Project At-a-Glance
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Design of 3 shafts and one near-surface structure
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3D Finite Element Analyses for shaft stresses
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Deep shaft excavation using reinforced concrete
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C-B approach walls with embedded steel piles
Project Narrative
The Westerly Storage Tunnel is one part of Northeast Ohio Regional Sewer District (NEORSD)’s Project Clean Lake, a $4.4B multi-year program to improve water quality of Lake Erie, Cuyahoga River and local streams through construction of large tunnels, new conveyances, treatment plant improvements, and green infrastructure. The $135M Westerly Storage Tunnel will control overflows at two locations along the Cuyahoga River and decrease wet weather storm event flooding. This project contributes to NEORSD’s overall goal of capturing 98% of all combined sewer flows for treatment and reduce combined sewer overflows (CSO) by 328 million gallons annually.
Nicholson Construction retained Brierley Associates to design the support of excavation for one offline shaft, a near-surface flow approach structure and two shafts that will be used to launch and receive the TBM that will mine approximately 2 miles of the 25-ft diameter CSO tunnel.
The three shafts each consisted of unreinforced concrete Diaphragm Walls ranging up to 54-ft diameter and 265-ft deep. Excavation support for the flow approach structure consisted of a 2-ft thick C-B wall with embedded steel piles to achieve a 25-ft x 100-ft x 50-ft deep work-space between the drop shaft and an existing 16.5-ft diameter brick stormwater tunnel.
Brierley also provided recommendations for work associated with the planned connection into an adjacent brick storm sewer including bracing, dewatering, and work sequencing.
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