Notes
Northwest Hydraulic Consultants (NHC) letter dated April 11, 2001, on behalf of the Airport Communities Coalition (ACC), addressed to Gordon White, Program Director, Shorelands and Environmental Assistance Program, Washington State Department of Ecology. Critiques the Ecology memorandum dated 3/9/2001 reviewing the December 2000 ‘Seattle-Tacoma Airport Master Plan Update Low Streamflow Analysis’ for the Sea-Tac Airport third runway project. Raises substantial technical concerns including: use of year 2006 future sub-basins to define ‘existing’ conditions; missing hydrology model input files for Walker Creek and Des Moines Creek; failure to consider low-flow impacts of Industrial Wastewater System lining program; failure to address low-flow impacts of large-scale gravel mining at Borrow Areas 1, 3, and 4; inconsistency between theoretical geotechnical runway embankment seepage assumptions and actual field measurements. Requests Ecology revisit its review of the low streamflow analysis and require applicant response to NHC’s 2/15/2001 letter before regulatory certification. Signed by William A. Rozeboom, P.E. and K. Malcolm Leytham, Ph.D., P.E. References King County’s 2/22/2001 review comments on the December 2000 SMP. AR 018941–018942.