The overall goal of this project is to demonstrate a new tool that can be used to map the in situ distribution of contaminants of concern (CoCs), such as PAHs, PCBs and heavy metals, in aquatic sediments. The tool will aim to address the problem that exists at present, namely that there are currently no means available to make detailed, high resolution maps of sediment contaminants in a timely and cost-effective manner. The tool will be especially useful for the rapid, pre-remedial, characterization of sites of concern, and in the assessment and monitoring of post-remedial effectiveness at DoD sites. Many DoD sites are located in environmentally sensitive areas; therefore, both the identification of CoCs in aquatic sediments and the eventual remediation of contaminated sites are of particular importance.

This project will be especially relevant to the majority sites where either risk assessment is ongoing; where CoCs have been identified and a spatial distribution is required; or where post-remediation monitoring is needed. The specific objectives of this project are to:

• demonstrate the application of the technology at three suitable DoD sites;
• compare the technology with traditional contaminant sampling methods and outcomes;
• obtain sufficient good quality data to undertake cost-safety benefit and scientific data analyses to demonstrate applicability and suitability to a range of DoD sites with different CoC issues; and
• develop guidance and design protocols to support technological transition to a wider DoD context, and acceptance of the technology within the regulatory community.

Sensor for Mapping In Situ Distribution of Chemicals of Concern

The technology uses a vessel-towed gamma spectrometer to provide rapid site characterization and mapping of CoCs with the requirement for a comparatively small number of sediment samples for calibration. The unique and innovative aspects of this technology are the use of naturally occurring radionuclides in sediments as proxies for mapping the contaminant content of the sediments. The project will attempt to demonstrate: 1) how an underwater gamma ray spectrometer can be used to map the spatial variation of the sediment contaminants (sensor based mapping); 2) how site specific calibration models can be established to translate the field measurements to quantitative maps of sediment contaminant levels (calibration); 3) how this approach performs in comparison with traditional contaminant mapping techniques by validating the approach at selected sites (validation of pollution maps); and 4) how mapping pre-remedial contaminant levels and more importantly the capability to map to post-remedial clean up levels can be achieved.

State of the art practice in the screening for CoCs at both regional and ecological levels, as well as post remedial detection of contaminants, comprises the collection of discrete sediment samples to produce a spatial ‘distribution’ of contaminants. The problem with discrete sampling is that the spatial scale at which contaminant content varies is not known a priori, so potential hotspots can be missed. The potential benefits of this technology are improved data on sediment contaminant distribution, faster screening methods, and ultimately improved site remediation at lower cost. It is expected that this technology will provide considerable cost reductions, resulting in favorable benefit/cost ratios, as well as benefits in terms of health and safety (exposure/handling of contaminated sediments). The project will be deemed successful if it can be demonstrated that mapping of contaminants at required clean up levels is possible, and that significant cost, health, safety and environmental benefits are achievable. (Anticipated Project Completion - 2024)