THE wash up from this month’s flooding event at Narooma continues for both Narooma oyster growers and residents of the Flat.
Oyster growers were facing a three-week closure after the more than 200mm rain event resulted in six sewerage pumping stations overflowing into Wagonga Inlet, while residents on the Flat continue to call on Eurobodalla Shire Council to review drainage in the McMillan Road and Riverside Drive area.
The oyster growers are hoping that the automatic three-week closure following a sewerage spill may be lifted for the top portion of the lake at least with water tests due back today.
NSW Food Authority meanwhile has authorised testing of the bottom half of the lake closer to town later this week.
Oyster grower David Maidment said while it was disappointing to have the six sewerage stations overflow, the rain event was massive and any rainfall over 50mm did require the estuary to be closed until the freshwater dissipated, a process that could up to 10 days.
“We’re hopeful the top half of the lake will be opened later this week,” Maidment said.
Other growers however continue to call on meetings with council to review the sewer system and its impacts on the estuary, also calling for council to be obligated to put up signage warning the general public of spills.
A council spokesperson said there had been two spills to the Wagonga Inlet in the past two years.
One of these was a few kilolitres and it was caused by a break in a sewer rising main.
The second spill was a few litres that had overflowed a sewer manhole following a sewer choke. This was caused by tree roots that had intruded into the sewer main.
In incidents such as the recent heavy rains in Narooma, ground water rises above the gullies that are located on individual properties, and the volume of storm water entering the system exceeds the capacity of the station to pump.
“When this happens, council’s sewer pumps work at their maximum capacity and continuously to minimise the emergency,” the spokesperson said.
“The flooding water also can enter the sewer station’s emergency relief pipe which further exacerbates the situation.”
Council also puts up signs to let the public know that it is unsafe to swim near the affected area and put emergency updates on its website to inform the community of poor water quality following significant wet weather events and sewer surcharges to the environment.
Residents deal with flood wash-up
RESIDENTS on the Narooma Flat meanwhile continue to deal with the aftermath of the flooding event on Tuesday, October 14.
This includes 76-year-old George Hulley who has lived in Narooma all his life and whose house on McMillan Road also flooded back in the 2010 heavy rainfall event.
He again lost all his carpets and some of his furniture in this latest deluge.
“The drainage is inadequate and overloaded and what we need is proper drainage channel into the inlet,” he said.
Growing up he recalls a creek flowing into the inlet where the current drainage pipes exit under Riverside Drive at Quota Park, and also a swampy area where Bill Smyth Oval sits today that funnelled water in the other direction toward the new roundabout.
He called on council to conduct a proper review of the drainage system as it was only a matter of time before it happened again.
The full council response to Narooma News questions:
Is there any scope to limit the number of overflows?
The pumping stations are located next to the estuary so that when there is an overflow it has someone to go...
What is the reason for these overflows other than the obvious flooding? How many spills have there been into Wagonga in the past year/two years?
There have been two spills to the Wagonga Inlet in the past 2 years. One of these was a few kilolitres and it was caused by a break in a sewer rising main. By putting works crews on the pumping station around the clock while the repair was carried out, Council was successful in minimising this spill as much as possible. The second spill was a few litres that had overflowed a sewer manhole following a sewer choke. This was caused by tree roots that had intruded into the sewer main.
The Plumbing Code of Australia set out regulations that emergency relief gullies must be installed 150mm below the floor level of a house, and 50 mm above the ground level. In incidents such as the recent heavy rains in Narooma, ground water rises above the gullies that are located on individual properties, and the volume of storm water entering the system exceeds the capacity of the station to pump. When this happens, Council’s sewer pumps work at their maximum capacity and continuously to minimise the emergency. The flooding water also can enter the sewer station’s emergency relief pipe which further exacerbates the situation.
In Australia, most sewer systems are designed to accommodate normal amounts of infiltration during wet weather events, but not flooding during extreme events such as experienced in Narooma last week.
The volume of storm water entering during a minor flood means that the discharge is highly diluted and is estimated to be a ratio of around 99.99% water to .01% solids.
Narooma’s sewerage system has 21 pumping stations and Council is continually monitoring and upgrading its sewer systems with the help of sophisticated computer modelling programs. By using flow modelling, Council can identify when pipes need upgrading or redirecting to neighbouring catchments.
Is there any obligation on council to notify the general public when a spill happens as the impact could be on the general public not just growers? Is there a protocol with signs etc?
Council has protocols to manage sewer discharges that are likely to enter waterways and these include sewer spill notification. In the event of a spill, Council notifies the NSW Office of Environment and Heritage, the Environmental Protection Authority, the Department of Health and the local Shellfish Quality Assurance Coordinator oyster representative of any potentially impacted oyster estuary.
Council also puts up signs to let the public know that it is unsafe to swim near the affected area. The signs remain in place until water sampling has returned results that meet water quality guidelines. Council puts emergency updates on its website to inform the community of poor water quality following significant wet weather events and sewer surcharges to the environment.
Additional general information
Oyster farmers in Narooma and other areas of the State, manage oyster growing and harvest areas in accordance with the NSW Shellfish Program which has adopted the Australian Shellfish Quality Assurance Program (ASQAP) as a minimum standard. The ASQAP is administered by the NSW Food Authority and sets out criteria for the closure of Oyster Harvest areas, which includes closures of harvest areas when rainfall reaches trigger levels. The NSW Food Authority works with the local oyster farmers to close harvest areas when necessary and re-open them when microbiological testing confirms that the estuaries are clean and shellfish have recovered.
Unfortunately poor quality water issues can impact local oyster businesses during storm events such as the recent heavy rainfall in Narooma which occurred as a result of the east coast low pressure system. Improvements in weather prediction technologies and the implementation of emergency contingency plans by oyster farmers such as harvesting stock prior to compulsory closures have reduced the disruption to supply and demand for growers.
Council supports the oyster industry by financing the shellfish and water quality testing and monitoring during these times and as recognition of the local oyster farmers’ commitment to maintaining a high level of quality assurance to ensure their reputation as one of the world’s best oyster producing areas.