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Glossary of Terms

A Abutment:

A structure built to support the end of a bridge.

Amtrak (National Railroad Passenger Corporation):

America's national rail operator.

Approach/Approach Span:

The part of the bridge that carries traffic from land to the bridge structure. The span connecting an abutment with the main span of a bridge.

Area of Potential Effect:

The geographic area within which a proposed project may directly or indirectly cause alterations in the character or use of historic properties, if any such properties exist.

B Barge:

A flat-bottomed boat for carrying freight, typically on canals and rivers, either under its own power or towed by another vessel.

Bascule bridge:

A movable bridge that utilizes gears, motors and counterweights to pivot its span upward at an angle and allow waterway traffic to pass beneath the bridge.

A Bascule Bridge
Bascule Bridge - West Seattle Bridge, Seattle Washington
Solid rock beneath soil or other loose deposits.
C Catenary:

An overhead wire that carries power to trains.

A Catenary
Overhead catenary system on the New Haven Line.

A watertight enclosure constructed in waterlogged soil and pumped dry so that construction can take place within a waterway.

A Cofferdam
A cofferdam on the Ohio River near Olmsted, Pulaski County, Illinois.
Provides overhead electric power transmission.
Connecticut Environmental Policy Act (CEPA):
Identifies and evaluates the impacts of proposed State actions that could have the potential to significantly affect the environment.
Conceptual Engineering:
Design phase that describes the proposed system in terms of integrated ideas about purpose, functionality, behavior and aesthetics.
Construction Engineering:
Responsible for the design, management and oversight of projects within the construction phase.
Construction Manager-General Contractor:
Plans, coordinates, budgets and supervises construction projects from development to completion. This model offers certain advantages in project delivery like a streamlined procurement process, greater accuracy and flexibility in regards to scope, schedule and budget, more effective risk management and the capabilities of the general contractor and design team are maximized to provide specialized expertise.
Construction Phasing:
Separating a project into manageable sections with different completion dates where the stages of design and construction may overlap.
Control House:
A small facility near a movable bridge where switches, signals and personnel controlling the movable span are located.
D Drilled Shaft Foundations:
A type of bridge foundation in which concrete is placed within a hole drilled into the ground, providing deep foundations for the bridge and retaining walls.
E Easements:
A right to cross or otherwise use someone else's land for a specified public purpose.
Environmental Assessment:
A level of environmental documentation prepared to detail impacts to the natural and man-made environment through study and analysis. For additional details regarding the Walk Bridge Program's Environmental Assessment, click here.
F Federal Navigation Channel/ Navigable Waters:
The limits of a defined channel where it is safe to operate a watercraft. Navigable waters provide a channel for transportation of people and goods as designated by federal code. The U.S. Coast Guard makes navigability determinations regarding specific waterways or portions of waterways to determine its jurisdiction on those waterways.
Final Design:
The last phase of a design project in which preparations of calculations, plans, and specifications for construction are made
Fixed Approach Spans:
Portion of the bridge, located outside the limits of the navigation channel, that carries traffic to the main part of the bridge and does not move to accommodate navigation.
Fixed Bridge:
A bridge whose height above a waterway is permanent.
The part of the ground surface inundated with water on a recurring basis.
G Geotechnical Screening:
Investigations of the ground, soil and rock used to identify foundation types for proposed structures.

A main supporting beam that carries a load along its length by resisting bending.

A Girder
Girders supporting the Ann Street Railroad Bridge, Norwalk CT
H High Tower:
A tall pier or frame supporting the cable of a suspension bridge.
I Intertidal Habitat:
A natural environment between land and sea that is above water at low tide and underwater at high tide.
L Life Cycle Costs:
Upon being placed into service, the accumulation of the expenses required to inspect and maintain a bridge (or other asset) during its projected life.
M Marine Traffic:
Water-going vessels traveling along a seaway, riverway, harbor or other navigable waterway.
Measures taken to minimize adverse impacts.
Movable Span:
A bridge across a navigable waterway that can temporarily move to allow for the passage of boats and barges.
N National Environmental Policy Act (NEPA):
Federal regulations outlining policies and procedures for documenting environmental impacts of a proposed action.
Northeast Corridor (NEC):
The rail line running from Boston, Massachusetts to Washington, D.C. with branches serving other metropolitan areas. The Northeast Corridor is owned primarily by Amtrak and is used by Amtrak's Acela Express and Northeast Regional services in addition to several commuter and freight rail services. The Northeast Corridor is the busiest passenger rail line in the United States by ridership and service frequency.
O Operational Redundancy:

The ability to maintain train service on a limited number of tracks following an event that would have otherwise rendered all tracks inoperable.

A Operational Redundancy
The Walk Bridge Replacement is a redundant structure with two, independent spans carrying two tracks each. If one span experiences an outage, service is maintained on the other span.
Overhead Counterweights:
Large weights used to offset the mass of a movable span, and located above the railroad tracks.
P Pile:
A long steel or concrete column driven deep into the ground to form part of a bridge foundation or substructure.
Pivot Pier:

The central support of a swing span around which the movable span rotates.

A Pivot Pier
The existing Walk Bridge rotates around a central support, or pivot pier to open for marine traffic.
Positive Train Control:
Technology designed to automatically stop or slow a train before a collision occurs by sharing information on a train's location and safe passage via on board computer systems.
Preliminary Design:
The first phase of the design process in which conceptual design is further refined.
R Rehabilitation:
Method of correcting the deficiency of a deteriorated condition.
The ability of a system or component to function under specified conditions for a determined amount of time.
Rest Piers:
Bridge substructure supporting the end of a span.
Retaining Wall:
A wall that holds back earth and minimizes the width of a railroad embankment supporting tracks.
Land dedicated to the transportation facility.
Run-Around Structure/Temporary Offset:

A construction staging strategy to shift traffic around the primary project location, resulting in no interruptions to traffic during construction.

A Run-Around Structure/Temporary Offset
Some Walk Bridge Replacement design alternatives call for a temporary run-around structure.
S Service Life:
Expected lifetime for acceptable period of use.
Span Length:
The horizontal distance between two support structures.
Steel Plate Girder:
A type of bridge span configured in an I-shape in which the elements are welded together, consisting of top and bottom horizontal elements (flanges) and a single vertical element (web).
The bottom portion or foundation of a bridge structure, including abutments and piers, that supports the superstructure.
Earth material underground.
The upper portion of a bridge which carries traffic.
Swing Bridge:
A movable deck bridge that opens by rotating about a pivot pier.
System Resiliency:
The ability to return the bridge to use in a relatively short time in the aftermath of a compromising event.
T Tidal Wetlands:
Wetlands that border or lie beneath tidal waters that are protected from direct wave action.
A temporary bridge structure composed of bents or towers and supporting girders forming the floor system.

A structure composed of slender members joined together at their end points.

A Truss Bridge
Truss Bridge on the Southern Pacific Railroad
U Utilities:
Public mains for electricity distribution, telecommunications, fiber optics, water mains, wastewater pipes, etc.
Utility Relocations:
Transfer of facilities to new locations to avoid conflict with a construction project.
V Vertical Lift Bridge (Through Truss Tower Drive Vertical Lift Bridge):

A movable bridge in which both ends of the span are simultaneously raised vertically and whose movement is guided by towers located at each end of the span.

A Vertical lift bridge
The Walk Bridge Replacement is a vertical lift bridge.
W Water-dependent use:
A recreational, commercial, or industrial use or facility which requires direct access to, or location in, marine or tidal waters and which cannot be located inland. Some examples of water-dependent uses are marinas, boatyards, marine transportation facilities, and public access.
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