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

Whittier Bridge/I-95 Improvement Project FEIR
Chapter 1.0: Changes Since the Draft Environmental Impact Report and Resolution of Additional Issues
The salt marsh enhancement and planting plan in the area below the existing stormwater outfall
to the Merrimack River was revised. The revisions provide for recovery of the salt marsh in the
area between two existing patches of salt marsh.
Additional information and minor revision related to the stormwater management system was also
provided, including:
- Information on additional proposed subsurface explorations based on peer review
comments;
- Incorporation of a groundwater monitoring well adjacent to Infiltration Basin 1;
- Incorporation of signage to inform emergency personnel on the location of drainage
infrastructure;
- Incorporation of traps in catch basins; and
- The location of the proposed outfall to the Merrimack River was relocated approximately 30
feet west in response to concerns on potential indirect impacts to salt marsh.
Amesbury Conservation Commission
Supplemental information provided to Amesbury included a memo detailing project impacts and
mitigation for the portion of project tributary to the area referred to as the Golden Triangle and:
Information on additional proposed subsurface explorations in response to peer review
comments;
Additional information in response to peer review comments, including:
- Information on additional proposed subsurface explorations;
- Revising the design of Infiltration Basin 4 and 5 to provide a four foot separation between the
bottom of the basins and the estimated seasonal high groundwater level;
- A rip-rap apron was added to the proposed outlet at station 232+50 RT;
- Drawdown calculations were provided for Infiltration Basin 4 and Infiltration Basin 5;
- Pre- vs. post-runoff rates were provided for Design Point 4 and Design Point 5;
Cross sections were provided for Infiltration Basin 3; and
Design point 3 StormCAD layout map were relabeled.
Details for riverfront area restoration were developed.
Additional information was provided on the proposed wetland mitigation area adjacent to Wetland H.
The NOI application was revised to provide additional descriptions of impacted Wetlands H, I and M,
and their impact areas specifically re-stating information previously presented in the ANRAD. The
design of the Wetland H compensatory wetland mitigation area was enhanced including the
submittal of hydrologic information based on field observations and the locations of three monitoring
wells to be installed shortly to collect water level data for the 2012 full growing season. Soil pit data
was provided for the adjacent Wetland H, and for existing upland areas at the mitigation site. The
existing vegetation in the vicinity of the mitigation area was described in the supplemental
information, and additional grading and planting detail for the replication area was provided. Finally,
the proposed access for construction was developed.
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