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Title: Final Supplemental Environmental Impact Statement for the Boston Harbor Inner Harbor Maintenance Dredging Project
Authors: Battelle Memorial Institute
United States. Army. Corps of Engineers. New England District
Massachusetts Port Authority
Earthtech Research Corporation
Keywords: Boston Harbor (Mass.)
Dredging spoil
Channels (Hydraulic engineering)
Environmental management
Environmental protection
Publisher: United States. Army. Corps of Engineers. New England District.
Abstract: This Final Supplemental Environmental Impact Statement builds on the lessons learned from the Boston Harbor Navigation Improvement Project (BHNIP) located in Massachusetts, which was the subject of a Final Environmental Impact Report/Statement (EIR/S) prepared in 1995 (Corps and Massport, 1995). The currently proposed Inner Harbor Maintenance Dredging Project (IHMDP) involves dredging approximately 1.7 million cubic yards (cy) of silty maintenance material from the Main Ship Channel located approximately half-way between Spectacle Island and Castle Island upstream to the Inner Confluence, the upper Reserved Channel, the upper portion of the Mystic River not previously deepened, and the approach channel to the Navy Dry Dock to their authorized depths. Approximately 1.3 million cy of the maintenance material is unsuitable for unconfined open water disposal and will be disposed into confined aquatic disposal (CAD) cells located in or near the sites identified in the BHNIP EIR/S (Corps and Massport, 1994, 1995). A Massachusetts Environmental Policy Act (MEPA) Notice of Project Change was included as part of the Draft Supplemental EIS for the IHMDP. The Massachusetts Secretary of Environmental Affairs determined that further MEPA review was not required based on the information contained in the Notice of Project Change. A copy of the Secretary’s Certificate is included in Appendix C. Recent geotechnical investigations in the Mystic River and the Inner Confluence (i.e., locations of the CAD cells identified in the BHNIP) revealed the presence of ledge that limits potential capacity of CAD cells in many of these locations. This constrains the construction of new CAD cells in these areas. Based on these geotechnical investigations, it was determined that a single CAD cell constructed in the Main Ship Channel could confine the majority of the dredged material unsuitable for ocean disposal. A “starter cell” for the Main Ship Channel maintenance material would be constructed in the Mystic River. The silty maintenance material suitable for ocean disposal and the approximately 1.5 million cy of parent material removed to construct the CAD cells will be disposed at the Massachusetts Bay Disposal Site (MBDS). The total amount of material to be dredged from the project and disposed into CAD cells or the MBDS is approximately 3.2 million cy. In addition to the dredged material, about 2,000 cy of rock will be removed. Recent surveys have identified some areas of ledge within the Federal navigation project that will also be removed as part of this maintenance dredging effort: a section of ledge, located in the Main Ship Channel between the 35 and 40-foot channels; as well as six separate ledge outcrops in the west end of the President Roads Anchorage. Dredging and disposal activities are expected to take about two years to complete. The Commonwealth of Massachusetts, in consultation with the U.S. Army Corps of Engineers and the Massachusetts Port Authority, are working together to compel Keyspan Gas to remove its gas siphon in the Chelsea River located south of the Chelsea Street Bridge. The continued presence of this pipeline prevented completion of BHNIP dredging in this area. If the line is removed prior to completion of the Inner Harbor Maintenance Dredging Project, the BHNIP maintenance and improvement dredging will be performed in this area to deepen the Chelsea River to its –38 foot MLLW authorized depth. If the line is not removed, then the Chelsea River area will be maintenance dredged to –35 feet MLLW. The material will be disposed into CAD cell C12, located north of the Chelsea Street Bridge, which was permitted and constructed for the BHNIP. The purpose of the proposed IHMDP is to restore the Federal navigation channels to their authorized depths. Dredging is needed to remove shoals in the navigation channel that are impacting ship traffic in Boston Harbor. In some instances, delays have caused vessels to cancel their stop in Boston because of the impact the delay would have on scheduled stops in other ports of call. In addition to the tidal delays, navigation interests have had to restrict the draft of vessels utilizing the project, because shoaling of up to five feet above authorized depths now exists in portions of the channel. This is seriously impacting the economic efficiency of the port by limiting vessel drafts that can use the harbor without significant delays or restrictions. It also has a significant impact on the economics of shipping through Boston since some ships need to be “light loaded” (vessels not loaded to capacity) or lightered (transfer of goods) to avoid delays. Light loading increases the cost of transportation and the cost of the shipped products to the consumer. Shoaling has also caused concerns regarding damages to vessels as well as safety conditions related to vessel movement, such as groundings.
Description: Supplemental Environmental Impact Statement
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Environmental Documents

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