaches to accommodating through pedestrian and bicycle movements: a
tunnel (Alternative #1), a boardwalk (Alternative #2), and at-grade improvements
(Alternative #3). Further description of each of these alternatives is provided
below.
3.1.
Alternative #1 –Tunnel Through Abutment
For purposes of exploring the tunnel option, a concrete box culvert was assumed
to reduce costs and minimize the overall length of the construction period. This
concrete box culvert structure would penetrate the bridge’s approach retaining
walls, immediately behind the mass concrete abutments. This option would
necessitate placing earthen fill into the Charles River to support the construction
of a 10-foot wide bituminous path approaching the tunnel structure. Retaining
walls would be used to reduce encroachment into the Charles River to the extent
possible.
As noted previously, portions of the existing shared use path is directly supported
by a granite block wall on both the Cambridge and Boston sides of the river. Stair
access is recommended adjacent to the intersections down to the tunnel opening
to enable pedestrians to return to grade if desired. New construction of storm
drainage structures and possible pumping stations as well as re-configuration of
existing storm drainage structures would be required. While the sketch plans
provided in Appendix A illustrate an earthen embankment, retaining walls would
be recommended to support the approaches to the underpasses and minimize
the permanent area of disturbance.
Reference Appendix A, pages A-1 & A-2
3.1.1. Tunnel: Structural Impacts
There is little vertical height at the abutments to accommodate a box culvert with
10-ft clear opening. With the floor of the box set at the flood elevation, there is
just enough room for the box to fit beneath the bottom of pavement. With this
minimal cover, exposure to high concentrated live loads becomes a concern and
is likely to complicate the structural design of the box.
Other concerns are related to stability of the bridge during excavation to install
the tunnel. The bridge is backfilled between the arches with soil. Care needs to
be taken during excavation for the tunnel to retain the soil and limit lateral
movement of the soil during construction. The construction activities should
consider proper staging of construction coupled with a survey monitoring
program for movements.
Extensive use of soldier pile retaining wall systems will be required as they are
likely the only system that can be installed within the narrow confines between
9
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
and around various obstructions. Utilities and high groundwater will make
traditional retaining walls with footings challenging.
Another structural issue is the resulting structural dimensions of the box culvert.
The next section, utility impacts, is related to and has a dependency on the
success of the box culvert structural design, and the assumptions made in this
assessment.
3.1.2. Tunnel: Geotechnical Considerations
The following geotechnical items need to be considered relative to construction
of the tunnel:
•
Subsurface Conditions. Subsurface conditions generally consist of fill (at
the abutments) overlying natural sand and gravel, clay, glacial till and
bedrock. The thickness of these deposits is variable, the organics and
clay are compressible soils, and the depth to till and bedrock is unknown.
The bottom of the proposed tunnel box will likely be in the fill and/or
organic soils. If these unsuitable soils are not removed or if the
foundations do not extend into the more competent sand and gravel or
clay layer, there is potential that differential settlement will occur that
results in cracking and overall poor performance of the tunnel structure.
•
Groundwater. The bottom of the tunnel box will be located at the flood
level of the Charles River. Construction of the box will need to consider
placement of a tremie slab and/or methods of groundwater control.
•
Utilities. There are a number of utilities that will need to remain active
throughout construction. These utilities will need to be protected, and in
some cases, relocated.
•
Obstructions. Construction of the tunnel will need to consider the location
of the mass concrete foundations and former cofferdams that were left in
place following construction of the bridge in the 1920s.
•
Method of Construction. As noted above, the top of the tunnel box will be
close to the existing roadway grade, therefore, the most practical method
for construction will be cut-and-cover.
•
Support of Excavation. We anticipate that soldier piles and timber lagging
may be the most feasible method of earth support in order to make
adjustments to avoid obstructions during installation and conflicts with
existing utilities and foundations. We anticipate soldier piles will be
installed in 30-inch predrilled holes as close as 4 feet on center and may
need to extend up to 50 to 60 feet below roadway grade. At least one
10
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
level of bracing may be required. The soldier piles will need to be
designed to support lateral soil loads to retain soil below the roadway as
well as vertical compression loads from temporary roadway decking.
•
Construction Staging. It is anticipated that the majority of work will need to
be performed at night and the work areas decked over during daytime
commuter hours. Alternatively, it may be possible to excavate and
construct the tunnel box in stages (i.e. close down one lane or one-half the
roadway).
•
Special Handling of Excavated Soils. The organic soils may contain
elevated levels of contaminants, normally associated with automotive
emissions. Special handling and transportation to an off-site disposal
facility will need to comply with local, state, and federal environmental
regulations.
•
Subsurface Explorations. Prior to proceeding with design of the tunnel
box and the support of excavation system, borings will need to be
performed, as a minimum, at each end of each tunnel box. The available
boring data is from the 1920s, which was obtained using non-standard
methods in comparison to those that are used today (i.e. ASTM) and the
data is based on borings taken in the river rather than at the ends of the
bridge where the tunnel boxes are proposed.
3.1.3. Tunnel: Utility Impacts
Numerous significant underground utilities exist at the underpass locations,
including 30” water mains, 30” natural gas mains, electrical, telephone, traffic
signal, and sewerage authority facilities. Vertically, it appears that there is not
enough elevation to route a concrete box culvert beneath the 30” water mains
while maintaining the floor of the culvert at the design flood elevation of 108.5.
Nor can the elevation of the box floor be increased due to the pavement
elevation at the approaches. Significant vertical and horizontal re-alignment of
the 30-inch water mains and gas mains will be required at both sides of the
bridge.
Investigation and location verification of active and abandoned utilities is a critical
step in completing a final design.
Another option to vertical utility offset beneath the tunnel may be under river
jacking/boring of the lines. At this time, jacking/boring new water and gas main
alignments beneath the Charles River is considered to be such a significant
detrimental cost and schedule impact that it is not further analyzed in this study
other than to mention it as a possibility.
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
Alternatively, placing the tunnel at lower than flood elevations in order to provide
utility clearance is also possible. However, the engineering, construction, and
maintenance additional cost is substantial. At this level of analysis, it appears
the cost premium to configure the underpass surface at less than flood levels
would accelerate short term and long term maintenance costs and user comfort
and safety.
3.1.4. Tunnel: Environmental Permitting Considerations
As originally envisioned, the bridge reconstruction project was expected to occur
within its existing footprint, and simply repair the bridges in place without any
alterations to the immediate environs. This approach was assumed in
recognition of the historic status of the River Street Bridge and its surroundings.
This subsection addresses additional permitting requirements or modified
permitting requirements that would result from incorporation of tunnel structures
and pedestrian/bicycle approaches to the tunnel.
3.1.4.1
Permits Required for In-Kind Reconstruction
Due to the nature of the work anticipated for a major rehabilitation project, it was
assumed that a number of permits and environmental review would be required
for in-kind reconstruction of the bridges. These permits and reviews include:
ƒ
National Environmental Policy Act (NEPA) Categorical Exclusion (if project
is constructed with federal funding)
ƒ
Massachusetts Environmental Policy Act (MEPA) consultation or Advisory
Opinion (in-kind replacement would not necessarily trigger an
Environmental Notification Form)
ƒ
Section 404 Category 2 General Permit (Category 2 triggered due to
potential effects on cultural resources; in the absence of effects on cultural
resources, only a Category 1, non-reporting, 404 permit would be
triggered)
ƒ
Section 401 Water Quality Certification, automatic issuance in conjunction
with Orders of Conditions
ƒ
Section 10 of the Rivers and Harbors Act of 1899 - Section 10 empowers
the USACE to regulate all work on structures in or affecting the course,
condition, or capacity of the navigable waters of the United States. It is
our understanding that the USACE has delegated its authority under
Section 10 to the USCG for bridge repair and maintenance work in the
Charles River (see Appendix A of the PGP for Massachusetts) and a
separate Corps review is not required.
ƒ
Chapter 91 Minor Modification (a process that only requires submission of
a letter, rather than a formal permit application)
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Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
ƒ
Local Notices of Intent/Orders of Conditions
ƒ
Massachusetts Historical Commission (MHC) Review (see discussion
under Section 3.1.5)
ƒ
Massachusetts Water Resources Authority (MWRA) 8(M) permit for work
within (MWRA easements)
ƒ
US Coast Guard (USCG) Construction Letter (provided that a project does
not alter navigation characteristics of bridges under USCG jurisdiction, no
formal permit application is required)
3.1.4.2
Permits Required for Tunnel Structure and Approaches
The incorporation of one or more tunnel structures and pedestrian/bicycle path
approaches would introduce substantial in-water work and removal of sediments,
alteration of river banks, changes in the floodway geometry, changes to the
navigability of the water sheet, direct filling of the river itself (which functions as
an anadromous fish run), and significant relocation of MWRA infrastructure.
As such, establishing pedestrian underpasses as depicted by the conceptual
designs presented in Appendix A would result in changes to the number and
types of permits required, and would alter the level of complexity associated with
environmental analyses required for those permits that had already been
anticipated.
Table 3.1 summarizes anticipated permits associated with the inclusion of tunnel
structures and approaches, noting changes in the complexity of each permit
process for those permits already required for an in-kind reconstruction of the
existing bridges.
Table 3.1
Summary of Permits and Environmental Reviews Required for
Addition of Pedestrian Tunnel and Approaches
Permit/
Review
Anticipated
previously?
Comments
NEPA
No (categorical
exclusion; if at
most)
May require Environmental Assessment due to impacts
to 4(f) parkland, water resources and water quality,
fisheries, and historic resources. (NEPA review
applicable if FHWA funds are used for construction or if
ACOE permit is considered a “major federal action”
MEPA
No – only
consultation or
Advisory Opinion
–no formal public
review
Alteration of river banks/impacts to parkland, reduction
of available water sheet, grading, drainage, fisheries
impacts, historic resource impacts & longer construction
period (traffic impacts) likely to necessitate full EIR and
more extensive analysis and discussion of issues.
13
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
MHC Review
Yes – but would
have proposed inkind replacement
More extensive discussions of alternatives, more
involvement in design/ selection of materials.
US Army
Corps of
Engineers
Review
(Section 10 of
the Rivers
and Harbors
Act and
Section 404 of
Clean Water
Act)
Yes – but 404
review was
previously less
involved; Section
10 was previously
assumed to be
delegated to the
USCG but may
now require
separate Corps
review.
More extensive discussions of alternatives justifying
discharge of fill material in the Charles River (per EPA’s
404(b)(1) Guidelines) and compensatory mitigation &
more in-depth analysis of public interest factors under
Section 10 including but not limited to fisheries impacts,
water quality impacts, and impacts to historic resources
Individual
Water Quality
Certification
(Section 401)
No (Order of
Conditions would
have served as
Water Quality
Certificate).
In-water work, including dredging required to establish
retaining wall foundations, will require individual water
quality certification. Dredging of greater than 100 cubic
yards would require development and approval of a
sediment sampling plan, laboratory analysis, and would
likely necessitate a dredge material disposal plan.
Section 401 application would also involve a
comprehensive alternatives analysis (similar to the
Corps review) and coordination with fisheries agencies.
(Likely fisheries time-of-year restriction would impact
construction schedule and increase costs)
US Coast
Guard Bridge
review
No – only Letter of
Construction
Permanent change in horizontal clearance would trigger
formal USCG review. See also Corp’s Section 10
discussion above.
Chapter 91
License and
Permit
No
Would require issuance of new license (in-kind
replacement of existing would not necessitate any
Chapter 91 notification, or minor modification letter at
most).
Wetlands
Protection Act
Notice of
Intent (NOI)
/Order of
Conditions
Yes – but
previously less
involved
Additional documentation would be required to address
changes to floodway, impacts to Land Under Water and
Bank, increased analysis required to characterize
sediment biochemistry, impacts to water quality and
wildlife and fisheries habitat (including preparation of
wildlife habitat evaluation and potential development of
compensatory mitigation plans per 310 CMR 10.60), and
impacts to groundwater. Would also require
development of more involved Stormwater Management
Plan to address increased impervious surfaces and
pumping/discharge of groundwater or stormwater that
may collect in tunnels. Likely to require increased
number of public hearings and longer review timeline.
See further discussion under Section 3.1.5
14
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
MWRA 8(M)
Yes, but primarily
administrative
review
Relocation of MWRA water lines would necessitate
close coordination with MWRA. The cost of such
relocation would be the responsibility of MassDOT, and
cannot be shifted to MWRA ratepayers. MWRA will not
allow existing water lines to be taken out of service
between May 15 and September 15
3.1.5. Tunnel: Architectural/Cultural Impacts
The Cambridge side improvements will cause a portion of the existing stone wall
to be removed and re-constructed. The condition of the wall is such that
reconstruction should be included in the proposed work. Current water levels in
the basin are kept below historic levels allowing the timber piling and cribbing
(supporting the walls) to deteriorate.
(This work shall be completed by the Public Archaeology Laboratory. Their work
requires most report subtasks to be completed prior to their involvement. )
3.1.6. Tunnel: Cost Impacts
3.1.6.1
Design/Permitting Cost
The greater complexity associated with design and permitting of a new tunnel
structure would involve a more intensive level of effort on the part of every facet
of the design team, including the structural engineers, geotechnical engineers,
traffic engineers (for construction staging), cultural resources specialist and
permitting consultant. Differentiating between costs attributable solely to the
design of a tunnel structure would itself involve a considerable amount of effort,
however a reasonable ballpark would be on the order of $600,000.
3.1.6.2
Construction Cost
The soldier pile construction required to support the existing roadway during the
box culvert installation may require heavy non-standard equipment. In addition,
installation of the drilled soldier pile and lagging earth support walls will likely
require night and/or weekend work (at a premium cost) to drill the soldier piles
and to construct temporary roadway decking. The existence of known
obstructions (such as existing utilities, concrete footings, walls, previous
cofferdams, and timber piles) and the potential for unknown obstructions in the fill
stratum will add complexity and cost to the construction project.
15
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
A boring program will need to be performed to evaluate existing subsurface
conditions at the tunnel boxes. It is presently assumed that the tunnel will be
constructed on grade after removal of any unsuitable fill and organic soils. The
borings are required to confirm these conditions so that the tunnel boxes do not
need to be supported on piles.
A cost summary is provided in Section 4 of this analysis, and a detailed
breakdown is provided in Appendix B.
3.1.6.3
Operations and Maintenance Costs
Additional ongoing costs would be incurred to operate and maintain the tunnel.
Such costs may include lighting, periodic inspections and repairs, litter and graffiti
removal, periodic surveillance or maintenance of surveillance cameras, pumping
of groundwater and ordinary sweeping/cleaning made somewhat more difficult
given the low elevation and enclosed nature of the tunnel.
3.1.7. Tunnel: Schedule Impacts
3.1.7.1 Design/Permitting Schedule
This alternative would significantly delay the issuance of a construction bid
package, due to the additional permitting and design related investigations
required.
16
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
3.1.7.2 Construction Schedule
In general due to the more complicated construction program, the overall
construction schedule would be increased to allow for establishment of a large
open cut trench with a multi-purpose structural roof for bracing horizontal load
and to maintain traffic. In addition, due to the anadromous fisheries habitat and
significant in-water work activities, it is anticipated that time-of-year restrictions
would be placed on any in-water activities (generally March 15-June 15 per MA
Wetlands Protection Act regulations although the Corps could require more
stringent restrictions based on consultations with the state and federal fisheries
resource agencies), while the MWRA will not allow water service to be shut off
for relocation of mains between May 15 and September 15.
Additionally, it is anticipated that work on the tunnel box will be required to occur
during limited night-time hours, and possibly in low headroom conditions below
decking. During construction, the complexity and potential for encountering
obstructions during installation of the earth support walls and excavation for the
tunnel box increases the probability for delays.
3.1.8. Tunnel: Traffic Impacts
This alternative will have negative traffic impacts during the tunnel construction
under the River Street Bridge approaches. Overnight/Weekend lane closures will
be required to make tunnel excavation preparations. It is anticipated that some
periods of complete bridge closure will be required to facilitate the extensive
utility relocation work, safely accommodate heavy equipment and cranes, and
manage construction materials.
Although traffic impacts relating to tunnel construction will be periodic, off-peak,
and brief, additional staging and phasing will be required to allow for excavation,
preparation, and temporary support of the existing roadway during tunnel
construction operations.
3.1.9. Tunnel: Recreational Considerations
The tunnel option would extend the period during which the shared use pathway
would not be accessible during construction, and would increase the length of
time that construction equipment may occupy the water sheet, thereby impacting
recreational boaters. Once constructed, the tunnel would benefit those path
users that choose to use it in lieu of the existing sidewalks and crosswalks.
There would be negligible impact to recreational boating once the tunnel and
approaches were constructed.
3.1.10.
Tunnel: Safety Considerations
The benefits associated with separating pedestrians and bicycles from vehicular
traffic include eliminating conflict with motor vehicles at intersections, significantly
increasing safety. Nonetheless, the introduction of tunnels may present certain
17
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
safety concerns due to the lack of visibility into the tunnels from nearby roads.
Such safety concerns can be mitigated to some extent by lighting and periodic
surveillance, or even introduction of surveillance cameras (in turn adding capital
and operational costs). A number of passageways along the Charles River, both
public and private, have been closed due to safety considerations.
3.2.
Alternative #2 – Boardwalk Beneath Arch
This option consists of constructing a pile supported boardwalk to pass through
the outer arches of the bridge. Pathway approaches would also be pilesupported, thereby minimizing the overall amount of direct fill into the Charles
River as compared to the tunnel alternative. However, this option would occupy
considerably more water sheet. This alternative is an approach similar to the
path connectivity constructed at the Boston University Bridge, however its
abutments are located considerably landward, such that the boardwalk in that
location remains very close to the shoreline. For purposes of this analysis, a
boardwalk with 12-foot clear railing to railing was assumed and would be routed
beneath the outer arches with the path surface at a minimum elevation of 108.5
(design flood elevation) and a minimum headroom of 10-feet for bicycle
compatibility. (Larger horizontal and vertical clearances were assumed for the
tunnel alternative to compensate for the effects of total enclosure)
A structural challenge of this option is the installation of piling beneath the bridge.
Due to the limited headroom and possible long pile embedment lengths, pile
splices may be required. Pre-augering of the piles may be required to prevent
settlement and damage to the existing arches.
(A floating path may also be considered as an alternative to a pile supported
boardwalk under the arch. Floating paths were not included at this level of
analysis, but may be considered under a future, more detailed analysis of the
boardwalk option.)
Reference Appendix A, pages A-3 & A-4
3.2.1. Boardwalk: Structural Impacts
No structural impacts to the bridge are required by the boardwalk option.
Drainage structures will also not be required. However, modification of the
existing stone retaining walls, guide rails, and park barriers will be required to
meet the boardwalk to the existing path.
3.2.2. Boardwalk: Geotechnical Considerations
The following geotechnical items need to be considered relative to construction
of the boardwalk:
•
Subsurface Conditions. Subsurface conditions generally consist of fill (at
the abutments) overlying natural sand and gravel, clay, glacial till and
18
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
bedrock. The thickness of these deposits is variable, the organics and clay
are compressible soils, and the depth to till and bedrock is unknown.
Support of the boardwalk will require installation of pile foundations.
•
Foundations. We anticipate that foundation loads will be relatively light and
(based on historic borings) could derive support primarily in side friction in
the natural clay stratum. Feasible foundations include driven timber or
composite plastic piles, except below the bridge arches where, due to low
headroom conditions, drilled mini-piles may be required. Pile spacing will be
specified by the structural boardwalk design, and pile locations will likely
need to be pre-augered or pre-excavated to clear potential obstructions from
rip-rap and debris along the river banks. Special precautions will need to be
used during drilled mini-pile construction (i.e. use of oversized temporary
casings and containment booms) to avoid potential loss of drilling fluids or
grout to the river.
•
Pile connections to the boardwalk would have to be incorporated directly
into the decking in order to avoid the need for construction of pile caps.
•
Subsurface Explorations. Prior to proceeding with design of the
boardwalk, borings will need to be performed, as a minimum, at each end
of the boardwalk. The available boring data is from the 1920s, which was
obtained using non-standard methods in comparison to those that are
used today (i.e. ASTM) and the data is based on borings taken in the river
rather than at the ends of the bridge where the boardwalks are proposed.
3.2.3. Boardwalk: Utility Impacts
No significant underground or above ground utility conflicts are anticipated by this
alternative.
3.2.4. Boardwalk: Environmental Permitting Impacts
Minor filling of open water and disturbance of freshwater wetlands is required by
this alternative. The most significant new environmental permitting
considerations include impacts to recreational use of the water sheet and
alteration of the historic setting.
A summary of permits anticipated for reconstruction of the bridge within its
current footprint was provided in Section 3.1.5.1. Table 3.2 below lists
anticipated permits required for the construction of Pedestrian Boardwalk and its
approaches.
19
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
Table 3.2
Summary of Permits and Environmental Reviews Required for
Addition of Pedestrian Boardwalk
Permit/
Review
Anticipated
previously?
Comments
NEPA
No
(categorical
exclusion; at
most)
May require Environmental Assessment due to impacts to 4(f)
parkland, water resources and water quality, fisheries, and
historic resources. (NEPA review applicable if FHWA funds are
used for construction or if ACOE permit is considered a “major
federal action”
MEPA
No – only
consultation
or Advisory
Opinion –no
formal public
review
Introduction of boardwalk element is more likely to be considered
an “adverse impact” by MHC, which in turn may make it more
difficult to develop a Memorandum of Agreement to stay below
MEPA review threshold for historic resources. MEPA may also
assert jurisdiction on the premise that a Superseding Order of
Conditions may be required for the project.
MHC
Review
Yes – but
would have
proposed inkind
replacement
More extensive discussions of alternatives, more involvement in
design/ selection of materials. Likely to be viewed more
unfavorably than a tunnel structure (which is likely to be viewed
unfavorably)
US Army
Corps of
Engineers
Review
(Section 10
of the
Rivers and
Harbors Act
and Section
404 of
Clean
Water Act))
Yes – but 404
review was
previously
less involved;
Section 10
was
previously
assumed to
be delegated
to the USCG
but may now
require
separate
Corps review.
More extensive discussions of alternatives justifying introduction
of fill from pile-supported structure (assumes the Corps
considers the piles to be fill material) and reduction in navigable
water sheet and other public interest factors under Section 10.
Water
Quality
Certification
(Section
401)
To Be
Determined
If total cumulative fill from piles exceeds 5,000 s.f. of impact to
land under water then an individual Water Quality Certification
would be required.
US Coast
Guard
Bridge
review
No – only
Letter of
Construction
Permanent change in horizontal clearance would trigger formal
USCG review.
See further discussion under Section 3.2.5
20
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
Chapter 91
License and
Permit
No
Would require issuance of new license (in-kind replacement of
existing would not necessitate any Chapter 91 notification, or
minor modification letter at most). Chapter 91 review would
consider impacts to recreational use of the water sheet.
Wetlands
Protection
Act Notice
of Intent
(NOI)
/Order of
Conditions
Yes – but
previously
less involved
The proposed pile supported boardwalk could be permitted as a
Limited Project under 310 CMR 10.53(3)(j). Additional
documentation would be required to address alternatives, pile
installation techniques including information describing flowage
of water and light conditions necessary to maintain aquatic
vegetation (if present within footprint). Time of Year restrictions
would likely apply. Likely to require increased number of public
hearings and longer review timeline.
3.2.5. Boardwalk: Architectural/Cultural Impacts
This option effectively eliminates the availability of the outer most arches to
accommodate rowing craft in the Charles River. Current marine traffic patterns
on the river promote use of the outer arches by skullers and minimal use of the
center arch by rowing crews with a coxswain or coach. Should the outer arches
be eliminated as an option for navigation, all traffic will be bottlenecked into the
center arch, creating a narrow bi-directional navigation pattern accommodating
all types of navigation and experience/skill levels. In addition, the Head of the
Charles Regatta currently uses the arches of the River Street Bridge for its race
course. The cultural impacts of this alternative on the rowing community would
be severely negative.
The boardwalk alignment required by this alternative places the boardwalk well
into the Charles River, nearly out to the centerlines of the outer bridge arches.
While a subjective assessment, it is expected that most observers and cultural
resource stewards would determine that this alignment would significantly alter
the river view in an objectionable manner.
3.2.6. Boardwalk: Cost Impacts
3.2.6.1
Design/Permitting Cost
The greater complexity associated with design and permitting of new boardwalk
and approach structures would involve a more intensive level of effort on the part
of every facet of the design team, including the structural engineers, geotechnical
engineers, traffic engineers (for construction staging), cultural resources
specialist and permitting consultant. Differentiating between costs attributable
solely to the design of a tunnel structure would itself involve a considerable
amount of effort, however a reasonable ballpark would be on the order of
$600,000
21
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
3.2.6.2
Construction Cost
This alternative requires significant in-water work which typically results in an
appreciable price premium over similar land based construction activities. As
previously mentioned, installation of the boardwalk on piles will require special
equipment and alternative construction methods due to the complexity of
installing piles in an environment with such low head room incurring an additional
cost premium. In addition, the complexity and potential for encountering unknown
obstructions during pile installation activities increases the probability for
additional costs to be incurred during construction.
A boring program will need to be performed to evaluate existing subsurface
conditions at each end of the boardwalk. It is presently assumed that the
boardwalk will be supported on pile foundations supported in the natural soils
underlying the fill and organic soils. The depth to the top of sand and gravel and
to the top of clay should be defined, as well as the relative density in order to
provide engineering parameters for design of the piles.
This feasibility analysis considers a generic timber structure of the dimensions
previously mentioned and assumes construction costs only, for project planning
purposes. Plastic piles and plastic decking are also possible, but not included in
this analysis. Plastic piles and decking generally have higher construction costs
and lower maintenance costs. A cost summary is provided in Section 4 of this
analysis, and a detailed breakdown is provided in Appendix B.
3.2.6.3
Operations and Maintenance Costs
Lifecycle cost of in-water marine structures varies with chosen construction
materials and method of weather/ice protection as well as maintenance
practices. Detailed cost comparison of the various available construction
materials corresponding to anticipated life cycle maintenance costs is not
presented here as it is beyond the scope of this feasibility study. It is only
mentioned because the facility is clearly expected to be used heavily by the
public and therefore will require regular inspection and maintenance for public
safety.
3.2.7. Boardwalk: Schedule Impacts
3.2.7.1
Design/Permitting Schedule
This alternative has negative impacts to the contract and design schedule due to
the additional permitting and design related investigations required.
22
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
3.2.7.2
Construction Schedule
In general due to the more complicated construction program, the overall
construction schedule would be increased to allow for installation of piles to
support the boardwalk as well as approach structures. In addition, due to the
anadromous fisheries habitat and significant in-water work activities, it is
anticipated that time-of-year restrictions would be placed on any in-water
activities (generally March 15-June 15 per MA Wetlands Protection Act
regulations although the Corps could require more stringent restrictions based on
consultations with the state and federal fisheries resource agencies).
In addition, the complexity and potential for encountering unknown obstructions
during pile installation activities increases the probability for delays during
construction.
3.2.8. Boardwalk: Traffic Impacts
The boardwalk option causes no significant impact to roadway traffic, but a
significant impact to river traffic, both during and after construction. Like normal
roadway maintenance and protection of traffic requirements, on the Charles
River, coordination of the work effort with river traffic has similar levels of effort
and importance.
3.2.9. Boardwalk: Recreational Considerations
The boardwalk option would have limited impact on pedestrian, bicyclists and
boaters during construction. However, once constructed, the board walk would
occupy a large area of the water sheet, and effectively eliminate water access to
the span(s) in which the boardwalk(s) were located. To minimize such impacts,
consideration could be given to constructing only one boardwalk (if any) per
bridge.
3.2.10.
Boardwalk: Safety Considerations
The benefits associated with separating pedestrians and bicycles from vehicular
traffic include eliminating conflict with motor vehicles at intersections, significantly
increasing safety. Like the tunnel but to a lesser degree, the boardwalk would
place pedestrians and bicyclists in a location that is not as visible to motorists
and others as at-grade paths, however only for a very short distance. Lighting of
the boardwalk should be considered to increase nighttime safety, however it is
anticipated that MHC and others would object to such lighting given how
prominent it would appear in relationship to the bridge and water sheet (vs tunnel
lighting, which would be largely shielded from view).
3.3.
Alternative #3 – At Grade Enhancements
This alternative involves the incorporation of improvements into the project which
promotes bicycle and pedestrian use and improves safety within the existing
footprint of the bridge and adjacent shared use pathway network. The at-grade
23
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
enhancements that would be considered include, but may not be limited to:
geometric (e.g., sidewalk width and configuration, particularly at corners),
visibility/sight triangle, signing and striping, signal timing, and curb ramp
improvements.
Significantly, part of this alternative is to include design features into the project
that will allow the bridge structure to facilitate future construction of an
underpass. Compared to the other alternatives, the at-grade enhancements
alternative has no impact to any of the areas covered by this feasibility analysis.
There are no negative impacts that prelude incorporating pedestrian and
structural improvements at the bridge approach intersections into the
rehabilitation work provided that these improvements do not encroach into the
river and do not adversely impact the historic integrity of the bridge itself and the
broader Charles River Basin National Historic District.
As part of this alternative, the bridge reconstruction program would include
provisions for wall knock-outs at potential tunnel locations with corresponding
structural reconstruction and compatible architectural treatments, location and
verification of buried utilities.
This alternative will be considered as part of the rehabilitation project whether or
not grade separation is feasible.
24
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
4.0
Summary of Findings
As previously stated, The Shared Use Paths and Greenways section of the 2006
MassDOT's PD&DG provides a set of factors for the designer to consider when
determining whether grade separation is an appropriate option at a given
location. The summary of the factors are provided in the following matrix, as well
as in a table matrix, attached as Appendix C.
4.1.
Alternative #1 - Tunnel Through Abutment
The most challenging alternative requires extensive utility locating and utility
owner coordination and assistance. The scheme has hidden uncertainties. It
also requires additional environmental permitting and review which clearly
impacts the desired construction schedule. It is the least intrusive alternative
with respect to the river, and its users, and has the potential to further reduce
intrusion into the water way with the application of additional retaining walls. The
trade off for less impact on the waterway is more impact to utilities, traffic, and
greater uncertainty.
4.2.
Alternative #2 - Boardwalk Beneath Arch
From an up front cost standpoint, the two alternatives presented here are
relatively even. However, the boardwalk alternative is likely the most difficult to
permit and obtain community approval. Where it trades for less road user
impact, it more than makes up for impact on the boating community. It is also
therefore likely to be a scheduling problem, although it is not an option that needs
to be connected to the already scheduled bridge rehabilitation work.
Construction of a boardwalk has the least physical obstacles, with respect to
utilities and road users, but is most probable to have insurmountable aesthetic
and cultural obstacles. It is also expected to be the alternative with the shortest
lifecycle, highest maintenance need, and highest public liability from a user
safety standpoint.
4.3.
Alternative #3 - At Grade Enhancements
The at-grade enhancements alternative, compared to the other considerations,
has no appreciable additional construction cost or schedule impacts to the
already planned bridge rehabilitation work. Significantly, this alternative would
not preclude the potential for constructing either a tunnel or a boardwalk at a
future date. Provisions to facilitate construction of a tunnel could be made to the
ongoing design for rehabilitation of the bridge. As previously stated, Alternative 3
will be considered as part of the rehabilitation project whether or not grade
separation is feasible.
25
Rehabilitation of the River Street Bridge
MassDOT Project Number605527
Bike & Pedestrian Underpass Feasibility Study
Cost Summary
Alternative #1
Concrete Tunnel
Alternative #2
Boardwalk
Boston (Memorial Drive)
$2,225,000
$1,551,000
Cambridge (Soldier’s Field Rd)
$2,218,000
$1,656,000
Total Cost
$4,443,000
$3,207,000
See Appendix B for itemized breakdown of the construction cost estimate
indicated in Table 1, above.
26
Appendix A – Exhibits
A-1
Appendix B – Cost Estimates
B-1
Project:
Job #:
Made By:
Checked By:
MassDOT Bridge Pedestrian/Bicycle Underpass
2589
JLA
TL
Alternative #1: River Street Boston Side, Tunnel Underpass
ENGINEER'S COST ESTIMATE - Feasability Study
SEQ NO.
PAY ITEM DESCRIPTION
PAY UNIT
QTY.
UNIT PRICE
COST
ADMINISTRATIVE
MOBILIZATION
MAINTENANCE & PROTECTION OF TRAFFIC
CLEARING SITE
SOIL EROSION & SEDIMENT CONTROL
FINAL CLEAN UP
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
$100,000.00
$75,000.00
$15,000.00
$26,000.00
$38,000.00
$100,000.00
$75,000.00
$15,000.00
$26,000.00
$38,000.00
ROADWAY
EXCAVATION
BORROW EXCAVATION
BASE COURSE
HMA, SURFACE COURSE
HMA, BASE COURSE
REINFORCED CONCRETE CULVERT PIPE
INLET
MANHOLE
HEADWALL
CURB
SIDEWALK
TRAFFIC STRIPING
SIGNS
BIKE PATH
CY
CY
SY
T
T
LF
U
U
U
LF
SY
LS
LS
SY
3000
3000
315
45
75
160
4
2
2
140
160
LS
LS
360
$138.00
$25.00
$14.00
$88.00
$72.50
$45.00
$3,125.00
$5,000.00
$2,500.00
$31.25
$62.50
$10,000.00
$4,000.00
$42.50
$414,000.00
$75,000.00
$4,410.00
$3,960.00
$5,437.50
$7,200.00
$12,500.00
$10,000.00
$5,000.00
$4,375.00
$10,000.00
$10,000.00
$4,000.00
$15,300.00
LS
LF
LF
LF
LF
LF
LS
LS
LS
140
$50,000.00
$675.00
$862.50
$912.50
140
LS
LS
$1,336.00
$20,000.00
$20,000.00
$50,000.00
$94,500.00
$0.00
$0.00
$0.00
$187,040.00
$20,000.00
$20,000.00
STRUCTURAL
GEOTECHNICAL INVESTIGATION & MONITORING
PRECAST CONCRETE BOX CULVERT, 10'X16'
COFFERDAM & DEWATERING OPERATIONS
BRIDGE PARAPET
EXCAVATION SUPPORT
MISC CONCRETE, STAIRWELL
RETAINING WALLS, 4 FT HIGH
RETAINING WALLS, 6 FT HIGH
RETAINING WALLS, 8 FT HIGH
RETAINING WALLS, 10 FT HIGH
LS
LF
LS
LF
SF
LS
LF
LF
LF
LF
LS
80
LS
140
2500
LS
$40,000.00
$3,625.00
$150,000.00
$800.00
$250.00
$10,000.00
$500.00
$800.00
$1,000.00
$1,500.00
$40,000.00
$290,000.00
$150,000.00
$112,000.00
$625,000.00
$10,000.00
$0.00
$0.00
$0.00
$0.00
ELECTRICAL/TRAFFIC SIGNAL
LIGHTING, TUNNEL
STREET LIGHTING
TRAFFIC SIGNAL STANDARD
TRAFFIC SIGNAL CONTROLLER
LS
LS
U
U
LS
LS
$15,000.00
$15,000.00
$12,000.00
$15,000.00
$15,000.00
$15,000.00
$0.00
$0.00
LANDSCAPING
FENCE
RAILING
PLANTING
LF
LF
LS
50
360
LS
$60.00
$85.00
$35,000.00
$3,000.00
$30,600.00
$35,000.00
UTILITY
UTILITY LOCATION & VERIFICATION
WATER MAIN RELOCATION, 30"
WATER MAIN RELOCATION, 42"
WATER MAIN RELOCATION, 60"
GAS MAIN RELOCATION, 30"
UNDERGROUND ELECTRICAL RELOCATION
UNDERGROUND TELEPHONE RELOCATION
TOTAL OF ADMINISTRATIVE ITEMS
TOTAL OF ROADWAY ITEMS
TOTAL OF UTILITY ITEMS
TOTAL OF STRUCTURAL ITEMS
TOTAL OF ELECTRICAL ITEMS
TOTAL OF LANDSCAPING ITEMS
INFLATION (percent, for 2 years)
SUBTOTAL ALL CONSTRUCTION ITEMS
2.5%
$254,000.00
$167,182.50
$371,540.00
$1,227,000.00
$30,000.00
$68,600.00
$107,000.00
$2,225,322.50
Project:
Job #:
Made By:
Checked By:
MassDOT Bridge Pedestrian/Bicycle Underpass
2589
JLA
TL
Alternative #1: River Street Cambridge Side, Tunnel Underpass
ENGINEER'S COST ESTIMATE - Feasability Study
SEQ NO.
PAY ITEM DESCRIPTION
PAY UNIT
QTY.
UNIT PRICE
COST
ADMINISTRATIVE
MOBILIZATION
MAINTENANCE & PROTECTION OF TRAFFIC
CLEARING SITE
SOIL EROSION & SEDIMENT CONTROL
FINAL CLEAN UP
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
$100,000.00
$75,000.00
$15,000.00
$26,000.00
$38,000.00
$100,000.00
$75,000.00
$15,000.00
$26,000.00
$38,000.00
ROADWAY
EXCAVATION
BORROW EXCAVATION
BASE COURSE
HMA, SURFACE COURSE
HMA, BASE COURSE
REINFORCED CONCRETE CULVERT PIPE
INLET
MANHOLE
HEADWALL
CURB
SIDEWALK
TRAFFIC STRIPING
SIGNS
BIKE PATH
CY
CY
SY
T
T
LF
U
U
U
LF
SY
LS
LS
SY
3000
5000
333
50
75
174
2
0
2
155
210
LS
LS
333
$138.00
$25.00
$14.00
$88.00
$72.50
$45.00
$3,125.00
$5,000.00
$2,500.00
$31.25
$62.50
$10,000.00
$4,000.00
$42.50
$414,000.00
$125,000.00
$4,662.00
$4,400.00
$5,437.50
$7,830.00
$6,250.00
$0.00
$5,000.00
$4,843.75
$13,125.00
$10,000.00
$4,000.00
$14,152.50
LS
LF
LF
LF
LF
LF
LS
LS
LS
120
$50,000.00
$675.00
$862.50
$912.50
120
LS
LS
$1,336.00
$20,000.00
$20,000.00
$50,000.00
$81,000.00
$0.00
$0.00
$0.00
$160,320.00
$20,000.00
$20,000.00
STRUCTURAL
GEOTECHNICAL INVESTIGATION & MONITORING
PRECAST CONCRETE BOX CULVERT, 10'X16'
COFFERDAM & DEWATERING OPERATIONS
BRIDGE PARAPET
EXCAVATION SUPPORT
MISC CONCRETE, STAIRWELL
RETAINING WALLS, 4 FT HIGH
RETAINING WALLS, 6 FT HIGH
RETAINING WALLS, 8 FT HIGH
RETAINING WALLS, 10 FT HIGH
LS
LF
LS
LF
SF
LS
LF
LF
LF
LF
LS
80
LS
140
2500
LS
$40,000.00
$3,625.00
$150,000.00
$800.00
$250.00
$10,000.00
$500.00
$800.00
$1,000.00
$1,500.00
$40,000.00
$290,000.00
$150,000.00
$112,000.00
$625,000.00
$10,000.00
$0.00
$0.00
$0.00
$0.00
ELECTRICAL/TRAFFIC SIGNAL
LIGHTING, TUNNEL
STREET LIGHTING
TRAFFIC SIGNAL STANDARD
TRAFFIC SIGNAL CONTROLLER
LS
LS
U
U
LS
LS
$15,000.00
$15,000.00
$12,000.00
$15,000.00
$15,000.00
$15,000.00
$0.00
$0.00
LANDSCAPING
FENCE
RAILING
PLANTING
LF
LF
LS
90
280
LS
$60.00
$85.00
$35,000.00
$5,400.00
$23,800.00
$35,000.00
UTILITY
UTILITY LOCATION & VERIFICATION
WATER MAIN RELOCATION, 30"
WATER MAIN RELOCATION, 42"
WATER MAIN RELOCATION, 60"
GAS MAIN RELOCATION, 30"
UNDERGROUND ELECTRICAL RELOCATION
UNDERGROUND TELEPHONE RELOCATION
TOTAL OF ADMINISTRATIVE ITEMS
TOTAL OF ROADWAY ITEMS
TOTAL OF UTILITY ITEMS
TOTAL OF STRUCTURAL ITEMS
TOTAL OF ELECTRICAL ITEMS
TOTAL OF LANDSCAPING ITEMS
INFLATION (percent, for 2 years)
SUBTOTAL ALL CONSTRUCTION ITEMS
2.5%
$254,000.00
$204,700.75
$331,320.00
$1,227,000.00
$30,000.00
$64,200.00
$107,000.00
$2,218,220.75
Project:
Job #:
Made By:
Checked By:
MassDOT Bridge Pedestrian/Bicycle Underpass
2589
JLA
TL
Alternative #2: River Street Boston Side, Boardwalk Underpass
ENGINEER'S COST ESTIMATE - Feasability Study
SEQ NO.
PAY ITEM DESCRIPTION
PAY UNIT
QTY.
UNIT PRICE
COST
ADMINISTRATIVE
MOBILIZATION
MAINTENANCE & PROTECTION OF TRAFFIC
CLEARING SITE
SOIL EROSION & SEDIMENT CONTROL
FINAL CLEAN UP
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
$150,000.00
$25,000.00
$15,000.00
$16,000.00
$25,000.00
$150,000.00
$25,000.00
$15,000.00
$16,000.00
$25,000.00
ROADWAY
EXCAVATION
BASE COURSE
HMA, SURFACE COURSE
HMA, BASE COURSE
REINFORCED CONCRETE CULVERT PIPE
INLET
MANHOLE
HEADWALL
CURB
SIDEWALK
TRAFFIC STRIPING
SIGNS
BIKE PATH, 10-FT WIDE
CY
SY
T
T
LF
U
U
U
LF
SY
LS
LS
SY
54
$138.00
$14.00
$88.00
$72.50
$45.00
$3,125.00
$5,000.00
$2,500.00
$31.25
$62.50
$10,000.00
$4,000.00
$42.50
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$2,295.00
$50,000.00
$675.00
$862.50
$912.50
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
UTILITY
UTILITY LOCATION & VERIFICATION
WATER MAIN RELOCATION, 30"
WATER MAIN RELOCATION, 42"
WATER MAIN RELOCATION, 48"
WATER MAIN RELOCATION, 60"
GAS MAIN RELOCATION, 30"
UNDERGROUND ELECTRICAL RELOCATION
UNDERGROUND TELEPHONE RELOCATION
STRUCTURAL
TIMBER BOARDWALK
LS
LF
LF
LF
LF
LF
LS
LS
$1,336.00
$20,000.00
$20,000.00
SF
4620
$265.00
RETAINING WALLS, 4 FT HIGH
RETAINING WALLS, 6 FT HIGH
RETAINING WALLS, 8 FT HIGH
RETAINING WALLS, 10 FT HIGH
LF
LF
LF
LF
0
0
0
0
$500.00
$800.00
$1,000.00
$1,500.00
ELECTRICAL/TRAFFIC SIGNAL
LIGHTING, TUNNEL
STREET LIGHTING
TRAFFIC SIGNAL STANDARD
TRAFFIC SIGNAL CONTROLLER
LS
LS
U
U
LS
LS
LANDSCAPING
FENCE
RAILING
PLANTING
LF
LF
LS
TOTAL OF ADMINISTRATIVE ITEMS
TOTAL OF ROADWAY ITEMS
TOTAL OF UTILITY ITEMS
TOTAL OF STRUCTURAL ITEMS
TOTAL OF ELECTRICAL ITEMS
TOTAL OF LANDSCAPING ITEMS
INFLATION (percent, for 2 years)
SUBTOTAL ALL CONSTRUCTION ITEMS
2.5%
40
LS
$1,224,300.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$85.00
$15,000.00
$0.00
$3,400.00
$15,000.00
$231,000.00
$2,295.00
$0.00
$1,224,300.00
$0.00
$18,400.00
$75,000.00
$1,550,995.00
Project:
Job #:
Made By:
Checked By:
MassDOT Bridge Pedestrian/Bicycle Underpass
2589
JLA
TL
Alternative #2: River Street Cambridge Side, Boardwalk Underpass
ENGINEER'S COST ESTIMATE - Feasability Study
SEQ NO.
PAY ITEM DESCRIPTION
PAY UNIT
QTY.
UNIT PRICE
COST
ADMINISTRATIVE
MOBILIZATION
MAINTENANCE & PROTECTION OF TRAFFIC
CLEARING SITE
SOIL EROSION & SEDIMENT CONTROL
FINAL CLEAN UP
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
$150,000.00
$27,000.00
$15,000.00
$16,000.00
$27,000.00
$150,000.00
$27,000.00
$15,000.00
$16,000.00
$27,000.00
ROADWAY
EXCAVATION
BASE COURSE
HMA, SURFACE COURSE
HMA, BASE COURSE
REINFORCED CONCRETE CULVERT PIPE
INLET
MANHOLE
HEADWALL
CURB
SIDEWALK
TRAFFIC STRIPING
SIGNS
BIKE PATH, 10-FT WIDE
CY
SY
T
T
LF
U
U
U
LF
SY
LS
LS
SY
32
$138.00
$14.00
$88.00
$72.50
$45.00
$3,125.00
$5,000.00
$2,500.00
$31.25
$62.50
$10,000.00
$4,000.00
$42.50
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$1,360.00
$50,000.00
$675.00
$862.50
$912.50
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
UTILITY
UTILITY LOCATION & VERIFICATION
WATER MAIN RELOCATION, 30"
WATER MAIN RELOCATION, 42"
WATER MAIN RELOCATION, 48"
WATER MAIN RELOCATION, 60"
GAS MAIN RELOCATION, 30"
UNDERGROUND ELECTRICAL RELOCATION
UNDERGROUND TELEPHONE RELOCATION
STRUCTURAL
TIMBER BOARDWALK
LS
LF
LF
LF
LF
LF
LS
LS
$1,336.00
$20,000.00
$20,000.00
SF
4980
$265.00
RETAINING WALLS, 4 FT HIGH
RETAINING WALLS, 6 FT HIGH
RETAINING WALLS, 8 FT HIGH
RETAINING WALLS, 10 FT HIGH
LF
LF
LF
LF
0
0
0
0
$500.00
$800.00
$1,000.00
$1,500.00
ELECTRICAL/TRAFFIC SIGNAL
LIGHTING, TUNNEL
STREET LIGHTING
TRAFFIC SIGNAL STANDARD
TRAFFIC SIGNAL CONTROLLER
LS
LS
U
U
LS
LS
LANDSCAPING
FENCE
RAILING
PLANTING
LF
LF
LS
TOTAL OF ADMINISTRATIVE ITEMS
TOTAL OF ROADWAY ITEMS
TOTAL OF UTILITY ITEMS
TOTAL OF STRUCTURAL ITEMS
TOTAL OF ELECTRICAL ITEMS
TOTAL OF LANDSCAPING ITEMS
INFLATION (percent, for 2 years)
SUBTOTAL ALL CONSTRUCTION ITEMS
2.5%
60
LS
$1,319,700.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$0.00
$85.00
$15,000.00
$0.00
$5,100.00
$15,000.00
$235,000.00
$1,360.00
$0.00
$1,319,700.00
$0.00
$20,100.00
$80,000.00
$1,656,160.00
Appendix C – Evaluation of Alternatives
C-1
Summary Comparison of Alternative Approaches to Shared Use Path Enhancements
Note: All data are preliminary and reflect 10% design information.
At-Grade Enhancements
Element to Be
Evaluated
Tunnel Underpasses
Boardwalk Structure
Score/Ranking:
A -substantial benefit
B - benefit
C - neutral/ minor (compared
to existing conditions)
D - negative impact
F - fails
Comments
Ped/Bike
Connectivity
C
Limited improvements; nonmotorized access still interrupted by
signals at intersections
C
Constructability /
Engineering Issues
No issues
C
Utility Impacts
negligible
Historic /
Archeological
Impacts
A
Provides most direct continuity
B
Uninterrupted,
circuitous route
somewhat
D
D
On Both Cambridge and Boston Side,
construction
MAY
NOT
BE
FEASIBLE. Piles to support tunnel
structure must be installed at angles
to avoid contact with bridge
abutments
Pile installation beneath bridge arches
will be difficult, time consuming, and
expensive due to low head room
D
C
Would require relocation of major
water and gas mains. Construction
season may be limited to activity
outside of peak demand for affected
utilities.
None
C
D or F
(tbd by MHC)
D or F
(tbd by MHC)
No adverse impact anticipated with
use of similar materials and
incorporation of appropriate details
Unknown potential archaeological
impacts associated with establishing
footings and excavation
Negative impacts associated with
introduction
of
new
structures
interrupting appearance of bridge
arches / setting of bridge structures
Negative impacts associated with
changes
to
bridge
abutments,
introduction of new approaches
2795/Rvr&Wstrn
but
1
At-Grade Enhancements
Element to Be
Evaluated
Tunnel Underpasses
Boardwalk Structure
Score/Ranking:
A -substantial benefit
B - benefit
C - neutral/ minor (compared
to existing conditions)
D - negative impact
F - fails
Comments
C
Wetlands/Waterways
/Water Quality
Impacts and
Permitting
D
F
(due to extent of impact
to water sheet)
No impacts beyond those
associated with bridge
reconstruction project
26,600 SF filling of Land Under Water
for tunnel approaches
Will require development of sediment
sampling plan
Comprehensive discussion of
alternatives required for 404, 401 and
WPA permit applications; agencies
may not concur that the approach is
the “Least Environmentally Damaging
Practicable Alternative”
Will require Chapter 91 license; DEP
will consider impacts to boating
community
Minimal direct alteration of Land
Under Water for boardwalk piers
(approx 2,000 SF)
Comprehensive discussion of
alternatives required for 404, 401 and
WPA permit applications; agencies
may not concur that the approach is
the “Least Environmentally Damaging
Practicable Alternative”
Will require Chapter 91 license; DEP
will consider impacts to boating
community
USCG may not allow significant
intrusion into navigable waterway
Necessitates USGC review
C
Safety & Security
Not as desirable as gradeseparation from safety perspective
Grade separation provides improved
safety, however security
compromised due to lack of visibility
into tunnel from vehicles/passers by
C
Implications for
Other Users
D
Grade separation provides improved
safety,
however
security
compromised due to lack of visibility
into tunnel from vehicles/passers by
D
F
(due to footprint of
occupied water sheet
Limited encroachment into vehicular
way
No impacts to boating community
No impacts to vehicular way
No impacts to vehicular way
Approaches would occupy a portion
of the water sheet, however newlyoccupied water sheet would be close
to existing shoreline (minimal impacts
to boating community)
Bridge design necessitates that the
boardwalk extend approx 100 feet
from existing seawall and 60 feet from
shoreline to clear abutment and pass
through arch with sufficient headroom
D
D
C
Cost
Cost neutral
2795/Rvr&Wstrn
D
$4,443,000
$3,207,000
2
At-Grade Enhancements
Element to Be
Evaluated
Tunnel Underpasses
Boardwalk Structure
Score/Ranking:
A -substantial benefit
B - benefit
C - neutral/ minor (compared
to existing conditions)
D - negative impact
F - fails
Comments
Operation/
Maintenance Issues
C
Negligible operations and
maintenance issues
D
Periodic inspections required
Ongoing
pumping
2795/Rvr&Wstrn
D
cost
associated
Moderate additional costs associated
with construction
with
Shortest life span among alternatives
before total replacement required
3