TO:Andrew P. Powers, City Manager
FROM:Nader Heydari, Public Works Director
DATE:September 9, 2025
SUBJECT: Hill Canyon Treatment Plant Tertiary Filter Rehabilitation Project (MI 2590)
RECOMMENDATION:
1. Authorize staff to advertise for construction bids for the Hill Canyon Treatment Plant (HCTP) Tertiary Filter Rehabilitation Project (MI 2590).
2. Find that the Project is Categorically Exempt from California Environmental Quality Act (CEQA) pursuant to 14 CCR 15301 (repair/maintenance of an existing facility).
LEVINE ACT ITEM: No
FINANCIAL IMPACT:
No Additional Funding Requested. $3,935,000 is included in the Adopted FY 2025-26 Wastewater Capital Fund Budget and $2,791,800 in available carryover budget for a total project budget of $6,726,800 for MI 2590. Additional funding for construction costs may be requested at the time of construction contract award depending on bids received.
BACKGROUND:
The City’s HCTP treats wastewater from the community of Thousand Oaks. There are a total of 10 tertiary filters, which are a critical component of the treatment process, improving water quality before it is released into the environment. Tertiary filtration removes contaminants that secondary treatment was unable to remove, such as bacteria, viruses, nutrients like nitrogen and phosphorus, suspended solids, and organic materials. Six filters were included when the plant was constructed in 1977, and four more were added during an upgrade in 2003. The filter building is a two-story, reinforced concrete structure with the filters located on the second level and the piping, mechanical, and electrical equipment located on the lower level (Attachment #1). Over time, the filter media needs to be replaced, and an analysis of media performance is required to evaluate the effectiveness of
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the filtration methodology and type of media used, as well as the frequency of media replacement and other operational factors. In addition to the media replacement, the filter building is in need of maintenance repairs, having developed severe concrete cracks, leading to concrete spalling and leaks in the lower levels. Furthermore, during rain events, certain electrical conduits and panels are flooded with rainwater.
On June 2, 2023, the City issued a Request for Proposals/Qualifications (RFP/Q) for the assessment of the tertiary filter systems, the development of a Preliminary Design Report (PDR) outlining recommendations from the assessment, and a set of ready-for-construction plans and specifications for rehabilitation work. After a review of the proposals by a team of Public Works staff, HDR Engineering, Inc. (HDR), a professional engineering firm, was selected as the most qualified consultant to complete the project. City Council awarded a contract for the PDR scope of work (Phase 1) on September 12, 2023. The original RFP/Q encompassed all phases of the project, but only Phase 1 was included in the original base contract.
HDR completed the Phase 1 PDR, which included a thorough evaluation of the filter configuration, internal equipment, concrete structure, and electrical systems.
The report made numerous recommendations for repairs, reconfiguration, and improvements to the filters, electrical, mechanical, and structural components of the tertiary filter building systems. The recommendations from the report served as the basis for the Phase 2 design. On August 27, 2024, City Council awarded a First Amendment to the Professional Services Agreement with HDR to prepare Phase 2 construction-ready plans for the improvements recommended in the PDR from Phase 1.
DISCUSSION/ANALYSIS:
The recommended improvements for the Tertiary Filter Rehabilitation Project include the following: rehabilitation of the filter walls, new electrical improvements (cabinets, conduits, conductors, and lighting), instrumentation improvements, identified concrete repairs, replacement of the filter internal assembly, piping and valve improvements.
The tentative schedule for completion of the project is as follows:
PROJECT TIMELINE
Bidding Fall 2025
Award of Construction Contract Late 2025
Start of Construction Spring 2026
Construction Completion Summer 2027
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A summary of the estimated project cost is shown below:
ESTIMATED PROJECT COST SUMMARY
Preliminary Design Report (previously authorized) $ 360,790 Final Design and Engineering (previously authorized) $ 462,970 Engineering Support During Construction (future) $ 250,000 Construction Phase Estimate (future) $ 7,500,000
Total Estimated Project Cost $ 8,573,760
The overall project cost (including contingencies, design services during construction/testing, and project management) is estimated at $8,573,760.
HDR completed the project plans and specifications. City staff have completed their review. The project plans and specifications are available for review by request to the Public Works Department by e-mail at [email protected] or by phone at (805) 449-2400. Staff recommend that the project be advertised for bid. Once bids are received, staff will make a recommendation at a future City Council meeting for award of the construction contract.
The project is categorically exempt from CEQA per section 15301 (repair/maintenance of an existing facility).
Community Outreach: This project will be limited to work at HCTP and is not expected to impact any neighboring residences.
This project meets City Council’s Top Ten Priorities #8 and #9, “Environmental Sustainability” and “Public Works Infrastructure Investments.” CIP PROJECT PRIORITY (as outlined in FY 2025-26 and FY 2026-27 CIP Program Budget)
Priority Two – Necessary, but not essential, and there could be consequences if deferred.
COUNCIL GOAL COMPLIANCE:
Meets the following City Council goals:
C. Operate City government in a fiscally and managerially responsible and prudent manner to ensure that the City of Thousand Oaks remains one of California's most desirable places to live, work, visit, recreate, and raise a family.
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F. Provide and enhance essential infrastructure to ensure that the goals and policies of the Thousand Oaks General Plan are carried out and the City retains its role and reputation as a leader in protecting the environment and preserving limited natural resources.
PREPARED BY: Paul Weinstein, Associate Analyst
Attachments:
Attachment #1 – Vicinity and Location Maps
Documents Provided Under Separate Cover:
#1 – Project Plans and Specifications
DPW: 850-20\ev\Council\2025\09092025\MI 2590\HCTP Tertiary Filter Rehab staff report.docx