TagACC(1534)

Annual Stormwater Monitoring Report for Seattle-Tacoma International Airport (STIA) covering the period July 1, 1998 through June 30, 1999, prepared by Port Of Seattle, September 1999. Report AR 042872 covers NPDES stormwater sampling at STIA storm drainage subbasins including grab and composite sample results for total petroleum hydrocarbons (TPH), fecal coliforms, suspended solids (TSS), turbidity,

Annual Stormwater Monitoring Report for Seattle-Tacoma International Airport (Sea-Tac Airport) covering July 1, 1998 through June 30, 1999, prepared by Port Of Seattle, September 1999 (AR 026459–AR 026461). Includes stormwater quality data tables for outfalls SDE4, SDS3, SDN1, and SDN4 with copper (CAS No. 7440-50-8) concentration measurements in micrograms per liter, hardness-dependent freshwater acute water

This is the Annual Stormwater Monitoring Report for Seattle-Tacoma International Airport, covering the period from July 1, 1998 through June 30, 1999, prepared by the Port of Seattle. The report documents water quality sampling results from airport storm drainage systems, including measurements of petroleum hydrocarbons, metals, fecal coliforms, and the effects of aircraft and ground deicing activities on runoff. It includes data summaries, outfall inspections, and source tracing studies aimed at tracking and managing stormwater pollution from airport operations.

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

Parametrix, Inc. summary (August 11, 1999) of key wetland findings from the Sea-Tac Runway Fill Hydrologic Studies Report (Pacific Groundwater Group 2000), prepared for the Port Of Seattle Master Plan Update Improvements JARPA review. Covers wetland delineation conservatism, limiting habitat characteristics of Miller Creek, Walker Creek, and Des Moines Creek, salmonid habitat significance, indirect embankment

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.

A 1999 memo from the Washington State Department of Ecology evaluates construction techniques for a retaining wall near Miller Creek at Sea-Tac International Airport's Third Runway project. The memo concludes that specialized methods such as tied-back walls, bored piles, soil nailing, or ground freezing can address difficult underground soil conditions while keeping construction within the approved wetlands disturbance footprint, though at significant cost. The author also recommends installing monitoring devices in the wall and backfill to confirm the structure performs as designed throughout its service life.