By ELEANOR BLACK
ROTORUA - A potentially explosive problem lurking in the depths of Rotorua's sewerage system has council staff on the alert for sneaky hazardous-waste dumpers.
For the fifth time in 18 months, thick waste oil has been illegally dumped into the sewers, releasing a toxic gas capable of producing an explosion.
Travelling through the city's 500km of sewage pipes, the explosion would throw manhole covers into the air and force thousands of litres of wastewater into the streets.
Sewage pump attendant Rex Kilmore was lucky he tested the sewer atmosphere at the Depot St pump station on Friday before climbing into the well. He said levels of explosive were so high a whiff of oxygen or a tiny spark would have been enough to create a fireball.
An hour later, a slug of about 100 litres of black oil passed into the nearby wastewater treatment plant, floating on top of the water.
"It could be accidental, but I think someone is trying to save some money," said pollution control officer Joseph Gielen.
Businesses which produce industrial waste are meant to pay a certified contractor to take it away.
Mr Gielen suspects that one of the more than 150 automotive businesses in the Old Taupo Rd area has been cheating.
Rotorua District Council, which has tightened wastewater regulations because of this danger, is trying to trace the culprit - who could face a $200,000 fine or imprisonment.
The council said the discharge also posed an environmental risk.
Fireball waiting in city sewers
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