Conference Agenda

Clackamas Water Environment Services (WES) owns and operates three pump stations and force mains, constructed in the 1980s, that collect sewage from West Linn, Oregon, and pump it across the Willamette River to an interceptor sewer in Oregon City. One of these pump stations, the 5.0 MGD Bolton Pump Station, includes a 16-inch-diameter ductile iron force main.

The force main experienced breaks in both May 2017 and February 2021 in the heavily-wooded area of Maddox Woods Park. After the second break in the force main, WES faced a decision to either remove many mature fir and cedar trees to replace the section of the force main that had experienced the breaks or realign the pipeline to follow a walking path that increased the static head on the pumps. Knowing the pump station needed additional maintenance and reliability improvements, WES decided to protect the trees and kick off a more comprehensive project.

This presentation will tell the story of the force main repairs and the follow-up evaluation and improvements to increase the pump head limits, increase firm pumping capacity, and replace additional sections of the force main that had significant corrosion. It will outline the approach to provide interim backup pumping, accelerate the schedule to procure long lead equipment, and report on the construction phase improvements. The audience will also learn about the unique system hydraulics and the use of an intertie connection with another pump station to assist with bypassing during construction.

The City of Sandy is a small community (population 11,000) located in the foothills of Northwest Oregon’s Mount Hood. The City operates 38 miles of sanitary mainline pipe, six pump stations, and a single wastewater treatment plant. Challenges facing this wastewater system include influent flows that frequently exceed plant capacity during wet weather, deferred maintenance on the plant, and a limited six-month discharge permit that results in dilution violations during the shoulder months (April and October).

In 2019, the City completed a Wastewater Facilities Master Plan for the City, which recommended balancing investments between improving treatment facilities and reducing flows from the collection system. Soon after the plan was published, the City commenced with an effort to reduce inflow and infiltration (I/I) from their collection system in order to minimize the need for increasing treatment plant capacity. At the same time, the City moved forward with much-needed improvements to the existing plant.

Because of regulatory and development pressures, the City moved forward with an I/I reduction program that leveraged alternative delivery to fast-track the construction, including work on private laterals. The City also implemented a flow monitoring program aimed at demonstrating the success of the rehabilitation to reduce flows. The flow monitoring allows for recalibration of the model and definitive quantifiable evidence of reduction of I/I during peak wet-weather events storms.

Less than four years later, the City has proactively rehabilitated over half of its collection system, including sanitary gravity mainlines and service laterals up to the structures they serve.

This presentation will discuss the planning efforts leading up to the development of an I/I program, the use of alternative delivery to assist with fast-tracked rehabilitation, the monitoring and modeling efforts needed to demonstrate compliance, the actual reductions achieved, and the funding mechanisms needed to finance the work.