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Dredging for Confined Aquatic Disposal (CAD Cell) and Re-use of Dredged Material

Background

The construction of New Bedford Port Authority (NBPA)’s Confined Aquatic Disposal (CAD) Cell No. 4 in the lower harbor area will provide disposal capacity for approximately 520,000 cy of contaminated dredge sediments from dredging participants throughout the harbor. The construction of CAD Cell No. 4 includes dredging and disposal of PCB- and heavy metal-impacted sediments into existing CAD Cells, disposal of suitable (cleaner) materials at the approved offshore disposal site, and beneficial reuse of structurally suitable dredged materials as cap/backfill at the proposed North Terminal expansion site, where between 250,000 – 350,000 ft3 of impacted sediments will be covered.

Approach

Foth developed this project from concept through design, permitting, bid and construction phases.  The cleanup effort will remove contaminated sediments from approximately 3,000,000 sf of the New Bedford Harbor, and provide a major boost to the local economy by maintaining berths and stimulating development of shoreline sites with improved navigable access. The planned dredging includes the navigational dredging of over 40 commercial and residential sites along the New Bedford and Fairhaven shoreline.

During the first portion of the CAD construction, Foth provided project management, contractor coordination, bathymetric surveys, and water quality monitoring.  Dredging for this phase was completed in Fall 2020, and Foth will lead a subsequent phase to complete construction of CAD Cell No. 4 in 2021.

Foth is also the design engineer for the terminal expansion which includes construction of a cellular cofferdam bulkhead and associated dredging of material within the cells, construction of a pile supported concrete deck, installation of stormwater, electrical, lighting, and water utilities, backfill and compaction of the cofferdam footprint and site infield area, installation of various site components, backfill and finished grading of the proposed site to create new upland terminal area.  Funding for the project includes local, state and federal sources, totaling over $43M.

Results

Dredging in New Bedford harbor, the largest commercial fishing port in the country, is vital to economic development of the port.  Foth’s expertise in dredging, management of contaminated sediments, marine infrastructure and port development provides significant value to the port, optimizing the environmental cleanup, navigation and commercial uses within the harbor.

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