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A 2000 engineering memorandum from HNTB and Hart Crowser advises the Third Runway Design Team against artificially increasing stormwater infiltration within the proposed runway embankment. The memo warns that enhanced infiltration would raise risks of slope instability, soil liquefaction during earthquakes, and long-term maintenance problems that could not be remedied once the embankment was built. The engineers concluded that these safety and structural risks outweighed any stormwater detention benefits that increased infiltration might provide.

Email dated October 26, 2000 from Chung K. Yee to Kevin Fitzpatrick regarding Sea-Tac Airport fill material contamination concerns. Yee reports a conversation with Paul Agid explaining Ecology and the public’s concerns about possible groundwater and surface water contamination from fill material, and sampling frequency to quantify soil characteristics. Paul Agid expressed interest in discussing

Internal email dated September 11, 2000 from Peter Kmet to Chung K. Yee (cc: Kevin Fitzpatrick) discussing new Method A soil cleanup levels under MTCA (Model Toxics Control Act) and their use as a basis for defining clean fill. Kmet addresses specific chemicals including arsenic (recommends 7 PPM background value from USGS statewide study instead

Draft memorandum J-4978-28 from Hart Crowser (Douglas Lindquist, Barry Chen PhD P.E., Michael Bailey P.E.) to Jim Thomson P.E. at HNTB, dated September 7, 2000, presenting methods and results of liquefaction analyses for the proposed Third Runway embankment and retaining walls at Sea-Tac, Washington. Analyzed 120 borings with Standard Penetration Test (SPT) results from 112

Draft subsurface conditions data report prepared by HartCrowser for HNTB regarding the Third Runway Embankment at Sea-Tac International Airport, project numbers J-4978-23, -26, -27, and -31. Covers additional field explorations and advanced geotechnical testing including auger borings, standard penetration tests (SPT), Shelby tubes, pocket penetrometer, test pits, piezocone penetrometer probes, cone penetration tests (CPT), and

Hart Crowser draft subsurface conditions data report (project J-4978.21) prepared for Port Of Seattle and HNTB, June 2000, covering the West MSE (Mechanically Stabilized Earth) Wall for the Third Runway Embankment at Sea-Tac International Airport. Report includes generalized geologic conditions, subsurface soil conditions, consolidation test results, CU and UU triaxial compression test results, hydrogeologic conditions,

Hart Crowser draft subsurface conditions data report (project J-4978-18) prepared for Port Of Seattle and HNTB, dated March 20, 2000, covering the North Safety Area Third Runway Embankment at Sea-Tac International Airport. Report includes generalized geologic description, subsurface soil conditions, hydrogeologic conditions, laboratory test results (consolidation, CU triaxial, UU triaxial, direct shear tests), hydraulic conductivity

A March 2000 Parametrix memorandum reports the results of pesticide and herbicide soil testing at the Vacca Farm site, part of the Port of Seattle's Third Runway Project. Of 59 compounds tested, only 12 were detected, primarily organochlorine pesticides, with Dieldrin slightly exceeding cleanup levels in shallow soil samples at two locations in the proposed floodplain area. The memo recommends removing the upper six inches of soil from the floodplain area for offsite disposal, while concluding that the proposed Miller Creek relocation corridor does not pose unacceptable risks to human health.

In November 1999, the Washington State Department of Transportation (WSDOT) wrote to the Port of Seattle offering approximately 120,000 cubic yards of excess fill material from the First Avenue South Bridge construction site for use in the Sea-Tac Airport third runway project. While most of the material was found to be environmentally sound, the top few feet of soil showed slightly elevated levels of petroleum hydrocarbons, which WSDOT offered to retest using a different procedure before any transfer. The Port was asked to confirm environmental acceptability and provide a haul route before an agreement could be finalized.

Hart Crowser subsurface conditions data report (J-4978-16) prepared for HNTB and Port Of Seattle, dated November 12, 1999, regarding Phase 3 Fill for the Third Runway embankment at Seattle-Tacoma International Airport. Report covers generalized geologic and subsurface soil conditions, hydrogeologic conditions, field explorations (auger borings HC99-B61, HC99-B63, HC99-B65, HC99-B71, HC99-B73), test pits HC99-TP26 through HC99-TP44,