Overcoming the Cleveland shale challenge
13 May 2014
Desiree Willis, Techincal Writer, The Robbins Company
- Rapid progress through soft Cleveland shales during the successful 1.7km (1-mile) Black River Wastewater CSO storage tunnel drive in Lorain, Ohio, left the conveyor system struggling to keep up with advance rates.
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7m Robbins double shield breakthrough in Ohio
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Minimal cutter wear during 1.7km drive
- The 7m (23ft) diameter Robbins double shield is now being disassembled before rebar tying and concrete pouring can begin to solidify the lining. Progress rates during the five-month drive that launched in November last year (2013) averaged 21m (70ft) per day. The job, carried out by contractor Super Excavators, is the first time Onsite First Time Assembly (OFTA) has been used in the USA.
- Gregg Rehak, for the contractor, said: “Cleveland shale made for speedy excavation; so fast that it was challenging for the continuous conveyor system to keep up at times. We only changed seven cutters during the bore, four of which probably could have made it to the end, but were changed for precautionary reasons.”
- Another feature of the drive was the use and training up of local labor. “We were able to hire locals and do on-the-job training with them. Not only did this boost the town of Lorain’s economy by creating jobs, but it also gave local construction workers experience in the tunneling industry. Our team was able to adapt and learn.”
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Ring beam and lagging lining
- Due to the geology, a unique tunnel lining method was used. Instead of traditional concrete segments, ring beams, wire mesh, and lagging were installed in 45cm (18in) intervals. Up to 25% of the soft shale geology consisted of layered and laminated rock that broke from the tunnel crown before ring beams could be expanded, requiring extra chipping and rock relief. Once workers fine-tuned the technique, they were able to set 12–14 rings/day, even in the sections of bad ground. In more stable sections production averaged 18–20 rings/day. Now that tunneling is complete, a final monolithic pour will solidify the lining.
- Once finished, the tunnel will have a storage capacity of 42 million liters (11 million gallons), which will provide a significant boost in water quality for Lorain. Final project completion is set for 2015.
Ring beam support for Lorain CSO drive
12 Dec 2013
Desiree Willis, Technical Writer, The Robbins Company
- TBM launch is complete on the latest CSO storage tunnel project in the USA: the Black River Storage and Conveyance Tunnel in Lorain, Ohio.
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Ring beam and lagging support
- The 7m (23ft) diameter Robbins double shield machine and continuous conveyor system started operations late last month (November 2013), and the TBM will operate in a unique manner for the duration of the 1.7km (1-mile) drive.
- "We are expecting decent production with minimal cutter wear, as the drive is in a softer shale. We are installing ring beams and lagging, and there will be a final monolithic pour after tunnel completion," said Gregg Rehak, Tunnel Supervisor for Super Excavators. Rather than concrete segments, ring beams are being erected within the tail shield for installation as the machine passes, said Rehak.
- The TBM was built using Onsite First Time Assembly (OFTA) - a Robbins-developed method that saves contractors in shipping time, costs, and man-hours worked. Robbins field service technicians worked for three months on location with crews from the Walsh/Super Excavators tunnel contractor JV to assemble the machine and provide support.
- "OFTA was a challenging process for everyone onsite. We had to make numerous adjustments, but, regardless, our team worked diligently to overcome the challenges and we were able to get the TBM assembled and launched relatively close to schedule," said Mike Garbeth, Project Manager for the Wisconsin-based contractor Super Excavators. In addition to the TBM, Robbins supplied an in-tunnel continuous conveyor system and a space-saving J-type vertical conveyor.
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Robbins double shield TBM
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Lowering the 7m diameter cutterhead
- As of earlier this month (December 2013) the machine had advanced approximately 60m (200ft) into the drive. "Tunneling started a bit slow while we made final adjustments to the TBM and conveyor assembly, but mining has picked up speed and we are beginning to reach anticipated production rates," said Garbeth.
- The major components of the US$65 million Black River Tunnel project include construction of a launch and reception shaft - both approximately 11m (36ft) in diameter and 50m (165 ft) deep - in addition to the tunnel, which will have a finished diameter of 5.8m (19ft). Ric-Man Construction was subcontracted to build the shafts.
- The alignment runs along city property roughly parallel to the Black River, beginning at the launch shaft near the Black River Wharf and terminating near the Lorain Black River Wastewater Treatment Plant.
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Excavation is through softer shales
- Mining is expected to be completed by Spring 2014 and final project completion is scheduled for 2015. When finished, the tunnel will have a storage capacity of 42 million liters (11 million gallons) per day, providing a significant boost in water quality for the City of Lorain, and providing relief from combined sewer overflows (CSOs) into Lake Erie. The storage tunnel is one of many being constructed in the USA as a way of meeting the requirements of the Clean Water Act, the aim being to significantly reduce CSOs into natural watercourses by storing contaminated water during high rainfall events ready for treatment at a later date.
- A screening facility will be built at one end near the wastewater treatment plant, where water will be diverted into the storage tunnel; and a pump station will be constructed at the launch shaft site. When complete, the pump station will move water from the storage tunnel back into an existing sewer interceptor.
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Green surge threatens CSO storage solution - TunnelTalk, June 2013
Ground conditions favor Indianapolis CSO tunnel progress - TunnelTalk, August 2013
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