Derrimut warehouse explosion: Contaminated ‘fire water’ set for Port Philip Bay and agriculture

Five Olympic-sized swimming pools worth of contaminated ‘fire water’ from a massive factory blaze will be released after remediation into Melbourne’s Port Philip Bay or used for agricultural purposes.

Authorities are still monitoring local waterways for lasting signs of chemical contamination more than two weeks after an inferno at the Derrimut warehouse, in the city’s west, that was so fierce it sent metal drums flying hundreds of metres skyward.

It was the biggest industrial fire the city has seen in years.

Chemicals stored onsite including kerosene, methylated spirits and methanol fuelled the flames as water and foam used to battle the blaze seeped into nearby creeks.

Authorities trapped 12 million litres of runoff in the days after the emergency before pumping it into sewers and on to the Western Treatment Plant at Werribee.

Sandbags, plugs and booms remain around the area to absorb pollutants.

Locals and their pets have been urged to stay away until further notice, with warnings in place for parts of Laverton Creek, Cherry Creek, Altona Beach and Doug Grant Reserve Dog Off Leash park.

“Contaminated firewater has entered the waterways and could still be there,” Environment Protection Authority Victoria western metropolitan regional manager Stephen Landell told AAP.

“Some of those materials can sometimes cause irritations and those sorts of things.”

Results from testing in the days after the fire revealed acetone in Laverton Creek which prompted “extra precautionary advice” but overall, the waterways were looking healthy, he said.

The agency is waiting on another round of results due within the week to determine what happens next.

“Thankfully with this incident, we we still haven’t seen any dead fish or impacted wildlife, which is fantastic,” Mr Landell added.

He said his agency still hadn’t been able to access the burnt factory site but there were hopes the situation could change next week, with Fire Rescue Victoria due to hand the area over to WorkSafe.

Melbourne Water, the EPA and the fire service captured the fire water and guided it into sewerage using sandbags and booms over four days but the treatment process has only just begun.

It can take up to three months before the water will be deemed suitable for release into Port Phillip Bay or used for non-drinking purposes within industry or agriculture, including for crop irrigation.

Western Treatment Plant Head Kris Coventry said bacteria would effectively ‘eat’ the chemicals and turn them into carbon dioxide.

“Having chemicals like hydrocarbons diesel, oil and gasoline coming to a treatment plant is always a better outcome than letting them go into a waterway,” he added.