Is Brunswick Valley STP overloaded?

Paul Bibby

It’s the morning of January 1, 2015, and locals are welcoming in the new year with strong coffees and sun salutations.

But down the end of Vallances Road, just outside Mullumbimby, something very unwelcome is bubbling up from the depths.

At the Brunswick Valley Sewerage Treatment Plant (STP), raw or partially treated sewage is flowing out of a processing unit.

Photographs of the incident obtained by The Echo show the wastewater bubbling up into a large, brown pool that is spilling out onto the grass surrounding the unit.

Council officers are sent to the site to clean up the mess, and a few days later the NSW Environmental Protection Agency (EPA) is informed of a ‘rainfall event’ and a ‘contained’ overflow incident.

There is no public announcement to report that an overflow incident has occurred.

Nor, according to one former councillor, were councillors given a clear and informed report about the incident.

In a statement to The Echo, Byron Shire Council staff said that all of the wastewater was contained in the site rather than flowing into the Brunswick River and that it met its reporting obligations by informing the EPA.

The statement said the ‘alleged overflow’ occurred owing to the combination of a design flaw in one of the processing units, and ‘a rainfall event where the area received some 250mm in a very short time’.

‘Council staff immediately responded to the incident… [and] resolved the issue in the process unit, while allowing the treatment plant to remain in service for the residents of Brunswick Heads and Mullumbimby.

‘The event highlighted a design deficiency in the process unit. This deficiency was rectified through modification of the treatment unit and there have been no overflow/bypass incidents since the 2015 modification works.’

One-off incident

So was this just a one-off incident with no implications for the sewerage system in this part of the shire?

When contacted by The Echo in relation to the incident, former local sewer operator Alan Dickens described the photographs as ‘deeply concerning’.

‘Those pictures show a sewage treatment plant that is experiencing significant hydraulic overload,’ said Mr Dickens, who is also a member of Council’s Water, Waste and Sewer Advisory Committee (WWSA committee).

‘Given that the plant had only been commissioned four years before, this is a very concerning situation.

‘You are not supposed to see raw or partially treated wastewater flowing out of a four-year-old STP.’

‘I would suggest that this was not the first time this had happened, or the last.’

Internal Council documents indicate that the Brunswick Valley STP has repeatedly experienced wastewater flows above its capacity (known as hydraulic overload), since it was opened in November 2011.

According to a draft water supply and sewerage report prepared for Council late last year by Hydrosphere Consulting, the hydraulic loading at the Brunswick Valley plant is more than triple the design standard during non-peak dry weather. When significant rain events occur, the load on the plant increases dramatically because large volumes of stormwater infiltrate the sewerage system.

Referring to a previous risk assessment, the report notes that, because of this very high hydraulic load, ‘the risk of inadequate treatment of pathogens… suspended solids and chemical contamination is very high’.

The report notes that while significant works undertaken by Council over the past seven years have resulted in a 15 per cent reduction in overflow incidents and a 39 per cent reduction in overflow volume, the Brunswick Valley STP is still regularly operating at above capacity.

In its statement, Council said that between 2011 and 2015 there had been ‘three other process bypass incidents, none of which resulted in any overflow into the Brunswick River.’

Mr Dickens and fellow WWSA committee member and former Greens councillor Duncan Dey said that the key cause of the overflow incidents was the infiltration of stormwater into the sewerage system.

‘We still have an old network of clay pipes throughout most of Mullumbimby,’ Mr Dickens said.

‘I’ve been down there a number of times when I was working for Council. They’re degraded, they’re cracked and in places there’s basically nothing to stop water getting out or getting in.

‘Prior to the construction of the Brunswick Valley plant, this infiltration resulted in wastewater bubbling up from the sewerage system before reaching a treatment plant.

‘During heavy rains raw sewage could be seen churning up in the Brunswick River at the northern end of Stuart Street, where the overflow relief system discharged underwater. When the Brunswick River plant went online, powerful pumps were installed to send the very large volumes of wastewater to the new plant for treatment and there are now questions over whether it is managing to cope.’

Mr Dey said it was deeply concerning that councillors had not been given a report about the incident.

‘This was directly relevant to the proposal to close the Ocean Shores STP and pipe all of that waste to the Brunswick Valley plant,’ he said.

‘We needed to know that Brunswick Valley STP was experiencing this kind of hydraulic overload.’

Council did not respond when asked why staff had not reported the incident to councillors. However, it defended its actions and environmental record.