TRIB TOWN: Estimates range up to $6.5 million to repair 7-year-old sewer line
SOUTHWEST - The city may soon have to spend up to $6.5 million to repair and replace a plastic sewer line in Southwest Portland that should have been made of steel.
The pressure line carries sewage from the Fanno Pump Station on Southwest 86th Avenue to the city's gravity sewer system at Southwest 31st Avenue and Multnomah Boulevard. It runs in two sections under portions of Southwest Garden Home Road and Multnomah Boulevard.
Although the line was installed just seven years ago, two major failures have already occurred, and officials with the Bureau of Environmental Services are afraid it will continue to fail and leak sewage.
'The lines cannot meet our 50-year lifespan requirement,' said Dan Hebert, the head of the bureau's Waste Water Pump Station Engineering Station.
Hebert said the original contract requirements called for steel pipe, but the contractors persuaded the city to allow them to use plastic pipes instead.
The Garden Home section is made up of 28-inch-diameter high-density polypropylene, or HDP, while the Multnomah section is 30-inch-diameter polyvinyl chloride, or PVC.
Hebert said he doesn't know why the city allowed the substitution, but noted that smaller-diameter PVC pipes have successfully been used in other pressured sewer lines.
In this case, a joint in the HDP section and a pipe wall in the PVC section have failed, leading officials to conclude that similar problems could occur at any time.
'Apparently, these type of pipes cannot withstand the pressure generated at the pump station,' Hebert said.
The bureau is studying how extensive the repairs need to be. Hebert said that at a minimum, 27 joints in the HDP section need to be replaced, at a cost of $500,000.
Although it might be possible to repair the PVC section without digging it up, if it needs to be replaced the cost could be as high as $6 million, Hebert said.
That is more than three times the $2 million it cost to install the entire line in late 1999 and early 2000.
Hebert said that although inflation accounts for some of the higher cost, a larger issue is the need to keep the line in use during the repairs, potentially stretching the project out to three years.
A decision on the extent of the repairs will not be made until June. In the meantime, the bureau has scheduled an open house to discuss the Garden Home section from 6 p.m. to 8:30 p.m. March 8, at the Garden Home Recreation Center, 7475 S.W. Oleson Road.
An open house on the Multnomah section will be held from 6 p.m. to 8:30 p.m. March 13, at the Multnomah Center Auditorium, 7688 S.W. Capitol Highway.