TagDes Moines Creek(162)

This August 2001 King County review evaluates the Port of Seattle's Low Flow Impact Analysis and proposed Flow Impact Offset Facility, which aims to mitigate reductions in stream flows in local creeks—including Des Moines, Miller, and Walker creeks—caused by future airport development. The review finds that while the proposed water storage and augmentation measures substantially offset low-flow impacts during the critical late-summer period, there are significant gaps in documentation, biological assessment, and design details that need to be addressed. Recommendations include professional engineering certification, enhanced biological monitoring, improved calibration documentation, and refinements to the reserve storage facility designs.

Parametrix, Inc. report prepared for Port Of Seattle on cumulative impacts to wetlands and streams from Seattle-Tacoma International Airport Master Plan Update improvements, August 2001 (AR 050792, Exhibit 1267). Covers land use changes in Miller Creek and Des Moines Creek watersheds, wetland inventories, soil survey maps, aerial photograph analysis, stream conditions and fish habitat in

Parametrix, Inc. report prepared for Port Of Seattle assessing the existing (1994) and future (2006) hydrologic divide of Miller Creek, Walker Creek, and Des Moines Creek following Master Plan Update (MPU) construction at Seattle-Tacoma International Airport (STIA). Analyzes compliance with Governor’s Certification requirement that the third runway project will not cause changes in the location

Port of Seattle letter dated July 23, 2001 to Ann E. Kenny, Washington State Department of Ecology, Northwest Regional Office, summarizing low streamflow impact analysis and flow impact offset facility proposal for Seattle-Tacoma International Airport Master Plan Update projects. Prepared by Parametrix, Inc. Analysis covers summer low streamflow impacts to Des Moines Creek, Miller Creek,

In a July 2001 letter to the Washington State Department of Ecology, Northwest Hydraulic Consultants raised concerns on behalf of the Airport Community Coalition that the Port of Seattle's ongoing low streamflow analyses for Des Moines, Walker, and Miller Creeks near Sea-Tac Airport were likely underestimating the airport's impact on local waterways. The consultants argued that the models were poorly calibrated for upper-basin conditions and failed to account for post-1994 improvements to the Industrial Wastewater System or the future loss of forested areas due to planned airport development. They requested that a final report on the streamflow analysis and any proposed mitigation measures be made available for public comment before Ecology used it to make its 401 Certification decision.

Letter dated July 23, 2001 from Port Of Seattle to Ann E. Kenny at Washington State Department of Ecology Northwest Regional Office regarding Low Streamflow Analysis and Summer Low Flow Impact Offset Facility Proposal for Seattle-Tacoma International Airport. Covers summer low streamflow impacts in Des Moines Creek, Miller Creek, and Walker Creek from airport Master

A water resources consultant raised concerns in a July 2001 letter to the U.S. Army Corps of Engineers and Washington State Department of Ecology about the Port of Seattle's stormwater management plans for Sea-Tac Airport expansion. The letter challenged the effectiveness of proposed biofiltration swales, noting they can actually increase bacterial levels rather than reduce them, and warned that releasing stored stormwater from detention vaults into nearby Class AA streams could discharge pollutant-laden, oxygen-depleted water into already stressed waterways. The consultant concluded that the Port's plans fell short of providing reasonable assurance that water quality standards would be met.

This table from a July 2001 Comprehensive Stormwater Management Plan summarizes drainage area measurements and changes in impervious surfaces (such as pavement and rooftops) across Miller Creek, Walker Creek, and Des Moines Creek watersheds at Seattle-Tacoma International Airport (STIA). It compares 1994 baseline conditions to projected 2006 future conditions, showing a total increase of approximately 305.7 acres of impervious area across all drainage basins. The data was compiled from GIS coverage to support stormwater management planning for the airport's master plan update.

This document describes the Integrated Water System (IWS) stormwater management configuration at Seattle-Tacoma International Airport (Sea-Tac), detailing storage lagoons totaling 76.9 million gallons and a treatment rate of 4.0 million gallons per day across approximately 435 acres. Simulations over a 50-year period confirmed zero overflow events under proposed conditions, with overflows only beginning to occur if treatment rates dropped below 3.1 million gallons per day. The system experienced only one historical overflow during an extreme rain-on-snow event in December 1996–January 1997, with no petroleum hydrocarbons detected downstream.