As floodwaters receded after the March 1 floods, some Broadwater residents were left with a black, oily sludge dripping from the walls of their homes and in their gardens.

The Environment Protection Authority has done assessments of those Broadwater homes with hydrocarbon contamination. Hydrocarbon includes oil, diesel and other fuels.

A specialist consultant is doing soil assessments and sampling from the yards of affected properties. The results of this testing will be provided to residents and used to decide remedial strategies.

The EPA has identified multiple likely sources of the contamination but are yet to announce those sources.

While many homes have already been cleaned up, the EPA is cleaning remaining houses as a matter of urgency.

The EPA is also conducting monitoring of waterways affected by the floods and is advising the community of any risks. 

It is recommend that water affected by diesel or oil is not consumed or used for any recreational or agricultural purposes. The community is encouraged to avoid contact with waterways if they are affected by pollutants.

When diesel and oil are released into the environment, natural degradation processes start to occur immediately.

Components of diesel and oil that are volatile evaporate (change from liquid to gas) first and get broken down quickly by oxygen in the air.

Based on the current absence of odours and the time passed since the flood event, it is likely volatile components of the spill have already evaporated and broken down.

Natural degradation by microorganisms in soil will continue to break down residual diesel and oil.

Diesel and oil also degrade by reaction with water to form a sludge like material in a process called hydrolysis. The sludge will be degraded further by the same soil microorganisms.

Up to 98% of the original contamination will be degraded within the first 30 days but it can take up to six months depending on the level of contamination, soil type and climactic condition such as cold weather.

This is why microbial degradation processes are used to remediate fuel and oil contaminated soils at service station sites.

The presence of earthworms in affected soil is a good indicator that microbial degradation is at an advanced stage and soil conditions are returning to normal.

An EPA spokesperson said they would make sure there were high levels of transparency for the community in their investigations.

Laboratory results will be tabled in the second week of April and by mid-April there will be a draft remedial action plan.

If you see a potential incident with serious environmental impacts please contact the Environment Line immediately on 131 555 or by email at info@epa.nsw.gov.au

This article appeared on indyNR.com on 5 April 2022.

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