TagWater Quality(478)

This 1999 internal memo from the Washington State Department of Ecology details the history of environmental cleanup oversight at Seattle-Tacoma International Airport, where 15 separate contaminated sites involving jet fuel and gasoline were managed individually under the state's Model Toxics Control Act. The memo describes a series of prepaid staff positions funded by the Port of Seattle to coordinate cleanup efforts with airline and pipeline companies, and the challenges in getting formal Agreed Orders signed. It concludes with an update that a key groundwater study Agreed Order was finally signed in May 1999 after receiving over 600 public comments in opposition.

A 1999 technical memorandum from Parametrix, Inc. to the Port of Seattle analyzes the sensitivity of stormwater discharge compliance determinations for Sea-Tac Airport's runways, focusing on dissolved copper concentrations in Des Moines Creek. The memo evaluates whether mixing zones and dilution factors could offset elevated copper levels in stormwater runoff, finding that ambient copper concentrations already exceeded water quality criteria in 37–65% of samples. The analysis concludes that dilution factors based on streamflow alone are unlikely to be significantly greater than 1.0, though accounting for the Northwest Ponds' reservoir volume raises the estimated dilution factor to approximately 1.7.

This draft memorandum from Parametrix (dated April 20, 1999) summarizes range-finding toxicity tests conducted as part of a water-effect ratio (WER) study examining copper levels in streams receiving stormwater runoff from Seattle-Tacoma International Airport (STIA). Water samples were collected from Miller Creek, Walker Creek, and Des Moines Creek during a storm event in February 1999 and tested using the organism Ceriodaphnia dubia to measure copper toxicity. Results showed water effect ratios ranging from 6.7 to 16.0, leading researchers to recommend pursuing a definitive WER study and a site-specific water quality standard for copper.

Conceptual Flow Model Boundary Presentation for the Seattle-Tacoma International Airport (STIA) Ground Water Study, prepared by Associated Earth Sciences, Inc. and S.S. Papadopulos and Associates, Inc. for Port Of Seattle. Document AR043187 includes a Project Area Map (Figure 1, dated 08/03/99) showing the data collection boundary, Airport Operations and Maintenance Area (AOMA), wellhead protection delineation

A 1999 internal technical memo from Parametrix, Inc. evaluates three alternative water-quality dilution modeling methods for assessing whether proposed stormwater outfalls at the Port of Seattle could exceed Washington State water quality standards. The methods range from a static single-event approach based on Ecology's Permit Writer's Manual to a dynamic continuous simulation using HSPF hydrologic models and a probabilistic EPA-funded model developed by researcher Dominic Di Toro. The memo recommends continuing with the continuous simulation approach while considering budget, Ecology's involvement, and the nature of ambient and effluent pollutant concentration data.

This document is a section of Washington State's Permit Writer's Manual covering Water Effect Ratio (WER) methodology for water quality permitting. It outlines procedures for determining how receiving water conditions affect the toxicity of discharged effluents, including required toxicity testing species, sampling schedules at critical and non-critical flow conditions, and guidelines for freshwater and saltwater discharge situations. The document is unrelated to Sea-Tac Airport noise policy.

Conceptual Flow Model Presentation for the Seattle-Tacoma International Airport (STIA) Ground Water Study, prepared by Associated Earth Sciences, Inc. and S.S. Papadopulos and Associates, Inc. for the Port of Seattle, presented to the Washington State Department of Ecology on June 30, 1999. Document outlines study area including Des Moines Creek, Miller Creek, Bow Lake, City

Memorandum from Ken Ludwa of Parametrix, Inc. to Elizabeth Leavitt, dated June 29, 1999, reviewing the Draft De-Icing Dissolved Oxygen Report related to Sea-Tac Airport runway and taxiway acetate washoff. Comments address dissolved oxygen (DO) water quality standards (8 mg/L Class A, 9.5 mg/L Class AA) in Miller Creek and Des Moines Creek, NW Ponds,

A 1999 draft assessment prepared by Parametrix, Inc. for the Port of Seattle outlines best management practices (BMPs) for managing stormwater runoff at Seattle-Tacoma International Airport as part of its Master Plan Upgrades. The document describes how the Port plans to implement water quality treatment measures—including filter strips, bioswales, and wet-vaults—across existing and newly developed stormwater drainage subbasins to meet Washington State Department of Ecology redevelopment requirements. Note that while archived alongside airport planning documents, this report focuses on stormwater and water quality compliance, not noise policy.

Technical memorandum prepared by HNTB Corporation for the Port of Seattle and Parametrix, Inc. (June 15, 1999) analyzing temporary wetland impacts during Seattle-Tacoma International Airport Third Runway embankment construction. AR 042490. Covers storm water management during construction, temporary fill in wetlands west of runway embankment toe, impacts to Wetland 37 (Miller Creek basin) and Wetland