TO:Andrew P. Powers, City Manager
FROM:Nader Heydari, Public Works Director
DATE:July 8, 2025
SUBJECT: Sewer Use and Discharge Local Limits Ordinance Updates RECOMMENDATION:
1. Read ordinance in title only, waive further reading, and if no objection, introduce ordinance to amend Thousand Oaks Municipal Code (TOMC) repealing certain sections of Title 10, Chapter 1, Article 5 “Service and General Discharge Regulations” and repealing Title 10, Chapter 1, Article 6 in its entirety and adding Title 10, Chapter 1, Article 6 entitled “Sewer Use Regulations.”
2. Read ordinance in title only, waive further reading, and if no objection, introduce ordinance Adjusting and Setting Rates, Discharge Limits and Fees of the City Wastewater Division (Local Limits).
3. Find that this action is exempt from further review under Section 15308 of the California Environmental Quality Act (CEQA).
LEVINE ACT ITEM: No
FINANCIAL IMPACT:
No Additional Funding Requested. Minimal staff time required to complete the ordinance updates is included in the Adopted FY 2025-26 General Fund Budget.
BACKGROUND:
The City of Thousand Oaks provides wastewater collection and treatment services to approximately 122,000 residents through its facilities, which include the Hill Canyon Treatment Plant (HCTP) operating at a current rate of eight million gallons per day (mgd), and a collection system of approximately 415 miles of gravity sewer pipelines, 8,300 maintenance holes, two lift stations, and 2.5 miles of pressure- pipe force-mains. HCTP has a dry weather design capacity to treat 14 mgd.
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HCTP is a Publicly Owned Treatment Works (POTW) that treats wastewater for the community and is regulated under the federal Clean Water Act. Per the Clean Water Act, HCTP is required to have a Pretreatment Program (Program) in place to regulate the discharge of pollutants from all sources, including industrial and commercial users, into the City’s sewer system. The Program functions by establishing rules, issuing permits, setting pollutant limits, conducting inspections, monitoring discharges, and taking enforcement action when necessary. This Program helps ensure the City stays in compliance with federal law while protecting the treatment plant, public health, and the environment. One key aspect of the Program is the establishment of Local Limits which are specific pollutant limits set by the City to prevent interference with the treatment process, protect worker safety, and ensure treated water meets environmental standards. The City’s Program is defined and enforced through the Sewer Use Ordinance (SUO) in the TOMC.
Staff is recommending an update to the SUO (Attachment #1) for the first time since 2009. The revised SUO consolidates all sewer use requirements into one article and updates language and definitions to meet current federal Program requirements (40 CFR 403). The updates were made in response to regular audits of the City’s Program conducted every two to five years by the United States Environmental Protection Agency (EPA) and now by the Los Angeles Regional Water Quality Control Board (LARWQCB). During the audits, these regulatory agencies examine how the City enforces pollutant limits, manages industrial permits, monitors facilities, and responds to violations. After each audit, the EPA/LARWQCB provides a report with findings and recommendations to help improve or update the Program. The proposed updates are based on the audit recommendations and are intended to bring the Program’s language and definitions in line with current federal standards.
The SUO update also includes a significant modification to the Program. The modification adds tiered wastewater discharge permits that will better define the obligations required of wastewater dischargers depending on the level of potential impact posed by a discharge to the City’s sewer system.
In response to the 2017 EPA audit recommendation, the City initiated a technical evaluation of its Local Limits to ensure they remain protective of the HCTP and its discharges to the environment. The City's existing Local Limits, originally developed in the 1980s, required reassessment under current conditions. HCTP operates under the National Pollutant Discharge Elimination System (NPDES) Permit No. CA0056294 (Order No. R4-2019-0137), adopted by the LARWQCB on November 14, 2019, and effective as of January 1, 2020. This permit mandated the City to submit a written technical evaluation of its Local Limits. Anticipating this requirement, the City contracted with Larry Walker Associates (LWA) in April 2019 to conduct the evaluation and, if warranted, to perform a Local Limits Study to Sewer Use and Discharge Local Limits Ordinance Updates
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develop updated, technically sound, and scientifically defensible local limits based on current water quality data.
The findings of the LWA technical evaluation concluded that the City’s Local Limits required updating. The existing limits were established based on conditions prior to major upgrades at HCTP that began in the 1990s and continued over subsequent decades, as well as changes in the local industrial base and federal regulatory requirements. To support the update, LWA conducted a comprehensive Local Limits Study, which involved extensive sampling and analysis of the City’s sewer system and various stages of the HCTP treatment process. This effort also incorporated several years of HCTP historical sampling and testing data. Based on the results, LWA recommended multiple revisions to the Local Limits to better align with current operational and environmental conditions and to ensure continued protection of the HCTP and the surrounding environment.
Key changes to the Local Limits include:
•Stricter limits for pollutants such as arsenic, biochemical oxygen demand (BOD), cadmium, chloride, chromium, copper, cyanide, lead, mercury, nickel, selenium, and total suspended solids (TSS)
•Less restrictive limits for silver and total dissolved solids (TDS) •New limits proposed for ammonia (as nitrogen), molybdenum, and sulfate (as SO₄)
•No changes to the limits for boron and zinc
•Removal of limits for fluoride, total phenols, sulfide, and total identifiable chlorinated hydrocarbons, which are no longer considered pollutants of concern at HCTP
The study determined that the proposed adjustments more accurately reflect current wastewater characteristics and HCTP’s capacity to treat pollutant loadings, thereby ensuring continued compliance with federal environmental standards and its permit.
Staff from the LARWQCB were actively involved throughout the processes noted above. They reviewed and provided comments on the updated SUO as well as the Local Limits ordinance (Attachment #2). Staff reviewed and incorporated LARWQCB’s feedback and edits into the final drafts. After confirming that their recommendations had been addressed, LARWQCB determined that the proposed ordinances comply with federal Program requirements for development and implementation by POTWs. LARWQCB found the changes acceptable and granted approval to proceed with the Public Notice on December 13, 2024.
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City staff regularly engaged with the four local industries that hold Industrial Waste Discharge Permits to keep them informed about changes to the SUO and Local Limits. As required by federal regulations, the City issued a Notice of Intent to Adopt the SUO and Local Limits Ordinance updates (30-day Public Notice) on February 21, 2025. No comments were received by the March 24, 2025, deadline; therefore, LARWQB conditionally approved the Ordinances without change.
DISCUSSION/ANALYSIS:
The following is a summary of the more substantive changes to the SUO and Local Limits:
The SUO was updated to incorporate elements identified in the United States EPA’s Model Sewer Use Ordinance (2006), including updated definitions and confidentiality language to meet the federal requirements.
The City will implement a tiered permitting system as follows:
•Tier I – Significant Industrial Users
•Tier II – Non-Significant Industrial Users
•Tier III – Temporary Wastewater Dischargers
•Tier IV – Food Service Establishments
While the City already had the authority to condition permits as needed, depending on the level of potential impact of a discharge, the tiered permitting system helps better define the obligations required of different types of wastewater dischargers.
Local Limits development and implementation involve strategies to control the discharge of conventional and toxic pollutants entering the HCTP from dischargers to the sewer (e.g., Industrial Users). The objectives of the City’s updated Local Limits are to protect HCTP from:
•Interference and/or upset of treatment processes or operations •Pass-through of conventional and toxic pollutants into the environment •Non-compliance with current NPDES permit effluent limitations •Harm to the HCTP and/or collection system infrastructure •Contamination of municipal biosolids
•Worker health and safety issues related to hazardous substance exposure The updated Local Limit concentrations developed through the Local Limits Study are based on the sampling and analysis of water quality data collected from the City’s sewer collection system, various stages of the HCTP treatment process, and biosolids. These revised Local Limits (Attachment #3, pages 24–25) are designed to ensure continued compliance with the HCTP’s permit requirements.
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The City provided multiple opportunities for engagement with its permitted industrial users during the development of the Local Limits by informing the users of the upcoming revisions. The City met with these industrial users to discuss the proposed updates to the Local Limits and responded to their questions and concerns prior to issuing the Public Notice. The industrial users currently meet the proposed Local Limits. No comments were received during the Public Notice comment period.
Staff recommends the adoption of the updated SUO and Local Limits. These revisions reflect changes in federal regulations, provide flexibility for permitting different types of wastewater dischargers, and protect HCTP and the environment.
Pursuant to CEQA (Public Resources Code Section 21000 et seq.) Guidelines Section 15308, Class 8, “Actions by Regulatory Agencies for Protection of the Environment,” this action is exempt from further review under CEQA. The development and implementation of local effluent limits and discharge prohibitions are a requirement of the LARWQCB and are exempt from CEQA because they are an action pursuant to a regulatory requirement to ensure the protection of the environment, and involve procedures for environmental protection.
COUNCIL GOAL COMPLIANCE:
Meets the following City Council goals:
B. Provide municipal government leadership which is open and responsive to residents, and is characterized by ethical behavior, stability, promoting public trust, transparency, confidence in the future, and cooperative interaction among civic leaders, residents, business representatives, and staff, while recognizing and respecting legitimate differences of opinion on critical issues facing the City.
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 Jorgensen, Water Quality Supervisor
Jason Siegert, Environmental Compliance Analyst
Attachments:
Attachment #1 – Sewer Use Ordinance
Attachment #2 – Local Limits Ordinance
Attachment #3 – Local Limits Report
DPW:610-10; 530-25;290-50\ev\Council\2025\070825\Sewer Use and Discharge Local Limits Ordinance Updates staff report.docx