California is considering the first-in-the-nation general industrial stormwater permit incorporating Total Maximum Daily Load (TMDL)-related numeric action levels (TNALs) and numeric effluent limitations (NELs). These new standards have the potential to further ramp up federal Clean Water Act (CWA) citizen suit litigation. Under the State Water Resources Control Board’s (State Board) proposed amendment to its stormwater general industrial permit (IGP), a “Responsible Discharger” whose stormwater discharge exceeds an applicable NEL automatically will be in violation of the IGP. Unless it complies with the permit’s existing exceedance response action process, it also will be in non‑compliance if its discharge exceeds an applicable TNAL.

Recognizing these consequences, and the difficulties some dischargers have complying with existing IGP requirements, the State Board is proposing two alternative compliance options. Touted as an effort to promote green infrastructure and water reuse, these options could revamp how industry manages stormwater. Both alternatives involve capture and reuse of the runoff from the 85th percentile 24-hour storm event, with the difference being the stormwater retention location. Under the “on-site” option, retention occurs at the facility. Under the “off-site” option, retention occurs at the local publicly owned treatment works (POTW).

TMDL Overview

TMDLs establish the maximum amount of a pollutant a water body can receive and still attain water quality standards. Under the CWA, states are required to identify “impaired water bodies,” i.e., water bodies that do not meet water quality standards. The TMDL establishes a pollutant reduction target and allocates load reductions among different pollutant sources. Point sources (such as discharges of stormwater under the IGP) are allocated waste load allocations (WLAs), and non‑point sources are allocated load allocations. In California, TMDLs are implemented by incorporation into State Board and Regional Water Quality Control Board (Regional Board) permits or orders.

Incorporating TMDLs into California’s IGP

Before TMDL obligations can be added to the IGP, the WLA attributable to industrial stormwater discharges needs to be “translated” to identifiable permit limits.

California TMDLs Applicable to Industrial Stormwater Discharges

Currently, four Regional Boards have adopted TMDLs applicable to industrial stormwater discharges. The Los Angeles Regional Board has adopted the most, with 25 for various water bodies or watersheds, each with its own specific pollutant(s) that include metals, nutrients, bacteria, toxics, pesticides, trash/debris, salts or sediments. The San Diego Regional Board adopted seven for water bodies impaired by bacteria, metals, nutrients, pesticides or sediments. The San Francisco Regional Board has a sediment TMDL for two discrete water bodies. Finally, the Santa Ana Regional Board has a single toxic pollutant TMDL.

Following their Spring 2016 release of proposed TMDL-specific permit requirements, the Regional Boards submitted their proposals to the State Board. Taking into account Regional Board and stakeholder input, the State Board proposed TMDL implementation limits (identified in revised proposed Attachment E). Citing the high variability of storm frequency and duration, the State Board proposed instantaneous maximum exceedances (rather than average annual exceedances), with compliance measured at the point of discharge. The proposed amendment anticipates incorporating future TMDLs applicable to stormwater discharges.

Responsible Dischargers

Only “Responsible Dischargers” need to comply with the State Board’s proposed TMDL-specific requirements. The proposal defines “Responsible Discharger” as an industrial discharger covered under the IGP that discharges stormwater to “impaired waterbodies or to any upstream reach or tributary to impaired waterbodies either directly or through a municipal separate storm sewer system (MS4) included in a U.S. EPA approved TMDL.” As drafted, this definition requires a discharger to know the water body receiving its stormwater discharge. Recognizing the difficulty this may pose, State Board staff are apparently working on interactive maps to assist dischargers in making this determination.

Provided a discharger discharges to an impaired water body with a stormwater-related TMDL, the proposed amendment envisions the discharger will utilize the existing pollutant source assessment process to determine whether its industrial activities are a potential source of a covered pollutant. Under the proposal, a Responsible Discharger needs to meet two prongs: (1) it discharges stormwater to an impaired water body with a WLA assigned to industrial stormwater dischargers, and (2) its activities are a potential source of a covered pollutant.

TMDL-Related Discharge Requirements

The State Board proposes three categories of TMDL-related discharge compliance actions: (1) IGP compliance; (2) TNAL compliance; and (3) NEL compliance. Which category applies to a Responsible Discharger depends on both the impaired water body and the pollutant at issue, with the specifics outlined in proposed Attachment E.

The State Board developed three categories because the information pertaining to industrial stormwater discharge WLA is not consistent among the various TMDLs. For example, IGP compliance is proposed where the TMDL development process limited WLA to generalized (as opposed to industrial) stormwater discharges. TNAL compliance is proposed where the receiving water body (rather than the point of discharge) was identified as the TMDL compliance point. Finally, NEL compliance is proposed where a WLA was specifically assigned to industrial stormwater discharges at the point of discharge.

Regardless of category, a Responsible Discharger still needs to comply with all other IGP requirements, including existing numeric action levels (NALs). Where TNALs apply, a Responsible Discharger whose discharge exceeds the TNAL remains in compliance with the IGP provided it follows the existing IGP exceedance response action process. However, a Responsible Discharger whose discharge exceeds an applicable NEL will no longer be in compliance with the IGP.

Alternative Compliance Options

Recognizing that many industrial dischargers subject to the IGP already struggle with meeting NALs and receiving water limits, and may have difficulty meeting the more stringent TNALs and NELs (e.g., a copper NEL of 0.0058 mg/L for Newport Bay, and a copper TNAL of <0.0098 mg/L for Los Cerritos Channel and Chollas Creek), the State Board has developed alternative “on-site” and “off-site” stormwater retention compliance options in its newly proposed Attachment I. While being offered as part of the TMDL incorporation process, these alternative compliance options, with their associated benefits, are available to all dischargers covered under the IGP. Both options involve capture and reuse of stormwater from the 85th percentile 24-hour storm event. The fundamental difference is where stormwater capture occurs.

On-Site Compliance Option

The on-site option provides dischargers with two choices for stormwater management:

  • Capture and on-site reuse, infiltration or evapotranspiration; or
  • Capture and diversion to a POTW.

Under either proposed approach, the discharger must capture the volume of stormwater runoff produced during the 85th percentile 24-hour storm event and recover this capacity within 24 hours, so that in the event of back-to-back storm events, the discharger has the ability to retain the required storm volume. While the 85th percentile 24-hour storm event design standard is part of the existing IGP advance BMP requirements, capacity to recover this amount within 24 hours is a new and substantially more stringent requirement. A host of additional requirements apply to the on-site infiltration option, including that influent entering the infiltration basin meet applicable drinking water maximum contaminant levels (MCLs). As needed, pretreatment is required to ensure MCL compliance, as is monthly groundwater monitoring.

For dischargers to utilize the capture and diversion approach, they must first obtain POTW approval, including a new or revised POTW permit. It remains to be seen whether POTWs will have the ability to accept the potentially large volumes of stormwater within 24 hours of a major storm event. Alternatively, discussions with State Board staff are ongoing that may enable Responsible Dischargers to retain stormwater for a longer period provided they have increased capacity.

Off-Site Compliance Option

California municipalities have begun to implement their municipal separate storm sewer system (MS4) permit requirements on a watershed scale, including regional projects that retain runoff from the 85th-percentile, 24-hour storm event. See, e.g., the Los Angeles County MS4 permit. The off-site option builds on the MS4 approach. With funding from industrial sources, municipalities will have additional revenue to support and expand their stormwater capture and reuse such that they are also able to retain the volume of runoff form the 85th percentile 24-hour storm event generated at industrial facilities. While not clear from the current proposal, according to State Board staff, off-site facilities will need to be able to recover the 85th percentile 24-hour storm event capacity within 24 hours for each industrial facility they cover.

As proposed, a discharger needs to comply with a variety of requirements to take advantage of the off‑site option including that its facility and the off-site facility are located in the same watershed, there is a “participation agreement” with the municipality that memorializes the discharger’s participation in the off-site option, and the Regional Board approves of the discharger’s participation. While the participation agreement is intended to define the parties’ respective obligations, the State Board’s proposal lacks detail on the agreement terms. At present, it is unknown what these agreements will look like and how liability for non-compliance with be allocated. Moreover, the proposed amendment provides little guidance on the Regional Board approval process.

Because the off-site option must be implemented and operational before it becomes a viable compliance option, and there are a host of details to be worked out with respect to the participation agreements and Regional Board approval, it could be years before dischargers will be able to take advantage of this compliance option.

Compliance Option Benefits

Under the proposal, once an alternative compliance option is “implemented and operational,” the discharger is deemed in compliance with the IGP’s receiving water limits, TNALs and NELs, NALs, general discharge prohibition, and technology-based effluent limitation requirements (but not industry-specific federal effluent limitation guidelines). Given the prevalence of CWA citizen suits, this relief is significant. This is particularly true with respect to NELs, where an exceedance could support alleged IGP non-compliance.

Next Steps

Public comment on the State Board’s proposal ended in February 2018. According to State Board staff, the Board is currently evaluating comments, and anticipates issuing a revised draft or a final IGP in fall or winter 2018.

Given the proposed amendment complexities and the potential for immediate non-compliance with the TMDL requirements, dischargers subject to the IGP who discharge stormwater to water bodies covered by the Los Angeles, San Diego, San Francisco or Santa Ana Regional Board TMDLs having industrial stormwater WLAs should evaluate whether they would be classified as a Responsible Discharger and, if so, what steps they may need to take to ensure compliance. At a minimum, this should involve (1) determining the TMDL-related limits applicable to their operation and re-evaluating their existing pollutant source assessment to ensure the findings remain accurate and current; (2) evaluating their ability to comply with applicable TNALs, and NELs (i.e., comparing their stormwater concentrations to applicable limits); (3) discussing with their municipality how it intends to proceed with the process of industrial stormwater discharger participation in the off‑site option, and the project construction timeline(s); (4) understanding the POTW requirements for, and willingness to accept, stormwater; and (5) evaluating the feasibility and cost of on-site retention of the 85th percentile 24-hour storm event.