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
mg/kg in the above referenced policies. Based on this result, the sediment represented by sample B-
2 would not be suitable for reuse at an unlined or lined landfill. The most likely disposal option for
dredged sediment not suitable for in-state reuse due to SVOCs is disposal at an out-of-state facility
such as Waste Management of New Hampshire Turnkey Landfill. Its physical properties would likely
not make it suitable for other reuse options such as asphalt batching.
Wood was detected in the tip of the sampling spoon at location B-2. The SVOCs detected in this
sample may be due to the presence of treated wood or other debris. Further sampling in the vicinity
of location B-2 could be used to further characterize sediment in this area, and may provide
additional information regarding SVOC concentration in the sediment. Further characterization may
reduce the amount of sediment characterized as not suitable for in-state reuse, and/or provide more
information regarding whether treated wood or other debris may be a partial source of the detected
SVOCs.
Two compounds detected in the sample from Boring B-2 exceed the RCS-1 reportable
concentrations. These compounds are the polycyclic aromatic hydrocarbons (PAHs) benzo(a)pyrene
and dibenzo(a,h)anthracene. Because the material sampled is river bottom sediment and not soil,
the reportable concentrations in the MCP do not apply. The PAHs may be present in the sediment
because of run-off from the roadway, because of the presence of treated wood or wood ash, or from
other sources. Wood debris was observed in the split spoon sampler.
Because of the presence of contaminants above RCS-1 concentrations, the sediment from location
B-2 may not be suitable for unrestricted reuse. In contrast, the sediment from locations B-1, B-3, B-
4, and B-5 appears suitable for reuse at a Massachusetts unlined landfill. Additional sampling and
testing may be required to satisfy the requirements of the receiving facility.
1.4.8 Flooding Events During Construction
The DEIR Certificate and the comment letter from the MassDEP requested that MassDOT
investigate whether there are contingency measures that could be implemented to reduce impacts to
resource areas as a result of flooding during the construction period.
MassDOT does not believe that special contingency measures will be required during the
construction of the new bridges in order to address potential impacts to wetland resource areas. The
construction sequencing and design of the project minimizes the impact and risk of increased
flooding during construction and demolition by limiting the number of cofferdams within the river and
optimizing the design of the cofferdams to minimize to the extent practicable flooding impacts. The
use of cofferdams will be sequenced between the construction of the I-95 northbound and
southbound bridges to minimize the number of cofferdams present within the river at any time.
1. During construction of the new I-95 northbound bridge, the cofferdams will be limited to the
area of the foundations of the new bridge piers with Piers 1 and 3 being in line with existing
Piers 1 (southerly) and 4 (northerly) on the existing Whittier Bridge. Pier 2 for the new I-95
northbound bridge will be located on the high rock outcropping between existing Piers 2 and
3. The rock outcropping is located outside of the main and steamboat channels; thus the
location of the new Pier 2 will minimize hydraulic impacts.
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