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Big Walnut Augmentation/Rickenbacker Interceptor

The Big Walnut Augmentation/Rickenbacker Interceptor was constructed by the City of Columbus, Division of Sewer & Drainage to increase the City’s sewer capacity.  Construction of 20,800 ft of 14-ft finished diameter sewer and 13,300 ft of 12-ft finished diameter sewer were performed under two separate contracts.  High groundwater levels and challenging glacial terrain consisting of very dense tills layered with highly permeable sands and gravels containing cobbles and boulders were present along the alignment; and one-pass tunneling using a pressurized face TBM, either slurry or earth pressure balance (EPB) was specified.  For each contract, the contractor opted to utilize an EPB TBM to deal with the difficult ground conditions.
During design, Lachel’s responsibilities included:

  • Development and coordination of the geotechnical investigation, preparation of interpretative geologic profiles, input to alignment selection, and development of tunnel and shaft design loadings.
  • Performing an optimization study for selection of shaft construction methods.
  • Full structural design of all shafts (slurry wall and cased auger) and design of associated ground improvement and grouting methods.
  • Full structural design the bolted and gasketed precast concrete segmental tunnel lining.
  • Development of the geotechnical instrumentation and monitoring program.
  • Preparing all tunnel and shaft related drawings and specifications and the project Geotechnical Baseline Report.

During construction, Lachel provided construction management services including onsite inspection and monitoring, contract compliance verification, and collection and analysis of data related to tunnel and shaft construction.  Lachel also provided technical review of submittals, alternative designs, and contractor claims.