DATE: June 24, 2025
TO: Mayor and City Council
FROM: Director of Public Works
SUBJECT
Title
Adopt a Resolution Authorizing the City Manager to Execute Amendment No. 1 to the Agreement with Redwood Painting Co., Inc., Increasing the Agreement Amount by $215,239, for the Final Project Cost of the Water Resource Recovery Facility (WRRF) North Vacuator Rehabilitation Project, Project No. 07818, and Appropriating Funds in the Amount of $230,239 from Sewer System Replacement Fund (Fund 611)
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RECOMMENDATION
Recommendation
That the City Council adopts the attached resolution (Attachment II) authorizing the City Manager to execute Amendment No. 1 to the Agreement with Redwood Painting Co., Inc., (Redwood) for the Water Resource Recovery Facility (WRRF) North Vacuator Rehabilitation Project in an amount not-to-exceed $215,239, and authorizing the City Manager to transfer and appropriate additional funds in the amount of $15,000 from the Sewer System Replacement Fund (Fund 611) for the final project cost, for a total appropriation of $230,239.
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SUMMARY
Additional funding is needed to complete the North Vacuator Rehabilitation Project. This effort will restore a key component of the treatment facility, improving overall plant performance and reliability. It will also reduce maintenance demands on existing sludge pumping systems until the new Grit Facility, part of the Phase II Project, becomes operational.
The North Vacuator structure has been out of service since January 2024 and needs repair. When in use, the Vacuator removes grit and floating debris (grease/scum) from raw wastewater prior to primary treatment. The approximately 50-foot-diameter, 20-foot-tall concrete structure was built in 1958 and includes mechanical components and a self-supported concrete dome roof. To return the structure to service, the rehabilitation project included the following project elements:
- removal of existing coatings on interior metal and concrete surfaces
- coating of interior metal components
- coating of interior concrete surfaces
- interior concrete surface repairs
- interior steel component repairs
- grinding of edges of sludge and scum collector equipment
Construction of the North Vacuator Rehabilitation Project at the WRRF started in February 2025 with a target completion date of August 2025. During construction, the removal of existing coatings from the concrete dome revealed that the entire concrete surface required repairs in accordance with the project specifications. The extent of repairs was unforeseen, as the bid documents only anticipated repairs to approximately 30 percent of the surface.
Repairing the entire concrete surface per project specifications would nearly triple the total project cost. Given that the project’s goal is to restore the structure to service for an interim period of 8 to 10 years until the Phase II upgrades are implemented; this approach was deemed cost prohibitive.
As a result, staff consulted with Redwood, the coating manufacturer (Global Eco Technologies), Coating Specialists and Inspection Services, Inc. (CSI), and a structural engineer (Carollo) to explore alternative solutions. An alternative coating system (Enduraflex EF-1988 Expanded) was identified that can be applied directly to the exposed concrete without extensive surface repairs. This system is considered adequate for achieving the desired operational life of the structure. Areas with exposed rebar will be treated with corrosion-inhibiting paint, and localized concrete repairs will be made where the rebar is not firmly embedded in the substrate. Implementing the expanded coating system will result in a change order in the amount of $165,841.
In addition, the existing concrete coatings were thicker than anticipated, exceeding ½-inch in several areas, which required Redwood to expend additional time, labor, and materials to complete the removal. This resulted in a change order of $31,900.
Furthermore, the abrasive grit material used to blast the coatings became saturated due to an apparent leak at the bottom of the tank. Because the wet abrasive could not be removed using vacuum equipment, it was manually removed using 5-gallon buckets. This issue caused four additional days of labor and resulted in a separate change order totaling $17,498.
To complete the project with the alternative coating approach, staff is recommending approval of Amendment No. 1 to the Agreement with Redwood in the amount not-to-exceed $215,239 and a time extension of 30 calendar days. An additional $15,000 in funds is requested to cover administrative change orders related to other project costs including scaffolding rental, structural engineering consultation, certified payroll reporting, and additional special inspection services, if required. A total of $230,239 is requested for all change orders and project costs needed to complete the project.
ATTACHMENTS
Attachment I Staff Report
Attachment II Resolution