Final Environmental Impact Report - Whittier Bridge/I-95 ...

Whittier Bridge/I-95 Improvement Project FEIR
Chapter 3.0: Mitigation and Commitments
Bridge Configuration (including design standards/complexities, structural safety,
constructability, context sensitive structures, maintenance and inspection and life cycle/cost);
Traffic (including travel time, level of service, and capacity);
Right-of-Way (including fee taking, permanent easement and temporary/construction
easement);
Cost (the relative cost differences of each alternative considering constructability, site access,
construction staging ease/restraints, traffic management, ease of demolition, and schedule
impact because of extended construction);
Construction (including utility relocation, constructability/demolition of existing structures, and
maintenance of traffic during construction);
Schedule (the relative difference between alternatives for the estimated construction schedule
duration of each alternative); and
Environmental (including stormwater [ability of each alternative to meet MassDEP stormwater
performance standards], drinking water quality [the degree of impact on local drinking water
supply protection areas], wetlands [total estimated impact to wetland resource areas within the
project area], visual/viewpoints [the level of visual impact], historic [potential impact on the
historic Whittier Bridge] and navigation [potential impacts to navigation on the Merrimack River]).
After a thorough evaluation of the river crossing and highway widening alternatives, the New 8-Lane
East Bridge River Crossing Alternative and the Inside Widening Highway Alternative (Northern
Terminus to Route 286) were identified as the Preferred Alternative. This alternative best met the
purpose and need, as well as highway configuration, traffic (capacity), bridge configuration (design
standards, structural safety, maintenance and inspection, and life cycle/costs), construction
(constructability), ROW, and environmental criteria.
3.16.5 Chapter 91 Waterways – MassDEP
Construction Term Navigation
During construction of the new bridge crossing, there would be barges, falsework, work platforms,
staging, and/or cofferdams constructed in the waterway in conjunction with constructing the
permanent bridge structures and demolishing the existing bridge. The type of temporary system will
be determined by the final design of the substructure and superstructure; however, the project
specifications will include provisions that the contractor must follow to ensure that navigation
beneath the bridges will be maintained, except for those circumstances where limited closures will
occur for public safety purposes. The directives will include: staging plans showing zones where
barges and equipment will be allowed to operate during each phase of construction and demolition;
locations where equipment could be moored or stored while not in use; provisions for temporary aids
to navigation, including temporary lighting; establishing temporary routes for marine traffic; and, most
importantly, timely notices to mariners throughout the construction and demolition duration. The
contractor will be required to prepare a navigation plan for review and approval by the USCG,
USACE, harbormasters, boating community, and other marine interests. The plan will address
methods to minimize impacts to all mariners, management of vessel traffic and overall safety issues.
Temporary closures of the waterway could be required for safety reasons; however, since there are
two channels, it is anticipated that the contractor will be able to maintain one channel at all times
during construction and demolition. If there are instances when both channels must be temporarily
closed for safety purposes or the channel that can only accommodate a larger vessel is closed, the
3-22