The Oregon Department of Environmental Quality (Oregon DEQ) has established a fast-track permitting pathway for data centers seeking a Standard Air Contaminant Discharge Permit (ACDP) through the exclusive use of EPA Tier 4-certified or Tier 2 certified diesel fired engines equipped with Tier 4-equivalent emission controls for critical generators. This initiative was developed in response to the rapid expansion of data centers in Oregon and aims to promote economic development of cleaner, lower-emission backup power technologies.

Data centers primarily rely on the electrical grid for normal operations, but use diesel fired engines to maintain operations during power outages. To ensure the engines are available during a power outage, data centers perform regular maintenance and testing operating engines for short periods of time on a regular cadence. Most facilities in Oregon currently operate EPA Tier 2 certified diesel fired engines. Tier 4 certified or Tier 4 equivalent engines have additional control of diesel particulate matter (DPM), particulate matter (PM/PM₁₀/PM₂.₅), nitrogen oxides (NOₓ), volatile organic compounds (VOCs), carbon monoxide (CO), and other hazardous and toxic pollutants.

To encourage industry transition to cleaner equipment, Oregon DEQ offers expedited ACDP processing for data centers implementing Tier 4 or Tier 4 equivalent systems on critical generators. The program streamlines the permitting process by removing the requirement for facility-specific dispersion modeling for short-term National Ambient Air Quality Standards (NAAQS) compliance. Additionally, Oregon DEQ has developed a Cleaner Air Oregon (CAO) Data Center Tool to eliminate the need for the previously required Level 3 Risk Assessment.

This permitting pathway is voluntary and used as an incentive program for data center facilities willing to implement more stringent pollution control devices. Facilities are still able to obtain a Standard ACDP through OAR 340-216 without additional controls.

Click here to learn more about this program on the ODEQ website.

How to Qualify for the Fast Track Application Process

To qualify for a permit under this expedited process, data centers must meet the following standards:

1. Engine Certification

All critical load backup engines must be EPA Tier 2 certified.

2. Emission Control Requirements

All critical load backup engines must be equipped with control technologies, including but not limited to:

1. Selective Catalytic Reduction (SCR), Diesel Oxidation Catalyst (DOC), and Diesel Particulate Filter (DPF); or
2. SCR and Catalyzed Diesel Particulate Filter (cDPF).

Each engine must include at least one of these combinations or equivalent control technologies to qualify for this program. Note Tier 4 certified units have the emission controls noted as part of their design. The certification standards for Tier 2 and Tier 4 engines are defined in 40 CFR Part 60, Subpart IIII, and the additional emission controls listed above must be incorporated to meet program requirements.

Note: A critical load engine refers to stationary engines that provide emergency backup power to equipment within one or more data center rooms. Non-critical load engines do not provide backup power for equipment but instead may be used onsite for ancillary facility-power needs.

Additionally, as part of this program facilities will have to demonstrate compliance with the data center SET for NO_x (50 lb/hr) by participating in one of the following options:

1. Testing and Maintenance (T&M) Plan with SET Analysis

The facility submits a T&M plan and supporting SET analysis demonstrating how operations will remain below the 50 lb/hr NOₓ threshold.

2. Operational Calculation Method

The facility calculates the maximum number of emergency generator engines that may operate simultaneously during one hour using the equation provided in Oregon DEQ’s permit template for short-term NAAQS compliance.

Note: When this option is used, the equation and associated limits will be incorporated as enforceable permit conditions.

Note: All planned maintenance and readiness testing of the engines must be initiated between the hours of 6:00 am and 5:30 pm and must conclude before 6:00 pm. This stipulation must be included in the T&M plan as outlined in the ACDP permit template for this program.

Oregon DEQ has created a data center-specific Standard ACDP permit template to standardize permit conditions for qualifying facilities and further expedite the overall permit drafting and review process. The template can be found here: Tier 4 Data Center Permit Template. A full description of the NAAQS and CAO application components are further detailed below.

The entirety of this application process will take place in the Your DEQ Online (YDO) program, and Oregon DEQ has developed a detailed submittal guide for the required YDO submissions here: YDO Submittal Guide: Tier 4 Streamlined Data Center Permit

Application Components – NAAQS Compliance Demonstration.

Data centers are unique for air dispersion modeling procedures due to the inherent intermittent nature of emissions. Oregon DEQ’s current pathways to screen out of more complex modeling and demonstrate compliance with short term NAAQS are created for facilities that are expected to operate continuously. As part of this program, Oregon DEQ has created data center specific pathways to showcase compliance with short term NAAQS standards for participating facilities. Based on these determinations, a site specific air dispersion model is not required to obtain a Standard ACDP, instead the facility is able to showcase compliance as described below.

1-hour NO₂ NAAQS: Oregon DEQ has established a data center-specific Significant Emission Threshold (SET) for NOₓ. The SET is 50 pounds per hour (lbs/hr) of NOₓ during scheduled maintenance and testing. This threshold excludes emergency operation and new engine commissioning. NOx controls have a startup period which will delay control of these emissions until the desired temperature is achieved. Therefore, a facility will be required to consider time then engine(s) are in operation with active NOx control and without in the determination of facility-wide emission rate(s). When facility-wide hourly NOₓ emissions remain below this 50 lb/hr level, refined dispersion modeling for short-term NO₂ compliance is not required.

PM_2.5 NAAQS: Oregon DEQ determined that a specific SET for PM₂.₅ is not necessary because facilities using this expedited permitting process are required to install Diesel Particulate Filters (DPFs) on Tier 2 engines or use Tier 4 certified engines. Oregon DEQ determined that any facility meeting the NOₓ SET will inherently comply with the 24-hour PM₂.₅ NAAQS.

SO₂ NAAQS: Compliance with the SO₂ NAAQS is expected since federal standards in 40 CFR Part 60, Subpart IIII (NSPS IIII) limit fuel sulfur content, and backup engines are required to use ultra-low sulfur diesel. As a result, Oregon DEQ determined that facilities meeting the NOₓ SET will also comply with the 1-hour SO₂ NAAQS.

Application Components – Cleaner Air Oregon.

Oregon DEQ has also developed a CAO Data Center Tool that performs a facility-specific risk assessment and generates annual and daily fuel limits based on site/engine specific information such as stack height, building height, and engine fuel usage, and regional meteorological data. The purpose of this tool is to provide a standardized and conservative modeling approach that any data center using the fast-track permitting program can apply to meet the requirements of a Level 2 Risk Assessment under the CAO program.

This tool was developed using Toxic Air Contaminant (TAC) source testing data collected from a variety of engines operating under different loads in Oregon. This expanded dataset allows for more representative and realistic emissions modeling for newer engine technologies. To allow a facility wide throughput determination, the tool identifies the top 10 highest-ranking generators for a specific facility design and calculates either a risk or fuel limit for each generator until the overall facility limit is reached. Each generator is initially assigned 100 hours per year and 12 hours per day of operation.

• If the facility-wide risk or fuel limit is not reached after assigning the top 10 generators, any remaining allowable risk or fuel is allocated to the 10th-ranked generator.
• Alternatively, if the limit is reached by the first-ranked generator, all remaining emissions are assumed to come from that generator.

The tool produces results based on the risk basis selected by the facility. Facilities can choose between two approaches, depending on how they wish to manage compliance with CAO requirements for TAC emissions:

1. Risk results based on desired fuel limits, or
2. Risk results based on specified Risk Action Levels (RALs)

Facilities may either base their CAO risk calculations on facility-wide fuel use limits (in gallons per year and gallons per day) or define specific RALs that align with their operational needs. The tool will then calculate the corresponding fuel limits required to maintain risk levels below the chosen RALs.

A final Level 2 Risk Assessment result summary and AQ520 form will be provided for submittal as the output of this tool and to include in the application.

For more information, contact Beth Ryder or the Trinity Portland Office today!