TagThird Runway(1084)

A 1999 technical memorandum from Parametrix, Inc. to the Port of Seattle analyzes the sensitivity of stormwater discharge compliance determinations for Sea-Tac Airport's runways, focusing on dissolved copper concentrations in Des Moines Creek. The memo evaluates whether mixing zones and dilution factors could offset elevated copper levels in stormwater runoff, finding that ambient copper concentrations already exceeded water quality criteria in 37–65% of samples. The analysis concludes that dilution factors based on streamflow alone are unlikely to be significantly greater than 1.0, though accounting for the Northwest Ponds' reservoir volume raises the estimated dilution factor to approximately 1.7.

This draft memorandum from Parametrix (dated April 20, 1999) summarizes range-finding toxicity tests conducted as part of a water-effect ratio (WER) study examining copper levels in streams receiving stormwater runoff from Seattle-Tacoma International Airport (STIA). Water samples were collected from Miller Creek, Walker Creek, and Des Moines Creek during a storm event in February 1999 and tested using the organism Ceriodaphnia dubia to measure copper toxicity. Results showed water effect ratios ranging from 6.7 to 16.0, leading researchers to recommend pursuing a definitive WER study and a site-specific water quality standard for copper.

Parametrix, Inc. summary (August 11, 1999) of key wetland findings from the Sea-Tac Runway Fill Hydrologic Studies Report (Pacific Groundwater Group 2000), prepared for the Port Of Seattle Master Plan Update Improvements JARPA review. Covers wetland delineation conservatism, limiting habitat characteristics of Miller Creek, Walker Creek, and Des Moines Creek, salmonid habitat significance, indirect embankment

A 1999 memo from the Washington State Department of Ecology evaluates construction techniques for a retaining wall near Miller Creek at Sea-Tac International Airport's Third Runway project. The memo concludes that specialized methods such as tied-back walls, bored piles, soil nailing, or ground freezing can address difficult underground soil conditions while keeping construction within the approved wetlands disturbance footprint, though at significant cost. The author also recommends installing monitoring devices in the wall and backfill to confirm the structure performs as designed throughout its service life.

Draft Wetlands Re-Evaluation Document prepared by Port Of Seattle in August 1999 for Seattle-Tacoma International Airport (STIA) Master Plan Update Improvements. Addresses new information on wetlands and aquatic resources affected by the planned new third runway and related improvements, not available during preparation of the 1996 Final Environmental Impact Statement (FEIS) or 1997 Final Supplemental

Report AR042353 prepared by HNTB, Hart Crowser Inc., and Parametrix for Port Of Seattle Aviation Program Management Group, evaluating retaining wall and slope alternatives to reduce impacts to Miller Creek at embankment station 174+00 to 186+00 for the Third Dependent Runway project at Sea-Tac International Airport. Transmitted July 13, 1999 by Barbara Hinkle to Tom

Memorandum dated July 9, 1999 from Reese P. Hastings and Michael J. Bailey, P.E. (Hart Crowser, Inc.) to Barbara Hinkle, Port Of Seattle, regarding Third Runway Project Borrow Areas 1, 3, and 4 and projected impacts to wetlands. Document J-4978-02 quantifies potential wetland resource impacts from excavation of borrow areas providing 7.9 million bank cubic

Hart Crowser subsurface conditions data report prepared for HNTB Corporation and Port Of Seattle, project J-4978-06, July 1999, supporting 404 permit for Third Runway embankment at Sea-Tac Airport. Covers generalized geologic and hydrogeologic conditions, subsurface soil conditions, hydraulic conductivity estimates, slug testing, water level data, SPT borings (HC99-B31 through HC99-B47), test pits (HC99-TP1 through HC99-TP21,

A 1999 draft assessment prepared by Parametrix, Inc. for the Port of Seattle outlines best management practices (BMPs) for managing stormwater runoff at Seattle-Tacoma International Airport as part of its Master Plan Upgrades. The document describes how the Port plans to implement water quality treatment measures—including filter strips, bioswales, and wet-vaults—across existing and newly developed stormwater drainage subbasins to meet Washington State Department of Ecology redevelopment requirements. Note that while archived alongside airport planning documents, this report focuses on stormwater and water quality compliance, not noise policy.

Technical memorandum prepared by HNTB Corporation for the Port of Seattle and Parametrix, Inc. (June 15, 1999) analyzing temporary wetland impacts during Seattle-Tacoma International Airport Third Runway embankment construction. AR 042490. Covers storm water management during construction, temporary fill in wetlands west of runway embankment toe, impacts to Wetland 37 (Miller Creek basin) and Wetland