State of the Practice − Sub‐Aqueous In‐Situ Solidification for Contaminated Sediment Remediation

ABSTRACT

In‐situ solidification (ISS) has emerged as a cost‐effective and versatile technology for sediment remediation, particularly for addressing contamination at greater sediment depths. This paper evaluates ISS in the context of conventional sediment remediation approaches, highlighting its advantages, design and implementation considerations, and effectiveness through case studies. ISS involves solidifying sediments in place with cementitious grout, thereby reducing contaminant mobility by lowering hydraulic conductivity and minimizing leaching to groundwater and surface water. The technique also enhances the geotechnical properties of treated sediments, reducing the need for excavation and minimizing impacts on adjacent infrastructure. Sub‐aqueous ISS offers potential cost savings over traditional methods by mitigating transportation and disposal costs and addressing challenges associated with emerging contaminants. However, the altered sediment conditions post‐ISS may not support benthic communities, necessitating the use of restoration caps for ecological recovery. ISS is particularly beneficial for sediments located more than five feet below the surface, near sensitive infrastructure, or in large volumes exceeding 10,000 cubic yards. Compared to dredging, ISS can reduce environmental disturbance, improve seismic stability, limit vapor and odor emissions, and require a smaller operational footprint, making it suitable for urban environments. The design and execution of ISS demand comprehensive site characterization, regulatory coordination, and careful planning of site preparation, water quality management, and mixing methods. Quality control measures such as GPS monitoring and appropriate grout dosing are critical for success, and long‐term monitoring is essential to ensure remedy stability and effectiveness. Overall, ISS represents a valuable addition to the sediment remediation toolkit, complementing other methods to address complex site conditions.