Background/Objectives: The USEPA Record of Decision (ROD) for the Gowanus Canal (2013) selected In situ Stabilization (ISS) to remediate native sediment in targeted areas with potential for upward non-aqueous phase liquid (NAPL) migration from the native sediment.
At the time the ROD was issued, the extent of the potentially mobile NAPL was not defined and while ISS is a proven technology for remediation of upland sites, ISS has not yet been implemented for full-scale remediation of submerged sediment in subaqueous environments. These two significant data gaps required pre-design data collection effort and multi-disciplinary design approach to ensure that ISS achieves the remedial action objectives (RAOs) established in the ROD.
Approach/Activities: The Gowanus Canal is a 1.8-mile-long canal and has been divided into three remediation target areas (RTA-1 through RTA-3). ISS of native sediments with potential for upwardly mobile NAPL is contemplated in RTA-1 and RTA-2. Our presentation will provide an overview of our approach to the remedial design. Specifically, we will highlight the design approach and pre-design studies implemented to obtain the data necessary to complete a design that meets the RAOs including:
- Evaluation of Potential Groundwater Upwelling Areas and Measurement of Discharge Rates
- Evaluation of Potentially Mobile NAPL in Native Sediments - Define the Boundaries of Anticipated ISS Implementation
- Groundwater Model - Predict ISS Effect on the Groundwater/surface water Interaction
- ISS Pilot Test -Performed by the USEPA to inform the ISS Design
- Iterative Design Process and Integration with a Multilayered Cap System
- Geotechnical and Structural ISS Design Elements
- Bulkhead Integrity and potential ISS Integration with Adjacent Bulkheads
Results/Lessons Learned: The presentation will conclude with an overview of the sediment ISS design. Results of the potential groundwater upwelling, potential NAPL mobility assessment, and ISS pilot test are available now. At the time of the presentation, Geosyntec expects that a minimum 35% Design will have been completed and we will be prepared to discuss how each of the pre-design studies were integrated and informed the ISS design.