TO:Andrew P. Powers, City Manager
FROM:Nader Heydari, Public Works Director
DATE:September 9, 2025
SUBJECT: Unit W Wastewater Interceptor Improvements Project (CI 5445) RECOMMENDATION:
1. Authorize staff to advertise for construction bids for Unit W Wastewater Interceptor Improvements Project (CI 5445).
2. California Environmental Quality Act (CEQA): A Mitigated Negative Declaration (MND) was approved for this project by City Council on February 22, 2022.
LEVINE ACT ITEM: No
FINANCIAL IMPACT:
No Additional Funding Requested. Minimal staff time and costs required to advertise for bids is included in the Adopted FY 2025-26 Wastewater Fund Budget. $1,199,039 in available carryover budget is included in FY 2025-26 Wastewater Capital Fund for CI 5445. Additional funding may be requested at the time of the mitigation planting construction contract award, depending on bids received.
BACKGROUND:
The City’s Hill Canyon Treatment Plant (HCTP) provides tertiary-level wastewater treatment for the community. As part of the overall wastewater collection and treatment system, large-diameter wastewater interceptor pipelines were installed to transport the wastewater from the community and deliver it to the HCTP. The Unit W Wastewater Interceptor is a gravity collection pipeline that originates near The Oaks Mall and transports a large volume of wastewater along the Arroyo Conejo Creek to the HCTP (Attachment #1).
The Unit W pipeline was installed in the 1960s, and improvements have been made over the past few decades. In the lower section of the interceptor is the original 1960s Unit W pipeline which consists of a 30-inch diameter pressurized pipeline featuring two main wastewater access structures (Structure W-1 and
Unit W Wastewater Interceptor Improvements Project (CI 5445) September 9, 2025
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Structure W/F). The structures enable the wastewater interceptors to be controlled and accessed by staff.
In May 2019, City Council approved a Professional Services Agreement with Padre Associates, Inc. (Padre) to prepare the required project regulatory permit applications as well as perform the environmental analysis for the project impacts and the CEQA compliant Initial Study/MND. As part of the regulatory permit process, the California Department of Fish and Wildlife (CDFW) required compensatory mitigation of the impacts associated with the project.
Padre prepared the required project regulatory permit application packages for the Regional Water Quality Control Board, CDFW, and the US Army Corps of Engineers. These regulatory permits are required due to the environmentally sensitive area of the project and the necessary construction work within the creek channel crossings and banks. In the CDFW permit, compensatory mitigation was required to offset the impacts of the construction project. The mitigation plan prepared by Padre consisted of planting native plant species in specific areas of the canyon and providing temporary irrigation for these plantings until they were established.
On August 27, 2019, after a competitive Request for Proposals (RFP) process, City Council approved a Professional Services Agreement with AECOM, a professional engineering firm, for the preparation of an initial asset assessment of the Unit W Pipeline Project. The project’s scope of work included exposing and reviewing the existing condition of the two main pipelines towards the south headworks at the HCTP, which included approximately 5,000 feet of 20- to 42-inch diameter pipes (Attachment #1). Successive amendments to AECOM’s agreement were approved by City Council for additional work, including design services, construction support services, and habitat restoration mitigation design consultant services.
DISCUSSION/ANALYSIS:
AECOM has prepared the construction-ready plans and specifications for the mitigation landscape planting to satisfy the regulatory permit compensatory requirements.
The work to be performed under this project includes planting native species cuttings and applying native seeds to the areas that were impacted by the project construction. There are 15 mitigation areas included in the restoration project, with a total planting area of 1.18 acres. Temporary irrigation of the planted areas is also included in the plans and specifications. The project documents include the required five years of monitoring of the planted areas (weeding, watering, replacing dead plant material, etc.) as required by the CDFW permit. The permit requires a Unit W Wastewater Interceptor Improvements Project (CI 5445) September 9, 2025
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specific successful plant survival/coverage rate at the end of the five-year period, which the contractor will be required to meet. Failure to achieve the success rate of the plants at the end of the five-year period will result in extending the mitigation monitoring timing.
The tentative schedule for completion of the project is as follows:
PROJECT TIMELINE
Bidding Fall 2025
Award of Construction Contract Fall 2025
Start of Construction Winter 2026
Construction Completion Spring 2026 The Unit W Wastewater Interceptor Project (CI 5445) has undergone several phases of work over the last few years, some of which continues, utilizing multiple contractors, vendors, and consultants, including services related to preliminary design, design, pipeline construction, construction monitoring, construction management, regulatory permitting and fees/deposits, and now habitat restoration.
The estimated overall project costs are as follows:
ESTIMATED PROJECT COST SUMMARY
Design and Environmental Support (previously approved) $ 514,817 Design and Engineering Extra Services (previously approved) $ 47,250 Engineering & Project Management Support (previously approved) $ 125,000 Isolation Valves Equipment (previously approved) $ 68,129 Unit W Construction Contract (previously approved) $ 3,440,000 Unit W Construction Contingency (previously approved) $ 344,000 Construction Phase Support Services (previously approved) $ 46,900 Const. Phase Support Extra Services (previously approved) $ 4,690 Construction Phase Environmental Monitoring (previously approved) $ 2,805 City Furnished Supplies and Materials (previously approved) $ 5,000 Bank Letter of Credit for CDFW Permit Obligations (previously approved) $ 550,000
Fee for Bank Letter of Credit for CDFW (previously approved) $ 22,000 Habitat Restoration Design Services (previously approved) $ 72,400 Habitat Rest. Mitig. Design Services Extra Services (prev. approved) $ 7,200 Plug Valves Equipment Purchase (previously approved) $ 126,555 Total Estimated Costs (through Previous Actions) $ 5,376,746 Permitting and Inspection: CDFW (future) $ 25,000
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Habitat Restoration as required by CDFW (future) $ 550,000 Total Estimated Project Costs (including Future Actions) $ 5,951,746 The overall project cost for the construction assessment project and the habitat mitigation project (including contingencies, design services during construction/testing, and project management) is estimated at $5,951,746.
The project plans and specifications were completed by AECOM and reviewed by City staff and are available for review upon request to the Public Works Department by e-mail at [email protected] or by phone at (805) 449-2400.
Staff recommends 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.
Environmental Review
As required under the provisions set forth in Section 15063 of the State of CEQA Guidelines, an Initial Study was prepared by the City of Thousand Oaks for the Unit W Wastewater Interceptor Improvements Project (CI 5445). The Initial Study evaluated the potential effects of this project on the environment. Although the Initial Study determined the project could have a potentially significant impact on the environment for certain receptors, the project design will reduce the impacts. Furthermore, feasible mitigation measures have been identified that would either avoid or reduce impact to a level of insignificance, or less than significant with mitigation. Based on these findings, a MND and Mitigation Monitoring Reporting Plan was prepared for the proposed project in compliance with the provisions set forth in Section 15070 of the CEQA Guidelines. On February 22, 2022, City Council adopted the construction project MND.
Community Outreach: This project will be limited to work in the lower Arroyo Conejo south fork area and is not expected to impact neighboring residences. The work area entrance will be at the south end of the plant and will have limited impact to plant operation. Construction-related impacts to hiking trail users are expected to be minimal.
This project meets City Council’s Top Ten Priorities #8 and #9, “Environmental Sustainability” and “Public Works Infrastructure Investments.” Unit W Wastewater Interceptor Improvements Project (CI 5445) September 9, 2025
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CIP PROJECT PRIORITY (as outlined in FY 2025-26 and 2025-26 CIP Program Budget)
Priority Two – Necessary, but not essential, and there could be consequences if deferred.
COUNCIL GOAL COMPLIANCE:
Meets the following City Council goal:
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\09092025\CI 5445\Unit W Wastewater Interceptor Improvement Project staff report.docx