TagMechanically Stabilized Earth(42)

Following the Nisqually earthquake of February 28, 2001, GeoSyntec Consultants wrote to the U.S. Army Corps of Engineers and Washington State Department of Ecology raising serious concerns about the seismic safety of the proposed Third Runway expansion at Seattle-Tacoma International Airport. The letter highlighted that the earthquake caused damage to mechanically stabilized earth (MSE) walls and widespread liquefaction despite being only a moderate event, reinforcing earlier warnings about flaws in the project's seismic design criteria and ground motion analysis. GeoSyntec argued that the airport's role as a regional emergency lifeline demands higher safety standards than those applied to ordinary residential structures.

Draft memorandum dated March 5, 2001 from Douglas Lindquist E.I.T., Barry Chen PhD P.E., and Michael Bailey P.E. of Hart Crowser Inc. to Jim Thomson P.E. of HNTB, project J-4978-30. Presents revised methods and results of liquefaction analyses for the SeaTac Third Runway embankment, based on revised probabilistic seismic hazard analysis (PSHA) and one-dimensional site

Email chain (Exhibit 2061, AR031718-AR031720) dated February 26, 2001, from Jerald LaVassar (Ecology Dam Safety Office) to Ann Kenny (Ecology), responding to Andrea Grad (Helsell law firm, representing ACC/Airport Communities Coalition). LaVassar explains why the Mechanically Stabilized Earth (MSE) wall at Sea-Tac Airport’s third runway project does not qualify as a dam under WAC 173-175-020,

In February 2001, GeoSyntec Consultants submitted a technical review letter to the U.S. Army Corps of Engineers and Washington State Department of Ecology on behalf of the Airport Communities Coalition, raising serious concerns about the proposed Third Runway expansion at Seattle-Tacoma International Airport. The letter identified significant deficiencies in the geotechnical investigation, analysis, and design of the planned embankment fill and West Mechanically Stabilized Earth (MSE) Wall, warning that the project's foundations involved weak peat and liquefiable sands in a highly seismic area. GeoSyntec concluded that the available data was insufficient to confirm the safety of what would be the tallest MSE wall in the world, and that approval should not be granted without a more thorough geotechnical review.

In February 2001, engineering firm GeoSyntec Consultants submitted a technical review letter on behalf of the Airport Communities Coalition, raising serious concerns about the proposed Third Runway expansion at Seattle-Tacoma International Airport. The review identified significant deficiencies in the geotechnical investigation and analysis supporting construction of the embankment fill and West MSE Wall, including insufficient soil strength data and inadequate seismic safety assessments. GeoSyntec warned that the proposed design — which would result in the world's tallest MSE wall built over weak, potentially unstable soils in a seismically active region — could fail under earthquake conditions, threatening both airport operations and nearby natural resources.

Sheldon & Associates letter dated February 15, 2001, responding to public notice comments regarding the Seattle-Tacoma International Airport Masterplan Update Projects Section 404/401 Permits. Addresses movement of water through embankment fill and Mechanically Stabilized Earth (MSE) wall, drainage layer design to prevent excess pore pressures, rock underdrain clogging prevention using Group 1A filter material, shallow

Email dated February 8, 2001 from Ann Kenny (Ecology Senior Environmental Specialist) to Andrea Grad, Peter Eglick, and Kevin Stock responding to PDA requests regarding Chapter 173-175 WAC Dam Safety review of Port Of Seattle Third Runway stormwater facilities. Covers ISW Lagoon #3, 25.5 acre-foot pond (SDW1A), 37.91 acre-foot pond (SDW1B), MSE wall Dam Safety

Letter dated February 8, 2001 from Hart Crowser Principal Geotechnical Engineer to U.S. Army Corps of Engineers (Jonathan Freedman) and Washington State Department of Ecology (Ann Kenny), documenting comments made at the January 26, 2001 public hearing on 404/401 permit applications J-4978-30-06. Comments focus on the design and independent technical review of mechanically stabilized earth

Exhibit 2059 (AR 031711–031713, ECY00010776–10778). Email from Gus Ordonez to Ann Kenny dated February 7, 2001, transmitting a memorandum from Jerald LaVassar, M.S., P.E. to Tom Luster reviewing the report ‘Evaluation of Retaining Wall/Slope Alternatives to Reduce Impacts to Miller Creek, Embankment Station 174+00 to 186+00’ for the Third Runway project at Sea-Tac International Airport.

Letter dated January 25, 2001 from Peter M. Douglass, P.E. (Technical Review Board Facilitator) to U.S. Army Corps of Engineers (Jonathan Freedman, Project Manager) and Washington State Department of Ecology (Ann Kenny, Environmental Specialist) summarizing findings of an independent expert panel convened by Port Of Seattle to review embankment fill and mechanically stabilized earth (MSE)