Paper_Lessons Learned Through the Implementation of In-Situ Stabilization for the Closure of a Coal Combustion Residue Site

Paper_Lessons Learned Through the Implementation of In-Situ Stabilization for the Closure of a Coal Combustion Residue Site

Grand Rapids, Michigan

Traditional means of remediating coal combustion residual (CCR) materials include excavation and off-site disposal. Site-specific geotechnical and hydrological features can dramatically increase the cost and complexity of remediation efforts. As such, it is often advisable to explore ways to properly leave material on-site. One such way may be via in-situ stabilization/solidification (ISS). ISS is a technically sound and economical solution for remediating CCR and other wastes and was recently used as part of the in- place closure of a 2.25-acre ash pond. In the project scenario described herein, the Contractor evaluated multiple means of ash stabilization through the use of vertical auger and hydraulic excavator mixing. In total, 48,000 cubic yards of CCR material was stabilized reaching depths of approximately 25 feet below a prepared working platform. A site-specific mixture of blast-furnace slag and Portland cement grout was used to improve the physical properties of the material contained within the pond footprint and to reduce its impact on the surrounding soil and water. This paper describes various lessons learned through the development and completion of the project scenario, including pre-construction considerations and full-scale implementation of ISS in an ash pond environment. The authors further outline general constructability concerns for future use of ISS in similar applications. Overall, this paper shows that the project achieved all performance requirements and did so safely, on budget, and within the estimated schedule.