Presentation Abstract

Esquimalt Harbour has historically been used for log rafting, log storage and wood mill operations over the last 70 years, resulting in the accumulation of over 200 hectares of wood waste deposits. As wood waste decomposes, it creates a biological oxygen demand in sediments that can reduce or eliminate oxygenated zones. This can lead to a buildup of compounds such as sulphides and ammonia, which are toxic to benthic organisms at higher concentrations. Public Services and Procurement Canada, on behalf of the Department of National Defence, has completed studies of wood waste sediments and is currently constructing a pilot project to address high sulphides in Esquimalt Harbour sediments. The studies include use of an innovative passive porewater sampling technique to quantify dissolved sulphide using the diffusive-gradient-in-thin-films (DGT) method to quickly and accurately measure porewater sulphide concentrations, which ranged from less than 1 mg/L to over 200 mg/L in harbour sediments. The DGT method is based on the reaction of sulphide with silver iodide and is becoming increasingly common as a reliable in situ technique for quantifying a range of sediment porewater constituents. Cleanup of wood waste impacted sediments has historically involved dredging, capping, or monitored natural recovery. However, in situ treatment amendments have the potential to oxidize or immobilize porewater sulphide. An innovative bench-scale testing program was conducted to assess the effectiveness of sand cover mixed with a range of treatment amendments to reduce bioavailable porewater sulphide concentrations in wood waste sediments. The results were used to design and construct a pilot project in Esquimalt Harbour to test the effectiveness of sand amended with iron carbonate to control sulphide concentrations and support a healthy benthic community. This presentation will describe the field investigations, bench scale testing, design and construction of the pilot project, and initial monitoring results.

Session Title

Session 1.1B: The Environmental Toxicology and Chemistry of the Salish Sea Ecosystem

Conference Track

Contaminants, Plastics, Microplastics, Toxicology & Stormwater

Conference Name

Salish Sea Ecosystem Conference (2020 : Online)

Document Type

Event

SSEC Identifier

2020_abstractID_4084

Start Date

21-4-2020 10:30 AM

End Date

21-4-2020 12:00 PM

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Language

English

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Apr 21st, 10:30 AM Apr 21st, 12:00 PM

Innovative Treatment of Wood Waste Sediments Using Reactive Amendments and DGT Passive Porewater Sulphide Testing Techniques

Esquimalt Harbour has historically been used for log rafting, log storage and wood mill operations over the last 70 years, resulting in the accumulation of over 200 hectares of wood waste deposits. As wood waste decomposes, it creates a biological oxygen demand in sediments that can reduce or eliminate oxygenated zones. This can lead to a buildup of compounds such as sulphides and ammonia, which are toxic to benthic organisms at higher concentrations. Public Services and Procurement Canada, on behalf of the Department of National Defence, has completed studies of wood waste sediments and is currently constructing a pilot project to address high sulphides in Esquimalt Harbour sediments. The studies include use of an innovative passive porewater sampling technique to quantify dissolved sulphide using the diffusive-gradient-in-thin-films (DGT) method to quickly and accurately measure porewater sulphide concentrations, which ranged from less than 1 mg/L to over 200 mg/L in harbour sediments. The DGT method is based on the reaction of sulphide with silver iodide and is becoming increasingly common as a reliable in situ technique for quantifying a range of sediment porewater constituents. Cleanup of wood waste impacted sediments has historically involved dredging, capping, or monitored natural recovery. However, in situ treatment amendments have the potential to oxidize or immobilize porewater sulphide. An innovative bench-scale testing program was conducted to assess the effectiveness of sand cover mixed with a range of treatment amendments to reduce bioavailable porewater sulphide concentrations in wood waste sediments. The results were used to design and construct a pilot project in Esquimalt Harbour to test the effectiveness of sand amended with iron carbonate to control sulphide concentrations and support a healthy benthic community. This presentation will describe the field investigations, bench scale testing, design and construction of the pilot project, and initial monitoring results.