TagDes Moines Creek(169)

In this October 1999 letter, the Washington State Department of Ecology reviewed a study by the Port of Seattle examining how de-icing chemicals used at Sea-Tac International Airport affect water quality in Miller and Des Moines Creeks. Ecology found significant deficiencies in the study, including incorrect water quality classifications, too few de-icing events sampled, and inadequate monitoring methods, concluding that dissolved oxygen levels in both creeks frequently failed to meet applicable standards. The agency requested that the Port resubmit the study with corrections before a determination could be made about whether de-icing operations were being properly managed to protect local waterways.

Dissolved Oxygen Deicing Study prepared by Cosmopolitan Engineering Group for Port Of Seattle Sea-Tac International Airport (AR042698, August 1999), examining impacts of de-icing agents from airport stormwater runoff on Miller Creek and Des Moines Creek, including BOD5 discharges to NW Ponds and Lake Reba. Accompanied by Washington State Department of Ecology (NWRO) response letter dated

In this October 1999 internal memo, Washington State Department of Ecology staffer Tom Luster describes a meeting with his supervisor Paula regarding the agency's water quality review of Sea-Tac Airport expansion. Luster explains that he cannot yet provide 'reasonable assurance' that the Port of Seattle's proposal will meet water quality standards for Des Moines Creek, citing inadequate stormwater treatment plans and the Port's removal of flow augmentation measures from its mitigation plan. He expresses concern that management pressure to approve the project quickly could compromise the integrity of the regulatory review process.

Internal email from Tom Luster (Ecology) to Raymond Hellwig, Kevin Fitzpatrick, Erik Stockdale, and Paula Ehlers, dated September 16, 1999, regarding SeaTac Airport 401 certification and compliance with water quality standards under the Clean Water Act. Discusses non-attainment of water quality standards in Des Moines Creek and Miller Creek, antidegradation requirements, Level 2 detention requirements,

Internal email from Tom Luster (Washington State Department of Ecology) to Raymond Hellwig, Kevin Fitzpatrick, Erik Stockdale, and Paula Ehlers dated September 16, 1999, outlining unresolved stormwater issues in the 401/CZM review of Port Of Seattle’s Sea-Tac Airport Master Plan Expansion. Topics include: definitions of ‘modified Level 1’ and ‘Level 2-type flow control’; role of

A 1999 technical memorandum from Parametrix, Inc. analyzes whether stormwater discharged near Des Moines Creek meets Washington State dissolved copper water quality criteria, using a Monte Carlo simulation model. The analysis finds that copper levels in the stormwater effluent consistently exceed water quality standards regardless of background ambient concentrations, with dilution factors generally less than 2. The study evaluates several potential remedies, including increased onsite detention, expanded mixing zones, and water effect ratio adjustments, finding that the Water Effect Ratio (WER) is the most influential factor in achieving compliance.

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.

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,

This 1999 email exchange between Washington State Department of Ecology staff debates the legal basis for requiring the Port of Seattle to restore water quality in Des Moines Creek as a condition of receiving a Section 401 water quality certification for the Sea-Tac Airport third runway project. The central question is whether Ecology can require a single applicant to fix broader watershed problems that pre-exist their project, or whether mitigation can only address the applicant's direct project impacts. Staff ultimately conclude that under antidegradation requirements, no further degradation of the creek can be permitted until existing beneficial uses are restored, meaning the Port's mitigation plan must include measures such as flow augmentation and stormwater controls to bring the creek into compliance with water quality standards.

Email chain (AR 033708–033710) among Washington State Department of Ecology staff Paula Ehlers, Tom Luster, and Raymond Hellwig, with ATG staff Tom McDonald and Joan Marchioro, dated June 1–13, 1999, regarding the Port Of Seattle third runway proposal and 401 water quality certification for Des Moines Creek. Discusses antidegradation requirements under Washington Water Quality Standards