A Surprise Around Every Bend: Great Lakes Legacy Act Sediment Remediation, Lincoln Park, Milwaukee River, WI

摘要

Overview. In 2011–2012, USEPA Great Lakes National Program Office (GLNPO), WisconsinDepartment of Natural Resources (WDNR) and Milwaukee County Parkspartnered together under the Great Lakes Legacy Act (GLLA) program to remediate contaminatedsediments and restore the riparian habitat on a portion of the Milwaukee Riverin Milwaukee, Wisconsin. This began as a dry excavation project during the remedial design.Once we started remedial action, however, changes happened, we encountered theunexpected and made adaptive changes in the field to address the issues. The focus of thispresentation is on the changes we made between remedy design and implementation,along with the surprises we encountered that resulted in a better over-all clean up.Background/Objectives. Lincoln Creek and the west oxbow of the Milwaukee Rivercontained approximately 70% of the PCBs remaining (by WDNR estimates) in the MilwaukeeRiver. The Milwaukee River is the largest of several rivers in the MilwaukeeEstuary Area of Concern (AOC). Heading into construction we expected to excavate100,000 cu yards of PCB contaminated sediment to a clean-up concentration of 1.0 partper million total PCBs.Approach/Activities. The design called for breaking the approximately 10-acre area into4 remediation zones, placing sheet pile down the center of Lincoln Creek, channeling thewater through one side, while excavating the other. Once complete, the water could beflipped, channeled down the newly cleaned side, and the first side could be excavated.Once we moved into the remaining zones, we encountered new challenges needing anadaptive management approach, essentially redesigning the project in the field as we progressed.Some of the challenges included: finding TSCA level PCBs, NAPL and PAHswhich required development of appropriate protective clean up numbers with new wastedisposal and health and safety concerns; finding potentially historically significant artifacts;needing to change bank stabilization and habitat restoration requirements based onthe changing approach to a downstream dam and future water levels in the MilwaukeeRiver; and missing planting time windows.Results/Lessons Learned. Under this GLLA project, we removed approximately120,000 cubic yards of contaminated sediment (5,000 lbs of PCBs and 4,000 lbs of PAH)and restored over 1 linear mile of riparian habitat. Communication, flexibility, andpatience are the keys to a successful sediment remedial action. That, and an on-siteearby laboratory capable of producing usable analytical results in a few hours.