TO:Andrew P. Powers, City Manager
FROM:Nader Heydari, Public Works Director
DATE:December 2, 2025
SUBJECT: Hill Canyon Treatment Plant Tertiary Filters Rehabilitation Project (MI 2590)
RECOMMENDATION:
1. Approve the project design, plans, specifications, and Addenda Nos. 1 and 2 for construction of the Hill Canyon Treatment Plant (HCTP) Tertiary Filters Rehabilitation Project (MI 2590).
2. Award construction contract for the HCTP Tertiary Filters Rehabilitation Project (MI 2590) to Cushman Contracting Corporation, of Goleta, CA, in the amount of $8,295,000, plus a contingency of $414,750, for a total construction contract value of $8,709,750.
3. Approve Second Amendment to Professional Services Agreement (Contract No. 13412-2023) with HDR Engineering, Inc. (HDR) of Ventura, CA, for Construction Phase Design Services on the HCTP Tertiary Filters Rehabilitation Project (MI 2590) in the amount of $611,600, for a revised not-to-exceed amount of $1,435,360 and a total not-to-exceed amount of $1,517,560 considering previously approved extra services of $82,200, as well as extending the term of the agreement to June 30, 2027.
4. Approve budget appropriation in the amount of $3,484,783 from A/C #624-0000- 341-9900 (Wastewater Fund – Net Position) to A/C #624-8250-682-5500 (Wastewater Fund – HCTP Tertiary Filters Rehabilitation Project, MI 2590).
5. Authorize expense in the amount of $9,321,350 ($8,295,000 construction contract, $414,750 construction contract contingency, and $611,600 for construction phase design support services and materials testing from A/C #624- 8250-682-5500 (Wastewater Fund – Capital Improvements, MI 2590).
6. Delegate authority to the City Engineer to approve changes in the design, plans, specifications and working details of the project on work directives and change orders up to the project approved contingency amount.
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7. 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: Yes
FINANCIAL IMPACT:
$3,484,783 Increase to Adopted FY 2025-26 Wastewater Fund Capital Budget. A $3,484,783 budget increase is requested for the HCTP Tertiary Filters Rehabilitation Project (MI 2590). $3,935,000 is included in the Adopted FY 2025- 26 Wastewater Capital Fund Budget for MI 2590, along with $2,982,527 in FY 2024-25 carryover budget for a total available project budget of $6,917,527. The estimated total project cost is $10,402,310.
BACKGROUND:
The City’s HCTP treats wastewater from the community of Thousand Oaks. There are a total of 10 tertiary filters at the HCTP, a critical component of the treatment process that improves water quality before it is released into the environment.
Tertiary filtration removes contaminants that secondary treatment systems are 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 were added during the 2003 HCTP upgrades. 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 on the lower level (Attachment #1).
Over time, the tertiary filter media degrades and needs to be replaced. An analysis of media performance was needed to evaluate the effectiveness of the filtration methodology, the type of media used, the frequency of media replacement, and other operational factors. In addition to the media replacement, the filter building requires maintenance repairs due to cracks in the concrete that have caused spalling and leaks in the lower levels. Furthermore, during rain events, electrical conduits and panels have been flooded with rainwater.
On September 12, 2023, the City awarded a Professional Services Agreement to HDR, a professional engineering firm, with a scope to assess the tertiary filter systems, produce a Preliminary Design Report (PDR) outlining recommendations from the assessment, and develop a set of ready-for-construction plans and specifications for the necessary rehabilitation work (Phase 1). The original Request for Proposals/Qualifications (RFP/Q) encompassed all phases of the project (preliminary design, design, as well as design services during construction), but only Phase 1 preliminary design was included in the original base contract. HDR completed the PDR as part of Phase 1, which included a thorough evaluation of the filter configuration, internal equipment, concrete structure, and electrical HCTP Tertiary Filters Rehabilitation Project (MI 2590)
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systems. The consultant’s report made recommendations for repairs, reconfiguration, and improvements to the filters, electrical, mechanical, and structural components of the tertiary filters building systems. The recommendations served as the basis for the Phase 2 design. On August 27, 2024, City Council awarded a First Amendment to the Agreement with HDR to prepare construction-ready plans for the improvements (Phase 2) that were recommended in the PDR during Phase 1.
DISCUSSION/ANALYSIS:
City Council authorized bidding of the project on September 9, 2025, and the Notice Inviting Bids was publicly advertised in the Thousand Oaks Acorn newspaper and posted on the City’s procurement website on September 12, 2025, per the Public Contract Code Section 22037 and Thousand Oaks Municipal Code 3-10.306. Three bids were received and publicly opened on October 22, 2025. The bid results are as follows:
Bidder Bid
1. Cushman Contracting Corp. (Goleta, CA) $8,295,000
2. Pacific Hydrotech Corp. (Perris, CA) $9,234,100
3. GSE Construction Company (Livermore, CA) $9,623,200
The lowest bid received was from Cushman Contracting Corporation (Cushman) for $8,295,000. The bid package submitted by Cushman has been reviewed and found to be in order, no bid protests have been received, and the bid protest period has ended. Staff recommend awarding the construction contract to Cushman in the amount of $8,295,000, plus a five percent contingency of $414,750.
All bids received for this project exceed the engineer's estimate of $7,350,000.
This estimate was based on prior construction project bids for wastewater installations; however, construction market costs remain volatile, particularly for specialty work, like that involved in this project. Staff recognize that a budget shortfall of $3,484,783 exists between the project's available budget ($6,917,527) and the total estimated project budget ($10,402,310). To offset the additional budget request, staff reduced the typical construction contingency amount from 10 percent to five percent. Additionally, staff have identified five wastewater capital improvement projects that can be deferred for a year without negative consequences to the City’s wastewater system in order to reduce the financial impact on the current fiscal year’s wastewater fund balance.
Engineering and design support services are required of HDR, the project engineer of record, during the construction phase of the project. Their scope of work includes reviewing and responding to requests for information, reviewing material submittals, preparation of a final project punch list, and preparing record drawings upon completion of construction. Services will also include material testing and HCTP Tertiary Filters Rehabilitation Project (MI 2590)
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inspection throughout the construction period. Staff recommends approval of the Second Amendment to Contract No. 13412-2023 (Attachment #2) with HDR in the amount of $611,600, for a not-to-exceed amount of $1,435,360 and a total not-to- exceed amount of $1,517,560, considering previously approved extra services of $82,200, as well as extension of the term to June 30, 2027. Construction Phase Project Management Support will be supplied under the existing City contract with Phoenix Civil Engineering, Inc. (Contract No. 13281-2023).
The estimated overall project cost breakdown is as follows:
Preliminary Design Report w/HDR (prev. authorized) $ 360,790 Final Des. and Engineering Amend 1 w/HDR (prev. authorized) $ 462,970 Design Extra Services w/HDR (prev. authorized) $ 82,200 Design Support During Construction w/HDR (this action) $ 611,600 Engineering and Proj. Mgmt. Support w/Phoenix (prev. authorized) $ 175,000 Tertiary Filter Construction Contract (this action) $ 8,295,000 Tertiary Filter Construction Contingency (this action) $ 414,750 Total Estimated Project Cost $ 10,402,310
This construction phase is anticipated to begin in January 2026 and be fully completed by Spring 2027. The project design, specifications, and Addenda Nos. 1 and 2 were completed by the consultant in October 2025 and are available for review by request to the Public Works Department by e-mail at [email protected] or by phone at (805) 449-2400.
The project is categorically exempt from CEQA per section 15301 (repair/maintenance of an existing facility).
This project meets City Council’s Top Ten Priorities #8 and #9, “Environmental Sustainability” and “Public Works Infrastructure Investments.” Community Outreach: The Project is located at the HCTP, which is situated in a canyon along the Arroyo Conejo, and is not expected to impact any neighboring residences.
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.
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LEVINE ACT (California Government Code § 84308):
This item is subject to the Levine Act. City Councilmembers who have received a campaign contribution of more than $500 (aggregated) within the preceding 12 months from a party or their agent/representative, or a financially-interested participant involved in this proceeding may do either of the following: (1) disclose the contribution on the record and recuse themselves from this proceeding; or if applicable (2) return the portion of the contribution that exceeds $500 within 30 days from the time the official knew or should have known about the contribution, and participate in the proceeding.
All parties and their agents/representatives must disclose on the record of this proceeding any aggregated contribution of more than $500 made to any Councilmember within the preceding 12 months. Councilmembers are prohibited from accepting, soliciting, or directing a campaign contribution of more than $500 (aggregated) from a party, their agent/representative, or a financially-interested participant during a proceeding and for 12 months following the date a final decision is made. In addition, a party, their agent/representative, or a financially- interested participant is prohibited from contributing more than $500 (aggregated) to a Councilmember during a proceeding and for 12 months following the date a final decision is made. The Levine Act disclosure form for HDR has been completed and is included as an exhibit in Attachment #2.
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.
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
Attachment #2 – Second Amendment to Contract 13412-2023 with HDR DPW: 850-20\ev\Council\2025\120225\MI 2590\HCTP Tertiary Filter Rehab Project staff report.docx