Publication Summary

The Washington State Department of Ecology is currently developing guidelines for the disposal of wastes generated by stormwater maintenance activities. This study characterizes contaminants in wastes removed from catch basins.

Decanted water and sediment samples were collected in 1991 and 1992 from vactor trucks operating in residential and commercial areas of Snohomish County and industrial areas of Seattle. Samples were analyzed for conventional water quality variables, physical characteristics, cyanide, metals, volatile and semivolatile organic compounds, total petroleum hydrocarbons, chlorinated pesticides, and PCBs.

The Washington State Department of Ecology is currently developing guidelines for the disposal of wastes generated by stormwater maintenance activities. This study characterizes contaminants in wastes removed from catch basins.

Decanted water and sediment samples were collected in 1991 and 1992 from vactor trucks operating in residential and commercial areas of Snohomish County and industrial areas of Seattle. Samples were analyzed for conventional water quality variables, physical characteristics, cyanide, metals, volatile and semivolatile organic compounds, total petroleum hydrocarbons, chlorinated pesticides, and PCBs.

Water and sediment generally had elevated concentrations of metals, especially zinc, lead, chromium, copper, nickel, and arsenic. Metals in water were attributed to high solids concentrations and were generally undetected in the dissolved phase. Concentrations in water frequently exceeded EPA quality criteria for surface water, and sediment concentrations occasionally exceeded recommended guidelines for freshwater sediment quality. None of the samples analyzed using toxicity characteristic leaching procedures designated as dangerous waste under the state's dangerous waste regulations.

Organics were infrequently detected in decanted water with the exceptions of toluene, ethylbenzene, and xylenes. Polycyclic aromatic hydrocarbons (PAH) and total petroleum hydrocarbons (TPH) were the predominant classes of organics in sediment. PAH and TPH concentrations exceeded the state Model Toxics Control Act cleanup standards, but did not surpass dangerous waste levels (PAH only). Neither chlorinated pesticides nor PCBs were detected.

Fecal coliform bacteria, lead, chromium, PAH, and TPH were considered highest priority contaminants. Concentrations of most contaminants tended to be highest in samples from industrial areas. Samples collected during the dry season generally had higher contaminant concentrations than those collected during the wet season.

Recommendations include establishing a program to periodically monitor vactor truck wastes, determining the value of solids removal from decanted water, and using disposal sites where wastes cannot degrade surface waters.