THE NORTHEAST Ohio Regional Sewer District (NEORSD) serves more than 1 million residents in the Cleveland region. In 2011 the district entered into a consent decree with the US Environmental Protection Agency, US Department of Justice and the Ohio Environmental Protection Agency to address CSOs to Lake Erie and its tributaries. Project Clean Lake is 25-year, USD 3bn program of which the main component is a network of deep tunnels.
A joint venture of Hatch Mott MacDonald and MWH Americas is in charge of design for the next tunnel in Project Clean Lake, the Dugway Storage Tunnel (DST). The approximately 15,000ft- (5km) long tunnel will connect directly to the Euclid Creek Tunnel (page 19), and be constructed to the same diameter of 24ft (7.3m). NEORSD awarded a USD 153M contract to a joint venture of Salini Impregilo/Healy in November 2014, and issued notice to proceed this February.
The tunnel will be also be constructed by TBM, through Chagrin Shale approximately 200ft (60.9m) below ground and include six shafts (see Figure 1). Completion is scheduled for 2019. There are five more tunnels planned for Project Clean Lake for a total of seven — not counting the Mill Creek Tunnel projects, which are already completed — as well as many other smaller diameter sewer projects.
INTERCEPTION
This September, contractor Super Excavators announced completion on microtunnelling work for the USD 66M Dugway West Interceptor Relief Sewer (DWIRS), some 60 days ahead of schedule. This 72in [1.8m] diameter sewer is a major connecting facility for almost all of the CSO control projects in NEORSD’s Easterly service area, which covers more than a dozen communities with a population numbering more than 500,000. The sewer will deliever flow to the Dugway Storage Tunnel and other tunnels being built as part of the Clean Lake Project.
NEORSD awarded a USD 10M contract to Aecom for the DWIRS’ design and construction management in April 2011, and a USD 57.5M contract in October 2013 to a joint venture of Walsh/ Super Excavators Inc (SEI).
Walsh Construction is working on ground work, including tie-in connections, and modifications to 39 existing combined sewer flow regulating structures. SX Foundations, Inc. is providing subcontracting for the installation of 15 secant pile drop shafts.
At its own initiative, SEI submitted a Value Engineering Change Proposal (VECP) for design modifications for the project which introduced a 700lft [213m] 72-inch tunnel curve in the alignment, replacing three shorter straight drives, and relocating one structure. "Our team at Super Excavators was prepared to construct a curved microtunnel, and this project presented a perfect opportunity," said Justin Kolster, SEI’s project manager for DWIRS. Benefits from the design modifications in the VECP included reduced community impacts and maintenance costs from elimination of the construction of two shafts in a residential neighborhood. These changes also accelerated the overall project construction, enabling completion 60 days ahead of schedule.
"Our VECP was accepted by a forward thinking owner, and it was a win for all involved," Kolster adds.
In total, Super Excavators constructed approximately 7,000lft [2133m] of 72-inch reinforced concrete pipe and 4,000lft [1,219m] of 48-inch reinforced concrete pipe microtunnel.
There were 17 separate drives of varying lengths with the longest being 1,079lft [328.9m]. Depths ranged from 25ft – 32ft (7.62m-10.6m) with the deepest drive at 42ft (12.8m).
Nine launch shafts and 11 receiving pits were constructed – one launch shaft and one receiving pit were eliminated from the original project design through implementation of the VECP design modifications.
