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Comment Period

Intalco aluminum smelter

Sulfur dioxide attainment plan

Sept. 7, 2022 - Oct. 15, 2022, 11:59 p.m.

We invite you to comment on the air quality attainment plan (State Implementation Plan revision) and Agreed Order to bring the area around the curtailed Intalco aluminum smelter back into compliance with federal regulations for sulfur dioxide pollution.

The proposed plan describes actions the facility will have to take, including:

  • Installing and operating new sulfur dioxide (SO2) controls
  • Merging and increasing the height of stacks
  • Limit facility-wide and unit-specific SO2 emissions
  • Different scenarios if the facility should restart before or after April 30, 2025

Why is this important?

Breathing elevated levels of SO2 causes inflammation and tightening of airways and can trigger asthma symptoms. SO2 typically dissipates very quickly, but people living or working close to sources may be exposed to short-term levels that pose a risk to those with pre-existing breathing or health issues. SO2 pollution also decreases visibility in the form of haze and contributes to acid rain.


All areas in Washington state must meets national air quality standards for the  six most common air pollutants. One of those pollutants is SO2.

  • From 2017-2019, when the aluminum smelter was operating, we worked with Northwest Clean Air Agency to evaluate air quality data from Whatcom County. Data from monitors near Intalco showed SO2 levels that exceeded national air quality standards.
  • In Dec. 2020, EPA designated part of Whatcom County near the smelter to be in nonattainment for this standard. (EPA's decision and response to comments)
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Comment by mail

Kelsey Holbrook
Industrial Section
P.O. Box 47600
Olympia, WA 98504-7600
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Anya Caudill
State Implementation Plan Lead

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