- Rehabilitation of 7,100-ft by 9-ft diameter water tunnel
- Brierley performed a detailed tunnel inspection and subsequently developed a repair scheme
- Completion and clean up was accomplished in 3 months, in time for the high-demand summer season
Constructed in 1920 this 7,100-ft by 9-ft diameter water tunnel has been in service ever since with only a few interruptions. Brierley Associates was retained by the City of Milwaukee Water Works (MWW) to perform a detailed tunnel inspection and subsequently develop a repair scheme. The six-month time frame for project completion, prior to high demand late spring and summer months, posed a logistics challenge.
Brierley assembled a solid team of in-house engineers and geologists as well as sub-consultants and constructors with specialized industry experience. Brierley’s contracting partner, Engineering & Construction Innovations, Inc. (ECI) of Oakdale MN, initially dewatered the tunnel and performed an end-to-end pressure cleaning. ECI’s Vice President, Robb Johnson, stated “The Brierley/ECI team worked well together on the Linnwood Tunnel Dewatering Project. We were able to work through several complex issues with the project owner’s representative to facilitate the necessary engineering, material testing, and construction tasks within the allotted time frame and exceed the client’s expectations.”
Given the need to efficiently document conditions of the tunnel, Brierley implemented a multi-crew approach consisting of a survey team to establish tunnel stationing, elevations, and dimensions, inspection by tunnel and structural specialists followed by video-documentation. Lastly, concrete cores were obtained to verify the actual tunnel thickness in selected areas. These cores were then augmented by Impact Echo testing to provide a thickness check. At the conclusion of the inspection and documentation phase, Brierley met with MWW to discuss findings and assign urgency ratings to the observed defects.
The goal of the follow-up repairs was to complete as much as possible before the tunnel was placed back into service. The prioritized repairs amounted to approximately 7,500 linear feet of cracks. Grout ports were installed along the entire length of the cracks to facilitate effective and efficient repairs.
Completion and clean up was accomplished in 3 months and in time for the tunnel to be placed back in service for the summer season.