Plans coming to keep stormwater out of sanitary sewers
WEST NORRITON — West Norriton officials are developing long-range plans to reduce the “inflow and infiltration” (I&I) of stormwater into sewer pipes and reduce the future sewage treatment volumes at the Norristown sewage treatment plant.
The November 2013 sanitary sewer system inflow and infiltration study prepared by Rettew Associates of Lancaster was a first step toward reducing the I&I problems. The study was recently made public and was placed on the West Norriton township website at www.westnorritontwp.org.
“The comparisons of the total flow to Norristown,” the study said, “indicates that approximately 13 percent of the sewage flow is due to inflow and infiltration, based on the computer modeling.”
The study identified four roadways and areas of the township where sewer lines, manholes and leaky sewer laterals from residential homes need remedial work to reduce the I& I problems.
At the top of the repair list were 14 manholes on Mystic Lane where the source of the I&I included stormwater “flow into manhole lids, sewer vents and into the manholes through the stone subbase of the roadway surface,” the report said.
A seven-manhole sewer line run in School Lane had stormwater leaks caused by exterior drain connections, low-lying sewer vents, stormwater flow into manhole lids, water leaks through the subbase of the macadam roadways into manholes and infiltration into the sewer pipe.
The area from Burnside Avenue to Trooper Road, on each side of Oakland Drive, had stormwater from exterior drain connections into sewer laterals, stormwater surface water flowing directly through manhole lids, through the subbase of roadways into manholes and broken sewer laterals.
The sewer lines flowing into the Whitehall Road Pump Station had stormwater infiltration from exterior drain connections, low sewer vents, leaky manhole lids, infiltration into the sewer lines and leaky manholes, the report said.
The township owns 17 sewer flow meters that are collecting flow data used to generate the November 2013 study.
Township Manager Jason Bobst said township officials and the sewer consultant, Christopher Frawley, were preparing a phased, five to seven-year plan to repair sewer lines and manholes that would be presented to the Board of Commissioners at the March meeting.
“We’re going to flesh out the recommendations and put together a multiyear plan to address the problems,” Bobst said. “We are not going to get all this done in a year or two years. You have to plot out the priorities.”
Bobst said that the sewer mains under Mystic Lane and School Lane would be televised this spring to determine which sections need to be replaced and which sections can be slip-lined to eliminate I&I.
“We hope to do that work in the springtime. Then we will design the solution in the summer and perhaps do the work in the fall,” Bobst said. “Mystic Lane could have groundwater infiltration from a (nearby) stormwater basin.”
Bobst estimated the televising work and engineering design for the two projects would cost $200,000 to $250,000. He said repairs might total $500,000. The township has $3 million from previous sewer tapping fees to finance the initial repair work.
At the same time, the township is proceeding with two sewer repair projects for the Forest Avenue pump station and the sewer line under Joseph Street. The repair costs were already included in the 2014 budget.