Notes
Northwest Hydraulic Consultants (NHC) letter dated February 15, 2001, submitted to U.S. Army Corps of Engineers (Jonathan Freedman) and Washington State Department of Ecology (Ann Kenny) on behalf of Airport Communities Coalition (ACC). Reviews the December 2000 Comprehensive Stormwater Management Plan (SMP) and Natural Resource Mitigation Plan (NRMP) by Parametrix Inc. for the Seattle-Tacoma International Airport Master Plan Update third runway project (Corps Reference No. 1996-4-02325). Raises dam safety concerns at SASA facility and vaults SDS7 and G1 (Basin SDW1A); notes violations of King County Surface Water Design Manual (KCSWDM) maximum vault depth of 20 feet for vaults SDS3, G1, SDN3, C1, M5, and C2; critiques inappropriate drain-time methodology for open water duration assessment versus continuous simulation; identifies Erosion and Sediment Control (ESC) deficiencies including clearing limits, tributary areas, pump sizing, and outer swale conflicts with seepage flow. References SMP Appendix D Exhibits C140, C151, C115, C24; Appendices L, O, R; King County core requirement 1.2.5.1; KCSWDM pg 5-37 and 5-38; Puget Sound precipitation conditions; and Port of Seattle Third Runway Embankment Construction Phase 4 plans (Work Order #101346, Project STIA-0104-T-01).