TagPollution Control Hearings Board(1532)

This technical report analyzes low streamflow conditions in three creeks near Seattle-Tacoma International Airport (Miller, Walker, and Des Moines Creeks) to assess the potential impacts of airport construction projects on summer water flows. Using a 47-year record of streamflow data and computer modeling tools, analysts determined target streamflow levels for each creek and evaluated how proposed runway and infrastructure improvements might affect seasonal low-flow periods critical to salmon habitat. The study found existing summer low streamflow targets of 0.33 cfs for Des Moines Creek, 0.77 cfs for Walker Creek, and 0.73 cfs for Miller Creek, which were used to guide mitigation planning.

This December 2001 report, prepared by Parametrix, Inc. and several partner firms for the Port of Seattle, analyzes low streamflow conditions and proposes a Summer Low Flow Impact Offset Facility as part of the Seattle-Tacoma International Airport Master Plan Update Improvements. The study examines how planned airport expansion may affect seasonal low-flow water resources in the surrounding area and outlines mitigation measures to offset those impacts. The report is organized across multiple volumes, with Volume 1 containing the main text and Appendices B through J.

Report prepared by Parametrix, Inc. with Aqua Terra Consultants, Earth Tech, Inc., Foster Wheeler Environmental Corporation, HNTB, and Pacific Groundwater Group for Port Of Seattle regarding Sea-Tac Airport Master Plan Update Improvements. Analyzes summer low streamflow impacts to Walker Creek and Des Moines Creek from planned airport projects and proposes an offset facility using underground

This December 2001 technical report, prepared for the Port of Seattle, analyzes low streamflow conditions around Seattle-Tacoma International Airport and proposes a facility to offset the impact of airport Master Plan construction on summer low flows in nearby creeks. It includes hydrologic modeling, water quality design considerations, and an operation and monitoring plan for a stormwater storage and release system intended to maintain stream levels during dry summer months. Note that while archived alongside airport planning documents, this report focuses on water resources and stream impact mitigation rather than noise policy.

This December 2001 technical report analyzes low streamflow conditions in Miller, Walker, and Des Moines Creeks near Seattle-Tacoma International Airport, assessing the hydrologic impacts of the proposed third runway embankment as part of the airport's Master Plan Update. The study found that the runway construction would reduce summer stream flows, requiring mitigation of 0.11 cfs in Walker Creek and 0.08 cfs in Des Moines Creek during the annual low-flow period (late July through October). To offset these impacts, the Port of Seattle proposed collecting and storing excess winter stormwater in underground vaults—approximately 18.5 acre-feet for Walker Creek and 13.5 acre-feet for Des Moines Creek—for controlled release during dry-season low-flow periods.

This technical document compares observed and model-predicted 7-day low streamflows for Walker Creek and Des Moines Creek near Seattle-Tacoma Airport for water years 1991–1996. Results show that calibrated (simulated) flows generally underestimated observed flows at most gage locations, with the exception of 1995, when the model overpredicted flows. Discrepancies at upstream gage locations are attributed to uncertain groundwater conditions within the watersheds.

Wetland Functional Assessment and Impact Analysis prepared by Parametrix, Inc. for Port Of Seattle, December 2001, project number 556-2912-001 (03). Assesses wetland functions and impacts associated with Seattle-Tacoma International Airport Master Plan Update Improvements including the new Third Runway, Runway Safety Areas (RSAs), relocation of South 154th Street, Borrow Area 1 excavation, South Aviation Support

Parametrix, Inc. report prepared for Port of Seattle, Seattle-Tacoma International Airport Master Plan Update Improvements, December 2001. AR 052659/052660/052661. Volume 1 includes main text and Appendices B through J. Sub-consultants include Aqua Terra Consultants, Earth Tech Inc., Foster Wheeler Environmental Corporation, HNTB, and Pacific Groundwater Group. Addresses low streamflow analysis and summer low flow impact

Citizens Against Sea-Tac Expansion (CASE), represented by Richard A. Poulin of Smith & Lowney P.L.L.C., files an Intervenor’s Notice of Appeal before the Pollution Control Hearings Board (PCHB No. 01-160) challenging Washington Department of Ecology Order No. 1996-4-02325 (Amended-1), issued September 21, 2001 — a reissued/amended Clean Water Act Section 401 Certification directed to the

Declaration by Brett Fish, President of Citizens Against Sea-Tac Expansion (CASE), filed in PCHB No. 01-160 (Airport Communities Coalition v. Washington State Department of Ecology and Port Of Seattle). Fish declares CASE’s interest in intervening in the ACC’s appeal of Ecology’s 401 Certification for the proposed third runway and master plan update at Sea-Tac Airport.