EPA Finalizes Court-Ordered Temperature TMDL For Columbia River

摘要

EPA Region 10 has finalized a plan to reduce the temperature in the Columbia and Lower Snake rivers by up to 3 degrees Celsius following a landmark 2019 appellate ruling that forced the agency to act, although industry concerns about the plan's modeling could lead to additional litigation. EPA finds in the temperature total maximum daily load (TMDL) that temperature impairments are widespread and primarily due to the cumulative impacts of climate change and dam impoundments, with these impacts being an order-of-magnitude higher than point sources, agricultural withdrawals and tributaries. Temperature reductions of up to 3.1 degrees Celsius are necessary to meet summer water quality criteria within the lower Columbia River, and reductions of up to 2.8 degrees Celsius are needed to meet summer water quality criteria in the lower Snake River, which are intended to protect threatened and endangered fish species like salmon, the TMDL says. Region 10 released a version of the TMDL for public comments in May 2020 and transmitted a revised version to Washington state and Oregon Aug. 13. EPA says it examined the impacts of climate change, 15 dams, 23 major tributaries, 127 individual National Pollutant Discharge Elimination System (NPDES) point sources, stormwater, upstream boundary temperatures, and withdrawals from the Banks Lake Pump Project and Dworshak Dam in developing the TMDL.