TO:Andrew P. Powers, City Manager
FROM:Nader Heydari, Public Works Director
DATE:January 13, 2026
SUBJECT: Hill Canyon Treatment Plant Slope Stabilization Project (CI 5736)
RECOMMENDATION:
1. Approve First Amendment to Professional Services Agreement (Contract No. 14071-2025) with Cotton, Shires and Associates, Inc. (Thousand Oaks, CA), for additional design/monitoring services in the amount of $75,000, for a revised not- to-exceed amount of $194,000, plus extra services of $7,500, for a total not-to- exceed amount of $213,400, considering previously authorized extra services of $11,900, with a term ending June 30, 2027.
2. Authorize expense in the amount of $82,500 ($75,000 agreement amendment, plus extra services of $7,500) from A/C #624-8250-682-8300 (Wastewater Fund – Capital Improvements, CI 5736).
3. Find that this action is not a project as defined under the California Environmental Quality Act (CEQA).
LEVINE ACT ITEM: Yes
FINANCIAL IMPACT:
No Additional Funding Requested. $2,465,000 is included in the Adopted FY 2025-26 Wastewater Capital Fund Budget and an additional $152,540 carryover budget for a total budget of $2,617,540 for CI 5736 Hill Canyon Treatment Plant (HCTP) Slope Stabilization Project. Additional funding for construction costs may be requested at the time of construction contract award depending on bids received.
HCTP Slope Stabilization Project (CI 5736)
January 13, 2026
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BACKGROUND:
The City’s HCTP is located at 9600 Santa Rosa Road, in a canyon in the northwest section of the city, between two creeks in a natural, unimproved environment. The treatment plant's original construction included an access road along the bottom of a cliff adjacent to the creek boundary. In FY 2022-23, the City constructed a new retaining wall along the eastern edge of the HCTP which required cutting of the existing slope. In addition, there is a large rock overhang adjacent to the access road to HCTP. Over time, the rock façade has deposited material onto the access road on a regular basis.
Staff previously solicited a formal Request for Proposals/Qualifications (RFP/Q) for the overall design and engineering services for the Slope Stabilization Project (CI 5736) which was to be done in phases starting with the preliminary design/design phase, to be followed by the final design and construction phase. Proposals were received on July 31, 2024. After a thorough review of the proposers’ qualifications and project approach, Cotton, Shires and Associates, Inc. (CSA) was identified as the most qualified engineering firm to fulfill the City’s requirements for the slope stabilization project. The City executed a Professional Services Agreement with CSA on September 16, 2024, in the amount of $66,500, with an additional $6,650 allocated for extra services, under City Manager’s signature authority. The First Amendment to the agreement in the amount of $10,500 was approved by City Council on November 19, 2024, for a revised not-to-exceed amount of $77,000 to include the area behind the maintenance building for a more comprehensive evaluation of all slope areas currently impacting HCTP.
CSA completed the slope stability study and preliminary design report (PDR) phase in March 2025. The PDR recommended that the slopes within HCTP be protected by a network of rock anchors and that a long-term mesh product be constructed to facilitate vegetative regrowth on the slope, allowing the mesh to be covered over time. The PDR recommended a 12-month survey monitoring the rock façade. This one-year monitoring effort is recommended to assess any movement of the rock slope/façade during construction. Staff requested a proposal from CSA for monitoring the rock façade (Attachment #1).
On August 26, 2025, City Council approved a single source designation and second Professional Services Agreement (Contract No. 14071-2025) with CSA for a total not-to-exceed amount of $119,000, plus extra services of $11,900, to complete the second phase of the design services project, which was to prepare construction-ready plans and specifications detailing the recommended slope stabilization products/design for the hillside areas within HCTP.
HCTP Slope Stabilization Project (CI 5736)
January 13, 2026
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DISCUSSION/ANALYSIS:
The completed slope stability study and PDR from March 2025, provided recommendations for the slopes adjacent to the HCTP. The rock façade adjacent to the HCTP access road was identified in the PDR and required extensive mitigation/slope protection. Staff consulted with CSA and determined that the best course of action would be to perform long-term monitoring of the rock outcrop/façade to determine whether the rock is moving and, if so, the extent of any movement. Ten survey prisms will be attached to the rock and surrounding areas, and the prisms will be surveyed once per month for 12 months to establish a baseline and identify any movement of the rock façade over that period. A report will be provided detailing the results of the 12 monitoring events, along with an analysis of the information. Staff requested a proposal from CSA to provide survey monitoring of the rock façade adjacent to the HCTP access road.
Staff recommend City Council approve the First Amendment (Attachment #2) with CSA, in the amount of $75,000 for a revised not-to-exceed amount of $194,000, as well as $7,500 in extra services, and extending the term to June 30, 2027, for the monitoring of the rock façade.
The preliminary project schedule is as follows:
Preliminary Design Report (previous contract) Completed Slope / Rock Façade Monitoring Period January - December 2026 Monitoring Report Deliverable December 2026
The estimated project cost is as follows:
Preliminary Design Report (previous) Contract No. 13764-2024 $ 66,500 Extra Services (previous) Contract No. 13764-2024 $ 6,650 1st Amendment – Design (previous) Contract No. 13764-2024 $ 10,500 Design Services (previous) Contract No. 14071-2025 $ 119,000 Extra Services (previous) Contract No. 14071-2025 $ 11,900 First Amendment (this action) Contract No. 14071-2025 $ 75,000 Extra Services (this action) Contract No. 14071-2025 $ 7,500 Construction Phase (future) $ 2,297,950
Total Estimated Project Cost for CI 5736 $ 2,595,000
HCTP Slope Stabilization Project (CI 5736)
January 13, 2026
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HCTP Slope Stabilization Project (CI 5736)
January 13, 2026
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This action is not a project as defined under the CEQA because this action will not result in a direct or foreseeable indirect physical change in the environment [14 CCR 15060(c)].
Community Outreach: This project will be limited to work at the HCTP, including the access road, and is not expected to impact any neighboring residences.
This project meets City Council’s Top Ten Priorities #9, “Public Works Infrastructure Investments.”
CIP PROJECT PRIORITY (as outlined in FY 2025-26 and 2026-27 CIP Program Budget)
Priority Two – Necessary, but not essential, and there could be consequences if deferred.
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 completed Levine Act Form is included in Attachment #2.
HCTP Slope Stabilization Project (CI 5736)
January 13, 2026
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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 – First Amendment to Contract No. 14071-2025 with CSA DPW: 850-20\ev\Council\2026\011326\CI 5736\HCTP Slope Stabilization Project staff report.docx