EXH1119041945

Des Moines Creek Regional Capital Improvement Project Preliminary Design Report November 1, 1999 Prepared for Des Moines Creek Basin Committee Tim Heydon,City ofDes Moines Tom Hubbard,Portof Seattle David Masters,King County Don Monaghan,City of SeaTac LorenReinhold,City of Des Moines Prepared by King County Capital Improvement Project Design Team Approved by Don Althauser, P.E. AR 041946 Table of Contents Page Executive Summary ................................................................................................................ 1 Introduction ............................................................................................................... 3 Methods .......................................................................................................................... 5 Assumptions ....................................................................................................................... 6 Results ...................................................................................................................................... 8 Hydrologic Evaluation .......................................................................................................... 8 Typical Water Year............................................................................................................. 29 Storm Events ....................................................................................................................... 33 Swanson Site Observations ................................................................................................. 36 Conclusions ............................................................................................................................. 37 Recommendations ................................................................................................................ 41 List of Figures Figure 1 Average Wet Season Inundation Areas (October--March) .................................... I I Figure 2 Average Dry Season Inundation Areas (April--September) ................................... 13 Figure 3 Current and Proposed Flood Inundation Areas (l-year) .......................................... 15 Figure 4 Current and Proposed Open Water Areas (I-year) .................................................. 17 Figure 5 Section A - A' through Northwest Ponds ................................................................ 19 Figure 6 Section B - B' through Approach Light Cell ........................................................... 21 Figure 7 Current and Proposed Flood Inundation Areas (10=year)........................................ 23 Figure 8 Current and Proposed Flood Inundation Areas (25-year) ........................................ 25 Figure 9 Current and Proposed Flood Inundation Areas (100-year) ...................................... 27 Figure l0 1995 Mean Daily Water Surface Areas, Northwest Ponds, Typical Water Year ...30 Figure I I Stage=Area Graph for I.O1=Year Event at Northwest Ponds .................................. 31 Figure 12 Stage-Area Graph for 2-Year Event at Northwest Ponds ....................................... 32 Figure 13 1995 Mean Daily Discharge, Northwest Ponds, Typical Water Year .................... 34…

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Add to CalendarMWednesday Mar 11, 9:00am - 11:35am
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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 [...]