DATE: December 5, 2023
TO: Mayor and City Council
FROM: Director of Public Works
SUBJECT
Title
Adopt a Resolution Authorizing the City Manager to Amend the Professional Services Agreement with Brown and Caldwell to Increase the Contract Amount by $8,023,117 to a Not-to-Exceed Amount of $16,672,828 for Final Design Services for the Water Pollution Control Facility (WPCF) Improvements Phase II Project No. 07760, and Authorize use of Contingency Funds for Design of the Existing Final Clarifiers Retrofit
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RECOMMENDATION
Recommendation
That Council adopts a resolution (Attachment II) authorizing the City Manager to amend the Professional Services Agreement with Brown and Caldwell to Increase the Contract Amount by $8,023,117 to a Not-to-Exceed Amount of $16,672,828 for Final Design Services for the WPCF Facility Improvements Phase II Project No. 07760, and Authorize use of Contingency Funds for Design of the Existing Final Clarifiers Retrofit.
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SUMMARY
The Water Pollution Control Facility (WPCF) core infrastructure was originally constructed in 1952 to treat wastewater flows from the City of Hayward’s residents and businesses prior to discharge into the San Francisco Bay. Over the years, the WPCF has undergone several major upgrades to meet more stringent discharge requirements, as well as increasing capacity as the City’s population and industry has grown. The WPCF now treats an average flow of approximately eleven million gallons per day (MGD) and meets current regulatory requirements for discharge of treated effluent to the deep waters of the San Francisco Bay (Bay).
Preliminary design for the Phase II Project will be complete in December 2023. Staff previously negotiated the scope and not-to-exceed fee for the entire project in the amount of $24,737,324, which includes preliminary and final design services, bid period services, engineering services during construction, optional services and design contingency for all three bid packages. Staff is requesting authorization of remaining final design services for the Phase II Project, bidding services for the Administration Building and Primary Effluent Equalization Tanks, and authorization of contingency funds for design of the existing final clarifiers retrofit. This authorization in the amount of $8,023,117 will increase the total authorized to date funding to $16,672,828.
The existing final clarifiers, originally commissioned in 2007 as part of the WPCF Improvements - Phase I Project have experienced issues with failure caused by high groundwater levels and failure of the perimeter groundwater relief system. The preliminary design called for a hydrological study to see if dewatering wells could be installed to lower groundwater levels prior to dewatering and removing a clarifier from service for maintenance. Dewatering wells and concrete patching would have been an economical way to repair and restore the service life of the existing clarifiers; however the hydrogeological investigation determined dewatering of the surrounding grade was not feasible.
Brown and Caldwell evaluated options to shore up the structural integrity of the clarifiers and recommended installing micropiles under the clarifier slabs to reduce buoyant uplift and install thicker walls and slab to both counteract the buoyant load and to resist external hydrostatic loading on the exterior of the walls. This option also requires installation of new clarifier mechanisms due to the change in the depth and diameter of the clarifier. Staff are requesting authorization of the use of $706,537 of contingency funds for final design and engineering services during construction for this additional design work. The design cost for dewatering wells and concrete patching was deducted from the fee estimate for the design of the clarifier rehabilitation. Both of the existing final clarifiers are critical to the treatment process and are required to meet the WPCF discharge permit requirements. The proposed retrofits will restore structural integrity to the clarifiers.
ATTACHMENTS
Attachment I Staff Report
Attachment II Resolution