TagMiller Creek(260)

A December 2001 letter from Azous Environmental Sciences challenges the Port of Seattle's wetland mitigation plan for the SeaTac Third Runway construction project, arguing that the plan inadequately offsets environmental damage to wetlands and streams. The letter contends that the Port has misclassified wetland 'enhancement' work at Vacca Farm as 'restoration,' inflating mitigation credits, and that the overall plan fails to meet no-net-loss standards required under Army Corps of Engineers regulations.

Northwest Hydraulic Consultants (NHC), retained by ACC (Airport Communities Coalition), wrote to Colonel Ralph H. Graves, Ms. Muffy Walker, and Ms. Gail Terzi of the U.S. Army Corps of Engineers Seattle District (Corps Ref. No. 1996-4-02325) identifying inconsistencies in Port Of Seattle proposals for site development and stormwater management at Sea-Tac Airport Master Plan Update

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 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.

Report by Pacific Groundwater Group (project JE0105) prepared for Port Of Seattle, dated November 27, 2001, analyzing embankment fill modeling in support of low streamflow analysis for the Sea-Tac Third Runway. Uses HYDRUS-SLICE modeling to assess vertical infiltration through embankment fill materials (General Fill and Type 1 Fill), saturated flow beneath the fill, and effective

Declaration by Roger A. Pearce, attorney for Port Of Seattle, filed in Pollution Control Hearings Board (PCHB) Case No. 01-160, Airport Communities Coalition v. Department of Ecology and Port Of Seattle. Identifies four exhibits submitted to Washington Department of Ecology under amended §401 Certification on JARPA Application No. 1996-4-02325: Exhibit A (Wetland A17 Restoration Plan,

This document presents site features and cross-sectional diagrams used for Hydrus-Slice hydrological modeling of the Sea-Tac Third Runway Embankment Fill project. It shows fill depths ranging from 0 to 160 feet across multiple modeled slices, with cross sections identifying impervious areas, elevation contours, and the watershed divide between Miller Creek and Walker Creek. The figures were produced in November 2001 as part of environmental engineering analysis for the third runway construction.

A 2001 technical memo from Hydrocomp, Inc.'s Norm Crawford outlines recommendations for hydrological modeling of Miller, Walker, and Des Moines Creeks near Sea-Tac Airport's new runways and taxiways. The document describes how surface runoff and groundwater flow from both impervious runway surfaces and surrounding pervious grasslands should be calculated and linked across three modeling tools: HSPF, Hydrus, and the Slice model. Key recommendations include properly accounting for infiltration, reducing till seepage by 33% for inactive groundwater recharge, and reconciling discrepancies in land area calculations between the different models.

Hart Crowser geotechnical summary report (project 4978-06) prepared for the Port of Seattle for presentation to the U.S. Army Corps of Engineers, November 2, 2001. Covers Third Runway embankment construction at Seattle-Tacoma International Airport: 17,000,000 cubic yards compacted earth fill, maximum fill thickness 165 feet, 2H:1V side slopes, three Mechanically Stabilized Earth (MSE) retaining walls

This November 2001 document from Parametrix, Inc. contains responses to U.S. Army Corps of Engineers questions regarding the Sea-Tac International Airport (STIA) Master Plan Update's natural resource mitigation project. It addresses technical questions about wetland mapping, watershed basin sizes, low-flow analysis, and cumulative wetland impacts across the Miller Creek, Walker Creek, and Des Moines Creek basins, showing projected wetland acreage reductions of approximately 3-4% with the project. The document also covers mitigation measures including wetland restoration sites and performance standards for invasive species control.