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Sewer Basin Areas and Progress Reports
Updated November 2025
The Inflow & Infiltration (I & I) Reduction Program includes work in seven sewer basins. The program addresses each basin separately, and each basin is prioritized differently by the Program.
New Map Coming Soon!
The program area was established per an Intergovernmental Agreement (IGA), between the City and Clackamas Water Environmental Services (WES). This agreement identified basins with the most severe I&I problems. WES offered to reimburse the City for 33% of the City's costs for fixing I & I in those specific basins; therefore, the City's I&I program is addressing those basins identified in the IGA.
Currently, the program is focused on the following basins:
- Rivercrest (10) – Rivercrest Phase 4 has been fully rehabilitated.
- Linn (8) – Has one completed project. The second project will start construction in early 2026.
- McLoughlin (5) – Has one active project in construction. A second project will start later in 2026.
- Newell (5B) – Will have a project starting in 2027.
The Falls (5A), Warner Parrott (12), and South End (12A) Basin areas are in the investigation stages and work is planned for later in the program.
To read current work details and future planning, of each basin, choose the basin you want to read more about below.
Phase: Investigate, Identify Solutions, Design, Construct and Monitor
Neighborhood Associations: McLoughlin, Elyville, and Two Rivers
In December 2021, the City entered a contract with Wallis Engineering to manage a comprehensive Inflow & Infiltration (I & I) Removal Program for all basins identified in the intergovernmental agreement (IGA) between the City and Clackamas County Water Environmental Services (WES).
Most of the McLoughlin Basin has been smoke tested and the mainlines surveyed, via closed-circuit television (CCTV). Testing revealed significant issues with gutter downspouts connected improperly to the sanitary sewer. The majority of mainlines also revealed leaks, with concrete and clay mains in the worst condition. In addition, damaged or leaking PVC sewer mains (which tend to be newer) were discovered, with a higher number than expected. More smoke testing and CCTV are still needed.
Three seasons of flow monitoring are complete, with a fourth season of monitoring beginning. Past monitoring provided a pre-repair base flow for the basin which is used to determine how effective program rehabilitation efforts are.
The upcoming 2026 Manhole Rehabilitation Project will address manholes with leaks (in the McLoughlin, Linn, South End and Rivercrest Basins). This work is to continue on an annual basis. The Manhole program fixes the manholes in I & I project areas, manholes identified by Public Works during routine maintenance checks, and I & I program areas that will not likely see mainline sewer repair.
The northernmost portion of the Molalla Avenue Project extended into the McLoughlin Basin. This project was completed in August 2025.
The McLoughlin Project 1 is the first, in a series of projects, that will focus on this basin. The pipes to be repaired, with this project, are still being finalized yet the design process will be accelerated. This is necessary to permit key work work (along Harrison Street) to be completed as part of the 2025 PMUF Roadway Reconstruction Project . Future I & I projects will continue coordination to complete its I & I work, prior to paving. A projected schedule of the roads to be paved in 2028 and 2029 are identified in the 5-year PMUF Plan and anticipated to receive I & I work over the next few years, in preparation for future paving.
McLoughlin Project 2, and Linn Project 3 are future projects anticipated to be designed within the next 5 years. Other future projects, in this basin, have yet to be defined but will address areas south of Division Street and southwest of 10th Street.
The I & I Program will continue scoping the project in the McLoughlin Basin until I & I peak flows have been significantly reduced – likely not until most of the basin has been rehabilitated.
Phase: Investigate, Identify Solutions, Monitor
Neighborhood Associations: Canemah, McLoughlin, and Two Rivers
In December 2021, the City entered a contract with Wallis Engineering to manage a comprehensive Inflow & Infiltration (I & I) Removal Program for all basins identified in the intergovernmental agreement (IGA) between the City and Clackamas County Water Environmental Services (WES).
Most of the Falls Basin has been smoke tested and the mainlines surveyed, via closed-circuit television (CCTV). There are isolated areas, needing additional surveys, however the majority of information gathered thus far is sufficient. The testing revealed this basin to have significant issues with improper gutter downspout and roadside catch basin (road drain) connections to the sanitary sewer. This basin's sewer collection systems are in poor condition, which was not unexpected.
Three seasons of flow monitoring have been completed, establishing a pre-repair base flow for this basin. These pre-repair flows will be used to evaluate how well future projects remove peak I&I flows.
The first project in the basin will focus on repairing sewer mains and lateral lines in the northerly half of the Falls Basin, mostly between Water Board Park and McLoughlin Boulevard. Linn Project 3 will likely be the first project in this area and will begin construction in Summer 2026. Additional projects are expected for this area, they will likely not occur until 2029 or later.
Phase: Identify Solutions, Design, Construct and Monitor
Neighborhood Associations: McLoughlin, Elyville, Rivercrest, and
In December 2021, the City entered a contract with Wallis Engineering to manage a comprehensive Inflow & Infiltration (I & I) Removal Program for all basins identified in the intergovernmental agreement (IGA) between the City and Clackamas County Water Environmental Services (WES).
Smoke testing and mainline surveys, done via closed circuit television (CCTV) is complete in this basin. This work revealed a few improper gutter downspout and roadside catch basin (road drain) connections to the sanitary sewer (mostly north of Pearl Street). The sewer system in lower Newell Canyon (downhill of Barclay Hills Park) is in quite good condition; however, the remainder of the basin’s sewer mains are in poor condition, with the worst pipes located north of Holmes Lane.
Three seasons of flow monitoring are complete, with a fourth season of monitoring beginning. Past monitoring provided a pre-repair base flow for the basin which is used to determine how effective program rehabilitation efforts are.
The Molalla Avenue Project covered both the McLoughlin Basin and the Newell Basin. This project was completed in August 2025.
Linn Project 2 includes some work in Newell Basin, with construction expected to start in Spring 2026. Because this project is heavily impacted by the Geologic Hazard Overlay Zone, a Type II Land Use Application process occurred during the design phase to ensure construction methods were appropriate for the area.
Newell Project 1 has started its design phase. This project will also need a Type II Land Use Application because of the Natural Resource Overlay District (NROD) and Geologic Hazard Overlay Zones. The NROD application protects the habitats and the associated functions of the streams, riparian corridors, wetlands, and regulated wildlife habitat found in Oregon City. The tentative timeline for construction of this project is 2027. There is a final, future project for this basin that will complete rehabilitation of this basin that will be determined at a later date.
Phase: Identify Solutions, Design, Construct, and Monitor
Neighborhood Associations: Rivercrest, McLoughlin, and
The City contracted with Wallis Engineering to evaluate the Linn, McLoughlin, Newell, and Falls Basins in December 2021. Wallis is managing the program with consultation from the City.
Smoke testing and mainline surveys, done via closed circuit television (CCTV) is complete in this basin. This basin has significant issues with improper gutter downspout connections to the sanitary sewer, in addition to sewer mains with leaks.
Three seasons of flow monitoring are complete, with a fourth season of monitoring beginning. Past monitoring provided a pre-repair base flow for the basin which is used to determine how effective program rehabilitation efforts are.
Linn Project 1 finished construction in Spring 2024. This was the first project delivered by the I & I program and the first project to implement the Lateral Program (approved by the City Commission in early 2023). This project was successful in rehabilitating & constructing damaged lateral lines. In addition, improvements to the Lateral Program were made after the construction on Linn Project 1.
Linn Project 2 is scheduled to begin construction in Spring 2026. Because this project is heavily impacted by the Geologic Hazard Overlay Zone, a Type II Land Use Application process occurred during the design phase to ensure construction methods were appropriate for the area.
Linn Project 3 is in design stage. This project is focused on the northern portion of the basin, with some work in the McLoughlin and Falls Basins. This project will be constructed in Summer 2026 to finish ahead of planned Pavement Maintenance Utility Fees (PMUF) construction.
Linn Project 4 and Linn Project 5 are in preliminary scoping. These two projects are likely to be in design phase in 2027 and 2028. At the completion of these two projects, the Linn Basin rehabilitation work will be completed.
Once Linn Project 4 is constructed, work in this area will be complete, pending evaluation of program success.
Phase: Construction, Design, Monitoring
Neighborhood Associations: Rivercrest, South End
In November 2020, the City decided to address the I & I issue with the City’s sewer system by implementing a pilot I & I program in the Rivercrest Basin, chosen due to its size. After utilizing closed circuit television (CCTV) to survey the main line, the City contracted with Century West Engineering (consultant) in December 2020, to evaluate the Rivercrest Basin (Basin 10) for Inflow & Infiltration (I&I) removal.
Based on data collected, Century West Engineering and the City developed a three-phase mainline sewer rehabilitation project based on which rehabilitation method was utilized. Using open trenching and pipe bursting, and Cured in Place Pipe (CIPP) , the mainline sewer and sewer lateral replacements were installed to the property lines. All three project phases were completed by late 2023.
During this period, the City contracted with Wallis Engineering to manage a comprehensive I & I Reduction Program with the City. The City and implemented the Lateral Program (approved by the City Commission early in 2023). The program determined that an additional project was warranted for the Rivercrest Basin to complete some repairs on previous work and repair private property sewer laterals.
Rivercrest Phase 4 construction is complete. This phase completes the I & I work for the entire Rivercrest Basin.
Three seasons of flow monitoring have been completed, the results of this and future years of flow monitoring will be key to evaluating program success in the Rivercrest Basin.
Phase: Investigate, Monitor
Neighborhood Associations: Rivercrest, South End, Tower Vista, Hazel Grove/Westling Farm
The City contracted with Wallis Engineering to evaluate the Linn, McLoughlin, Newell, and Falls Basins (previously Basins 5 and 8) in December 2021. Wallis is managing the program with consultation from the City. Wallis will evaluate the Warner Parrott Basin for infiltration - if the program has funding remaining after work on the other basins.
Some smoke testing and Closed Circuit Television (CCTV) surveying (a method using cameras to check underground pipes for leaks) of main lines has been done and more is needed. Wallis and the City may also decide to do supplementary dye testing (a method in which non-toxic dye is inserted into cleanouts to detect connections), if needed.
Flow monitoring equipment has been set up for this new basin to define pre-improvement base flows. No projects are planned, or currently scheduled.
Phase: Investigate, Monitor
Neighborhood Associations: South End, Tower Vista, Hazel Grove/Westling Farm
In December 2021, the City entered a contract with Wallis Engineering to manage a comprehensive Inflow & Infiltration (I & I) Removal Program for all basins identified in the intergovernmental agreement (IGA) between the City and Clackamas County Water Environmental Services (WES).
Some smoke testing and Closed Circuit Television (CCTV) surveying (a method using cameras to check underground pipes for leaks) of main lines has been done and more is needed. Wallis and the City may also decide to do supplementary dye testing (a method in which non-toxic dye is inserted into cleanouts to detect connections), if needed.
The entirety of this basin flows to the Parrish Pump Station - a pump station with existing flow monitoring equipment installed. These pumps operate at different speeds, depending on the amount of flow entering the pump station. Because of this, pump flows will be observed to provide data for the program, of similar data to an in-main flow monitor and eliminate the need for a separate monitoring location. No projects are planned or currently scheduled.
The City is aware of high Inflow & Infiltration (I&I) levels in the Two Rivers, Forsythe, Holcomb and Settlers' Point Basins. These basins are not being addressed by the current I&I Program nor the Clackamas Water Environment Services (WES) Intergovernmental Agreement (IGA).
- Two Rivers (0) – This basin includes the northwestern tip of Oregon City's Downtown, the McLoughlin Neighborhood, and areas around Clackamette Cove.
- Forsythe (1) and Holcomb (3) – These two basins encompass the western half of the Park Place neighborhood.
- Settler’s Point (16) – This basin includes neighborhoods near Meyers Road, west of Molalla Avenue.
Of these basins, Settler’s Point (16) sewer collection system has the most leaks. This Pump Station serves much of this area and must work hard to keep up with routine winter sewer flows. All of these basins have old sewer pipes with leaks.
The City may add one, or more, of these basins to the I&I program in the future. Currently flows are being monitored in Settler’s Point to better understand where high flows are coming from. No decision will be made until more data has been acquired. There are not plans to monitor, or add, the other basins into this program.
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