Project Update by Dan Dobbels, PE
The Shoreline Storage Tunnel (SST) project is part of Project Clean Lake, a $3 billion, 25-year program that the Northeast Ohio Regional Sewer District (NEORSD) began in 2011 to meet Clean Water Act standards and address water quality issues. The SST is the fifth of seven new large-diameter tunnels, along with other projects, that NEORSD will use toward Project Clean Lake’s overall goal to reduce the 4.5 billion gallons of wet weather combined sewer overflows (CSOs) released into Lake Erie and its tributaries in the Greater Cleveland area.
The SST includes nearly 3 miles (4.8 km) of 23-foot-diameter (7 m) soft ground tunnel 75 to 140 feet (23–43 m) below ground that will capture and store overflows from CSO outfalls along the Lake Erie shoreline. The SST will then convey these overflows to other NEORSD tunnels and sewers, which will transport them to the Easterly Wastewater Treatment Plant for treatment before they are released into the environment.
General Layout of SST, Developed after an Intensive Alternatives Analysis
McMillen Jacobs Associates is leading the final design team for the project, in association with DLZ. In addition to overall management of the design team, we are responsible for tunnel and shaft design and geotechnical engineering. DLZ is leading hydraulic analysis and design work as well as civil and near-surface structure design.
The SST is part of the larger Shoreline Tunnel system that includes the Shoreline Consolidation Sewer (SCS) and other sewer and regulator improvements. At its upstream end, the SST will receive flow from the SCS. A unique aspect of the SST design scope included hydraulic design of both the SST and SCS project areas. Early in the design process and working closely with NEORSD staff, McMillen Jacobs demonstrated that there was available capacity in the District’s existing Easterly Interceptor Main Branch sewer that could be utilized in lieu of portions of the SCS and SST. This analysis resulted in the elimination of several drop shafts and reduction of almost 7,000 feet (2 km) of the SCS alignment, resulting in a significant cost savings for the SST/SCS System.
The main work shaft, SST-1, will be located at Forest Hills Park, where a connection between the SST and an existing CSO tunnel drop shaft will be made to allow drainage of the SST by gravity. Shaft SST-2 will be an online drop shaft, and the tunnel boring machine (TBM) will be extracted from Shaft SST-3. Shaft SCS-1 will also be a drop shaft and will be the connection point to the SCS. A short, 9-foot-diameter (2.7 m) tunnel will connect Shaft SCS-1 to the SST.
Design Notice to Proceed was provided in November 2018. The project is currently in the 90% design stage, with design to be completed in November 2020 and bidding planned for December 2020.
The SST is the fourth Project Clean Lake project that McMillen Jacobs has worked on for the NEORSD. We began in 2013 with work on the CSO Advanced Facilities Plan and Program Support Services project, then led a joint venture for the design of the Doan Valley Storage Tunnel system, and are the prime designer for the West 3rd Quigley / Westerly Miscellaneous CSO Control project.
Dan Dobbels is a Principal in our Boston office. For more information contact dobbels@mcmjac.com.
Related: DVT Project Prepares for TBM Excavation in Urban Cleveland