TagMiller Creek(260)

Northwest Hydraulic Consultants submitted follow-up technical comments in May 2000 raising serious concerns about flawed stormwater modeling used to assess the impact of a proposed third runway at Seattle-Tacoma International Airport. The consultants identified major inconsistencies in soil-type assumptions and runoff parameters in the hydrologic models, concluding that the Stormwater Management Plan's predictions of detention facility performance were unreliable and required a complete overhaul. The letter also flagged a lack of adequate local regulatory oversight to ensure that Port of Seattle stormwater designs complied with King County surface water standards.

A technical review by Northwest Hydraulic Consultants, submitted to the U.S. Army Corps of Engineers and Washington State Department of Ecology in May 2000, raises serious concerns about the stormwater management plan for Seattle-Tacoma International Airport's proposed third runway. The report identifies major flaws in the hydrologic modeling used to assess drainage impacts, including inconsistent soil-type assumptions and unreliable flow predictions for Miller Creek. The consultants call for a complete overhaul of the modeling process, independent technical review, and clearer regulatory oversight of the Port of Seattle's stormwater design work.

This April 2000 draft memorandum from the Port of Seattle summarizes range-finding toxicity tests conducted to evaluate water-effect ratios (WERs) for copper in streams receiving stormwater runoff from Seattle-Tacoma International Airport (STIA). Water samples were collected from five sites—including Miller Creek and Des Moines Creek—during a storm event on April 15, 2000, and tested using Daphnia magna to measure how site water chemistry affects copper toxicity compared to clean laboratory water. The results were intended to help determine whether full definitive WER studies were warranted, which could support the establishment of site-specific water quality standards for copper in receiving streams.

A draft memorandum dated April 2000 summarizes range-finding water-effect ratio (WER) toxicity tests conducted for the Port of Seattle to measure copper levels in streams receiving stormwater runoff from Seattle-Tacoma International Airport (STIA). Water samples were collected from five sites — including Miller Creek and Des Moines Creek — during a storm event on April 15, 2000, and tested using Daphnia magna organisms to compare copper toxicity in site water versus clean laboratory water. The results were intended to determine whether more expensive definitive WER studies would be warranted, and to help establish site-specific water quality standards for copper.

Draft memorandum dated April 20, 2000, authored by Doug Henderson and Linda Logan (job number 556-2912-001) for Port of Seattle project files, summarizing range-finding water-effect ratio (WER) toxicity tests for copper in streams receiving Seattle-Tacoma International Airport (STIA) stormwater. Tests used Daphnia magna as indicator species; copper was spiked into site water and synthetic laboratory

Field Sampling Data Forms (AR 027906–027908) documenting environmental sampling at Miller Creek and Des Moines Creek survey sites including 144th St S and S 157th Pl, dated April 17, 2000. Water quality measurements recorded: temperature 53.2°F/11.0°C and 49.5°C (4/19), pH 7.5, dissolved oxygen 9.5/100, hardness 84 PPM CaCO3 (site IA) and 120 ppm (site IB).

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.

Email from Erik Stockdale (Ecology NWRO) to Raymond Hellwig and Tom Luster, dated February 17, 2000, summarizing a February 15 meeting with Jim Kelley of Parametrix regarding public comments on the Sea-Tac Airport third runway project (AR 018438–018440, Exhibit 173). Issues raised by commenters Sarah Cooke and Andy Castelle concerned incorrect wetland mitigation ratio calculations

A February 2000 email from hydraulic consultant Bill Rozeboom argues that the proposed expansion of Sea-Tac Airport's Integrated Wetlands System (IWS) lagoon—tripling its storage capacity—is primarily driven by the airport's Master Plan Improvements, including the proposed third runway, rather than being a routine water quality project. Rozeboom notes that the planned increase in impervious drainage area (roughly 521 additional acres) closely mirrors the proposed increase in IWS storage volume, supporting his conclusion that the third runway is the primary driver of the expansion. He also raises concerns that the environmental documents fail to adequately assess the impact of large-scale out-of-basin water transfers on aquifer recharge and stream base flows in the Miller Creek and Des Moines Creek basins.

NMFS (National Marine Fisheries Service) Office of Counsel comments dated 12/17/99 on the Biological Assessment (BA) for Seattle-Tacoma International Airport Master Plan Update Improvements. AR 043243. Comments identify deficiencies in action area definition (50 CFR 402.02), matrix/checklist completeness, direct and indirect effects analysis, and cumulative effects regarding Puget Sound Chinook salmon critical habitat, Coho salmon,