DNREC Shares Information on Delaware City Refining Repair Work and Air Monitoring

^{DNREC is advising the public about planned Delaware City refinery repairs that could temporarily increase sulfur dioxide emissions.  /DNREC photo}

Delaware City Refining Company (DCRC) has notified the Delaware Department of Natural Resources and Environmental Control (DNREC) it will begin repairs on equipment at its coker carbon monoxide boiler that will cause it to shift from a primary pollution control process to a secondary emissions control. This change to the alternative process means that the facility will be emitting sulfur dioxide at a significantly higher level than normal. This is the same shift to secondary emissions control that happened for 17 days in May-June 2025 while the facility undertook repairs.

DNREC will monitor the situation and fully expects that these increased emissions – which are expected to last for four weeks – will exceed the limits of the facility’s permits and will be assessed for violation and penalties.

For the Delaware City community, DNREC is providing the following information and guidance during this event:

• The use of the secondary pollution control process will result in increased sulfur dioxide being released from the facility’s “stack” high in the air, so that it disperses into the atmosphere. Any concern for public health impact would occur if conditions caused the sulfur dioxide to be increased at ground level. A facility can have increased emissions and exceed its permit and still have ambient air readings at ground level remain in the green, or good, range.
• DNREC and the public can monitor sulfur dioxide readings at ground level at two DNREC-maintained air monitoring stations in the Delaware City area located east of the refinery on Route 9 and west of the refinery near Lums Pond. That data, updated hourly, is continuously available at de.gov/airdata. Those two stations are part of a statewide network of 11 air monitoring stations for various pollutants.
• The U.S. Environmental Protection Agency health standard for sulfur dioxide is 75 parts per billion in the ground level air, when people with asthma or other breathing related issues are advised to limit time outdoors or wear masks to reduce exposure. During the May-June 2025 refinery increased emissions, the highest hourly measurement at DNREC’s Delaware City monitor during the incident was 29.6 parts per billion, and most hourly values over the 17 days were 2 parts per billion or less.

As a result of a DNREC order from a previous incident finalized this week, the refinery has acquired fenceline sensors to measure air quality on the edges of the refinery property and to make that data publicly available. The refinery has indicated four of those sensors are being immediately put into place to begin operations and provide air quality readings; however, the publicly accessible website for those readings has not been completed. DNREC is urging the refinery to complete that website as soon as possible to share information during this period, and until the website is available, also to publicly report out the results on a regular basis until it does.

• The public can expect to see notice of these increased emissions from the refinery posted on DNREC’s Delaware Environmental Release Notification System (DERNS), available at de.gov/derns, which provides reports about environmental releases statewide, from small fuel spills to significant air emissions.
• After the repairs are complete, DNREC will assess the total level of increased sulfur dioxide emissions for violation and potential penalty. The May-June increased emissions, along with a number of other incidents, resulted in DNREC assessing a $300,000 penalty to DCRC, the maximum allowed by law for those violations. That penalty has been appealed by the refinery to the state Environmental Appeals Board.

Over the last year, DNREC has also been working to expand air quality monitoring and public access to information in and around Delaware City. The Clean Air Council will be installing two community air sensors and partnering with local organizations to engage the community, funded in the state bond bill through efforts of Rep. Melissa Minor Brown and Sen. Nicole Poore, along with DNREC. Through a grant from the Community Environmental Project Fund, the Department is funding additional community-scale air quality sensors to measure sulfur dioxide, nitrogen oxides, particulate matter 2.5, volatile organic compounds and hydrogen sulfide in residential corridors affected by industrial and traffic sources at three locations, including a home in Delaware City.

As part of an Environmental Improvement Project funded through Delaware City Refining enforcement, a PurpleAir sensor to measure particulate matter was deployed at Rose Hill Community Center last week. In addition, DNREC ordered the refinery to install the fenceline sensors following a butane leak in November, has coordinated with the Delaware National Guard and Delaware Emergency Management Agency on possible emergency sensor deployment locations and has begun the regulatory process to require permanent fenceline sensors at some industrial facilities.

DNREC will continue to monitor the refinery’s repair work closely, compare the company’s information with state air monitoring data and keep the public informed as new information becomes available.

About DNREC
The Delaware Department of Natural Resources and Environmental Control protects and manages the state’s natural resources, protects public health, provides outdoor recreational opportunities and educates Delawareans about the environment. The DNREC Division of Air Quality monitors and regulates all emissions to the air. For more information, visit the website and connect with DNREC on YouTube, Facebook, X or LinkedIn.

Media contacts: Michael Globetti, michael.globetti@delaware.gov; Nikki Lavoie, nikki.lavoie@delaware.gov