Council hears report on two oil‑loss events at Columbia Generating Station; lab results reported below detection limits

Kelly Elsa Thagan, speaking for Columbia Generating Station, told the Energy Facility Site Evaluation Council that Energy Northwest reported two separate oil‑loss events and has taken corrective actions.

Thagan summarized the Aug. 15, 2025 event as caused by a leaking TOHX‑2 delta heat exchanger. She said an engineering evaluation "determined that approximately 380 to 463 gallons of nonhazardous oil were released between May 31 and 08/17/2025." Thagan said the failed exchanger was removed from service, inspections and corrective actions are planned during the next refueling outage in spring 2027, and Energy Northwest has "strengthened spill prevention awareness, enhanced monitoring, and increased inspection frequency."

On the second event, Thagan said that on Feb. 15, 2026, during startup after a manual shutdown, "an unexpected oil water mixture was observed" on the turbine oil heat exchanger (TOHX‑2 alpha). She reported the maximum estimated release rate for that incident as "5.79 gallons of non hazardous oil." Thagan told the council that circulating‑water samples collected after both events showed fats, oil and grease concentrations "below the laboratory detection limit." She also said Energy Northwest completed telephone notifications to Ecology, FSEC and the National Response Center on May 27, 2026, and submitted a written report to FSEC the same day.

Graymar Environmental, the contractor brought in to inspect nearshore areas, assessed that an apparent sheen observed in 2025 "was most likely biological growth rather than oil," Thagan said. Thagan added that plant operators restored circulating water blowdown to the Columbia River after confirming water quality and that site protections implemented after the 2025 event enabled faster recognition and response in 2026.

Council discussion focused on the numbers and on the value of improved monitoring. One council member praised the process changes for "catch[ing] things earlier and to identify issues faster," noting the contrast between the larger estimated total release in 2025 and the much smaller maximum estimate in 2026.

The council did not take formal action on the update. Thagan said inspections and a thorough engineering review will occur during the scheduled spring 2027 outage to confirm root causes and any further corrective measures.

The council moved on to other project updates after Thagan concluded the report.