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

total amOl,mt ofresomce area impacts could exceed the amount allowed under the wetland
regulation's performance standards. To avoid this possibility, MassDEP requested that the work
yard/lay down locations be identified in the DEIR. Subsequent to the filing ofthe DEIR,
MassDOT provided to MassDEP a summary ofthe contractual and field oversight measures it
will institute to ensure that any areas outside ofthe plan approved work areas that the contractor
proposes to utilize will be appropriately delineated and controlled to prevent impacts to wetland
resomces areas.. Details ofthose measures should be provided in the FEIR. As MassDOT is
pursuing issuance ofthe wetlands authorizations from conservation commissions prior to
completion ofthe MEPA process, the Orders ofConditions issued by the three conservation
commissions may need to incorporate these impact avoidance measures in the Order of
Conditions.
Riverfront Area
The project will involve redevelopment within previously developed riverfront areas (310 CMR
10.58(5». Specifically, the project will alter approximately 23,000 square feet in Amesbury and
approximately 36,000 square feet in Newburyport ofundisturbed and previously developed
(engineered side-slopes and previously graded areas) riverfront area along the Menimack River
for which mitigation must be provided. The project will move existing abutments 50-feet back
from the river, remove riprap and restore the median and an 80' slope with bioengineering
teclmiques. This will result in an improvement over existing conditions (10.58(5)(a». Mitigation
will also include in-situ restoration oftemporary impacts, and on-site restoration ofexisting
degraded areas at a ratio ofapproximately 1: 1 in accordance with 10.58(5)(1). Additional
degraded riverfront area will also be altered. MassDEP recommends MassDOT consult with
local stakeholders including Merrimack River Watershed Council and Eight Towns and A Bay in
devising appropriate mitigation or restoration for impacts to riverfront area as well as other
wetland resource areas. However, all mitigation must meet the Wetland Protection Act
performance standards for the specific resource area impacted. As part ofthe NO! review,
MassDOT will need to specify the riverfront area mitigation or restoration to be provided on a
square footage basis. Local conservation commissions will need to apply the restoration
standard at 310 CMR 10.58(5)(1), and the stormwater management standards established at 310
CMR I0.58(5)(b) as part ofits Riverfront Area findings.
Bordering Vegetated Wetland Replacement Areas
The proponent is obligated to provide detailed plans ofBVW replacement areas to the issuing
authority, including groundwater elevation information conducted in accordance with the
MassDEP March 2002, Massachusetts Inland Replication Guidelines, to demonstrate that the
site could support the proposed Replacement Area designs. As described in MassDEP's
guidelines, the hydrology at the replacement site is critical in controlling the plant community
that develops, and many ofthe ecological functions ofthe site. Further, inadequate hydrology is
often a result ofinadequate evaluation ofthe replacement site before construction, particularly
when replication sites depending on ground water are not excavated deeply enough to provide
water in adequate quantity and at appropriate seasons. Conversely, establishing wetland
vegetation in a replacement area may be compromised and fail when the site is over-excavated
resulting in excess standing water. Failure ofreplacement wetlands can also occur as a result of
inadequate soils which are critical in providing substrate for plants and supporting wildlife
habitat. It is MassDEP's experience that leaving the details ofreplacement area design to
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