To comply with their Consent Decree with the Environmental Protection Agency (EPA) mandate of reducing sewage overflow into Lake Erie, the Northeast Ohio Regional Sewer District (NEORSD) retained NTH Consultants Ltd. (NTH) as Prime Engineer for design of a relief sewer/storage tunnel along River Road and Elm Avenue in Cleveland, Ohio.
The Westerly Low Level Relief Sewer (WLLRS) Project includes regulator modifications, upsizing of dry weather outlet (DWO) sewers, and approximately 2,600 lf of new 72- in. diameter relief/storage sewer with relatively shallow depths of 8 to 25 ft. The project also includes new regulators connecting to the existing interceptor that ties into the pump station, pump station modification design, force main design, and local sewer stormwater offloading design. The project is also planned to increase the WLLI system resiliency during larger rain events.
NTH completed the design of this project in 2016. The contractor (Ward & Burke) holed out on Sept. 8, 2017, The 2,650-ft long tunnel was completed using a slurry microtunnel. High-strength RCP was used as the final liner in the tunnel and was strong enough to take the expected jacking forces even on an 1,850-ft long drive. Ward & Burke is forming and pouring the permanent structures.
The 1,850-ft drive has been the longest microtunnel drive ever for NEORSD. NTH has been involved regularly throughout construction for construction support services, including submittal, RFI, change order, and pay application reviews, regular attendance at progress meetings, design change reviews, etc.