Notes
Memorandum dated October 13, 2000 from Michael Bailey P.E. and Michael Kenrick P.E. of Hart Crowser to Jim Thomson P.E. at HNTB (project J-4978-06), analyzing infiltration into the proposed Third Runway embankment at Sea-Tac Airport and effects on shallow water-bearing zone base flow to Miller Creek and adjacent wetlands. Analysis uses three sequential models — Rosetta (moisture-conductivity-suction relationships), EPA HELP model (lateral drainage layer simulation), and SoilCover (real precipitation records, saturated/unsaturated groundwater-atmosphere linkage) — applied to embankment soil Groups 1A through Group 4. Findings consistent with Pacific Groundwater Group (PGG, 2000) Hydrus-2D model: groundwater flow rates slightly lower in wet years, slightly higher in dry years, with seasonal hydraulic lag producing net increase in summer base flow to Miller Creek. AR numbers AR 046165–AR 046167.