Cotati City Council
Agenda Staff Report
Item type: REGULAR AGENDA (ACTION)
To: City Council
Subject: Scope Change for Sewer Inflow and Infiltration Reduction Project Date: February 22, 2022
Written by: Craig Scott, Director of Public Works/City Engineer Recommendation
It is recommended the City Council of the City of Cotati approve by motion revising the scope of services for the Sewer Design Contract with Brelje and Race Consulting Engineers to focus on the replacement of existing undersized sewer pipelines along West Sierra Avenue from Olof Street to Water Road
Background
City staff is requesting City Council authorization to move forward with revised scope of services for a sewer design contract, originally approved on November 9th, 2021. The contract is to design, prepare construction drawings and prepare for bidding a project to repair sewer defects in locations identified by videotaping sewers in the vicinity of the City’s hub. This effort would repair sewers, preventing their failure in the future, upsize as needed to accommodate General Plan growth, and reduce surface water flowing into the sewer and groundwater infiltration into the sewers. During design, the repair locations have been matched up with the City’s planned street paving projects and the repair locations have been reprioritized to be located under streets slated for paving early next year to avoiding digging up newly paved streets.
Analysis/Discussion
Nearly seventy percent of the City’s sewer utility budget is to pay the City of Santa Rosa for treatment of the wastewater. All sewer systems have some amount of rainwater and groundwater that seeps into the pipelines, but this flow takes up valuable sewer pipeline capacity and unnecessarily increases the City’s wastewater treatment bill. This inflow comes in through manholes and through defects in the pipe.
Last year, the City completed video inspections of areas suspected of having high inflow and infiltration. As part of this inspection process, sewer defects were located and described. This information was provided to Brelje and Race Consulting Engineers to design a project to repair the defects. After evaluating alternative repair methods and costs and reviewing the City’s street paving program, City staff has identified West Sierra Avenue sewer replacement as a high priority project. The sewer pipeline in West Sierra Avenue is undersized for existing and future flows, has sewer defects, and is entirely within the area to be repaved as part of the City’s Downtown Connectivity and Safety Project (aka Quick Strike). Paving is scheduled for early 2023, and, once paved, is off limits for planned excavations for at least 5 years, but preferably closer to ten years.
Brelje and Race Consulting Engineers has submitted the attached revised scope of services to use the same authorized budget amount to design and bid the project to replace or repair the sewer in West Sierra Avenue extending from Olof Street to Water Road. The intent is to replace the sewer from Olof to Cypress Avenue and potentially do spot repairs of any defects between Cypress Avenue and Water Road, which will reduce the construction cost.
Financial Considerations
The revised scope is to be done within the budget amount authorized by City Council on November 9, 2021. Staff is currently working on an update to the sewer and water rate study, which will include recommendations for construction funding.
Environmental Issues
The Sewer Repairs are Categorically Exempt under Section 15301 of the California Environmental Quality Act (CEQA) Guidelines as it consists of the repair and maintenance of an existing facility.
Attachments:
Design Scope of Work (PDF)