Notes
Technical memorandum from Gresham Smith (Tim Arendt, Melanie Knecht, Tom Dietrich) to Jana Braaten at Port Of Seattle, dated March 13, 2024, evaluating capital cost-reduction alternatives for the Industrial Wastewater Treatment Plant (IWTP) Enhancements project at Seattle-Tacoma International Airport (SEA). Analyzes alternatives to the Basis of Design (BoD) concept involving an aerated gravel bed (AGB) biological treatment system, dissolved air flotation (DAF) system upgrades, high BOD storage tank, Lagoon 3/4 split, pump stations, and force mains. Performance objectives include NPDES permit compliance (BOD limit 45 mg/L), King County Industrial Waste Discharge (IWD) permit compliance (flow limit 4 MGD, future load limit 10,000 lbs BOD/day), and surface water overflow avoidance. Model uses 52 winter seasons of historical hourly weather data at SEA and projects to SAMP Near Term Projects (NTP) Constrained Operation Growth Scenario (COGS) development milestone circa 2032. Key drivers include deicer runoff, increased flight operations, lagoon storage capacity limitations, and anticipated IWD permit BOD mass loading reduction. Gresham Smith Project No. 44846.22.