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
Wetland G. Wetland G is part of a large wetland complex located west of I-95 and south of the
on-ramp to I-95 southbound from Route 110. This site occurs at the southern end of Wetland G
near wetland flags G-1 to G-5. This portion of the wetland is forested with relatively mature red
maple (Acer rubrum), with soil piles within the wetland providing evidence of former disturbance.
The potential creation area includes an area of gentle slopes surrounded by steeper slopes.
Areas of ledge have been mapped immediately south of this site. All uplands in this vicinity are
dominated by mature second-growth forest.
Wetland H, Site 1. This site occurs adjacent to the north end of the large wetland associated
with Wetland H near flags 10-12 to 10-16. The wetland to the south of the site is emergent,
dominated with invasive species (common reed [Phragmites australis] and purple loosestrife
[Lythrum salicaria]), with soils indicating saturated or flooded conditions. The drainage adjacent
to the highway is forested, partially paved, and provides drainage from a smaller wetland to the
north and stormwater flows from I-95. The potential creation area consists of a steep, sandy
slope with a mix of trees, saplings, and grasses, attesting to dry conditions and relatively recent
disturbance.
Wetland H, Site 2. This site occurs north of Wetland H, Site 1 along the ROW near wetland flags
H-2 to 10-6. The wetland is dominated by emergent and shrub species, many of which are
invasives, primarily common reed, purple loosestrife, and bush honeysuckle (Lonicera cf
morrowii). This wetland was relatively dry at the time of the site visit, suggesting hydrology is
provided by a combination of stormwater flows from I-95 and periodic high groundwater levels.
The adjacent upland on the east side has gentle grades in second-growth deciduous forest that
could be pulled back to create additional wetland.
Wetland J. Wetland J is located west of I-95 and north of Exit 58 (Route 110), and consists of a
predominantly forested wetland complex that drains to the west. Mature red maple dominates
within the wetland, and a mix of mesic forest species dominates the adjacent upland. Within the
ROW occur several gentle slopes adjacent to the wetland boundary which potentially could be
graded to create wetland. Field observations indicate that a shallow water table supports most of
this wetland; therefore it is likely that adequate hydrology exists for wetland creation along the
edge of Wetland J.
After review, the list of potential mitigation sites was prioritized according to the potential of each site
to support additional wetland, the existing conditions of the upland, and the likelihood that the site
could provide replication for the wetland impacts from the project.
The Wetland G site has mature forest in both the upland and wetland. Given the suburban setting of
the region, this was viewed as less desirable for mitigation than a disturbed site. Wetland G also has
a strong potential for ledge to occur within the creation area, which would greatly complicate grading.
The Wetland H, Site 1 has an early successional community with adequate hydrology in the adjacent
wetland, both of which are attributes conducive to wetland creation. Its proximity to the Wetland H
impact area is also beneficial. The presence of invasive species in the adjacent wetland located on
private property and the large amount of fill to be removed are limitations to use of this site.
The Wetland H, Site 2 has gentle grades and is adjacent to a shrub and emergent wetland, both of
which are desirable, but it is higher in elevation and likely has marginal hydrology, which could
complicate successful wetland creation at this site.
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