Document 85moxqxkxp3g4GajDa9Q5GDbd

ENCLOSURE 4 Description of the 3M Decatur Inactive Landfill Containment Structure At the 3M Decatur site, a RCRA interim remedial measures (IRM) program is currently underway to construct a containment structure for an inactive landfill. This IRM program is being undertaken by 3M pursuant to an IRM Work Plan that was approved by the Alabama Department of Environmental Management (ADEM) on December 16, 2002. The first part of the IRM program was completed in March 2004 and it consists of a subsurface sheet-piling barrier around the entire landfill. This barrier will reduce the impact of any affected groundwater beneath the inactive landfill on the environment by containment of the affected groundwater within the barrier. In March, 2004, the second major component of the IRM program began to be implemented. This will involve an upgrade of the existing cap on the inactive landfill to meet current RCRA standards. The upgrade to the existing cap will result in the installation of a RCRA multilayer cap that will prevent precipitation from entering the inactive landfill and thereby reduce the potential for movement of constituents from the landfill. It is anticipated that the construction of the landfill multilayer cap will be completed by the first quarter of 2005. The last component of the IRM program will be the installation of maintenance pumping wells inside the sheet-piling barrier, after the multilayer cap has been installed. These wells will be used to pump and regulate the amount of groundwater that may accumulate inside the barrier from minor leakage through the sheet-pile barrier. These wells are to be installed by the end of 2004. Based on the findings of the RCRA Facility Investigation (RFI) at the site, 3M will be implementing remedial measures in the Chemical Plant at the site. While the exact nature of the remedial measures that will be implemented at the Chemical Plant will be identified through the RCRA Corrective Measures Study (CMS) process, these corrective measures will also.be focusing on retarding the movement of affected groundwater underneath the Chemical Plant towards the Tennessee River. The CMS report will be submitted to ADEM by the end of June, 2004. Upon receipt of ADEM's approval of the CMS report, 3M will initiate the RCRA Corrective Measures Implementation (CMI) program by preparing the design for the Corrective Measures. It is anticipated that the construction of the Chemical Plant Corrective Measures will commence in the fourth quarter of 2004 and be completed by the end of 2005. April 7, 2004