TagStormwater(373)

Fax cover sheet dated 8/9/01 from Ralph Wessels (Port Of Seattle, 3rd Runway/Airfield, Westside Office, 1006 S 170th, Seatac WA 98148) to Ann Kenny at Washington State Department of Ecology (fax 425-649-7088), requesting attached documents. Attached is an April 4, 2001 certified mail letter from Ecology to Ralph Wessels granting coverage under the Stormwater General

Department of Ecology memorandum dated August 7, 2001, from Director Tom Fitzsimmons to Governor Gary Locke, briefing on Ecology’s decision to approve with conditions a 401 Water Quality Certification to Port Of Seattle for construction of a third runway at Seattle-Tacoma International Airport (Sea-Tac Airport). Covers project impacts including 18.37 acres of wetlands, 980 linear

A August 6, 2001 letter from Water Resources Consulting L.L.C. on behalf of the Airport Communities Coalition critiques the Port of Seattle's 'Low Flow Analysis - Flow Impact Offset Facility Proposal' submitted in support of its Section 404/401 permit application for SeaTac Airport expansion. The letter argues that the Port's plan fails to provide reasonable assurance that the airport's stormwater management will meet water quality standards in Miller Creek, Walker Creek, and Des Moines Creek. Key concerns include an incomplete and unfinished proposal, insufficient stormwater storage capacity, unproven water quality treatment methods, and reliance on vague future 'adaptive management' rather than concrete, enforceable designs.

This August 2001 letter from Northwest Hydraulic Consultants, submitted on behalf of the Airport Communities Coalition, raises technical concerns about the Port of Seattle's Low Streamflow Analysis for the proposed Sea-Tac Airport third runway project. The letter argues the Port's document is incomplete, inconsistent with the Stormwater Management Plan, and lacks critical design details needed to demonstrate that impacts to low streamflows in Walker, Des Moines, and Miller Creeks will be adequately mitigated. Key issues identified include missing sections in the analysis report, unaddressed impacts from airport expansion activities, conflicting information about proposed storage facilities, and failure to account for water transit losses during dry periods.

A technical review letter from Northwest Hydraulic Consultants, written on behalf of the Airport Communities Coalition, raises serious concerns about the Port of Seattle's Low Flow Analysis related to the proposed 3rd runway at SeaTac Airport. The letter identifies the July 23, 2001 document as incomplete and inconsistent with other project plans, citing missing sections, absent facility drawings, and unresolved questions about how water storage and release systems would function in practice. Key technical issues flagged include inadequate accounting for water transit losses, potentially impractical small-orifice flow controls, and poor calibration of streamflow models for Walker Creek.

This August 2001 draft document outlines Water Quality Certification conditions (#1996-4-02325) governing stormwater management at Seattle-Tacoma International Airport (Sea-Tac). It sets requirements for the Port of Seattle to implement and maintain a Comprehensive Stormwater Management Plan, including retrofitting existing impervious surfaces, meeting state water quality standards, and obtaining Ecology approval before discharging stormwater to receiving waters. The document also addresses scheduling, flow control benchmarks, and the use of all known available and reasonable treatment methods (AKART) for runoff from impervious surfaces.

Letter dated August 3, 2001 from Pam Bissonnette, Director of King County Department of Natural Resources, to Ann Kenny, Senior Permit Specialist at Washington Department of Ecology Northwest Regional Office, conveying King County’s technical review findings on the Port Of Seattle’s Comprehensive Stormwater Management Plan (SMP) for Master Plan Update (MPU) Improvements at Seattle-Tacoma International

In August 2001, King County's Department of Natural Resources submitted a technical review letter to the Washington Department of Ecology evaluating the Port of Seattle's Low Flow Impact Analysis and proposed offset facilities for stormwater management near Sea-Tac Airport. The review found the proposal goes well beyond the basic requirements of the King County Surface Water Design Manual and represents substantial mitigation for low flow impacts in affected drainage basins, including Miller and Walker Creeks. Reviewers noted several inconsistencies and data gaps in the documentation and recommended that a final consolidated document be prepared incorporating all corrections and technical memoranda.

This August 2001 draft document outlines Water Quality Certification conditions for Sea-Tac International Airport (STIA), requiring the Port of Seattle to implement a Comprehensive Stormwater Management Plan covering treatment, flow control, and retrofitting of stormwater facilities. Key requirements include obtaining Ecology approval before discharging operational stormwater to state waters, conducting a Water Effects Ratio Study, and ensuring all runoff from impervious surfaces is treated using all known available and reasonable treatment methods. The Port must also retrofit existing stormwater facilities at a rate proportional to new impervious surface construction, with progress documented in quarterly reports.

In August 2001, King County's Department of Natural Resources wrote to the Washington Department of Ecology confirming that the Port of Seattle's Comprehensive Stormwater Management Plan for Sea-Tac International Airport Master Plan improvements met the technical requirements of the 1998 King County Surface Water Design Manual. The review found that the plan demonstrated a feasible conceptual strategy for managing stormwater from proposed airport construction projects. Reviewers noted that while the plan showed compliance with design standards, additional oversight and monitoring would be needed as individual projects moved from planning into construction.