EXH0645024681

Subject:- Sensitivity Analysis of Mixing Zone Parameters (continued) cc: Ken Ludwa Project Number: 55-2912-61-01 Project Name: Port of Seattle Stormwater Management Questions The following list identifies the questions raised concerning the outcome of the stormwater mixing zone analysis: 1. Will the stormwater discharge comply with the State dissolved copper water quality criteria (WQC) if the background (ambient) concentration is zero? A correlated question is whether additional ambient sampling should be conducted to develop better data for WQC compliance calculations? 2. How sensitive are the compliance calculations for WQC to each of the parameters used? 3. How would the outcome of the water effect ratio (WER) testing effect the results of the compliance calculations? 4. Would greater control over the stormwater release rate help the Port meet the WQC? 5. Can higher hardness (at lower ambient flows) help meet WQC compliance? Approach used a spreadsheet to calculate the reasonable potential to exceed WQC in an approach that can be classified as a dynamic modeling technique. This is the same spreadsheet referred to in a previous memo (August 20, 1999). You may recall that this memo discussed three methods; one of these methods used herein (in the spreadsheet) is atso recommended by EPA (Technical Support Document For Water Quality Based Toxics Control, 1991). The method is identified in the referenced document as a Monte Carlo simulation model approach. The calculations apply to the Des Moines Creek point of compliance, which is assumed to be the outlet of the NW Ponds. The effluent…

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 [...]