Notes
EXH AR026126. Fax from Norm Crawford of Hydrocomp, Inc. dated November 7, 2001, addressed to NWRO ECY CF, containing technical notes and recommendations on HSPF modeling of Miller Creek, Walker Creek, and Des Moines Creek in connection with Sea-Tac Airport third runway construction. Document describes linkages between HSPF, Hydrus, and Slice models for simulating groundwater, surface runoff, and infiltration through new runway and taxiway fill areas at Sea-Tac (Seatac). Key topics include PERLAND outwash grass segments, IMPLAND impervious surface runoff (SURO), AGWI active groundwater inflow, DEEPFR parameter, Vashon till seepage, Vashon advance formation, drain layer hydraulic gradient, and INFLOW IVOL routing. Lists 11 specific recommendations including reducing till seepage by 0.33 (multiply by 0.67) to account for inactive groundwater recharge (DEEPFR), reconciling Miller/Walker Creek Master Area Table discrepancies (128 acres Hydrus/Slice vs. 124.27 acres removed from HSPF), and fixing lost base flows from SDW1A and SDW1B in HSPF. Administrative Record numbers AR 026126–AR 026128.