Agenda Item Wording:
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Water Reclamation Facility (WRF) - Condition Assessment and Facility Plan Update - Receive a report and update presentation on the Condition Assessment, Facility Plan and Master Plan Update for the Water Reclamation Facility.
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Deadline for Action: 2/20/2024
Submitting Department: Public Works
Contact Name and Phone Number: Nick Bartsch, Public Works Director, nick.bartsch@visalia.city <mailto:nick.bartsch@visalia.city>, 713-4052
Department Recommendation:
Staff recommends that Council receive a report and update presentation on the Condition Assessment, Facility Plan and Master Plan Update for the Water Reclamation Facility (WRF).
Background Discussion:
In 2018, the City completed a $150 million upgrade to the City’s Water Reclamation Facility (WRF). This project made various improvements throughout the plant utilizing a tertiary treatment process, thus creating the ability to produce California Title 22 compliant recycled water using membrane bioreactor (MBR) treatment, and ultraviolet (UV) disinfection technologies. This upgrade was necessary as a result of the Central Valley Water Board’s adoption of the National Pollutant Discharge Elimination System (NPDES) permit (NPDES No. CA0079189) under Waste Discharge Requirements (WDR) Order R5-2014-0076, which increased regulation on processed wastewater discharge into Mill Creek in 2014. Therefore, these improvements to the facility allowed for treatment and disinfection for up to 22.0 million gallons of wastewater per day (mgd) and the rerouting of the plant’s effluent to alternative destinations and uses. The treatment processes remove greater than 99% of traditional pollutants and allows the permitted ability to provide disinfected tertiary effluent to not only the City’s basins, but also to Tulare Irrigation District canals, the Visalia Municipal Airport, Plaza Park, the golf course and nearby farmland.
However, the significant upgrades completed in 2018 made major changes to the treatment processes and increased Plant-wide efficiencies, focused on certain components and processes within the Plant, but did not increase the overall design capacity of the entire facility. When the last Facility Master Plan was updated in 2008, the design capacity was 22 mgd. Since that time, upgrades and changes to individual components have made expansion provisions to bring most systems up to the 22 mgd, but have not increased it. Based on projected growth, the current 2008 Master Plan calls for capacity increasing improvements to be completed by 2030, thus expanding the Plant capacity to 26 mgd. To date, those proposed improvements have not yet been completed. Additionally, since the last major upgrade project in 2018, influent industrial flow loadings for biochemical oxygen demand (BOD) and total suspended solids (TSS) have increased drastically over the past few years. This coupled with successful water conservation efforts throughout the City, while beneficial from a water usage standpoint, have changed and impacted the consistency of flows entering the plant. These changes have skewed the overall perception of available capacity of the Plant. While the rated capacity of the facility is 22 mgd (but would require additional upgrades to meet), and current annual average flows are 12.6 mgd, higher loadings cause strains and upsets on the solids handling system including the thickening, digestion, and dewatering processes. These changes have affected the operations of the facility and its overall available capacity.
While the WRF discharge continues to meet effluent limitations, it was prudent for the City to evaluate the long-term impacts of the changes on the plant and its ability to maintain discharge requirements, continue efficient operations, and accommodate future growth. Due to the deteriorating condition of some process areas, the increased loading at the WRF, along with several other operational and maintenance issues, Staff identified the need for an overall facility assessment and the development of a Facility Plan to evaluate the current flows, loads, and facility conditions.
On April 3, 2023, Council approved a contract with Carollo to perform a Condition Assessment, Facility Plan and Master Plan update. The Facility Plan provides a 6-year strategy for near-term improvements, and the Master Plan Update will include a 20-year roadmap to plan for build-out growth conditions and long-term improvements. This process will help evaluate the current planned Capital Improvement Projects Program, prioritize improvements, and address any needs for future expansion.
Since that time, Carollo has completed the Condition Assessment and Facility Plan. Their detailed findings and recommendations are included in the attached report, which includes a comprehensive summary. However, to summarize, Carollo found the majority of the facility to be “generally in good to acceptable condition.” But, using their process model to analyze the flows and loadings throughout the Plant, Carollo found it to be effectively functioning at a significantly lower capacity than currently designed. Whereas the limiting factors in the Plant were designed to accommodate 18 mgd (as currently configured), given the current make-up of the wastewater entering the facility, the results showed the Plant’s current total capacity is effectively 13.9 mgd. For context, the Plant experiences average annual flows of 12.6 mgd. The report also identifies deficiencies in “firm capacity,” defined as “the capacity with the largest unit out of service,” or effectively the necessary redundancy required of each treatment process to account for equipment failures, breakdowns, or required service. While the facility is able to accommodate existing and immediately projected growth volumes, improvements are necessary to address projected growth, meet ongoing regulatory requirements, and provide for necessary operational reliability and redundancy. With this information, Carollo identified several near-term projects needed to meet and improve existing operational compliance, while maintaining the ability to accommodate ongoing increased demand. The report includes estimated costs and a proposed timeline for these near-term improvement projects, totaling an estimated $50 million. Of which, around $6 million of these projects are recommended to be completed over the next 24 months.
The immediate near-term projects consist of:
24 months:
- Thickened waste activated sludge (TWAS) pump replacements to increase the amount of sludge being sent to the Plant’s digesters, thus increasing the overall digestion capacity, currently limited by the hydraulic retention time.
- A dewatering capacity expansion will add a third screw press to account for the increased loadings, and provide for critical redundancy to improve operations and the reliability of the of the solids handling process.
6-Years:
- The anaerobic digestion capacity expansion will construct an additional digester, sized to match the largest existing digester, allowing for it to be taken out of service for maintenance or repairs, while maintaining efficiency and compliance.
- The ultraviolet (UV) disinfection system capacity expansion will install an estimated four additional UV modules to accommodate projected 2030 peak wet weather flows (PWWF), while maintaining regulatory effluent compliance.
Carollo continues to make progress on the Master Plan Update, incorporating information recently received from the Goshen Community Services District to address their long-range growth projections in conjunction with a mutually agreed upon contract amendment. The Master Plan update is expected to be completed in the Spring of 2024 and will be brought back to the City Council for review once completed.
Fiscal Impact:
The report identified a list of the necessary near-term projects to be completed within the next 6 years. It also included a proposed timeline and the estimated costs of each project. These cost estimates total approximately $50 million, of which, around $6 million of these projects are recommended to be completed over the next 24 months. Currently, the Wastewater fund has sufficient funding to address the immediate projects over the next 24 months. Staff will be exploring additional funding opportunities to complete the remaining projects identified in the report.
Ultimately, once the Master Plan has been completed, a rate study has been proposed to evaluate current rates and fees to determine if additional adjustments are necessary to cover the ongoing costs of operations and any necessary capital improvements.
Prior Council Action:
April 3, 2023: Council approved a contract with Carollo to perform a Condition Assessment, Facility Plan, and Master Plan Update for the WRF.
December 18, 2023: Council approved Contract with Carollo for engineering services related to the identified near-term projects.
December 18, 2023: Council approved a request from the Goshen Community Services District to increase sewer discharge capacity.
Alternatives: None
Recommended Motion (and Alternative Motions if expected):
recommendation
No motion required.
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Environmental Assessment Status: N/A
CEQA Review: N/A
Attachments:
WRF - Facility Plan - Final Report
WRF - Facility Plan Update - Carollo Presentation 2_20_2024