WP20 Contaminated Harbor and River Sediment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(MCW-1117-564493) Characterization of Heterogeneous Sediment and the Development of a Prioritization Strategy for Remediation.

McWilliams, L.¹, Fitzgerald, B.², Santiago, R.³, Vieira, C.⁴, Mahoney, M.⁵, Spadaro, P.⁶, ¹ Blasland, Bouck & Lee, Inc., Portland, Oregon² Hamilton Port Authority, Hamilton, Ontario, Canada³ Environment Canada, Toronto, Ontario, Canada⁴ Ministry of the Environment, Ontario, Canada⁵ Blasland, Bouck & Lee, Inc., Boston, Massachusetts⁶ Blasland, Bouck & Lee, Inc., Seattle, Washington

ABSTRACT- Contaminated sediment in the vicinity of Randle Reef, Hamilton Harbour, Ontario, is distributed in a thin, uneven (0.25-3 m), chemically heterogeneous layer, over a large (>1 km wide) region with locally steep topography. Given this challenging geometry, the proposed remediation strategy involves: 1) construction of an engineered containment facility (ECF) to contain (and subsequently cap) the most highly contaminated sediment in-situ, and 2) dredging of the surrounding less contaminated sediment and placement into the ECF. To maximize use of the ECF volume, a strategy was developed to ensure that the most contaminated sediment is remediated first, followed by progressively less contaminated sediment. This was accomplished by dividing the site into sub-areas, each of which was assigned to one of four sediment priority categories. These priority categories were formulated to identify those areas where remediation would be the most effective in meeting the project objectives of 1) reduction of mass of chemicals of interest (COIs, including PAHs and selected metals) in site sediment and 2) removal/containment of site sediment with demonstrated toxicity. Contaminated sediment thickness was constrained using chemical and sediment core information. The volume for each sub-area was computed by integrating the total contaminated sediment volume within sub-area. A representative average concentration was calculated for each COI within the contaminated sediment layer in each sub-area. Finally, total contaminant mass was computed for each of the COIs, as well as the mass distribution for each COI amongst the prioritized sub-areas. This analysis quantifies the COI mass that will be contained in place beneath the ECF, as well as the COI mass that will be remediated as the contaminated sediment in each successive sub-area is dredged. This tool will be used during dredge plan design to ensure that the greatest possible environmental benefit is achieved in the most cost effective manner.

Key words: contaminated sediment, remediation, PAHs, dredging prioritization