The Bay Area Air District (the District) is seeking public input on its April 16, 2026 concept paper outlining various proposals for a Warehouse Indirect Source Rule (ISR) to regulate emissions of nitrogen oxides (NOx), Particulate Matter (PM), and Diesel PM (DPM) for emissions sources related to warehouse functions. While no draft regulatory language has been proposed yet, the concept paper contemplates various applicability criteria and potential compliance obligations based on the implementation of other ISRs across the state. The District is mainly evaluating the activity-based South Coast Air Quality Management District (SCAQMD) Warehouse Actions and Investments to Reduce Emissions (WAIRE) rule and the facility-specific target-based San Joaquin Valley Air Pollution Control District (SJVAPCD) Rule 9510. The District has signaled that whichever pathway is chosen, there will be an emphasis on reducing emissions and focusing on health-risk benefits in overburdened communities (OBCs).
Potential Applicability
In the concept paper, the District contemplates applicability criteria that pull in various numbers of facilities. For reference, SCAQMD’s WAIRE Rule applies to warehouses of a floor area of 100,000 square feet or larger. SJVAPCD’s Rule 9510 applies to new developments which meet various square footage criteria, depending on project classification (e.g., 125,000 square feet of light industrial space for a large development project).
At this time, the District’s applicability would be based total square footage and location for its ISR applicability. The level of square footage that would be regulated is under consideration, depending on the number of potentially regulated facilities, the overall emissions benefit, and implementation burden (both on the District and regulated community). A sensitivity analysis is presented in the table below. Additionally, the District has also signaled that location as another criterion (i.e., whether the warehouse is in an OBC).
| Warehouse Floor Area (square ft) | Number of Warehouses | Total Floor Area (square ft) | Number of Warehouses in OBCs | Percent of Total Warehouse Floor Area | Percent of Warehouse Floor Area in OBCs |
| 450k+ | 50 | 38,865,787 | 15 | 8% | 30% |
| 350k – 450k | 36 | 14,167,491 | 12 | 3% | 33% |
| 250k – 350k | 121 | 34,819,276 | 46 | 7% | 38% |
| 150k – 250k | 297 | 57,399,770 | 119 | 12% | 40% |
| 100k – 150k | 521 | 62,061,949 | 194 | 13% | 37% |
| 50k – 100k | 1,268 | 88,539,393 | 442 | 18% | 35% |
Additionally, the concept paper discusses that there may be different applicability thresholds depending on the location of the warehouse. Similar to its permitting rules (Rule 2-1 and Rule 2-5), the District will likely have a lower applicability threshold for its ISR for warehouses in OBCs.
The potential ISR would apply to warehouse owners and operators who are responsible for facility operations and logistics decisions. Compliance with the District’s ISR would be achieved through the potential options discussed below.
Implementation of the ISR would occur in a two-phased structure. The first phase would focus on collecting data and realizing near-term emissions benefits via establishing reporting requirements and offering a menu of compliance options. Fleet and operational data collected during this phase would be used to inform the second phase. The second phase would implement more targeted requirements based on health risk and/or operational characteristics. In particular, the second phase would focus on reducing health risk exposure in OBCs (including AB617 communities). Phase in requirements could be similar to WAIRE’s three-year phase-in based on facility size or location. Baseline and target structure could be considered to cater compliance to each specific site.
Compliance Mechanisms
The District is also contemplating various compliance mechanisms for warehouses that are pulled into the ISR. The options include the following:
- WAIRE-style annual obligation based on truck activity but aligned with Bay Area goals, such as targeted reduction specific to exposure disparities in impacted communities.
- A facility-specific emissions reduction requirement (e.g., % reduction from baseline by a target year) with the possibility of more stringent or accelerated targets in OBCs.
- A simplified, screening-based approach based on facility size, location, number of loading docks, etc., that places facilities into tiers of compliance obligations without requiring truck activity data.
- A two-stage approach involving setting an initial obligation with refinement after additional data or health risk assessments are completed.
WAIRE-Like Compliance
The District has specified that WAIRE’s menu-based compliance structure remains an attractive option due to the effort needed to establish quantitative baseline and emissions targets for individual facilities. In WAIRE, facilities earn points or credits through actions such as:
- Utilizing zero-emission (ZE) or near-zero-emission (NZE) trucks;
- Acquiring or using ZE or NZE equipment at their sites;
- Electrifying transport refrigeration units;
- Installing cleaner forms of emergency power generation;
- Increasing electric vehicle charging capacity of hydrogen fueling infrastructure;
- Installing anti-idling technology such as zero-emission auxiliary power systems;
- Increasing operational efficiency (e.g., decreasing number of truck trips) to reduce emissions;
- Installing exposure-reduction measures (e.g., indoor air filters) at nearby sensitive receptors; and/or
- Paying a mitigation fee.
The mitigation fee would be structured to support locally-focused incentives or emission reduction programs, particularly in OBCs.
Other compliance options the District is contemplating include:
- Custom compliance plans;
- Limits on point transfers; and
- Compliance structure options.
Reporting
The District plans to implement a robust and consistent reporting structure for the ISR. The potential reporting mechanism contemplates:
- An initial Warehouse Operations Notification (WON) with identifying information for each facility (warehouse area, tenant occupancy, contact information);
- An Initial Site Information Report to establish applicability and a baseline. This report would include fleet composition, truck trip data, onsite infrastructure, and planned compliance actions; and
- Annual Report that would include truck trips, fleet changes, and compliance activities.
Additionally, the District signaled that the reporting elements may go beyond those used in the WAIRE program, such as information related to fleet ownership vs contracted fleets, and other necessary data to further the District’s health-focused approach such as truck classes and distance from sensitive receptors.
Timeline
The District is accepting public comments on the concept paper through June 1, 2026. Public comments can be submitted through email at [email protected] or by mail. The District plans to hold public workshops and targeted meetings during the Summer of 2026. Based on prior meetings, it would take about three years for the ISR to undergo the rulemaking process and be finalized. Interested parties can review the concept paper and additional documents when they become available on the District’s website.
If you would like to discuss the potential ISR and how it may impact your facility please contact Stephen Cao Trinity’s Oakland office or call 510.285.6351.
