At 9:38 a.m., September 27, 2021, the damaged portion of the pipeline has been replaced, inspected by x-ray and the excavation ready for backfill. Backfill was completed at 1 p.m. NuStar is projecting getting the line back in service in the next 24 hours.

With the ammonia source secured and no indications of current or potential ammonia releases to impact the community, EPA demobilized at 11:30 a.m., and ADEM will be demobilizing at 1:30 p.m. and returning command to the Calhoun County Sheriff.

As of the morning of September 27, 2021, the Stopple's previously installed upstream and downstream of the damaged portion of the pipeline remain secured and preventing further release of ammonia from the pipeline allowing NuStar to remove and replace the damaged section of the pipeline. The damaged portion of the pipeline was excavated and cleared. EPA and Arkansas Division of Emergency Management observed the damaged portion of the pipeline this morning prior to NuStar removing the damaged portion and replacing it. NuStar is projecting to complete the replacement today and get the line back in service in the next 24 hours.

With the ammonia source secured and no indications of current or potential ammonia releases to impact the community, EPA will be demobilizing on September 27, 2021.

This morning, equipment arrived to enable NuStar to continue the repair and reopening of the damaged pipeline. Valves were placed on the previously installed Stopple T's. Then a drilling assemble was placed on top of the valve. The entire assembly was tested for leaks. A hole is then drilled into the pipeline. After the pipeline is opened, a Stopple plug is inserted into the pipeline.

The above actions were started at 0810 and completed at 11:35 a.m. on both the upstream and downstream Stopple T's.

Once both sides of the damaged section were plugged, it was cleared of any remaining ammonia.

Due to the amount of potential residual ammonia left in the dirt covering the original leak, the decision was made to allow it to dissipate until tomorrow morning.

Ammonia concentrations measured by EPA in the community from mid-day on September 24 to present have continued to be zero ppm with only a few exceptions up to approximately 4 ppm. NuStar ammonia concentrations measured in the community between 6 p.m. on September 24, 2021 and this update were consistently zero, with some measurements up to 6 ppm.

EPA and Arkansas Division of Emergency Management remain on-site and working with county and local authorities and NuStar to protect public health and the environment.

At approximately 7 p.m. Thursday September 23, 2021, a gravel company digging in an area just south of Hampton, Arkansas ruptured a gas line.  This incident caused the release of anhydrous ammonia into the air. Out of an abundance of caution, and based on elevated ammonia air monitoring measurements emergency personnel issued a voluntary evacuation order for people living in proximity to and downwind of the site, and closed Highway 167.

The Fire Department reported to EPA measured ammonia concentrations at 99 ppm in the community at approximately 12:30 a.m. on September 24. By approximately 2:00 a.m. the Fire Department reported to EPA that the ammonia concentrations had dropped to 30 ppm at the same locations they were previously measured at 99 parts per million (ppm). EPA began conducting roving ammonia air monitoring in the community after arrival on scene at approximately 4:30 am on September 24, 2021. Initially, while highway 167 closed, EPA measured ammonia at concentrations up to approximately 60 ppm. By 10 a.m. on September 24, EPA measured ammonia on highway 167 at 5 ppm or less.

The NuStar Energy (NuStar) response team mobilized and joined the Unified Command on the morning of September 24, 2021. NuStar maintains Site control of the incident location and has taken efforts to secure the punctured 10-inch pipeline from the continued high velocity release of ammonia into the atmosphere. Control measures have included covering the punctured pipe with an earthen mound and installing a “burn box” or a vent and flare box atop the earthen pile to burn the continued ammonia emissions.

NuStar also brought in contractors on the morning of September 24 who began roving air monitoring for ammonia with teams on-site and in the community. NuStar contractors also set up stationary air monitors in the community.

As of 11:15 a.m. on September 24, 2021, the pressure of the ammonia releasing from the punctured pipeline reduced significantly, and air monitoring by Unified Command measured ammonia in the community at concentrations of 4 ppm or less. The local authorities lifted the evacuation order and opened highway 167 for use.

On September 25, 2021, NuStar reported they are installing Stopple T’s on the pipeline upstream and downstream of the puncture on September 26, 2021 that seal the pipeline upstream and downstream from further releasing. The portion of the pipeline between the two Stopple T’s will be evacuated of contents on September 27, 2021 and then repairs or replacement sections made to the damaged pipeline.

Ammonia concentrations measured by EPA in the community from mid-day on September 24 to 9 p.m. on September 25^th have continued to be zero ppm.

EPA and Arkansas Division of Emergency Management remain on-site and working with county and local authorities and NuStar to protect public health and the environment.