By identifying the substances in the sediment.
By comparing the concentration of the contaminants in the sediment to known chemical benchmarks.
By examining sediment-dwelling organisms.
By testing fish, birds and animals in the area of the contamination.
By analyzing the water in the river.
The toxicity of the sewer sludge pulled from the river exceeds safety benchmarks.
Tests on birds living near the river revealed physical defects.
Tests on fish caught in the river showed contamination.
Reduced fish populations, degraded physical habitats, and alterations in the benthic vertebrate community are all evidence of contamination.
Increased physical defects in fish, increased water staganation and increased populations of sediment dwelling organisms are all evidence of contamination.
They did not have a complete list of the contaminants.
The contaminants combined to make several unknown substances.
Chemical benchmarks were not available for several of the identified substances.
Only a limited area of the WBGCR was contaminated.
The study funding was too limited to permit exhaustive testing of the substance.
The injury to the sediment is greatest in these locations.
The most highly contaminated sediment is close to the source of the contamination.
The turbidity of the water causes contaminants to congregate in certain parts of the river.
People should be warned about fishing in these parts of the river.
The most precise results of the levels of contaminants can be found in these locations.
Dumping from ships in the river.
Rainwater runoff from the surface streets.
Airborne pollution that settled in the river.
The contamination occurred naturally.
Untreated manufacturing waste directly dumped into the water.