Conner Creek Sediment Removal Dredging Engineering & Remediation
During the summer of 2002, NTH Consultants was hired to investigate removal of more than 140,000 cubic yards of contaminated sewage sediments from the bottom of Conner Creek in Detroit. NTH engineers sampled sediments, conducted waste characterization analysis, and developed recommendations for sediment disposal. We also designed and performed bench-scale and field-scale drying studies to evaluate various sediment handling and dewatering methods. In addition, we participated in public hearings with stakeholders to seek input and integrate concerns within the project parameters. We also prepared plans and specifications for the sediment dredging contract.
Underwater Condition Survey To investigate the potential extent of sludge on the creek bottom, NTH completed an underwater condition survey of the entire creek using hydrographic soundings and core sampling. The survey determined that there was approximately 140,000 cubic yards of sewer sludge sediment on the creek bottom. To complete this survey, NTH:
Reviewed historical topographic drawings and dredging plans of the creek to evaluate its design depth.
Completed a hydrographic survey of the entire creek bottom to establish an existing bottom contour.
Collected core samples through up to 12-feet of sediment for characterization and chemical analysis.
Computer modeled the creek to estimate sediment volume.
Worked with MDEQ and US Army Corps of Engineers to develop recommendations for disposal of sediments.
Sediment Dredging Once hydraulic dredging was selected as the method for dredging, NTH assisted the owner during permit negotiations with the State of Michigan. NTH was instrumental in convincing the State to allow the owner to conduct a full-scale trial of the sediment dewatering operation. During this trial, NTH collected near daily discharge samples for low-level mercury and PCB analysis. After the trial was over, NTH again negotiated with the State on behalf of the owner. Instead of requiring a formal permit, the State allowed the dredging to continue under an agreement with reduced sampling and reporting requirements. NTH developed a correlation that was incorporated into the agreement with the State, which allowed the owner to monitor for turbidity in the discharge as a surrogate for contaminants. NTH implemented a real-time discharge monitoring system that allowed