Notes
Northwest Hydraulic Consultants (NHC), retained by Airport Communities Coalition (ACC), submits follow-up technical comments dated June 25, 2001 to U.S. Army Corps of Engineers (Muffy Walker, Gail Terzi) and Washington State Department of Ecology (Ann Kenny) regarding stormwater, hydrology, and hydraulics aspects of the proposed third runway at Seattle-Tacoma International Airport, Corps Reference No. 1996-4-02325. Document is Exhibit 234 (AR 018945). Comments respond to Port of Seattle’s April 30, 2001 response to NHC’s February 15, 2001 letter. Issues addressed include: ambiguity in stormwater standards under SMP Section 2.1.4 vs. NPDES permit requirements; absence of independent post-SMP design review; King County 1998 Surface Water Design Manual compliance scope and limitations; cost estimates for stormwater vaults (Vault SDE-4, SDS-3 Vault 3, SMP Appendix M); reserve storage water quality for low-flow augmentation; hydrologic model calibration against King County Gage 11F; groundwater inflow discrepancy (1,240 acres vs. 512 acres, SMP page B1-10); Lagoon 3 open water bird attraction hazards; NPDES major modification; Section 401 Certification conditions.