City plans to line cracked sewer mains
June 12, 2008 · Updated 10:10 AM
"Port Orchard public works officials will line Bay Street sewer mains this week to prevent circumferential fractures from becoming split pipes.The cracks - 10, so far - which run all the way around the 12- to 18-inch sewer mains, are the result of old age, according to City Engineer Larry Curles.They were discovered when public works crews lowered a camera into the pipes and ran it along the inside. Public works regularly checks the pipes for breaks.It's preventive maintenance, Curles said. It's not like they're about to crumble, but when you see they're broken, you need to fix them.The petrified clay pipes, which were laid between 1940 and the 1960s, have fallen victim to natural ground vibrations and pressure. Over time, subtle movements weaken the integrity of the pipes. Meanwhile, salts and chemicals from household sewage corrode them internally, making them susceptible to fractures.Pipes with longitudinal fractures are normally repaired by shooting grout inside and allowing it to harden, but that process could blast these pipes apart.To line the pipes, public works crews first blow resin down the main so the liner will adhere to the pipe. They then lower a launcher with a liner folded over it into a connector. As the launcher travels down the length of the pipe, the liner unrolls - like turning a sock inside out over a foot - and it sticks to the resin. The liner then hardens to the pipe, covering the cracks and strengthening the main.The Port Orchard City Council allocated about $30,000 for the project on Sept. 9. Councilmembers opted for lining the pipes rather than excavating the streets.While a broken sewer main would not pose a public health risk, Curles said, the pipes do need to be regularly maintained.If a crack is left untreated, groundwater could seep in, taxing the water treatment facility. One gallon of water per minute flowing through a crack into the pipes over the course of a year would equate to water treatment for three households, Curles said.Because sewage flowing through the pipes is not pressurized, like water service is, sewage would not erupt from a manhole if a pipe did break. If a pipe broke, you would never know it, Curles said.Over time, a pothole might appear in the road where sewage and groundwater eroded the soil underneath the pavement. If a pipe cracked and dropped, sewage might leak into the ground around the fracture. "