DATE: October 15, 2024
TO: Mayor and City Council
FROM: Director of Public Works
SUBJECT: Adopt a Resolution Authorizing the Specification of Sole Source Equipment to be Provided by Hydro International for the Water Resource Recovery Facility (WRRF) Grit Removal System in an Amount Not-to-Exceed $2,117,202
RECOMMENDATION
That Council adopts a resolution (Attachment II) authorizing staff to specify grit removal equipment manufactured by Hydro International for the WRRF Improvements, Phase II Project, in an amount not-to-exceed $2,117,202.
SUMMARY
Grit removal at the WRRF is currently performed by the North Vacuator, which is nearing the end of its useful life, is inefficient, and technologically obsolete. In addition, the structure, originally commissioned in 1958, is hydraulically restricted such that when flows in the plant exceed 18 million gallons per day during wet weather events, flows bypass the grit facility and are directed to the primary clarifiers partially treated. Replacement of this facility is included in the WRRF Improvements – Phase II Project (Phase II Project). Modern grit removal systems generally require a specifically shaped structure to be built around them, effectively requiring a specific product be specified early in the design and prior to formal bidding. The Design Consultant, Brown and Caldwell, has analyzed several grit removal technologies and determined that the multi-tray vortex tank system provided by Hydro International, coupled with the OpTeaCup classifier and Grit Snail dewatering system, would be the most effective system for removing grit, minimizing maintenance, and minimizing the space required for grit removal. Staff is requesting authorization to specify, with no equal, grit removal equipment to be provided by Hydro International, in an amount not-to-exceed $2,117,202. This would be purchased and installed by the construction contractor following formal bidding of the Phase II Project.
BACKGROUND
The WRRF performs preliminary, primary, and secondary treatment on the City’s wastewater. Part of the preliminary treatment is the removal of grit, which is currently performed by the North Vacuator. The North Vacuator was constructed in the 1950’s to complement the previously existing South Vacuator and was originally designed to remove scum from the extensive canning operations which were prevalent in the City at the time. The South Vacuator is no longer in use, and the North Vacuator is no longer an appropriate form of grit and scum removal and has reached the end of its useful life. The North Vacuator is also not appropriately sized for peak wet weather flows resulting in a portion of the flows bypassing the unit without grit removal impacting downstream processes. It is important to have a proper working grit removal system to decrease potential damage or other impacts to downstream mechanical equipment (pumps), piping, and other equipment downstream of the preliminary treatment system.
On February 27, 2018, Council approved execution of a Professional Services Agreement (PSA) with Black & Veatch (B&V) to develop the Facilities Plan to identify improvements needed to meet upcoming regulatory requirements and guide the WRRF infrastructure needs for the next 25-years. The Facilities Plan was completed in July 2019 and included development of a nutrient management strategy and related capital improvements. These capital improvements are being implemented as part of the Phase II Project, with a primary focus on nutrient removal. One of the related capital improvements that the Facilities Plan recommended was the replacement of the North Vacuator with a dedicated modern grit removal system.
The City subsequently hired Brown and Caldwell for final design of the Phase II Project, which includes the design of a new grit removal system. The grit removal system would be constructed in the location currently occupied by the west trickling filter. However, some of the space currently occupied by the west trickling filter is being reserved for a future expanded headworks as the current headworks is unable to pass the design wet weather flows. The grit facility layout is being coordinated with a future headworks facility.
DISCUSSION
As part of the preliminary design phase, Brown and Caldwell investigated several alternatives for the grit removal system including the following:
Aerated grit chambers consist of tanks with coarse bubble aeration to mix the flow and reduce the specific gravity of the sewage/grit solution that results in enhanced grit settling in the chamber. Aerated grit chambers are considered to be an outdated technology that is not as effective as the alternatives, especially when considering removal of relatively small grit particles. They typically have the largest footprint and the most equipment to maintain and are not feasible in the constrained footprint available for the grit facility.
Induced vortex grit chambers use either mechanical paddles or natural wastewater flow to create a vortex that causes relatively dense solids to impact the side walls and settle to the bottom of the tank. Grit slurry is then removed by pumps and conveyed to the grit washing and dewatering process.
Muti-tray vortex tank systems use a stack of trays that each receive a portion of the influent flow. Flow follows a vortex pattern similar to induced vortex systems. The grit slurry settles on each tray and drops to the bottom of the tank, where it is removed by pumps and conveyed to the grit washing and dewatering process.
Due to the significant space requirements, equipment needs, and generally poorer performance, aerated grit chambers were not considered in detail for this project. Both induced vortex grit chambers and multi-tray vortex tanks have complicated concrete structures associated with the units including specific inlet and effluent channel designs, differing diameters, and depths that require different structural and mechanical detailing, as well as inlet and outlet piping design specific to each technology. This effectively requires a specific grit removal system be specified early in the design so that the appropriate structure can be designed around it. Without such a sole source, the design engineer would be either required to provide two separate designs as bid alternatives, or the design would be based on one manufacturer, and the contractor would be required to redesign the system with the alternative manufacturer at considerable additional cost associated with selecting the alternative. This approach could also result in inflated bids from the manufacturer who was the design basis as they would be able to bid higher knowing the alternative manufacturer includes additional design cost to be borne by the contractor.
It should also be noted that there would be significant additional effort borne by the design engineer to review the contractor’s design and reconcile all the other disciplines such as electrical, instrumentation, civil, and piping layouts and design. Therefore, it was decided to select a technology to base the design on and negotiate a price to be held firm and included in the bid documents.
After several workshops with Brown and Caldwell, City staff ultimately selected multi-tray vortex tanks as the preferred design alternative for the following reasons.
Multi-tray vortex tanks have a smaller footprint than induced vortex grit chambers. This allows for a smaller structure to be built around them and allows greater space for a future expanded headworks.
Multi-tray vortex tanks have proven to be more effective than induced vortex grit chamber at removing all sizes and densities of grit particles.
Multi-tray vortex tanks have fewer moving parts and require less maintenance than induced vortex grit chambers.
Multi-tray vortex tanks have been selected as the preferred alternative for various recent projects in the Bay Area, including for the City of Sunnyvale, City of San Jose, Silicon Valley Clean Water, San Francisco Public Utilities Commission Southeast Plant, and West County Wastewater District (Richmond).
Currently, Hydro International is the only manufacturer of multi-tray vortex systems with a substantial number of installations and operating experience. Hydro International’s system is named Headcell.
Grit slurry pumped from grit removal tanks is normally washed and dewatered in a separate process. Grit slurry washing/dewatering equipment can be categorized into three main types: cyclone/classifier systems, vortex-induced systems, and conical systems. Upon review of these systems, the City, in conjunction with Brown and Caldwell, selected the Hydro International OpTeaCup system coupled with the Grit Snail dewatering system for the following reasons:
Utilizing the same manufacturer for the grit removal system and grit washing system provides overall responsibility under a single manufacturer for meeting the performance guarantee whereas if multiple manufacturers are involved the enforcement of a performance guarantee may be more difficult with multiple parties involved.
The grit snail dewatering is similar to existing equipment on site that is used for snail shell removal. Matching existing equipment on site streamlines maintenance and is an appropriate reason to sole source equipment per California Public Contract Code Section 3400 Paragraph C.2.
Brown and Caldwell solicited a quote from Hydro International that includes furnishing the HeadCell Grit Concentrators, OpTeaCup solids classifiers, grit snail dewatering units, grit pumps, control panels and related appurtenances. In addition, startup services, preparation of submittals and operations and maintenance manuals, and training services is also included. In response to the City’s request, Hydro International provided reference quotes for several other installations to justify their quote. The City and Brown and Caldwell reviewed and determined the pricing that Hydro International proposed for this project is fair and reasonable based on the backup quotations furnished. Hydro International’s price quote is for $2,117,202 including California and local sales taxes. Installation would be performed by the selected contractor for the Phase II Project.
ECONOMIC IMPACT
The current construction cost for the Phase II Project (at 60% design stage) is estimated to be $224 million with a range between $190 and $269 million. These costs do not include any soft costs such as design or construction management costs, or the construction cost of the Administration and Laboratory Building. The cost of the proposed grit removal system is included in the Phase II Project estimate. It is anticipated that these improvements overall will substantially impact rates, resulting in doubling of the current sewer service rates and sewer connection fees over the next ten years.
FISCAL IMPACT
The funding for this procurement contract is included in the Sewer Improvement Fund, 612-07660 (WRRF Phase II Improvement Project) with no impact on the City’s General Fund. There is no immediate fiscal impact of this action, as this equipment will not be procured until a contractor is selected for the Phase II Project in FY 26.
Staff submitted an application for Water Infrastructure Financing and Innovation Act (WIFIA) funding in the amount of 49% of the total project costs which is currently in the early stages of the review and approval process. The remainder of the project would primarily be funded through tax exempt municipal bonds, which are not yet issued. As the design progresses, the estimated project cost is expected to be adjusted, especially as construction costs become better defined in the future as the design is more complete. Staff continue to monitor if applying for a State Revolving Fund (SRF) loan is feasible and are seeking grants as well. Budget adjustments will be brought forward to Council through the annual budget approval process.
STRATEGIC ROADMAP
This agenda item supports the various goals of Council’s Strategic Roadmap. The Phase II Project will address infrastructure needs and improvements to increase the reliability of the City’s treatment plant, and construct process improvements to meet more stringent nutrient limits in accordance with upcoming regulatory requirements, while supporting the goals of Council. Specifically, this item relates to the implementation of the following projects:
Confront Climate Crises & Champion Environmental Justice.
Mitigate Climate Crisis Impacts through Resilient Design and Community Engagement Project C14b: Implement Shoreline Master Plan, including mitigating sea level rise in the industrial corridor through building requirements and outreach Invest in Infrastructure.
Invest in Water Supplies, Sanitation Infrastructure & Storm Sewers Project N19: Update Water Pollution Control Facility Phase II Plan
SUSTAINABILITY FEATURES
The Phase II Project will help maintain and improve the biology and health of the San Francisco Bay which is vital for the region and the State. The Phase II Project will also satisfy the nutrient removal requirements specified in the 3rd Watershed Permit to reduce nitrogen loads to the Bay.
The effects and risks of rising sea water levels have been reviewed and will be incorporated into the design of the new facilities.
The Administration and Laboratory Building design will meet State and local requirements related to sustainability (i.e., California Building Code, California Energy Code, etc.) which require a minimal level of energy efficiency, resource conservation, material recycling, etc. In addition, the building will be designed and constructed to meet Leadership in Energy and Environmental Design (LEED) standards for a Silver Certification, or better. The Administration and Laboratory Building will also include a 75kW solar array in the parking lot to generate renewable energy.
PUBLIC CONTACT
As part of the funding process, an environmental study (Initial Study and Mitigated Negative Declaration) was posted for public review and comment.
There is currently a website hosted on the City’s website that posts periodic updates throughout the multi-year duration of the project. This will continue.
NEXT STEPS
If Council approves, staff will specify the herein described equipment by Hydro International to be included in the plans and specifications for the Phase II Project. This project is expected to be released for public bidding in September of 2025.
Approval of Plans and Specifications and Call for Bids for the Phase II Project September 2025
Award of Construction Contract for the Phase II Project January 2026
Grit Facility Installation
Calendar year 2029
WRRF Improvements – Phase II Project Construction Completion June 2030
Prepared by: Kyle Carbert, Senior Utilities Engineer Reviewed by: Suzan England, Utilities Engineering Manager Recommended by: Alex Ameri, Director of Public Works Approved by:
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Dustin Claussen, Interim City Manager