Attempting to plan for potential issues arising from COVID-19, the U.S. Army Corps of Engineers notified Washington and Oregon authorities that if total dissolved gas or gas bubble trauma monitoring is disrupted by pandemic restrictions, the Corps will revert to spill levels of 110 percent TDG at eight Snake and Columbia river projects.
The Corps began spilling to 125 percent TDG on April 3 at the four lower Snake River dams, and on April 10 at the four lower Columbia River dams as part of the flexible spill agreement for 2020.
"Our current monitoring is proceeding as planned, and there's no indication there will be restrictions at this point. But there are things that are out of our control," Dan Turner, who represents the Corps on the Columbia River Technical Management Team, told TMT members on April 8.
Turner said water quality standards for Washington and Oregon clearly state that the Corps can only spill to 125 percent TDG if both TDG and gas bubble trauma monitoring is occurring. "If no monitoring is in place, the criterion goes to 110 percent TDG," he said.
The Corps outlined this concern in an April 6 letter to the Washington Department of Ecology and Oregon Department of Environmental Quality.
According to the letter, the Corps relies on an array of monitoring stations maintained by the U.S. Geological Survey to collect hourly TDG data above and below each of the eight dams, which informs its fish-passage spill operations. In addition, juvenile salmonids at five of the eight dams are collected and examined at least weekly by the Pacific States Marine Fisheries Commission or the Washington Department of Fish and Wildlife to determine incidence of gas bubble trauma caused by the elevated TDG, with requirements to reduce spill when certain thresholds are detected.
"As a result of the rapidly evolving responses to the COVID-19 pandemic, however, required monitoring activities may be interrupted at some point in the near future by restrictions enacted by the federal or state government that would restrict access to each dam, or by the entities that collect TDG or GBT data," the letter stated.
Turner said the Corps sent the letter to be "transparent," and to give states a chance to change or clarify the rules if necessary. The states have not yet responded to the letter, he said.