linn basin sanitary sewer i & i rehab project 2 (ci 23-002) 

This project is one of many projects identified in the Inflow and Infiltration (I & I) Program.  Inflow and infiltration are when stormwater and groundwater enter the sanitary sewer system.

Through this project, sanitary sewer mains (large publicly owned sewer pipes in the street) will be rehabilitated and repaired as priority repairs due to the current conditions of these systems. Sanitary sewer systems located on the west side of the Promontory (overlooking Waterboard Park - Brighton and Terrace Avenues) and various streets in the vicinity of East Street (below the Promontory) and Pearl Street just west of Molalla Avenue will be addressed. 

To carry out these repairs, various construction methods will be used according to the rehabilitation needs and unique characteristics of each site. However, the exact method used for each property will be determined during construction and may involve any of the  construction methods either alone or in combination.   You can find detailed explanations of these methods, along with helpful YouTube videos, here

Project Details

• Repairing approximately 1,100 linear feet of sewer mainline. 
• Replacing approximately 1,000 linear feet of sewer lines.  A new sewer line will be installed in East Street to consolidate two older lines. A new sewer main will be added to Terrace Avenue (above the cliff) to replace an existing sprawling network of laterals to various properties.
• Replacing two sewer mains located at the Promontory. 
• Inspecting about 42 sewer laterals and repairing, or replacing those in poor condition. These types of lines connect private homes or businesses to the public sewer system and are often referred to as plumbing pipes.
• Installing 14 new manholes. 

Promontory Work Details

Through the Inflow and Infiltration ( I & I) Program the project team consults with geotechnical engineers (specializing in slope stability and groundwater) with every project located within a Geologic Hazards Zone. The City is taking extra precautions to ensure homes (located above and below the cliffs) will not be endangered due to the digging.  

• Limited Open Trench Length:  Trenches must be back filled as soon as possible, with no more than 20 feet of trench left open in any work area at at time.  
• Limited Work Period: Excavation near steep slopes or historic landslides in only permitted between May 1 and October 31, 2026.
• Preserve & Protect Existing Vegetation: Vegetation will not be removed unless necessary. Any plants removed during excavation on steep slopes, whether grasses, shrubs or trees, must be replaced after work is completed to help stabilize the soil.  
• Avoid Cliff Edges: No equipment or materials will be stored within 15 feet of the cliff edge. Digging near or on the Promontory will be minimized to protect its stability.
• Erosion Control and Slope Protection: Special erosion measures will remain in place and be inspected regularly for one year after construction to reduce the risk of landslides along the Promontory.

A key strategy for removing Inflow & Infiltration (I&I) is addressed in the City's Lateral Program. Through this program, eligible property owners may receive free sewer lateral line inspections and free lateral line repairs or replacements.  The inspections will be offered during construction and restorations will be provided, free of charge, for applicable property owners if inspections reveal problems with the lateral lines.  The city will pay for repairs of the portion of lateral to within 5-feet of the home), along with any landscaping, patio, sidewalk, or other hardscaping that is disturbed by the repairs – eligible program participants will not be billed for this work! 

Eligible property owners have been identified and mailed Right of Entry and Access Forms.  Signing and returning this form is all that’s needed to sign up for the program!

If you have not received a form and believe you should have, need a replacement form, or have any questions about Lateral Program in general, please contact the project manager, Kenneth Cannady-Shultz .

Right-of-Entry and Access Forms will be accepted up until construction begins. There will also be opportunities to sign up during construction. If you want to participate in this Program, you still have time to submit the form. The sooner you submit, the more likely the City will be able to honor any special requests or accommodations included in the form.

This project is part of Oregon City’s Inflow and Infiltration Program (I&I Program) - a program created to address stormwater and ground water entering the city's sanitary sewer system.  To understand the I & I program and this project, several key terms are defined: 

Groundwater is stormwater (rain, snow) that soaks into the ground. It doesn’t flow like a river above ground—instead, it fills up the tiny spaces between rocks, sand and dirt under the surface. It’s like water hiding in a sponge, but underground! 

Infiltration happens when groundwater leaks into the public sewer system. This usually happens through cracked pipes, broken manholes or improperly connected roof drains. Infiltration increases during winter and spring or after storms, and can overload the sewer system, leading to backups and system failures. Since this extra water must be treated at the wastewater treatment plant, it adds to the costs for the city and utility customers. Oregon City utilizes the Clackamas County Water Resource Recovery Facility, which is designed to handle higher flows. 

Inflow is when stormwater enters the sanitary sewer system through direct connections such as downspouts, groundwater sump pumps, catch basins, or improperly connected stormwater pipes. Inflow can significantly increase flows during rainstorms, which can overload the system, leading to sewage backups. Like infiltration, inflow increases treatment and maintenance costs and puts extra strain on wastewater facilities. Most importantly, it poses risks to the environment and public health. Inflow is the main cause of peak sewer flows during storms. 

Oregon City currently experiences high levels of Inflow due to old stormwater collectors that were connected to the sanitary sewer system before codes changed which no longer allow this. During the winter and spring, most flow in the sanitary systems comes from Inflow and Infiltration (I & I). However, newer sections of the City’s system have very low levels of I&I year-round.

Lateral Lines (laterals) Sewer laterals are small pipes (typically 4” in diameter) that connect a home or business to the public sewer system. These pipes carry wastewater (sewage or used water from sinks and showers), away from the buildings into the public mainline sewer, which then transports it to the city's wastewater treatment facility for processing. 

Typically, each home or business has a single sewer lateral.  In Oregon City, maintenance of sewer laterals are divided between the property owner and the City. The City is responsible for the section of the lateral line that runs from the public mainline to the back of the sidewalk (in most cases). The property owner is responsible for the section that runs from the edge of  the (if the sewer main is under the road), or from just past the connection point between the lateral line and the sewer main More information can be found in the City's Sanitary Sewer Lateral Policy. For properties that are eligible for the  City's Lateral Program, the City will pay for repairs or maintenance.

Manholes are holes in the ground covered by heavy, round lids. Manholes allow workers to access underground pipes to inspect or repair; to change the direction of sewer pipes (like turning a corner); shift pipes from one side of the road to the other, or to combine flows (from two or more pipes into one main pipe (done for sanitary sewer systems). 

Public Right of Ways (ROW) are portions of land dedicated for uses like sidewalks, roads, and access to public utilities (such as water, sewer, etc.). Government agencies (city, county, state) are responsible for maintaining and managing these spaces. Think of it like the Oregon City Public Library. The city (government) owns it, but everyone can use it, and the city workers are like janitors who keeps it clean, safe and working properly. The ROW is a shared community space, and is protected by important rules and regulations. 

Rehabilitation (Rehab) restores the current system and keeps existing sewer pipes or manholes together, at their current locations, using different construction methods. Rehab improves the conditions to help make them last longer. 

Repairs, unlike rehabilitation,  are long-term solutions. For the I & I program, repairs fix the system by removing most (or all) existing sewer pipes or manholes, and replacing the removed portions with brand new materials using pipe bursting and trenching construction methods. 

Sanitary sewer lines are underground pipes that carry sewage away from buildings (homes, businesses, etc.), to ultimately be treated at a treatment plant. 

Sewage and "wastewater" are often used to mean the same thing, but there's a small difference.  Sewage is a type of wastewater that specifically comes from toilets, bathrooms, and sometimes kitchens, and contains human waste.

Sewer Systems are pipes, manholes, and pumps that are maintained by the city to transport different types of water (stormwater and sewage)  

Storm Sewer/Stormwater pipes are underground pipes that carry rainwater away from neighborhoods, streets and buildings to help prevent flooding. The rainwater is collected from surfaces like roads, roofs, and driveways (which don't absorb water) via storm drains or catch basins. Stormwater can also include clean groundwater that slowly enters stormwater pipes small cracks, joints or faulty seals in those pipes (“infiltration”).  

Main lines are large pipes designed for higher volumes. Mainlines connect to the (smaller) lateral lines to transport wastewater to pump stations or treatment plants to be remove contaminants. 

Stormwater is rain, snow, sleet or hail that is not treated. It flows over surfaces like cars, roads, roofs, etc. 

Stormwater collectors collect rainwater or channel rainwater. Examples include catch basins and roof gutters. 

Treatment is the process to remove pollutants from wastewater (and sewage) to make the water safe for reuse or release into the city's waterways.

Wastewater is dirty/used water from toilets, sinks, washers, showers and other household or commercial sources. The combination of items is the main reason why sewage "stinks." This water travels through the sanitary sewer system - which includes service lines, lateral lines and main lines - to a treatment facility.  "Sewage" and "Wastewater" are often used to mean the same thing, but there's a small difference.  

Wastewater Treatment Facilities are also referred to as "wastewater treatment plant" or "sewage treatment plant" are the locations where wastewater is treated (cleaned) to remove harmful substances (like human waste, chemicals, and food scraps). Once cleaned, it is safe enough to be sent back to the natural water cycle (usually into rivers, lakes or oceans) or be reused for things like irrigation. It doesn't mean it's drinkable, but it's clean enough to not harm the environment or public health. This system is designed for sewage only.