U. S. STEEL’S CLAIRTON PLANT

At U. S. Steel, environmental stewardship is a top priority.

U. S. Steel has invested hundreds of millions of dollars in environmental improvements, including over $50 million in Clairton improvements as part of the plan we submitted to the Allegheny County Health Department (ACHD) in August 2018 and to which the ACHD approved. Those improvements, as well as the hiring of over fifty new employees to work at Clairton Plant on coke oven battery operations and maintenance, have helped make 2018 the best year ever recorded for PM2.5 at the Liberty Monitor in Allegheny County.

In 2018, we also completed an over $40M investment on time, as committed to the ACHD, to improve SO2 ambient air levels. In addition, we recently announced an over $1B investment that includes new technology and a cogeneration facility at Mon Valley Works, which will secure steel making and good paying union jobs for decades to come in the Mon Valley. The planned cogeneration facility at Clairton Plant is a part of that $1B investment and will turn coke oven gas into electricity and include state-of-the art emissions controls which, with the other investments at Edgar Thomson Plant announced this May, will make further improvements in SO2, PM 2.5 and greenhouse gas emissions.

Additionally, U. S. Steel is absolutely committed to making even more substantial investments in Clairton to make further environmental improvements and we have been working with the ACHD for input and assistance before implementation.

As the Allegheny County Health Department has confirmed, at no time during the brief disruption to our facility following the small electrical fire on June 17, was there any public health risk. Protecting our shared environment remains a top priority for U. S. Steel and we are thankful to crew members who worked tirelessly to restore operations as quickly and safely as possible.

On June 28, the company announced that it reached an agreement with the Allegheny County Health Department to resolve the company’s appeal of enforcement orders associated with battery compliance at the Clairton Plant. The full announcement is available here and the full agreement can be read here.


Our Operations

Mon Valley Works Facts

U. S. Steel’s Mon Valley Works includes four facilities, three of which are in the Pittsburgh area. Learn more about these facilities, as well as U. S. Steel’s other operations and locations in Southwestern Pennsylvania.

Coke Making Process

Coke is a critical raw material in the blast furnace method of steel production used by U. S. Steel. Learn more about the process used to transform coal into coke.

Frequently Asked Questions

On Dec. 24, 2018, at approximately 4:15 a.m., U. S. Steel’s Clairton Plant experienced a significant fire which required the immediate shutdown of the No. 2 control room and No. 5 control room, which house the equipment and controls necessary to clean the coke oven gases. The fire was successfully extinguished by plant and external fire departments by approximately 9:30 a.m. and no injuries were reported.

Our coking facilities convert coal into coke which is used in the making of liquid iron for the steelmaking process. The coking process produces coke oven gas (COG) as a by-product. No. 2 control room is the facility where clean coke oven gas is separated from the other gases that are generated during the coking process. After this separation, the other gases go through the remaining processes of No. 2 control room and No. 5 control room for additional gas cleaning steps.

However, the fire caused significant damage to the No. 2 control room building roof structure, and the related equipment used to clean coke oven gases, known as vacuum machines. This prevented us from restarting those processes.

The control room that was affected by the fire is about the size of a football field.  Portions of its roof and supporting structure were significantly damaged and presented a safety risk.  As soon as that area was cleared for entry on Tuesday, Jan. 8, a comprehensive safety and fire investigation team that included an independent fire investigator began their work.   It has been determined that the fire originated from a mechanical failure in the C-521 vacuum machine area, however, what caused that failure is still being investigated by the experts.

The damaged equipment impacted a process that performed desulfurization.  This is the process that removes sulfur from coke oven gas. After the removal of the sulfur, we recycle the remaining Coke Oven Gas (COG) to fuel our processes at our Clairton, Edgar Thomson and Irvin plants=U. S. Steel is now utilizing a blend of coke oven gas and natural gas in our process units.  Many mitigation techniques are also being used to minimize the environmental impact of the No. 2 and No. 5 control rooms being down, including flaring the coke oven gas at the Irvin facility for better dispersion. 

We are also decreasing coke production by further increasing coking times on all batteries. This will result in a net of about 8,000 tons of coke produced per day, another 15% decrease in production over previous increases in coking times already made, with an overall decrease in production of around 30%. Details of these specifications can be found the ACHD’s revised enforcement order here.  This is an evolving process in which we continue to adjust the techniques to maximize the mitigation results. To view our weekly updates provided to the ACHD click the "updates" tab.

The Liberty Borough Monitor, located at South Allegheny High School, tracks PM2.5 daily National Ambient Air Quality Standards (NAAQS) and hourly SO2 NAAQS. Since the incident, the Liberty Borough monitor has recorded exceedances during seven individual hours over five days during the first 16 days immediately following the fire that were above the 1-Hr SO2 standard of 75 ppb. The exceedances over the 75 ppb occurred on:

12/26/2018 – 10 a.m. – 79 ppb

12/26/2018 – 11 a.m. – 80 pp

12/28/2018 – 10 a.m. – 145 ppb

1/2/2019 – 9 p.m. – 81 ppb

1/3/2019 – 11 p.m. – 85 ppb

1/8/2019 – 12 midnight – 80 ppb

1/8/2019 – 4 a.m. – 76 ppb

3/28/2019  3 a.m. 82 ppb


The last Liberty monitor exceedance of the hourly standard was on March, 28, 2019. There have been no SO2 NAAQs exceedances at the Liberty monitor since that date.

The Department also regularly monitors SO2 at the North Braddock monitor.  Since the incident there were two hours in which the North Braddock monitor recorded exceedances of the hourly SO2 standard:  January 7 at the 11pm and February 4 at the 10 pm hour.  The last North Braddock monitor exceedance of the hourly standard was on February 4, 2019 at the 10 pm hour. This exceedance occurred on a day when there was an air quality alert in approximately twenty counties across Pennsylvania – as the Department explained in its public statements.  There have been no SO2 NAAQS exceedances at the Braddock monitor since February 4, 2019.

In addition, in full cooperation with the Department, U. S. Steel agreed to providing sufficient funding for additional temporary air quality monitors to determine air quality impacts and whether the mitigation efforts have been successful.  The Department installed two additional monitors to measure SO2 in the ambient air at Clairton and West Mifflin. These locations were selected by the Department to assess air quality impacts from U. S. Steel’s redirection of the combustion of coke oven gas.  The Clairton monitor began monitoring SO2 on January 24, 2019.  There have been no SO2 NAAQS exceedances at the Clairton monitor. The West Mifflin monitor began monitoring SO2 on February 21, 2019.  This monitor was strategically located downwind of the flares at U. S. Steel’s Irvin plant where most of the coke oven gas was redirected and is being combusted.  There have been no SO2 NAAQS exceedances at the West Mifflin monitor.

On February 2, 3, and 4 the Liberty air quality PM2.5 monitor recorded 24-hour average exceedances of the PM2.5 NAAQS above the standard of 35µg/m3.  These exceedances occurred on days when there was an air quality alert impacting approximately twenty counties across Pennsylvania, including western Ohio and central and eastern Pennsylvania.

We are committed to our community, our shared environment and our role as a good corporate citizen.

Upon extinguishing the fire, we devoted all available resources and personnel toward mitigation efforts that could be implemented immediately. Hot idling means to shut down and stop operating coke making, and it is not possible to shut down a coke making facility rapidly as hot idling is a deliberate and lengthy process (due to the extreme temperatures of the ovens and need to safely control explosive gas). In this instance, diverting resources to begin a hot idle would have redirected efforts away from remedying the problem and created additional environmental and economic impacts.

Long-term, a hot idle at Clairton could mean the permanent closure of some of the impacted batteries, and other batteries would sustain damage that would adversely impact the facility’s operation and environmental performance for several years. Such a hot idle action would likely have an adverse impact on the operating levels of all of our Mon Valley facilities and could result in workforce reductions.

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