Alcoa Intalco

All areas in Washington state must meet national air quality standards for the six most common air pollutants. One of those pollutants is sulfur dioxide (SO₂).

• From 2017 – 2019, we worked with the Northwest Clean Air Agency to evaluate air quality data from Whatcom County. Data from monitors near Intalco showed SO₂ did not meet the national standard.
• In December 2020, the U.S. Environmental Protection Agency (EPA) designated part of Whatcom County near the smelter to be in nonattainment for this standard. (EPA's decision and response to comments).

State Implementation Plan

A State Implementation Plan (SIP) is a general cleanup plan for air.  It describes how Washington carries out, maintains, and enforces national air quality standards.

The SIP explains how Washington will lower air pollution from sources like transportation, wood smoke, and industry. Sections of the plan are customized to meet regional air quality needs.

We propose to send EPA the revised air quality State Implementation Plan (SIP).

The revised SIP:

• Shows that the Intalco‑Ferndale Sulfur Dioxide Nonattainment Area has improved air quality and is meeting (attaining) the federal air quality standard for sulfur dioxide.
• Includes a 10‑year maintenance plan for the area.

The Intalco-Ferndale Sulfur Dioxide area is a 5.5-square mile area in Whatcom County around the site of the former Intalco aluminum smelter. The smelter permanently closed in 2023. No other areas in Washington are affected by this action.

The federal Clean Air Act requires a maintenance plan in order to redesignate a nonattainment area.

Next steps

A public comment period is now open through April 26, 2024.

EPA’s oversight of the plan is required under the federal Clean Air Act, and it will provide an opportunity for an additional public comment before making a final decision. Once approved by EPA, the requirements of the state implementation plan become federally enforceable.

Why this is 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.

Join our sulfur dioxide attainment email list to learn more about our efforts to monitor and evaluate SO₂ levels in Washington.

Updated March 28, 2024