Stream temperature has a significant effect on the health of many of the Northwest's native aquatic species. The purpose of Oregon's temperature standard, like all water quality standards, is to protect the beneficial uses of the waters of the state and to preserve the health
of our aquatic ecosystems. The goals of the temperature standard are to prevent or minimize surface water temperature warming caused by human activity and to maintain the “normal” temperature regime throughout the year Oregon's temperature standard for basins that exceed
the numeric temperature criteria states that no measurable surface water temperature increase from anthropogenic sources is allowed unless specifically permitted under a surface water Temperature Management Plan approved by the Oregon Department of Environmental Quality (DEQ). The goal of
the Temperature Management Plan would be to reduce, mitigate or eliminate the thermal load or the effect of the thermal load to the receiving water. The Oregon Association of Clean Water Agencies (ACWA) recognized the number of stream segments within the state identified as water quality
limited for temperature and the number of its member agencies that may be required to develop Temperature Management Plans. Based on this, ACWA developed a Temperature Management Plan guidance manual. This paper will discuss Oregon's current temperature standard, the proposed revisions
in response to Endangered Species Act provisions and the review by the US EPA, the reasoning behind these changes, and the potential impact on POTWs and industry. This paper will also present information contained in the guidance manual including temperature measurement methodologies and data
analysis procedures for assessing the effect of the POTW discharge on the receiving water. Once this effect is quantified, best management practices (BMP) and/or temperature control technologies should be evaluated as part of each POTW's Temperature Management Plan if the discharge
is seen to have a negative impact. Evaluation methodologies and criteria are also included in this manual and will be discussed. This is a rapidly evolving area of scientific research and emerging public policy as the Federal Clean Water Act and Endangered Species Act requirements are attempted
to be simultaneously imposed.
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