Dredging Contaminated Sediments: A Monitoring Plan for Boston Harbor

by James D. Bowen, ENSR Consulting and Engineering, Acton, United States,
Steven H. Wolf, ENSR Consulting and Engineering, Acton, United States,
Curtis A. Meininger, ENSR Consulting and Engineering, Acton, United States,

Document Type: Proceeding Paper

Part of: Ports '92


Dredging and blasting will be conducted in Boston's Inner Harbor over approximately a one-year period during construction of the Third Harbor Tunnel. The silty organic surface sediments to be dredged contain elevated levels of priority pollutant metals, polychlorinated biphenyls (PCB's), and polycyclic aromatic hydrocarbons (PAH's). Dredging techniques, mitigation methods, and environmental monitoring plans were assessed during permitting of the dredging/blasting activity. Fate and transport modeling of sediments suspended during dredging was used to assess the impacts to water quality and biological resources for various dredge scenarios including open and closed clamshell dredging and silt curtains. A recommended monitoring approach included frequent, spatially intensive turbidity surveys integrated with periodic measurements of a limited set of conventional and toxic pollutants. A related plan, included as part of the Water Quality Certification, included less frequent sampling but increased the overall sampling effort by adding additional toxics analyses and by sampling during several tidal stages. Additional requirements of the Water Quality Certification included closed clamshell dredging of surface sediments but did not include mandatory use of silt curtains. Requirements regarding dredging technology and environmental monitoring indicate the level of agency concern with concentration of toxics in the water column and provide guidance for the permitting of contaminated sediment dredging in Boston and other harbors.

Subject Headings: Silt | Toxicity | Dredging | Pollution | Ports and harbors | Soil pollution | Water pollution | Water quality | Boston | Massachusetts | United States

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