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As a follow up to past NPDES stormwater sampling, the Port of Seattle used the microbial source tracking (MST) technique to evaluate potential sources of fecal coliform (FC) bacteria present in runoff from Seattle-Tacoma International Airport. This genetic “fingerprinting” technique indicated that overall, more than 90% of the fecal contamination in runoff was attributable to animals. More than 60% of the “fingerprints” matched bird sources and 30% matched small mammals and domestic pets. Pigeons accounted for 20 to 25% of the bird sources for two outfalls in particular, and were most likely linked with a pigeon colony found on the terminal rooftop. Overall, less than 10% of the isolates matched human sources, and these were limited to certain sampling stations and events. Baseflow samples from the principal outfall investigated, as well as others at the airport, did not contain human isolates. Instream samples collected up gradient from the airport exhibited human isolates in storm and baseflow samples. Many of these receiving water samples had FC counts that would exceed the current state water quality standard of 50 CFU/100ml. Overall, E. coli represented 62% of the fecal coliforms present.

Overall, the MST study showed that human sources were present sporadically for two airport outfalls and two stream locations, but occurred in small numbers relative to animal sources. Coupled with this low incidence of human source fingerprints, the FC concentrations point to minor contributions from human sources. The highest FC concentrations found in airport runoff were several orders of magnitude less than FC counts found in local raw domestic sanitary and aircraft lavatory wastewater. Several source-specific fingerprints linked the E. coli strains of human origin found in the airport's storm drain system to aircraft lavatory wastewater handling. Although this study shows that this potential source is very limited, the Port is currently investigating improvements to best management practices. The Port already has an active aircraft bird-strike and rodent control program, which has been adapting to reduce nuisance populations.

Document Type: Research Article


Publication date: January 1, 2002

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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