WASHINGTON COUNTY (KSNT) – A new report has revealed the cause of the Keystone Pipeline oil leak in Washington County last year.

Canada-based TC Energy released its report on the Milepost 14 Incident Thursday, Feb. 9. It shows the initial findings of an investigation focused on the cause of the oil spill, which dumped an estimated 588,000 gallons of oil into a Kansas creek.

Investigators conducted an independent analysis of the failed pipe, saying that the leak was caused by several factors. These include bending stress on the pipe and a weld flaw at a pipe to fitting girth weld that was completed at a fabrication facility.

The weld flaw led to a crack that grew over time as a result of bending stress fatigue, which eventually led to the pipe breaking. The cause of the bending stress is still under investigation, according to TC Energy.

The metallurgical analysis found no problems with the strength or material properties of the pipe or manufactured fitting, according to the report. The pipeline was working within its operational design and within the pipeline design maximum operating pressure.

“Our focus continues to be the safe operation of the pipeline system. Additional operational mitigations, such as reduced operating pressure, are in place to support the safe operations of our system while we continue our response and investigation. Our team is progressing a remediation plan, including an analysis of other areas with potentially similar conditions, the use of additional in-line inspections, and further operational mitigations.”

TC Energy Feb. 9 statement excerpt

The report states that TC Energy has revised the volume to 12,937 barrels from the original estimated maximum of 14,000 barrels. The revised volume is the actual measured volume of crude oil injected during the re-fill of the pipeline system in its safe restart.

The Keystone oil spill was reportedly contained as of Dec. 13, after it released thousands of gallons of oil into Mill Creek. This caused alarm among conservationists who feared the environmental impact of the spill and what impact it would have on the Kansas River. The damaged pipeline section was put back into service on Dec. 29.

To read the report from TC Energy in full online, click here.