New Los Angeles Regional Industrial Stormwater Permit

Author: Nathan Jong

On July 23, 2026, the Los Angeles Regional Water Quality Control Board (LARWQCB) adopted Order No. R4-2026-0226, National Pollutant Discharge Elimination System (NPDES) Permit No. CAS004005 (Order), a new regional stormwater permit that becomes effective on October 31, 2026. Unlike California’s statewide Industrial General Permit (IGP), this Order targets commercial, industrial, and institutional (CII) facilities located within the Dominguez Channel/Los Angeles and Long Beach Inner Harbor Watershed and the Los Cerritos Channel/Alamitos Bay Watershed.

The applicability of the Order depends on a couple of factors, primarily the type of operation and size of the facility, as well as the current coverage a facility might have. The Order identifies CII sites as privately owned parcels or contiguous parcels of land that are commercial, industrial or institutional based on Los Angeles County Tax Assessor land use codes 1000 through 2900, 3000 through 3920, 6000 through 6910, 7000 through 7710, and 8100 through 8400. Those sites that meet the CII definition must obtain coverage under the new Order if any of the following are true:

• Facility has five (5) or more acres of impervious surface (i.e., rooftop, concrete, asphalt) and is not covered by another NPDES stormwater permit.
• Facility has five (5) or more acres of total area and coverage under another NPDES stormwater permit (e.g., IGP), including those facilities where the following might apply:
  • Portions or all areas covered by a no exposure certification (NEC)
  • Facility has submitted a notice of non-applicability (NONA)
  • Facility has coverage under another NPDES stormwater permit for a portion of their facility, but additional area remains that is not included in that coverage (that additional area now requires coverage under the new Order)

Finally, facilities operating under an individual NPDES permit with requirements at least as stringent as the Order are exempt from requiring coverage. For affected facilities, this Order introduces a compliance framework that aligns with local water quality objectives and Total Maximum Daily Loads (TMDLs).

An Addition to the Traditional IGP Framework

Under the IGP, facilities are generally regulated through Numeric Action Levels (NALs), Numeric Effluent Limitations (NELs), and the Exceedance Response Action (ERA) process. In contrast, the Order focuses on achieving compliance with watershed-specific goals, targeting pollutants of concern associated with water quality impairments and TMDLs, such as metals, organics, legacy pesticides, and biological indicators. To accomplish this, the Order provides three compliance options. Facilities may participate in a regional watershed project, implement an on-site stormwater retention standard, or directly demonstrate compliance through monitoring and sampling. Once a facility selects a compliance option, it generally cannot change to another option for two years, making early planning and evaluation critical.

Three Compliance Pathways

Compliance Option 1: Participate in a Regional Watershed Project

The first option allows facilities to satisfy Order requirements by entering into an agreement with a local Watershed Management Group (e.g., Los Cerritos Channel Watershed Group, Beach Cities Watershed Management Group, and Long Beach Near Shore Watershed Management Area Group) and contributing funding toward an approved regional stormwater project. The required contribution is based on the facility’s proportion of runoff generated in the watershed. The funding level is calculated using the following formula:

Volume_{CII Facility} = On-site non-stormwater discharge (NSWD) volume plus stormwater runoff volume generated up to and during an 85^th percentile, 24-hour storm event minus the volume reduced by on-site Low Impact Development (LID) implementation

Volume_{Total Watershed} = Total watershed NSWD plus stormwater runoff volume from the applicable Watershed Management Program (WMP)

Total WMP Cost = Total cost to implement the Watershed Management Group’s WMP

For facilities with limited space or feasibility issues for on-site stormwater controls, this option may be the most practical solution. Facilities that comply with their funding agreement are compliant with the Order.

Compliance Option 2: Implement On-site Stormwater Retention

Facilities that choose the second option must design, construct, operate, and maintain stormwater controls capable of managing all non-stormwater discharges and runoff generated by the 85th percentile, 24-hour storm event.

Potential stormwater management approaches include:

• Infiltration systems
• Stormwater capture and reuse systems
• Evapotranspiration features
• Diversion to the sanitary sewer where approved
• Other structural and non-structural best management practices (BMPs)

This option places the responsibility for compliance directly on the facility through implementation of an approved design system. Facilities that maintain the required stormwater retention capacity are compliant with the Order.

Compliance Option 3: Direct Demonstration Through Monitoring

The third option allows facilities to demonstrate compliance through monitoring and analytical data and is most similar to the IGP. Facilities selecting this approach must develop and implement a site-specific Monitoring and Reporting Plan (MRP) and collect samples from four Qualifying Storm Events (QSEs) per reporting year. A QSE is a precipitation event that produces a discharge for at least one drainage area and is preceded by 48 hours with no discharge from any discharge area. The required monitoring schedule consists of:

• Two QSEs between July 1 and December 31
• Two QSEs between January 1 and June 30

Samples must be collected from all applicable drainage areas and discharge points within the required sampling window during each QSE. Although the number of sampled storm events is similar to the IGP, the pollutant list and monitoring expectations are considerably more extensive. Facilities that conduct the required sampling and reporting and demonstrate that their discharges meet the Order’s applicable water quality-based effluent limitations and watershed-specific requirements are considered compliant with the Order.

Annual Fees

Regardless of the compliance option chosen, facilities are required to pay an appropriate annual fee in accordance with the California Code of Regulations, title 23, section 2200 et seq. These fees are assessed by the State Water Resources Control Board based on the facility’s threat to water quality and complexity. Facilities are responsible for these recurring annual fees unless a valid Notice of Termination (NOT) is officially submitted and approved via SMARTS. Facilities should plan to account for these regulatory costs alongside any option-specific expenses, such as regional project contributions under Option 1, system maintenance under Option 2, or laboratory analysis costs under Option 3.

Expanded Monitoring and TMDL-Focused Requirements

One of the most significant differences from the IGP is the expanded monitoring tied directly to regional water quality impairments and TMDL requirements. Existing facilities must complete an initial characterization sampling effort and submit analytical results within 18 months of the Order’s effective date. This evaluation is intended to determine whether a facility has the potential to discharge pollutants at levels that could contribute to exceedances of applicable water quality objectives. In addition, facilities may be required to monitor for a broader range of pollutants than those associated with the IGP. Depending on facility operations and pollutant sources, monitoring may include:

• Metals
• Polychlorinated biphenyls (PCBs)
• Polycyclic aromatic hydrocarbons (PAHs)
• Indicator bacteria
• Legacy pesticides such as dichlorodiphenyltrichloroethane (DDT), chlordane, and dieldrin
• Pyrethroid pesticides including bifenthrin, cyfluthrin, cypermethrin, and permethrin
• Fipronil

Unlike the IGP, which relies primarily on written logs for visual observations, the Order introduces mandatory photographic documentation requirements. Dischargers must provide timestamped photographs matching the exact date and time of visual observations. These photographs must document authorized NSWDs, BMPs, outdoor equipment, and the presence or absence of pollutants such as oil, grease, turbidity, and trash. Additionally, if no discharge occurs during a QSE, dischargers must still take timestamped photographs of the discharge locations to prove the absence of discharge. They must also photograph any bypass events exceeding the design volume of on-site controls.

Reporting Requirements

Reporting timelines have changed compared to the IGP. Under the IGP, analytical results are typically uploaded via SMARTS within 30 days of receiving laboratory results. Under the Order, routine monitoring data must be reported within 45 days after the end of each semi-annual monitoring period. Reporting periods remain July 1 through December 31 and January 1 through June 30. Facilities should also be aware of the revised annual reporting schedule. Annual reporting is due by December 15, replacing the familiar July 15 reporting deadline used under the IGP. Facilities should account for this new reporting cycle when planning sampling, data review, and SMARTS submittals.

What are My Next Steps?

For existing dischargers transitioning from the IGP, a Notice of Intent (NOI) and an updated site-specific Stormwater Pollution Prevention Plan (SWPPP) must be submitted via SMARTS within 12 months of the Order’s effective date (by October 31, 2027). As previously mentioned, initial characterization sampling and laboratory analytical results must be submitted within 18 months (by April 30, 2028). Facilities must also submit their final Compliance Option Documents, such as a signed agreement with a local Watershed Management Group for Option 1 or site-specific MRP for Option 3, via SMARTS within 3.5 years of the effective date (by April 30, 2030). For new dischargers, they must submit Permit Registration Documents (PRDs) via SMARTS at least 45 days prior to discharging, which includes a completed NOI, an updated SWPPP, initial characterization sampling results, and selected Compliance Option Documents.

Key Takeaways

The Order has some significant differences from the IGP. Facilities that are currently under the IGP and meet the applicability criteria must obtain coverage under the new Order. Rather than relying primarily on NAL exceedances and the ERA process, the Order provides facilities with three distinct compliance pathways: participating in regional watershed projects, implementing on-site stormwater retention controls, or demonstrating compliance through expanded monitoring. Facilities located within the affected watersheds should begin evaluating site conditions and monitoring obligations well before the Order’s October 31, 2026 effective date to determine which compliance option best supports their stormwater compliance strategy. For questions about this topic or how it may affect your facility, contact Nathan Jong (njong@all4inc.com) or Lizzie Smith (lsmith@all4inc.com).