Environmental Services is working on pilot projects aimed at reducing the possibility of sewage overflows in parts of southwest Portland, where pipes that carry sewage from homes and businesses can also fill with rain and groundwater during wet weather. This inflow of stormwater runoff and infiltration of groundwater can cause sewers to back up through manholes or household drains and threaten human health and the environment. Inflow and infiltration, also known as I&I, sends relatively clean water to the treatment plant and increases the cost of treatment.
Infiltration and inflow of stormwater and groundwater reduce the pipe’s capacity to carry sanitary sewage. This can be a problem throughout Portland, but especially in southwest Portland due to its unique geology, geography, and the lack of storm sewers. Smoke testing in 2012 located a number of cracked sewer pipes that allow groundwater infiltration and direct connections that allow stormwater inflow directly to the sanitary sewer.
The most successful efforts to control I&I in other parts of the country include partnerships between local government and private property owners. Making programs voluntary for property owners and providing financial incentives increase both participation and project success. For pilot projects in southwest Portland, Environmental Services offers to repair or replace eligible privately-owned lateral pipes that connect properties to the public sewer at no cost to the property owners.
Pilot projects in Upper Hillsdale, Middle Hillsdale, and the area around SW Pendleton and 45th will help determine how effective different approaches are in reducing inflow and infiltration.
Work started in 2013 on pilot projects in Upper Hillsdale, Middle Hillsdale and the area around SW Pendleton and 45th to replace or repair public sewers in the street and private laterals that connect properties to the public sewer. Future pilot projects may disconnect downspouts, foundation drains and other stormwater connections from the sewer system. Participation in these pilot projects is entirely voluntary.
Why This Approach?
Environmental Services doesn’t usually repair or replace laterals on private property. There are three main reasons that the bureau is pursuing this option:
- Environmental Services has an agreement with the Oregon Department of Environmental Quality (DEQ) to eliminate persistent sewage overflows at SW Dewitt and 25th that are caused by inflow and infiltration.Programs in other jurisdictions show that repairing or replacing private sewer laterals can reduce inflow and infiltration quickly and cost-effectively.
- Replacing sewer laterals on private property will benefit sewer ratepayers citywide by reducing stormwater and groundwater flow to the treatment plant and avoiding additional treatment costs.
- If the pilot projects are successful, the city may avoid building an expensive separate stormwater system in southwest Portland.
If you agree to participate in this project, the city will require you to sign a participation agreement and a ten year easement over your sewer lateral. The easement will give the city access to monitor pipe warranty and installation.
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