Notes
Exhibit 238 (AR 018964–018966). September 7, 2000 letter from the Airport Communities Coalition (ACC) to Ray Hellwig, Regional Director, Washington State Department of Ecology Northwest Regional Office, regarding 401 Certification for Seattle-Tacoma International Airport Master Plan Update (MPU). ACC submits preliminary review comments on the August 2000 ‘Preliminary Comprehensive Stormwater Management Plan Seattle-Tacoma International Airport Master Plan Update Improvements’ (SMP). Issues raised include: discrepancies in HSPF model parameters for fill embankment baseflow analysis (Appendix F vs. Table A-4), re-analysis showing 44% vs. 63.6% groundwater/interflow of average annual rainfall, predicted reductions in average groundwater inputs to Miller Creek from subbasins SDW1A and SDW1B (0.10 cfs July, 0.09 cfs August), speculative water rights acquisition analysis (Appendix G) overstating domestic withdrawals at 0.01 cfs per user (6,460 gallons/day), cumulative impacts of commercial development in acquisition area, inconsistencies between new SMP and Natural Resource Mitigation Plan (100-year discharge Miller Creek at SR-509: 198 cfs vs. 71 cfs; detention volume: 42 acre-ft vs. 100+ acre-ft), failure to preserve existing basin boundaries under Governor’s certificate, and proposed diversion of Walker Creek headwaters (Wetlands 44a and 44b) to Des Moines Creek basin SDS7.