EXH0649024703

Subject: Summary of evidence demonstrating the absence of impacts to Miller and Des Moines Creeks from STIA stormwater Project Number:. 556-2912-001 (61) Project Name: Port of Seattle The purpose of this memorandum is to descn'be the test_g and monitoring of STIA stormwater - conducted thus far and to provide reasonable assurance that stormwater _om STIA does not and will not Lrnpact aquatic life m Miller and Des Momes Creeks. The test_g and monitoring can be divided into three categories, each demonstrating that impacts fi-om STIA stormwater are unlikely. In summary these are: I) Whole EffluentToxicity(WET) testingon STLA SDS ouffallshas demonstrateda lackof acutetoxicitym threeoffore"dischargestested.The sourceoftoxicityidentifiedfortheone ouffa]lhasbccntracedandthePortispursuingsourcecontrolmeasures. 2) Water EffectRatio(WER) range-findingstudiesdsmrminedtheapproximatemagnitudeofa WER usingsimulatedsitewatersamples.Basedon nominalconccnn-ationsfortotalcopper, copper WERs for Miller, Walker and Des Moines Creeks were approximately 16, 7, and 15, respectively. These data dcmonsmate the mitigating effects of receiving water on the toxicity of copper. 3) Metals monitoring of Miller and Des Momes Creeks downstream of the SDS ouffalls during a storm event on Jantmry 14, 1999 shows that concentrations of copper fan below water quality criteriaandofinnbelow detectionlimits. Thesethreecategoriesaredescribedm more detailbelow. Whole Effluent Toxicity During 1998 and 1999, the Port of Seattle conducted acute toxicity testing on four SDS outtalks using the water flea (Daphnia pu/ex) and the fathead minnow (Pimephales promelas). This testing, required by Section S10 of the Port's NPDES permit for STIA, was conducted on stormwater entering Miller and Des Momes Creeks (i.e. not diluted by creek water). The four outfaLls tested, SDS1, SDN4, SDS3, and SDE4, account for 68%…

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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 [...]