EXH0242019003

Sent: Wednesday, December 20, 2000 5:23 PM To: Eglick, Peter J.; Stock, Kevin L. Re: SeaTac 3rd Lagoon Expansion Following is a summary of excerpts on IWS issues from Northwest Hydraulic Consultants' previous comment letters. From letter of November 24, 1999: Comment 4- KCSWDM Core Requirement 1: Discharge at the Natural Location. (Similar to Ecology's Minimum Requirement #2) The objective of this requirement is to protect downstream properties from increased or reduced flows due to changes in basin area. The SMP does not address this requirement, and provides insufficient basin mapping to understand how sub-basin divides will be affected --- by the development. There are several areas of probable non-compliance. For example, peak flow control in the Miller Creek and Des Moines Creek basins is proposed to be provided in part by diverting a total of 45.7 acres (SMP Table 4-5) of new impervious area to the Industrial Wastewater System (IWS). Significant basin area reductions will reduce erosive peak flows but will also reduce the middle-range and low flows which support habitat functions. Actual impacts in the Miller, Walker, and Des Moines Creeks are not known because the core requirement for discharge at the natural location has not been addressed in the SMP. Comment 18- It is unclear how stormwater runoff from areas tributary to the Industrial Wastewater System (IWS) has been handled in the modeling and what effect this has had on model calibration and target flows. Si_nificant land areas are involved: the IWS handles runoff from about 254…

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 [...]