SUCCESSFUL REMEDIATION AT A FORMER MGP SITE IN A HIGHLY POPULATED URBAN SETTING

摘要

The former South Station manufactured gas plant (MGP) site, owned by The Peoples Gas Light and Coke Company (Peoples Gas) is approximately 4 acres in size, and is located in urban Chicago, along the Chicago River and directly adjacent to residential and light industrial properties. The MGP began operations as a production and storage facility in the late 1870’s and was dismantled between 1920 and 1961. In the early 1970’s a 41,600 square foot warehouse/building was constructed on the site and still exists. The initial interim remediation objective was to remove source material that was present at a depth of 30 feet bgs (20 feet below the river level) adjacent to the river and the building, underneath the building and on both the landward and river side of an earth retention system installed to facilitate source removal. Remediation was challenging because of concerns related to working adjacent to the river and the existing building, the proximity of a nearby playground and residential homes and current and future development of the City of Chicago’s ever expanding riverwalk system. In order to accomplish the remediation of this site, a state-of-the-art earth retention system was designed and constructed, to remain in place as a permanent dock wall. The system was also designed to conduct wet or dry excavation, as it was uncertain how successful dry excavation would be prior to commencement. Community related design considerations included intensive perimeter air monitoring, truck routing, truck tarping and washing, working hours, and street cleaning. Approximately 80,000 tons of impacted material was excavated, managed and disposed of offsite at an Illinois-approved landfill as special waste. Activities were conducted so that dry conditions were obtained for the majority of the excavation. Remediation activities exceeded the objectives in that the interim action was expanded to provide a permanent remedy and no further remediation is required. The project resulted in a 4 acre site suitably restored for industrial/commercial use, including use of the site’s 41,600 square foot building. Visual aesthetics were greatly improved from the residential and the river perspectives.