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

Whittier Bridge/I-95 Improvement Project FEIR
Chapter 3.0: Mitigation and Commitments
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.
Impacts and Mitigation
Two Bordering Vegetated Wetlands (BVW) would be directly affected by the proposed highway
widening including Wetlands I and H in Amesbury. Total permanent impacts will be 3,560 square
feet of BVW and total temporary impacts will be 1,400 square feet. BVW replication for permanent
impacts will consist of expanding Wetland H in Amesbury by excavating approximately 4,960 square
feet of upland at its northern end within the ROW. The proposed mitigation ratio for permanent
impacts is 1.4:1 which exceeds the 1:1 ratio mandated under the Massachusetts Wetlands
Regulations at 310 CMR 10.54(4)(b). Temporary impacts to BVW, as well as temporary impacts to
isolated vegetated wetlands, will be mitigated by restoration of the impacted area after construction
activities are completed.
Isolated Vegetated Wetland (IVW): One IVW, Wetland M in Salisbury, will be temporarily impacted
by the construction of detention basin 7A. Total temporary impacts are estimated at 240 square
feet. The basin is located to the west of I-95 immediately south of the I-495 northbound overpass.
Temporary alteration of Wetland M is assumed to be required for purposes of construction access
and installation of inlet and outlet pipes for the detention basin. The impact areas will be restored
after the completion of construction activities.
Land Under Ocean (LUO): Construction of six piers for the proposed I-95 bridges would result in
permanent and temporary impacts to LUO in the Merrimack River in Newburyport and Amesbury.
The permanent impacts will be offset in part by removal of the four existing bridge piers and
restoration of the river bottom. The new bridges would alter 17,100 square feet of river bottom
habitat under state jurisdiction as Land Under the Ocean and Banks of or Land Under the Ocean,
Ponds, Streams, Rivers, Lakes or Creeks that Underlie an Anadromous/Catadromous Fish Run. An
additional 28,520 square feet of temporary impact to river bottom (LUO) would result from the
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