“Following the inspection, we determined that the culvert carrying these flows had collapsed and we immediately initiated an emergency pumping contract to bypass the culvert and direct flows around the culvert collapse,” said James Jones, Jr., P. E., collection systems construction manager with the Northeast Ohio Regional Sewer District (NEORSD).
In May 2017, NEORSD initiated a design-build request, known as the Emerald Parkway Culvert Repair, between the engineering firm of Northville, Michigan-based NTH Consultants Ltd., and Columbus, Ohio-based contractor Turn-Key Tunneling Inc. The Emerald Parkway Culvert Repair Project was funded by a stormwater program started several years ago by NEORSD to address stormwater issues.
Collecting data was the first order of business.
“This was an emergency project so the owner (NEORSD) retained a consultant to prepare whatever technical information through topographic survey and site investigation that it could gather,” said Charles Roarty, P. E., project manager with NTH Consultants. “The issues we faced were basically how to design the primary living system while working through a collapsed zone of soil. We made rather conservative assumptions, used an observational approach, and discussed stabilization methods for various circumstances that might be encountered. The more challenging portion of the job was the contractor’s.”
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Brian Froehlich, P.E., vice president of Turn-Key Tunneling, said the contract addressed the issue under critical conditions using a collaborative approach.
“The project involved the replacement of a 250-lf section of the collapsed corrugated metal pipe (CMP) with ground cover measuring up to 60 ft,” he explained. “Because of the depth of construction, the repair required multiple trenchless technologies through fill soils containing substantial obstructions.”
Froehlich said operations were performed from a strategically placed 24-ft diameter working shaft that Turn-Key Tunneling installed. “This shaft swallowed up a significant bend in the existing CMP and utilization of the HOBAS pipe allowed for a significant curve to be negotiated on site by trimming the pipe ends and utilizing stainless steel bands to couple the closure together.
“The rest – about 117 ft – was slip lined downstream of the shaft inside the existing CMP,” Froehlich added. “When the shaft with liner plates and ribs was installed at a depth of approximately 70 ft, workers found massive construction and demolition debris which included asphalt, concrete slabs and a duct bank.”
According to Froehlich, 60 yards of grout were used to fill a large void outside the liner plate. “The crew also discovered a significant concrete collar/ headwall between the CMP sections, which ultimately had stopped failure in the CMP,” he said.
The installation of a gravity flow dewatering system of the impoundment area was desired to replace the existing pump system, so the project team planned two auger bores to lower and carry the storm water through and around the work zone.
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Froehlich pointed out that after workers encountered hefty construction and demolition debris at 140 ft, the final 90 ft was converted to a 24-in. diameter bore. This bore protruded into the reservoir beneath 4 ft of water and dropped the reservoir overnight.
“A modified flume system was constructed within the shaft, switching steel casing to rubber hose and maximizing shaft space to allow placement of the lower auger,” he said. “This bore met an obstruction at 205 ft and video equipment was deployed to evaluate the situation. The culprit was found to be a large granite boulder which had to be removed by drilling and splitting and hand removal.”
Once the boulder was removed, the bore was advanced a total of 230 ft. A soil plug was left in place to hold back the water until the boring equipment could be removed and the gravity dewatering system fully connected. After that work was completed, a long reach excavator was deployed to expose the end of the bore which was 12 ft below the water surface. When a pathway opened through the lower casing, the water shot through the system and lowered the reservoir to the original design elevation overnight.
To protect the auger bore from debris, a 54-in. casing with a bar rack and riprap was installed. Finally, pumps were removed.
“The process was followed by hand-mining 11-ft ribs and lagging primary tunnel liner through and around the existing, collapsed culvert,” Froehlich said. “The Turn-Key/NTH proposal to install the new tunnel and HOBAS in the same profile as the existing failed CMP required a different approach. This proved to be a viable solution to replace a failed culvert without moving the alignment which may have required additional right-of-way and permitting.”
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Additional trenchless operations included culvert relining beyond the collapse and secondary tunnel liner installation within the rib and board support. In total, the project used 370 ft of 104-in. diameter HOBAS flush reline pipe.
“HOBAS is a product that was familiar to NEORSD, as they have used HOBAS pipe on several other projects,” Froehlich explained. “This pipe was selected for its low Manning’s co-efficient which allows the 104-in. HOBAS to carry an equivalent flow as the pre-existing 132-in. CMP. This, coupled with the thin wall thickness, allowed us to downsize the tunnel and still gain better flow capability.”
The Emerald Parkway Culvert Repair, which re-established stream flow and ensures community safety, was substantially finished in early October 2018.
“The Emerald Parkway Culvert Repair was urgently needed to prevent flooding within a one-square-mile drainage area,” Jones said. “Had these repairs not been made, residents and businesses upstream of the collapsed culvert would have been severely impacted by flows not able to reach the Rocky River.”
Jones explained that as part of NEORSD’S Stormwater Master Plans, the SWIM investigators will walk all streams within the regional stream network. “As they continue to find culverts in need of repair, they will flag potential problems and conduct repairs as necessary so that residents and businesses will not be impacted,” he said.