Blue Heron Trunk Sewer Replacement

This project will rehabilitate pipelines in Blue Heron Canal and Cardinal Drive.

Project Background / Summary: 


Blue Heron 2 Trunk Sewer Replacement will extend the operational life of the Blue Heron sewer trunk line and reduce sewer system infiltration and inflow reaching the Lake Oswego Interceptor Sewer. 

Because the majority of the City of Lake Oswego’s wastewater enters the City of Portland’s Tryon Creek Wastewater Treatment Plant, Lake Oswego is required to meet Compliance Conditions and Schedules in the City of Portland Bureau of Environmental Services’ National Pollutant Discharge Elimination System Waste Discharge Permit (NPDES). The goals of this program are to decrease the wastewater flow volume from the Lake Oswego system and to limit wastewater overflows during any rain event.


The City of Lake Oswego completed an update to its Wastewater Collection System Master Plan (Plan) in March 2013 that identified historically high wet-weather peak wastewater flows attributed to excessive inflow and infiltration (I/I) in several basins. The Plan identified approximately $20 million of infrastructure work focused on reducing I/I.  The City also recently partnered with BES on the Tryon Creek wastewater treatment plan facility update.  Both parties are interested in finding ways to reduce flows to the plant and are evaluating I/I reduction goals.

The Plan recommends the City implement an aggressive Infiltration and Inflow (I/I) reduction program to reduce I/I within the existing wastewater collection and conveyance system.  Although several of the City’s many wastewater collection and conveyance system basins need I/I reduction, a portion of the Blue Heron Basin has been chosen for an initial I/I reduction effort. Though not described in the Plan as having the highest I/I rate, the Blue Heron Basin is described as having a significantly high I/I rate, and it is tributary to the recently completed Lake Oswego Interceptor Sewer (LOIS). Aggressive I/I reduction within basins tributary to the LOIS is mandatory, if the LOIS is to continue to alleviate system overflows.

Value to the Sewer System

Replacement or rehabilitation of the Blue Heron Trunk will extend the service life of the trunk line and provide additional maintenance access via property line cleanouts. Additionally, reduction of I/I entering the sanitary sewer system reduces the treatment volume reaching the Tryon Creek Wastewater Treatment plant, possibly reducing the City’s water treatment costs.

Additional outcomes the City wants to achieve if determined to be feasible and/or cost-effective under the Blue Heron Trunk (T-BH- 2) project include the following:

1.  Improve conditions related to maintenance of the sewer segments in the canal. This could include:

  • ​Reducing the length of the 882-foot long sewer segment 100109.
  • ​Placing a debris trap on the sewer that conveys flow from the easterly portion of the Blue Heron service area near manhole SMH06285 in Blue Heron Dr.

2.  Reduce inflow and infiltration of storm water and groundwater into the sewer system within the project area.

3.  ​Reduce nuisances associated with sewer segments and laterals located in the canal. The primary nuisance being interference with work by the Lake Corp. to clean sediment and debris deposits from the canal. Reducing this nuisance could include re-configuring the trunk sewer to significantly reduce sewer lateral lengths in the canal; especially those laterals that cross the canal.

Project Updates: 

July 21, 2021

A team from Carollo Engineers, AKS Engineers, and ProPipe will be locating sanitary sewer laterals along Cardinal Drive, Wren Court, Cedar Road, Blue Heron Road, and Blue Heron Drive.

While many of the laterals connect to sewer mains in the public right-of-way, homes with sewer laterals draining toward the sewer main in Blue Heron Bay will have lateral located at the sea wall. For those properties, Carollo Engineers will be reaching out to property owners directly to schedule the lateral locate. Where there is exterior access to the sewer cleanout, representatives from ProPipe will need to access the back yard. Where outside access does not exist, ProPipe will need to access a basement or floor drain inside the home.

This work is expected to take place between August 9, 2021 and September 3, 2021.

March 30, 2021

The Blue Heron Trunkline Rehabilitation Project is currently in preliminary design. As design progresses, there will be public meetings to get resident input on the proposed sewer line replacement design alternatives. These meetings have yet to be scheduled.

Construction is expected to coincide with the Fall/Winter lake drawdown in 2023.

Project Details
WO 298
Project Contact: 

Stefan Broadus, Assistant City Engineer