Cortland-Homer Former MGP Remediation-A Case History

An integrated approach was used to remediate the Cortland-Homer former Manufactured Gas Plant in Homer, New York. The record of decision (ROD) for the former plant area required excavation of impacted soils to depths of nearly 14 m. In contrast, the ROD for the area downgradient of the former plant called for in situ solidification (ISS). The former plant area and the downgradient area are separated by U.S. Route 11, and impacted soils under the roadway were judged inaccessible. New York State Electric & Gas (NYSEG) and AECOM jointly proposed an alternative, integrated remedy, using auger-mix ISS treatment in both areas. This alternative facilitated installation of vertical barrier walls to contain impacted soils under the highway, enhancing the remedy's overall effectiveness. It also resulted in substantial cost savings. This paper summarizes the remediation design and construction. It discusses the use of rotosonic drilling to characterize coarse-grained glacial outwash soils, with focus on determining the size and frequency of cobbles and boulders. Furthermore, it reviews laboratory bench studies that were used to develop preliminary ISS mix designs and subsequent field trials to optimize the ISS grout mix. Construction is also discussed, including lessons learned.