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ACHD Announces SO2 Exceedance, Says June 17 Edgar Thomson Plume Due to Valve Failure

Updated: Sep 14, 2022

The Allegheny County Health Department (ACHD) on Thursday announced that according to preliminary data from the North Braddock air quality monitor, there was a sulfur dioxide exceedance earlier today. It also announced that an emissions plume emanating from U.S. Steel’s Edgar Thomson Works was due to a valve failure at the plant.

Here’s the message ACHD sent out through the Allegheny Alerts system:

ACHD has preliminary information that the North Braddock sulfur dioxide (SO2) monitor measured .079 parts per million (ppm) at 2 a.m. this morning.

This level exceeds the federal standard for an hourly SO2 exceedance of .075 ppm. ACHD is investigating this potential exceedance, including verifying the data.

Additionally, ACHD received many questions and concerns regarding an emission plume observed at U.S. Steel’s Edgar Thomson Works the evening of June 17. U.S. Steel has told ACHD that a valve failed to open during the startup of a blast furnace after being shut down for routine maintenance.

ACHD continues to investigate this incident.

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