1-Hour SO2 Data Requirements Rule
1-HOUR SO2 DATA REQIIREMENTS RULE
On August 21, 2015, the Environmental Protection Agency (EPA) finalized the Data Requirements Rule (DRR) for the 2010 sulfur dioxide (SO2) standard. This rule required state agencies to characterize ambient SO2 levels in areas with large SO2 sources having the potential to impact compliance with the standard. Characterization was either through monitoring or modeling around sources that emit 2,000 tons per year or more of SO2. Based on the DRR, under 40 CFR §51.1203, each state was required to submit a list of applicable SO2 sources identified pursuant to 40 CFR §51.1202 by January 15, 2016. The second key requirement of the DRR was for the air agency to identify, for each listed source, the approach it would use to characterize air quality in the respective area by July 1, 2016. Please refer to the following documents for implementing the DRR and choosing ambient air quality monitoring to characterize SO2 air quality:
| Hawaii Submittals | EPA Response to Submittal |
| Modeling for Monitor Placement 1-hour SO2 DRR, Source List Submittal | |
| Amendment 1 to Final Report, Modeling for Monitor Placement 1-hour SO2 DRR, Source Characterization Submittal |
Two ambient air monitoring stations were installed on Oahu to satisfy the SO2 DRR which began collecting data on January 1, 2017. One monitor was located in the Pearl Ridge area to characterize SO2 air quality for the Waiau Generating Station. The other monitor was located in Makakilo to characterize SO2 air quality for the Kahe Generating Station, Kalaeloa Cogeneration Plant, and AES Hawaii, Inc. Cogeneration Plant.
Upon request by the state of Hawaii, EPA approved the discontinuation of the two DRR monitoring stations since the Waiau monitor showed design values less than 50% of the 1-hour SO2 standard and there was low chance of exceeding 80% of the standard for the Kahe/Kalaeloa/AES monitor. The request was made to close the Waiau SO2 monitor on May 15th 2020 and was approved by the EPA on October 8th, 2021. The request for the discontinuation of the Kahe/Kalaeloa/AES SO2 monitor was made on April 30th 2024 and was approved by EPA on July 26th, 2024. Please refer to the following documents:
| Hawaii Requests | EPA Response to Request |
| Waiau DRR Monitoring Station | |
| Kahe/Kalaeloa/AES DRR Monitoring Station |