Tetra Tech supported the U.S. Army Corps of Engineers (USACE) by conducting sediment testing for the characterization of sediment to be removed during routine maintenance dredging for five commercial harbors in Hawaii, including Honolulu, Kalaeloa (Barber’s Point), Nawiliwili, Kahului, and Hilo. Tetra Tech conducted sediment toxicity and bioaccumulation testing following USACE and U.S. Environmental Protection Agency protocols to determine suitability of the sediment for open water ocean disposal. Our team completed seven different evaluations to characterize the potential toxicity of sediment and elutriate created during dredging, as well as characterize the potential bioaccumulation of contaminants from the sediment if disposed of in approved open-ocean disposal areas.

Tetra Tech’s team in Honolulu, Hawaii, provided field support for collecting and analyzing sediments for the concentrations of chemical contaminants of interest (COI), while Tetra Tech’s ecological testing facility in Owings Mills, Maryland, characterized the sediment’s toxicity using standard marine test organisms and assessed the bioaccumulation potential of COIs in sediments by standard marine test organisms. 

Tetra Tech’s ecological testing facility provided toxicological and bioaccumulation support for 22 sediment samples collected at five harbors and regional reference locations. Our team characterized sediment toxicity using whole sediment and sediment elutriate testing. Whole sediment toxicity tests consisted of exposure of Leptocheirus plumulosus and Neanthes arenaceodentata for 10 days, while 96-hour sediment elutriate characterization was completed using Americamysis bahia, Menidia beryllina, and Mytilus galloprovincialis. The bioaccumulation of contaminants of interest was characterized by chronic exposure (i.e., 28 days) to the clam, Macoma nasuta, and the polychaete worm, Nereis virens. Tetra Tech provided standard quality assurance in terms of positive controls (i.e., reference toxicant tests) and negative controls (i.e., clean sediment tests conducted concurrently).

Tetra Tech completed this work over a four month accelerated time frame to keep with USACE’s ambitious schedule. Follow-up evaluation of one dredged material management unit (DMMU) that did not pass initial screening evaluation indicated all sediment was qualified for open ocean disposal. Open water ocean disposal of the sediment avoided the need for costly upland disposal.