Innovative Use of Multispectral Multibeam Surveying for Characterizing Benthic Conditions at the Raisin River Area of Concern
By Craig A. Jones, Ph.D., Managing Principal, Business Director - Marine, Coastal, Climate, and Technology Services
Presented at Battelle Sediments, January 30, 2025, Tampa, Florida.
Background/Objectives
The River Raisin, located in Michigan’s Monroe County, has a history of environmental degradation due to industrial activities, leading to its designation as an Area of Concern (AOC) under the 1987 Great Lakes Water Quality Agreement. The river’s contamination primarily stemmed from the discharge of polychlorinated biphenyls (PCBs), heavy metals, and other contaminants. Remediation efforts have focused on removing contaminated sediments and restoring habitat, with significant progress made in recent years. However, ongoing monitoring and restoration activities are necessary to fully address the remaining Beneficial Use Impairments (BUIs) and eventually delist the site as an AOC. Ensuring the long-term effectiveness of these remediation efforts is critical, requiring precise monitoring techniques. This study explores the innovative application of Multispectral Multibeam Surveying (MMBES) to assess the post-remediation state of the riverbed. The objective was to accurately and remotely map the presence and distribution of capping material, evaluate the density variations of sediment in different river sections, and identify any potential hazards that could compromise the remedy’s effectiveness.
Approach/Activities
The MMBES was conducted across the remediated areas of the Raisin River. MMBES utilizes multiple acoustic frequencies to capture detailed imagery and data about underwater environments, including the composition and structure of sediments and benthic habitats. The data was instrumental in identifying the current distribution of capping material and provided insights into sediment composition variations. The survey results were used to strategically plan coring activities, aimed at validating the performance of the dredging and capping remedy by confirming the presence and integrity of the cap and the underlying sediment.
Results/Lessons Learned
Preliminary results from the MMBES indicate a successful remote identification of capping material across the majority of the surveyed area, with clear distinctions in sediment density correlating with expected post-remediation conditions. The survey also identified potential hazards, such as areas of low sediment accumulation that could pose risks to the cap’s stability. These findings guided a coring plan, ensuring that sampling efforts were focused on critical areas, thereby optimizing the cap assessment process. The innovative use of this technology has demonstrated the value of MMBES in post-remediation monitoring, offering a robust, low-cost method for ensuring the long-term success of sediment remediation efforts without requiring extensive sampling.