AGENDA TITLE:
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Accept Improvements Under Contract for Aeration Diffusers System Replacement at White Slough Water Pollution Control Facility Project, and Adopt a Resolution Approving Change Order No. 3 and Ratifying City Manager Approval of Increased Expenses (PW)
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MEETING DATE:
November 5, 2025
PREPARED BY:
Public Works Director
recommendation
RECOMMENDED ACTION:
Accept improvements under contract for Aeration Diffusers System Replacement at White Slough Water Pollution Control Facility Project, and adopt a resolution approving Change Order No. 3 and ratifying City Manager approval of increased expenses.
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BACKGROUND INFORMATION:
There are six aeration basins measuring 30 feet wide, 135 feet long, and 18 feet deep at the White Slough Water Pollution Control Facility (WSWPCF). The basins are a part of the secondary treatment process that supply dissolved oxygen for the micro-organisms that work to reduce concentrations of nitrogen and ammonia in the wastewater.
The City’s prior aeration diffuser system had presented increasingly difficult maintenance and operational challenges for WSWPCF operations staff since its installation in 2007. Council authorized Robertson-Bryan, Inc. (RBI), the project design consulting firm, to prepare a technical memo identifying appropriate replacement options for the aeration system design for replacement of the aeration system. In January 2021, RBI completed the technical memo, which recommends replacing the membrane diffuser panels with a system that utilizes an array of disk filters. This technology requires substantially less labor when performing maintenance operations and eliminates the need to employ a crane.
Specifications for this project were originally approved by Council on June 21, 2023. The project was advertised on August 12, 2023.
On October 18, 2023, Council awarded the contract for Aeration Diffusers System Replacement at the White Slough Water Pollution Control Facility, to WM Lyles Co., of Rocklin ($2,441,500).
All work was completed in substantial conformance with the contract requirements approved by City Council on September 5, 2025.
On May 15, 2024, City Council approved Contract Change Order No. 1 in the amount of $47,447.44 and authorized the City Manager to execute change orders not to exceed an additional $250,000, for total Change Order Authority of $297,447.44.
The original contract was $2,441,500.00 with the final contract amount being $2,742,860.33. This increase (through three change orders) of $301,360.33 was primarily due to a combination of unforeseen conditions and additional work requested by the City. A description of each change order is as follows:
Change Order No. 1 ($47,447.44): Included cleaning of Aeration Basins 3 and 4, which had been out of service for several years.
Change Order No. 2 ($134,319.31): Included groundwater pumping and monitoring system procurement, operation and maintenance; modification of diffuser laterals to permit ladder access and cleaning of Aeration Basins 1 and 2.
Change Order No. 3 ($119,593.58): Owner requested OSHA required repairs to Aeration Basin guardrails, dewatering and cleaning of Aeration Basins 5 and 6; and removal of existing spray water piping. This request inadvertently exceeded the Change Order Authority by $3,912.89.
Photos of the completed project are attached as Exhibit A.
Following acceptance by the City Council, as required by law, the City Engineer will file a Notice of Completion with the County Recorder’s office. The notice serves to notify vendors and subcontractors that the project is complete and begins their 30-day period to file a stop notice requiring the City to withhold payments from the prime contractor in the event of a payment dispute.
Therefore, staff recommends that Council accept improvements under the contract for Aeration Diffusers System Replacement at White Slough Water Pollution Control Facility Project, and adopt a resolution approving Change Order No. 3 and ratifying City Manager approval of increased expenses.
STRATEGIC VISION:
3D. Fiscal Health: Anticipate and advocate against unfunded mandates.
5A: Infrastructure: Develop and maintain a robust infrastructure to support a World class city.
FISCAL IMPACT:
This project is necessary to minimize maintenance costs, maintain wastewater treatment compliance and to avoid potential fines and penalties from the State. This does not impact the General Fund.
FUNDING AVAILABLE:
This project was funded through Wastewater Capitol.