TagStormwater(385)

A December 2001 technical letter from Northwest Hydraulic Consultants, written on behalf of the Airport Communities Coalition, identifies inconsistencies in the Port of Seattle's stormwater management plans for Sea-Tac Airport expansion. The letter argues that the Port's hydrologic modeling failed to account for the planned commercial redevelopment of borrow pit areas by 2006, and that the Natural Resource Mitigation Plan reverted to an outdated stormwater approach relying on regional detention facilities to be built by others. These gaps, the consultants contend, prevent a full assessment of the airport Master Plan Update's environmental impacts.

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

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 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 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.

Third declaration of William A. Rozeboom, professional civil engineer with Northwest Hydraulic Consultants, filed before the Pollution Control Hearings Board (PCHB), Case No. 01-160, Airport Communities Coalition (ACC) v. State of Washington Department of Ecology and Port Of Seattle. Declaration concerns Section 401 Certification No. 1996-4-02325 and CZMA concurrency statement. Rozeboom identifies significant technical deficiencies

Third Declaration of Paul S. Fendt (Parametrix, Inc.) filed in PCHB No. 01-160, Airport Communities Coalition v. Department of Ecology and Port Of Seattle. Fendt, licensed PE with 18+ years stormwater engineering experience, addresses calculation of summer low streamflow impacts on Miller Creek, Walker Creek, and Des Moines Creek for the Port Of Seattle Master

This 2001 legal declaration by civil engineer William Rozeboom, submitted to Washington's Pollution Control Hearings Board, challenges the Port of Seattle's stormwater and low-flow mitigation plans for the proposed third runway at Sea-Tac Airport. Rozeboom argues that the Port's analysis underestimates low-flow impacts on local streams and that the proposed underground storage vaults—equivalent in volume to more than seven Olympic-size swimming pools—are undersized. The declaration also disputes claims by Port engineer Paul Fendt that the water volumes involved are small and that mitigation can be easily adjusted.

This legal declaration by stormwater engineer Paul S. Fendt, filed before Washington's Pollution Control Hearings Board, addresses the Port of Seattle's Master Plan Update and its potential impacts on local stream flows in Miller, Walker, and Des Moines Creeks near Sea-Tac Airport. Fendt explains the use of the HSPF hydrologic model and a 2-year, 7-day low flow standard to assess and mitigate summer streamflow impacts resulting from planned airport expansion projects. He concludes that revised analysis shows no significant changes to previously calculated low flow impacts.

Respondent State of Washington Department of Ecology’s revised preliminary witness and exhibit list filed before the Pollution Control Hearings Board in PCHB No. 01-133 and 01-160, Airport Communities Coalition v. Ecology and Port Of Seattle. Lists 11 Ecology witnesses including Ann Kenny, Erik Stockdale, Kevin Fitzpatrick, Dave Garland, and others from Ecology Northwest Regional Office