In the late 1990s, the Puget Sound Regional Council concluded its sole option for expanding commercial aviation capacity was at Seattle-Tacoma International Airport. At the time, the Port of Seattle determined it could not establish a third runway without wetland encroachment and needed permits requiring control of both quantity and quality of stormwater discharge.
In 1999, while
conducting Whole Effluent Toxicity (WET) testing as part of implementing requirements
for its National Pollutant Discharge Elimination System (NPDES) permit, the
ports surface water management team discovered that stormwater at a particular
location in the drainage system showed aquatic toxicity. Although this runoff
was non-toxic at its eventual discharge point into Miller Creek, the port elected
to investigate the source of toxicity in the runoff.