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

Whittier Bridge/I-95 Improvement Project FEIR
Chapter 3.0: Mitigation and Commitments
installation of cofferdams around the six new permanent piers during construction, around each of
the four existing Whittier Bridge piers during demolition, and from construction of up to three
temporary support structures during construction of the I-95 northbound bridge. Approximately
10,130 square feet of new river bottom (LUO) habitat will be restored when the existing piers are
removed down to the substrate (a portion of the new southern pier for the I-95 southbound bridge
overlaps the existing southern pier for the existing Whittier Bridge). The net permanent loss of Land
Under the Ocean is 5,600 square feet (17,100 square feet for new piers – 11,500 square feet for
existing piers).
Riverfront Area (RFA) would be affected on both sides of the Merrimack River in Newburyport and
Amesbury. The impact would consist of fill associated with the proposed bridge abutments for the I-
95 northbound and southbound bridges.
Temporarily impacted RFA in Newburyport will be mitigated though 20,360 square feet of in situ
restoration. The permanent alteration to previously developed RFA will cumulatively result in
alteration of over 10 percent of the RFA (310 CMR 10.58(5)(e)); therefore, the additional 939 square
feet of alteration requiring mitigation will be mitigated through 12,200 square feet on-site restoration
of existing degraded areas (in accordance with 310 CMR 10.58(5)(f)). The mitigation in Newburyport
will consist of demolishing the existing Whittier Bridge abutment, building the new abutment
approximately 50 feet behind the existing abutment, removing existing riprap, reclaiming and
restoring median, and restoring the proposed approximate 80-foot slope with slope protection
covered by soil, seed and plantings to create a natural riverfront corridor.
Temporarily impacted RFA adjacent to the Merrimack River in Amesbury will also be mitigated
though 11,650 square feet of in situ restoration. The permanent alteration to previously developed
RFA will cumulatively result in alteration over 10 percent of the RFA (310 CMR 10.58(5)(e));
therefore, the additional 6,000 square feet of alteration requiring mitigation will be mitigated with
11,800 square feet of on-site restoration of existing degraded areas (in accordance with 310 CMR
10.58(5)(f)). The mitigation in Amesbury will consist of demolishing the existing Whittier Bridge
abutment, building the new abutment approximately 50 feet behind the existing abutment, removing
existing riprap, reclaiming and restoring median, and restoring the proposed approximate 80-foot
slope with slope protection covered by soil, seed and plantings to create a natural riverfront corridor.
An area of Land Subject to Coastal Storm Flowage (LSCSF) on the south bank of the Merrimack
River in Newburyport would be temporarily affected by installation of temporary I-95 northbound
bridge support and a temporary work zone on the south bank. An additional area of LSCSF located
within Wetland I in Amesbury would be affected by construction of a highway retaining wall.
Additional temporary impacts to a small area of LSCSF on the north bank in Amesbury would result
from the construction of a temporary support during construction of the I-95 northbound bridge. The
total impact to LSCSF from these activities is 2,797 square feet. The project will not result in a
measureable impact to the 100-year floodplain or the Regulatory Floodway in the Merrimack River;
therefore, no mitigation measures are proposed.
Coastal Beach: Construction of one of the proposed temporary bridge supports on the Amesbury
shoreline would temporarily affect approximately 190 square feet of Coastal Beach. The temporary
supports would be in place for up to six months, and then removed and the area restored.
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