Fiberglass-reinforced concrete pipe rehabilitates interceptor
An 84-inch brick-and-mortar interceptor, constructed in 1889, lay in the path of transportation improvements. Fearing vibrations from heavy machinery and loads from new downtown growth would collapse the pipe, the Metropolitan Council Environmental Services hired engineering firm Brown and Caldwell to assess it. They found crown cracks, sags and bulges, leaking joints, and dislodged bricks and stonework. There was no way to bypass the sewer given the time constraints.
The engineers recommended sliplining the 1,300-foot-long interceptor with centrifugally cast, fiber-reinforced, polymer-mortar pipe from HOBAS Pipe USA. Working at night in 50-foot-deep pits, Lametti and Sons from Hugo, Minn., pulled in 200 and 950 feet of 78-inch pipe and 350 feet of 72-inch pipe with a short radius curve.
To navigate the curve, HOBAS engineers designed 4-foot-long segments with special joints that the installers could open a little to ease the sections around the bend without jeopardizing the pipe’s watertight integrity. The new pipe was blocked into place and grouted using cellular concrete.
Rehabilitating the interceptor was completed on schedule for $4 million. 800/856-7473; www.hobaspipe.com.
Fabricated fitting repairs rupture
Water erupting from under the parking lot adjacent to the Sawgrass Water Treatment Plant brought workers on the run from the Sunrise (Fla.) Utilities Department. Excavation of the site revealed a failed 30-inch mechanical joint restraint. Unable to close the control valve, they feared the water pressure would blow the pipe apart.
Related: From the Editor: Fixing the Leaks
City officials contacted Smith-Blair. Two representatives made rough sketches of the failed assembly, then factory computers turned them into shop drawings. The parts for the 30-inch bell-pack encapsulation fitting were fabricated, welded together, and shipped.
Factory engineers assisted in the installation. Repairs were completed in less than 10 hours with the pipe live. 800/643-9705; www.smith-blair.com.
PVC pipe expedites rehabilitation
In December 2009, the Rainbow Municipal Water District in Fallbrook, Calif., detected falling water levels in the 50-million-gallon Morro Reservoir. Crews discovered a significant leak in a 300 psi 24-inch epoxy-coated, steel transmission line. Inspecting the 2,000 feet of pipe revealed large amounts of sediment and sand where it had failed.
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To achieve the required 305 psi pressure rating and higher flow needed from the carrier pipe, J.C. Heden and Associates specified DR14 16-inch fusible C-905 pressure-rated PVC pipe from Underground Solutions. Working within the 20-foot easement, Golden State Boring & Pipe Jacking cleaned the pipe, then sliplined a single 2,100-foot section in one day. They strapped four tremie lines to the pipe during pullback, then injected heavy aggregate grout to displace high groundwater and stabilize the line.
After pressure testing the pipe at 355 psi for five hours, workers installed the gauges on the end caps and held the pressure at 100 psi to monitor the external forces imposed during grouting. The project passed all testing and the line was returned to service. 858/679-9551; www.undergroundsolutions.com.