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Back to Signature Projects
Picture
Client:
Detroit Water and Sewerage Department

Location:
Detroit, MI

Prime Consultant:
NTH Consultants, Ltd.

Total Project Budget:
$9 Million

NTH Project Budget:
$1.4 Million



Conner Creek Sediment Removal
Dredging Engineering & Remediation

During the summer of 2002, NTH 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.