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 Wetland J site is in mature forest adjacent to mature forested wetland, and disturbance of these
types of habitat is undesirable. This wetland also drains west into a different subwatershed than
either of the project impact areas. Additionally, at the north end, the construction of Stormwater
Basin 5 will occur in the area most suitable for wetland creation.
After review of these sites, Wetland H, Site 1 was selected as having the highest potential for
success, and the fewest adverse impacts to the surrounding habitats. Its setting is also best able to
meet criteria 1 through 5 in the Inland Wetland Replication Guidelines summarized at the beginning
of this section. Figure 1-9 illustrates the location of the selected mitigation area in relation to
Wetlands H and I.
Existing Conditions at Wetland H Mitigation Site
The existing upland in the proposed mitigation area (Wetland H, Site 1) consists of a relatively
disturbed steep sandy slope leading down to the wetland. The canopy is open and patchy, and
contains mostly small trees and saplings with grasses and early successional shrubs in the
understory. The bank ranges from 20 to 25 feet above the surface of the wetland. Considerable
trash was observed in the upland near the mitigation site.
Vegetation
Plant species observed on the sideslope and top of the sand bank include trees and saplings of
sugar maple (Acer saccharum), red maple, Red and black oak (Quercus rubra and Q. velutina), and
white pine (Pinus strobus); saplings and/or shrubs of staghorn sumac (Rhus hirta), eastern red cedar
(Juniperus virginiana), gray birch (Betula populifolia), and black cherry (Prunus serotina); vines of
poison ivy (Toxicodendron radicans); and an herbaceous layer containing little bluestem
(Schizachyrium scoparium)and other grasses, poison ivy, rose (Rosa sp.), black raspberry (Rubus
occidentalis) , goldenrods (Solidago spp.), dewberry (Rubus cf flagellaris), bedstraw (Galium sp.),
and celandine (Chelidonium majus). A few butternut (Juglans cinerea or hybrid) trees were observed
growing along the edge of the wetland east of the proposed mitigation area. Evidence of disease
(i.e., dead branches and fungus) was observed on some of these trees. Relatively few invasive
plants were encountered in the mitigation area and adjacent upland. The percent cover of invasives
was estimated to be less than 5%. The invasives observed include scattered shrubs of bush
honeysuckle, a few scattered saplings of black locust (Robinia pseudoacacia), vines of oriental
bittersweet (Celastrus orbiculatus), and sparse shrubs of Norway maple (Acer platanoides) and
glossy buckthorn (Frangula alnus).
Immediately south of the proposed mitigation area is a large area of emergent wetland dominated by
stands of the invasive common reed. Purple loosestrife and goldenrod are also present in this marsh
area outside of the common reed stands. The estimated cover of invasives in the area of this
wetland adjacent to the mitigation site is close to 100 percent.
A man-made swale is located west of the mitigation area and extends roughly north-south and
parallel to the highway. The swale receives flow from a small area of mostly emergent wetland at the
northern end of Wetland H and directs it to the south into the emergent marsh located south of the
mitigation area. The swale is mostly paved. During the site visit it was observed to be dry in the
middle (and surrounded mostly by upland vegetation) and wet at its northern and southern ends
where it connects to wetland. Vegetation observed along the edges of the swale include trees and/or
saplings of green ash (Fraxinus pennsylvanica), black oak, white pine, eastern red cedar, and
Scotch pine (Pinus sylvestris); vines of poison ivy; and shrubs of red maple, green ash, and bush
honeysuckle. At its southern end, the swale is bordered by common reed, silky dogwood (Cornus
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