EXH0265019463

5808 Lake Washington Blvd. N.E., Suite 200 Kirtdand, Washington 98033-7350 December 2000 556-2912-001 (28) AR 019463 TABLE OF CONTENTS Page EXECUTIVE SUMMARY Lx I. INTRODUCTION ................................................................................................................ 1-1 1.1 PURPOSE ................................................................................................................. l-1 1.2 GOALS AND OBJECTIVES .................................................................................. 1-2 1.3 DOCUMENT ORGANIZATION ........................................................................... 1°2 2. STORMWATER MANAGEMENT STANDARDS .......................................................... 2-1 2.1 WATER QUANTITY MANAGEMENT STANDARDS ...................................... 2-1 2.1.1 Definition of Level 1 and Level 2 Flow Control Standards ........................ 2-1 2.1.2 Base Year ..................................................................................................... 2-2 2.1.3 Target Watershed Flow Regime .................................................................. 2-3 2.1.4 Updated Detention Requirements ................................................................ 2-4 2.2 WATER QUALITY MANAGEMENT STANDARDS ......................................... 2-5 2.2.1 Regulatory Requirements ............................................................................. 2-5 2.2.2 Water Quality Treatment Requirements for New, Redeveloped, and Retrofitted Surfaces ...................................................................................... 2-6 3. DESIGN CONSIDERATIONS AND HYDROLOGIC ANALYSIS METHODOLOGY3-1 3.1 A/RPORT-SPECIFIC DESIGN GUIDELINES ..................................................... 3-1 3. I. I Overall Guidelines ....................................................................................... 3- I 3.1.2 Wildlife Proximity to Open Detention Ponds .............................................. 3- I 3.1.3 Proximity to Aircraft Movement Art)as....................................................... 3-4 3.1.4 FeasibiLityof Creating Artificial Aquifer Storage in New Embankments.. 3-5 3.2 DAM SAFETY ......................................................................................................... 3-7 3.3 HYDROLOGIC ANALYSIS METHODOLOGY .................................................. 3-8 4. EXISTING CONDITIONS ..................................................................................................4-I 4.1 DRAINAGE BASINS .............................................................................................. 4-1 4.2 CONVEYANCE SYSTEMS ................................................................................... 4-5 4.2.1 Storm Drainage System ............................................................................... 4-5 4.2.2 Industrial WastewaterSystem......................................................................4-7 4.2.3 Pump Facilities ............................................................................................. 4-9 4.2.4 Recent SDS to MS Reroutes .................................................................... 4-10 4.3 STORM'WATER DETENTION ............................................................................ 4-10 4.4 HYDROLOGIC MODELING/WATER QUANTITY ......................................... 4- ! 2 4.4.1 Model Development ................................................................................... 4-12 4.4.2 Long-term Simulation ................................................................................ 4-13 4.4.3 Flow Duration Analysis of Target Watershed Flow Regime .................... 4-13 4.5 EXISTING BMPs AND WATER QUALITY ...................................................... 4-13 4.5.1 Best…

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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 [...]