Manhole Rehabilitation Project – 2022

This project consists of mobilization, construction traffic control and infiltration correction of 90 sanitary sewer manholes. A map of rehabilitation manholes with existing sanitary sewer manhole photos is available at this link.

This is the 2nd year of a 5-year project.  The overall focus of this project is to reduce inflow/infiltration (I/I) of groundwater into manholes located where the river contributes to groundwater getting inside the manholes.  The wastewater treatment & resource recovery facility (WWTRRF) provides biological treatment of sanitary sewer collection flows.  WWTRRF does not provide any treatment of groundwater entering the collection system, and groundwater contribution through the WWTRRF has to be pumped and impacts the overall biological treatment.

This project provides for measures to seal the contact points between the manhole base and the first, and in some cases the second barrel rings.  Imagine sections of 4-foot diameter pipe, turned on its side and stacked on top each other.  The contact points where the pipes are stacked will be sealed from this project work to keep groundwater from entering.  The project will focus on 90 manholes located downstream of the 92 manholes completed in 2021. 

Funding

Why It's Needed
This project will assist with reducing I/I that was identified as an issue in the 2015 Adopted Sewer Collection System Master Plan and 2019 WWTRRF Facility Plan.  It will provide benefit to lower pumping costs at the WWTRRF to move the groundwater within the facility and assist with the biological treatment process.  Reducing groundwater inflow/infiltration (I/I) also provides for more future capacity for biological treatment at the WWTRRF under the National Pollution Discharge Elimination System (NPDES) permit.WWTRRF dry weather flow is about 2.2 million gallons per day.  Groundwater contribution begins when Umatilla River flow reaches about 1,500 cubic feet per second (CFS), which occurs during the late fall through early spring.  The river also typically has two flushing flow events, ranging from 4,000 CFS to 10,000 CFS.  The proposed project is focused on reducing groundwater contributions above 1,500 CFS. 

Address
SE Alexander Pl & SE 18th St, Pendleton, OR 97801, USA

Additional Links:

Manhole Rehabilitation Project Documents