2021 Manhole Rehabilitation Project

The overall focus of this project is to reduce inflow/infiltration (I/I) of groundwater into manholes located where there is river influence contributing 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.  This groundwater is mixed with sanitary sewer flow.  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 92 manholes located at the east end or our collection system on the Mission gravity trunk line.

This project work, expected to be completed in fall 2021, will be evaluated for consideration to continue to do about 100 to 150 manholes per year over a 4- to 5-year period to reduce groundwater influence and provide for a consistent flow and treatment at the WWTRRF.

Funding

This project is funded through the Sewer Fund and is budgeted under capital outlay.