TagThird Runway(1098)

Port of Seattle Natural Resource Mitigation Plan figure (AR017604, Exhibit 46, dated 12-20-01) showing Master Plan Update Improvement Projects at Seattle-Tacoma International Airport (STIA). Map depicts Third Runway construction area, Runway Safety Areas (RSAs), MSE retaining walls used to avoid and minimize wetland impacts, relocated section of Miller Creek, Miller Creek Detention Facility, Lora Lake,

Natural Resource Mitigation Plan for Seattle-Tacoma International Airport (STIA) Master Plan Update, November 2001, document reference 556-2912-001 (03). Table 1.3-1 lists all proposed Master Plan Update improvement projects including: third parallel runway 16X/34X (8,500 ft), Runway Safety Areas (RSAs) for 16R/34L and 16L/34R, South 154th Street relocation, South Aviation Support Area (SASA) for cargo/maintenance, embankment

A study at Seattle-Tacoma International Airport found that galvanized metal roofing on cargo buildings was the primary source of elevated zinc levels in the airport's stormwater runoff, which drains into salmon-bearing streams including Miller Creek and Des Moines Creek. Researchers used whole effluent toxicity (WET) testing and source-tracing methods to identify the problem, focusing on one outfall (SDN1) that consistently showed higher zinc concentrations and toxic effects on aquatic organisms. The findings prompted the Port of Seattle to investigate remediation options as part of its stormwater pollution prevention program under its NPDES permit.

Memorandum dated November 1, 2001 from Elizabeth Leavitt (Port Of Seattle) to Muffy Walker (U.S. Army Corps of Engineers) regarding Army Corps Section 404 review of on-site borrow areas for Sea-Tac Airport Third Runway embankment fill. Covers Borrow Areas 1, 3, and 4 located in Des Moines and SeaTac; combined 6.1 million cubic yards of

This 2001 email chain discusses how fill materials used in the construction of Seattle-Tacoma Airport's Third Runway Embankment should meet environmental criteria under a 401 water quality permit. State regulators and Port of Seattle staff debated which materials — including topsoil, utility backfill, base course, and general embankment fill — required testing, supplier certification, or quality assurance plans to demonstrate compliance. Officials agreed that highly processed materials like topsoil could be covered by supplier certification, while bulk embankment fill would require a statistical sampling and QA/QC program.

A November 2001 email chain discusses a meeting held on October 30, 2001, regarding errors discovered in a low flow analysis related to environmental modeling near Seattle. Raymond Hellwig of NWRO confirms that revisions to the low flow analysis may be considered to correct previous modeling errors, but stresses that any revised submissions must include thorough documentation and clear rationale. The correspondence involves multiple agencies and contractors, including Floyd Snider McCarthy, Inc., the U.S. Army Corps of Engineers, and Port of Seattle representatives.

This technical memo from Hydrocomp, Inc. (authored by Norm Crawford) outlines recommendations for improving hydrological computer modeling of Miller, Walker, and Des Moines Creeks near Seattle-Tacoma International Airport's new runway construction. It describes how rainfall and runoff from the new impervious runway and taxiway surfaces and surrounding pervious grasslands are tracked through a linked series of models (HSPF, Hydrus, and Slice) to estimate groundwater movement and seepage through underlying soil layers. The document identifies several discrepancies in the existing model setup and recommends corrections to better account for water flow paths, drainage areas, and groundwater recharge in the fill areas created by airport expansion.

These draft meeting notes from October 30, 2001 document a technical review session in which Port of Seattle consultants disclosed and explained several errors found in the low streamflow modeling for the Sea-Tac Airport Third Runway project. The key errors included a 1/24th magnitude conversion factor mistake in embankment fill data input, incorrect input files used for embankment modeling, and an overlap in which approximately 8 acres of the Walker Creek embankment appeared to be counted in both the Hydrus embankment model and the HSPF stream model. The meeting outlined corrective steps to be taken by the Port's consulting team to fix these errors before finalizing the revised Low Streamflow Analysis required under 401 Permit conditions.

Memorandum dated October 30, 2001 from Michael Kenrick of Hart Crowser, Inc. to Jim Thomson of HNTB, CC Elizabeth Leavitt of Port Of Seattle, project number 4978-06. Addresses wetland hydrology impacts of Third Runway Embankment Fill construction at Sea-Tac Airport, covering depression wetlands, slope wetlands, and riparian wetlands. References Miller Creek and Walker Creek baseflow,

Meeting notes from an October 30, 2001 technical session addressing errors discovered in the low streamflow modeling for Sea-Tac International Airport's Third Runway project. Consultants identified six modeling errors, including a conversion factor mistake that caused embankment flow contributions to be understated by a factor of 24, along with incorrect input files and improper groundwater routing. Representatives from the Port of Seattle, King County, the Department of Ecology, and the Army Corps of Engineers agreed on corrective revisions to be incorporated into a revised Low Streamflow Analysis and Summer Low Flow Impact Offset Facility Proposal required under the 401 Permit.