JUNEAU (AP) -- State officials have identified the substance that shut down part of the Mendenhall Wastewater Treatment Plant this month as aromatic mineral spirits, but they are not sure where it came from.
The city estimated 50 gallons of the material were illegally dumped into Juneau's sewer system Dec. 10.
The solvent may have been used as an automobile degreaser, paint thinner or drying agent, according to Lester Leatherberry of the Department of Environmental Conservation.
''We sent it to the DEC lab in the Valley, where they're really familiar with trying to fingerprint material and trying to figure out what it is,'' he said.
The material most likely came from a business, not a private residence, he said.
The mineral spirits killed sewage-eating microorganisms in one of eight treatment basins at the plant. Plant workers pulled the basin out of service and processed the sludge inside before bringing it back online, said supervisor Roger Hulse.
''We reacted rapidly. We called ADEC to analyze and collect samples and we captured as much as possible,'' he said. ''We captured most of it in the facility. Very little went into the river.''
The plant was never out of compliance because of the incident, Hulse said.
The person or business responsible for the spill may face state and city penalties. A state penalty would depend on the situation and the circumstances, Leatherberry said. Disposal of solvents and similar materials into the sewer system is a misdemeanor under city ordinance.
Each basin at the Mendenhall plant can hold 350,000 gallons of sewage. Killing microorganisms in an entire tank is unusual and an indication of how powerful the spill was, Hulse said.
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