Improving Molalla's Wastewater System

Consent Decree

City of Molalla WWTP 2019

In 2015, in the wake of a law suit against the City of Molalla under the Clean Water Act, the City entered into a consent decree that, in pertinent part, requires the City to construct a new Wastewater Treatment Plant, complete several I & I projects, and remove a certain quantity of biosolids from the lagoons.

Please read below for a summary of the work being done to address the City's Wastewater Treatment System, and see the documents widget on this page for additional information!

What improvements is the City making?

1. New Wastewater Treatment Plant & Modified Discharge Permit - Project 19-10 - Expected Completion December 2025

• New Plant - The City is in the final design stages of a new "Sequence Batch Reactor" type of wastewater treatment plant that will displace the existing Lagoon type plant. The new plant is currently slated to be open and operational no later than December of 2025.
  • The new plant will be engineered to bring the City into compliance with its National Pollution Discharge Eliminations System (NPDES) permit, Recycle Water Use Plan (RWUP) and all other applicable regulations. Additionally, the new plant will be sized to service a population of more than 15,000 people (Molalla's population is 10,229 people as of December 2022).
• Modified NPDES Permit - In 2004, Molalla invested in a new pipeline and pump station so the wastewater treatment plant could discharge to the Molalla River instead of Bear Creek. The Molalla River is larger with a much greater capacity to accept treated wastewater – the City’s discharge permit doesn’t currently reflect that.

2. Biosolid Removal - Project 18-04 - Expected Completion December 2025

This project consists of removal, dewatering, and transport of biosolids accumulated in the existing lagoons. Part of the design plan for the new wastewater treatment plant is to line the existing lagoons and use them for clean effluent storage until discharge to the Molalla River (wet months) or Land Application (dry months). The removal process is very delicate, an overly aggressive approach can upset the biological process the existing lagoons use to clean wastewater. With that in mind, this project is expected to continue until the new plant is online and operational. At that point a more aggressive approach can be used to remove remaining biosolids because the biological process happens in the SBR instead of in the lagoons.

3. Sewer Inflow and Infiltration (I/I) Work

Several major projects will be completed between 2019 and 2025 which are both system needs and are aimed at reducing I/I. Reductions in I/I reduce flows going to the treatment plant and ultimately save the city money:

• Sanitary Sewer Manholes - This project inspected all manholes for leaks and other damage, and repaired all 70 that were found to be in need of attention.
  • Project Complete.
• Fenton Sewer Main - This project was two phases, both of which replaced and/or rehabilitated large portions of the sanitary sewer main and associated laterals along Fenton Ave.
  • Project Complete.
• Patrol Sewer Main - This project replaced and/or rehabilitated the sanitary sewer main and associated laterals along Patrol St.
  • Project Complete.
• Eckerd, Lola, 2nd Sewer Mains -This project will replace and/or rehabilitate the sanitary sewer main, manholes, and associated laterals along Eckerd Ave, 2nd St, and Lola Ave.
  • Project In Work, Expected Completion Spring/Summer 2023.
• S Molalla Pump Station Sewer Line - This project Rehabilitated the sanitary sewer main serving the S Molalla Ave lift station.
  • Project Complete.
• Toliver & S Molalla Sewer Main - This project will rehabilitate the sanitary sewer lines along portions of Toliver Rd., and S Molalla Ave with cured in place piping at a fraction of the cost of replacement.
  • Project In Work, Toliver - Complete, S Molalla Ave Expected Completion Winter/Spring 2022-2023.
• Additional Projects - Will be added as City Staff begins setting up the project file for execution.