The Northside Sewer Relief Tunnel (NSRT) was constructed in the mid-1980s in the city of Houston using reinforced concrete pipes with a liner of polyethylene. It is the largest and the deepest tunnel in the city with some depths reaching 3.5 meters.
But the time passed and the sections of the liner began to fail leading to overflows and the reinforced concrete pipes showed signs of corrosion. The city faced a challenge of sewer tunnels rehabilitation. The city adopted the Northside Sewer Rehabilitation Program, which along with patching the holes involved the complete replacement of more than 1.6 km of concrete pipes with composite ones.
They used centrifugally cast, fiberglass reinforced, polymer mortar (CCFRPM) pipes from a local manufacturer – Hobas Pipe USA of Houston, that had never manufactured the pipes over 3 meters in diameter before.
Replacing 3-meters pipes in 3.4-meters tunnel at about 15-meters depth was a real challenge for the experts from Boyer, Inc., the company that was doing rehabilitation.
The target is met and HOBAS Pipe USA insists that they see a trend in the sewer market toward larger diameters, so they are investing in their facility to ensure they meet the needs of their customers.