2.1 Regulatory Framework

The Alaska Department of Environmental Conservation (DEC) is required by 40 CFR 58.10 to establish and maintain an air quality surveillance system, including State and Local Air Monitoring Stations (SLAMS), National Core Multi-Monitoring (NCore) stations, PM_2.5 Chemical Speciation Network (CSN) stations, and Special Purpose Monitoring (SPM) stations. This plan ensures compliance with federal regulations, including 40 CFR 58, Appendices A, C, D, and E, which cover data quality assurance, monitoring methods, network design criteria, and specific location criteria. DEC’s monitoring network is designed to meet these requirements while addressing Alaska’s unique environmental and geographic challenges.

2.2 Monitoring Priorities and Strategy

DEC prioritizes monitoring the six criteria pollutants regulated under the National Ambient Air Quality Standards (NAAQS): particulate matter PM_2.5 and PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), ozone (O₃), and lead (Pb). Monitoring efforts are focused on population centers such as Anchorage, Fairbanks, and Juneau, as well as rural and remote areas where unique sources like wildland fires, road dust, and biomass burning significantly influence air quality. DEC collaborates with local governments and tribal villages to ensure comprehensive coverage, particularly for PM₁₀ in rural communities and PM_2.5 during wildfire seasons. This strategy aligns with federal requirements while addressing Alaska’s distinct air quality challenges.

2.3 Current Monitoring Network

As of May 2024, Alaska’s ambient air monitoring network includes the following sites, strategically located to meet minimum monitoring requirements for Alaskan Core-Based Statistical Areas (CBSAs).

Detailed information for each site, including sampling methods, operating schedules, and compliance with siting criteria, is provided in Section 3 of this plan. The network exceeds minimum requirements in several areas, particularly for PM_2.5 and PM₁₀, ensuring robust data collection for public health protection.

2.4 Compliance with Federal Standards

DEC ensures compliance with federal standards through:

• Network Evaluation Forms: Completed for each criteria pollutant under 40 CFR 58, Appendix D, confirming that the network meets design and minimum monitoring requirements.

• Siting Evaluation Forms: Completed under 40 CFR 58, Appendix E, ensuring proper siting of all monitors.

• Data Quality Assurance: Adherence to 40 CFR 58, Appendix A for SLAMS and SPM monitors.

• Monitoring Methods: Compliance with 40 CFR 58, Appendix C for approved monitoring methods.

• Waivers: Any waivers requested or granted by the EPA Regional Administrator are detailed in Section 8.

2.5 Planned Enhancements

To enhance monitoring capabilities, DEC is expanding its low-cost sensor network, currently consisting of 55 QuantAQ Modular^TM sensor pods. These sensors provide real-time data in rural and outlying communities, improving coverage and enabling quicker responses to air quality events. As of May 2025:

• Regulatory Sites: 5 pods are operational at NCore (Fairbanks), Garden (Anchorage), and Floyd Dryden (Juneau).

• Rural Communities: 36 pods are deployed across Alaska, including Big Lake, Cordova, Denali National Park, and others.

• Future Expansion: Research into WiFi-enabled sensors is underway to expand coverage in areas with limited cellular service.

Additionally, DEC plans to discontinue CO monitoring at the Garden site, pending EPA approval of a State Implementation Plan (SIP) modification, to optimize resources while maintaining compliance.

2.6 Public Engagement

This plan was made available for public inspection and comment for at least 30 days prior to submission to the EPA, as required by 40 CFR 58.10. The plan is accessible via the DEC website. All comments received have been reviewed and addressed as appropriate in this final version. DEC values public input and encourages continued engagement to ensure transparency and stakeholder involvement.

3.1 Minimum Monitoring Requirements

3.2 Current Monitoring Sites

The DEC operates and maintains a network of regulatory monitoring sites to ensure compliance with the NAAQS. Table 5 provides the site name, address, geographic coordinates, and identification number for all air monitoring sites submitting data to the EPA Air Quality System (AQS) database as of May 2025.

The parameters measured at the NCore site include PM₁₀, PM_2.5, PM_10-2.5 (coarse fraction), CO, O₃, SO₂, NO_y, NO, PM_2.5 chemical speciation, and meteorological parameters.

There are three collocated sites: Garden (PM_2.5 and PM₁₀), Hurst Road (PM_2.5), and A Street (PM_2.5), which are described further in Table 22. All the primary and secondary monitors at these locations are situated within one to four meters of each other to ensure data comparability. A full list of parameters measured at each site is described in Table 5.

3.3 Siting Criteria

The DEC ensures that its eight ambient air monitoring sites comply with siting criteria outlined in 40 CFR Part 58, Appendix E. These criteria guarantee accurate and representative air quality data, critical for public health and regulatory compliance.

In 2014, EPA Region 10 provided site evaluation forms to assess compliance with the probe and monitoring path siting criteria specified in 40 CFR Part 58, Appendix E. These forms were distributed to the individual site operators for completion. Summaries of the completed site evaluation forms are organized into three tables – PM, CO and all other gaseous pollutants – and are presented in Section 10 of this report.

Monitoring site photos and location maps can be found at: https://dec.alaska.gov/air/air-monitoring/instruments-sites/.

The operation of each monitoring site complies with the requirements outlined in 40 CFR Part 58, Appendix A. Furthermore, all SPM sites are operated following the same protocols as SLAMS, thereby ensuring full compliance with these requirements.

3.4 Monitoring Methods, Designation, and Sampling Frequency

The Alaska Department of Environmental Conservation (DEC) operates an ambient air monitoring network to measure air quality across eight sites in Alaska. This section details the monitoring methods, designations, and sampling frequencies used to collect data on pollutants such as particulate matter (PM_2.5, PM₁₀), carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), reactive nitrogen compounds (NO_y), and meteorological parameters. These methods ensure compliance with federal regulations under 40 CFR Part 58, providing accurate data for public health protection, regulatory compliance, and research. Detailed data for each site, including pollutant parameters, AQS codes, and equipment, is presented in Table 9, Table 10, Table 11, Table 12, Table 13, Table 14, Table 15, and Table 16, with summaries provided below.

Monitoring Methods and Designations

Monitoring methods are the techniques used to measure air pollutants, designated as reference or equivalent by the U.S. Environmental Protection Agency (EPA). Reference methods are federally approved standards, while equivalent methods meet specific performance criteria. Designations indicate the purpose of the data collected, categorized as:

• SLAMS (State and Local Air Monitoring Stations)

  • Demonstrate compliance with National Ambient Air Quality Standards (NAAQS).

• SPM (Special Purpose Monitors)

  • Conduct general air quality assessments, such as research and trend analysis.

• CSN (Chemical Speciation Network)

  • Evaluate atmospheric chemistry to understand pollution sources.

The EPA’s Air Quality System (AQS) database uses specific codes to standardize data:

• Parameter Codes

  • 5-digit codes identifying pollutants (e.g. PM₁₀, SO₂, wind speed).

• Parameter Occurrence Codes (POCs)

  • 1-digit codes indicating the sampler’s role:

    • 1: Primary data source

    • 2: Secondary (collocated) source

    • 3: Continuous measurement

• Method Codes

  • Describe analytical techniques (e.g. chemiluminescence for nitric oxide, gravimetric analysis for particulate matter).

Sampling Frequency

Sampling frequency indicates how often pollutant concentrations are measured, determined by federal regulations to ensure sufficient data for NAAQS compliance and public health monitoring. Frequencies are tailored to each pollutant and site, based on 40 CFR Part 58, Appendix D for particulate matter and Appendix C for gaseous pollutants.

Common notations include:

• 1/6

  • One sample every sixth day, following EPA’s national monitoring schedule¹⁴.

• Continuous

  • Real-time or near-real-time measurements (e.g. 1-minute SO₂ readings, 1-hour PM_2.5 readings via BAM).

Equipment and Additional Monitoring

Each monitoring site uses specific equipment tailored to the pollutants measured, listed in Table 9, Table 10, Table 11, Table 12, Table 13, Table 14, Table 15, Table 16, and Table 17 with corresponding AQS parameter codes. The DEC also operates additional sites for rural road dust and wildland fire monitoring, which are not submitted to the AQS database; details are in Section 11. Alaska participates in the Interagency Monitoring of Protected Environments (IMPROVE) network, focusing on scenic visibility in National Parks and wilderness areas, described in Section 12. A Summary of pollutant concentration data (NAAQS design values, maxima, averages) is provided in Section 6.

Compliance Summary

The DEC’s monitoring methods, designations, and sampling frequencies meet or exceed federal standards, ensuring reliable air quality data across Alaska. By adhering to 40 CFR Part 58, the network supports public health, regulatory compliance, and research. Detailed information is available in Appendices A, E, F, and G, and on the DEC’s Air Monitoring Website.

3.5 Monitoring Waivers

4.1 Anchorage Garden Site CO monitoring

Over the past two decades, carbon monoxide (CO) concentrations in Anchorage have declined significantly, with no exceedances of the NAAQS reported. For the past three years, 8-hour maximum CO values have remained below 30% of the NAAQS and have not exceeded 41% in the last 10 years.

Given these sustained low concentrations, the DEC will seek a State Implementation Plan (SIP) modification to conclude the second 10-year Limited Maintenance Plan period. The DEC plans to continue CO monitoring as long as the instrument remains operational until the modification is approved. If the monitor fails and is not repairable, DEC has a sensor pod at the station with a collocation history with the regulatory monitor and may inform DEC of any need for contingency measures, until the SIP modification is approved.

4.2 National Core Multipollutant Site

In 2025, the BAM 1020 PM_2.5 monitor was upgraded to FEM status, by replacing a sharp cut cyclone (SSC) with a very sharp cut cyclone (VSCC).

5.1 Regulatory Monitoring Stations

At this time, the DEC does not anticipate any changes to the regulatory ambient air monitoring network for 2026.

5.2 Low-Cost Sensor Network

While the existing long-term regulatory monitoring network meets federal requirements for the number of stations and pollutants monitored, it is primarily limited to Alaska’s population centers and does not adequately characterize conditions in outlying and rural communities.

Recent advances in sensor technology have enabled the development and commercial availability of smaller, portable, and more affordable air quality sensors. This new generation of low-cost sensor technology provides the DEC with the opportunity to expand air quality monitoring into areas that were previously cost-prohibitive to reach.

Beginning in 2023, the DEC launched the Community-Based Air Monitoring project, deploying QuantAQ MODULAIR^TM low-cost sensor pods across the state. The sensor network is designed to provide real-time air quality data and trend information, empowering community members to better understand baseline air quality in their areas. While the data collected are non-regulatory, they are available to the public upon request and are displayed in real time on the DEC’s website²⁰.

The QuantAQ MODULAIR^TM sensors measure particulate matter (PM_2.5 and PM₁₀), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO₂), ozone (O₃), temperature, and relative humidity. As of 2025, the DEC operates 55 Quant AQ Modulair^TM sensor pods statewide.

These sensor pods are deployed in a wide range of communities, including: Anchorage (Campbell Creek Science Center), Big Lake, Cordova, Delta Junction, Denali National Park, Fairbanks (2 sites: Goldstream and Badger Road), Galena, Glennallen, Haines, Homer, Hoonah, Juneau (2 sites: 5^th Street and the State Museum), Kenai, Ketchikan, Kodiak, Kotzebue, Napaskiak, Nenana, Ninilchik, Nome, Palmer, Seward, Sitka, Skagway, Soldotna, Sutton-Alpine, Talkeenta, Tok, Tyonek, Valdez, Wasilla, Willow, Wrangell, and Yakutat. Additionally, six quality assurance sensor pods are collocated at regulatory monitoring sites: Fairbanks NCore (3), Anchorage Garden (2), and the Juneau Floyd Dryden (1).

During the initial rollout, the DEC identified that cellular network coverage in some Alaskan communities was incompatible with the communication systems of the primary sensor pod manufacturers. To address this, the DEC is actively researching alternative WiFi-enabled sensors to further expand the network in areas where cellular service is limited or unavailable.