EXH0668024917

- From: Doug Henderson / Lmda Logan 556-2912-01 (61)" Subject: Update on the Stares of the Site-Specific WQC for Copper This memorandum summarizes our efforts to date to develop a site-specific water quality crit_vion for copper in Miller, Walker, and Des Moines Creeks. The need for such development is based on the assumption that the quality ofstormwater from the third runway will be sirn/lar to that eurre_atlydischarged from SDS-3. Prior to collecting any d_allmll_m_mmBwas proposed to preventunnecessary data collection (Figure 1). The---tworecommended methods for developing a site-specific WQC were the Water-Effect Ratio OVEP,) and the site-specific metals translator. The WER approach uses toxicity tests to evaluate the r_lative toxicity of copper-spiked site water compared to copper-spiked laboratory water. The ratio of these results is usexl to adjust the state water quality criterion, which is based on copper-spiked labomtor7 tests. The site-specific metals translator approach uses in-stream monitoring data to estimate the ratio of dissolved to total copper in the receiving water. This ratio is then used to calculate a new total copper permit limit based on the dissolved state WQC. Although the site-specific metals translator is quicker and less exp_asive to develop th_ a WER, it is a less accurate estimate of copper bioavailability, as the bioavailable fraction of a metal is generally less than the dissolved fraction. Therefore, a _rER will likely result in higher permit limits than a site-specific metals la'anslator. For example, if the dissolved copper concentrations are half of the total copper concenla-ations, then the site-…

Open full document

Upcoming Events

PSCAA Advisory Council Meeting Agenda
Add to CalendarMWednesday Mar 11, 9:00am - 11:35am
1904 3rd Avenue, Suite 105, Seattle, WA 98101
Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]