Northern Indiana Public Service Company (NIPSCO) announced today that an environmental remediation project is scheduled in October at the site of a former manufactured gas plant located at the northwest corner of Superior and Lafayette Streets.
The work will focus on addressing impacts from historic gas manufacturing byproducts, primarily coal tar, which remain beneath the river. The top two feet of sediment in a limited area will be dredged, followed by installation of a clay layer and a mat designed to capture and isolate material that had seeped from the riverbank on the west. Additional work will improve a City combined-sewer outfall and the surrounding riverbank on the west to prevent migration of any potential tarry seepage through this corridor, as well as halt erosion on the bank. These activities are expected to take three-to-four months to complete, although fluctuating river levels could alter the schedule.
NIPSCO is conducting this project in cooperation with the Indiana Department of Environmental Management’s (IDEM) Voluntary Remediation Program (VRP). As required by the VRP, IDEM has reviewed and approved the remediation plan for the site to ensure that the remedy achieves a satisfactory level of human health and environmental protection.
The dredged material will be prepared for transport within a secured area on the City’s Old Fort property, then moved offsite to an approved landfill. The Old Fort will remain open throughout the river work. The St. Marys Pathway will be marked with detours, and roadway safety measures will be utilized when needed. The Barr and Duck Streets intersection and river channel access will be closed for a
limited time. Closure signs will be posted for boat traffic and detour signs will be posted for Headwaters Park patron convenience.
Manufactured gas plants, common across America beginning in the early 1800s through the mid-1950s, produced “town gas” by heating coal, coke and/or oil in a closed vessel. The gas was captured and cleaned of impurities before being stored in large round structures known as gas holders. Town gas was distributed first for lighting streets, homes and businesses, and then for cooking and home heating. The plant at the Superior Street site operated between 1851 and 1948.
NIPSCO has a program to evaluate environmental conditions where the plants were located and take remedial actions when necessary. In the 1990s, contractors removed coal tar from the base of a gas holder at 320 E. Superior Street and from three underground structures beneath the parking lot at 305 Superior Street.
Early in 2009, impacted soil was excavated from the 305 Superior Street parking lot for offsite disposal; additional impacted soil at depth below that property and a small strip of land in Headwaters Park were stabilized in place by mixing the soil with a cement-based grout. As a part of the 2009 work, an interceptor trench was installed along the bank of the St. Marys River to prevent small amounts of coal tar that may remain in the ground from entering the river. Additional sampling has been conducted at 320 Superior Street and west of Barr Street. Cleanup options are under consideration for these portions of the site.