EXH0671024967

To: Port of Seattle project files April _O_2000 From: Doug Henderson / Linda Logan 556-2912-001 (61) Subject: Range-Finding Water-effect ratio results _0_trx_ Z. This memorandum summarizes results of range-finding toxicity tests conducted as part of the water-effect ratio (WER) study for copper in streams receiving STIA stormwater. The purpose of these range-finding WEKs is to determine if the fmaI WElLs would be robust enough to warrant the expense of conducting definitive studies. Although range- finding WElLs were conducted in February 1999, these tests were conducted on simulated receiving water samples that were mixtures of outfall SDS3 stormwater and imtream receiving water. Mixture ratios of these two samples were prepared in the laboratory by combining measured volumes of stormwater and upstream receiving water in proportions estimated to occur in the receivingwater (based on hydrographs generated using HSPF). In the event thin mixing zones cannot be granted for the creeks, it was agreed that two additional types of range-finding WERs be conducted, one without any mixing with stormwater (i.e., receiving water only) and the other one aft= complete mix, below outfall discharges. Sampling Samples Were collected at five pre-deterrnined locations during a qualifying storm event on the morning of 15 April 2000. This storm event started at Xh on 15 April and ended at Xla on 15 April 2000. The dry antecedent period preceding this stoma was at least 24 hours. Approximately X inches of rain fell at STIA during this x-hour storm. Taylor Associates collected flow-weighted composite samples for X hours…

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 [...]