Bray Park Weir Tidal Protection Project

23 August 2017, 12.30pm:

Council has begun scouring the mains pipe from the Bray Park Water Treatment Plant to King Street, Murwillumbah, to remove the likely highest salt concentrations from the top end of the Tweed water reticulation system.

A dredge is expected to arrive on site at Bray Park Weir late this afternoon to begin pumping out the heavier salty water from the bottom of the weir as a continual release from Clarrie Hall Dam refreshes with good water at the top of the pool.

Intake baffles at the weir have been closed at deeper depths and the main pump has been set to run at minimal capacity to reduce – as much as possible – the draw of salty water from the bottom of the pool. A smaller floating surface pump has been installed and is running at maximum capacity to draw good water from the top of the pool into the treatment plant.

“With these actions in place to reduce the salty water within the reticulation system and draw in as much ‘good’ water as possible, we have started to dump about one-fifth of the poorer quality water ready for release into the reticulation system in anticipation of producing better quality water tonight,” Manager Water and Wastewater Anthony Burnham said.

“Still, all going well, it is going to be at least three to four days before we get the salty taste out of the water and at least a week before we will be able to produce our normal high-quality drinking water.”

Further investigation into the climatic conditions leading up to the overtopping of the weir wall on Monday night confirms a perfect storm of events.

Bureau of Meteorology and tide data confirms a run of higher-than-expected tides up to 420mm above predicted levels; higher salinity levels offshore; and, warmer ocean temperatures.

Mr Burnham thanked Tweed residents for assisting by minimising their use of water.

“Hospital Hill reservoir is holding relatively steady at this stage which shows people are responding to our request to minimise water use. This effectively buys us time to rid the system of salt before the demand for water forces us to release more poorer-quality water into the system.”

The Australian Drinking Guidelines advise that the current salt levels are not harmful to human health. However, residents are advised to use bottled water for drinking if the taste of the water is too unpalatable.

The water at Uki and Tyalgum is not affected and no restrictions apply in those villages.

22 August 2017:

Council has released water from Clarrie Hall Dam to flush salt water out of Bray Park Weir after high tides overtopped the weir wall on Monday night.

The flush of water from the dam should reach the weir by 5pm today.

More water tests will be conducted about 10 o’clock tonight and if the release has sufficiently reduced the salt content in the weir, the reticulated water supply will be switched back on and should be recharged by tomorrow morning allowing water restrictions to be lifted.

If the release from the dam does not sufficiently flush the weir pool, a second release will occur tomorrow morning, meaning restrictions will remain in place longer.

Council also has drained the salt-charged water from the Bray Park Water Treatment Plant and water mains. It has not drained the affected Hospital Hill reservoir in Murwillumbah as any residual salty water will dilute once fresh water enters the system.

“This morning’s release from the dam also should be sufficient to hold back any salt water from tonight’s high tide, which is expected to be 200mm above predictions,” Manager Water and Wastewater Anthony Burnham said.

Tidal data recorded at the entrance to the Tweed River confirms that since Saturday actual tides have been up to 380mm higher than the predicted tides. The predicted tides at Bray Park were to be 1.79 (Monday pm) and 1.81m (Tuesday am) respectively. The actual tides were 2.17m (Monday pm) and 2.11m (Tuesday am).

“Council uses tide prediction information available through the Bureau of Meteorology to manage the risk of the weir wall being overtopped by salty water. Plus, the natural flow of the Tweed River also helps to hold back a king tide.

“Last night’s incident occurred because the predicted tides, together with the fact that the natural water flow from the Tweed River was still going downstream over the weir wall, informed Council’s decision that sandbagging to raise the height of the weir wall was not warranted.

“In the past, we have had no issues with tides of 1.87m but, this time, the downstream river flows were not strong enough to hold back the salt water.”

The amount of salt water in the weir is significant but not unacceptably high. The Australian Drinking Water Guidelines rule <600mg/litre as being of ‘good’ quality; 600-900mg/litre as being of ‘fair quality; and, >1200mg/litre as being of ‘unacceptable’ quality. The water in the weir was tested this morning and the confirmed total dissolved solids were 620mg/litre.

Council has advised the North Coast Public Health Unit of the situation.

People with medical conditions, such as those using dialysis, are advised to contact their usual medical provider for advice.

Residents are asked NOT to use any water for outdoor uses, such as gardening, washing cars etc.

Residents should also be alert not to use the water on salt-sensitive plants, such as avocadoes, or in fresh-water fish tanks.

At this stage, indoor water use and commercial operations are not restricted. The drinking water supplies of Uki and Tyalgum are not affected.

23 August 2017, 9am:

Council is asking all residents to minimise their use of water to limit the amount of salty water entering the Tweed reticulation system.

The large water pulse released from Clarrie Hall Dam yesterday to flush salt water from the Bray Park Weir pool has had limited success.

“The wave that went down the river yesterday evening prevented further salt water getting into the weir from another higher-than-predicted tide overnight,” Manager Water and Wastewater Anthony Burnham said. “But the salt levels in the Bray Park Water Treatment Plant are higher than yesterday and more residents will have salty water in their taps today.

“The salt concentration will spike shortly and then we will see a gradual decrease in the salinity over the coming days. So it is important that the residents work with us and limit their use of water to minimise the quantity of salty water being drawn into the system. Basically all the salty water drawn in will have to be released via household taps so the less drawn in, the quicker this situation can be resolved.”

Yesterday’s large release of water from Clarrie Hall Dam refreshed the top strata of water in the weir but the heavier salty water had sunk to the bottom of the pool.

“Our tests have confirmed that the water being drawn into the Bray Park Treatment Plant is saltier than the water we tested yesterday morning,” Mr Burnham said.

“We have closed the deeper baffles where the water intake occurs to limit the draw of salt water from the lower water stratum within the weir pond and are only drawing from the top strata, which was refreshed by yesterday’s release from the dam.

“Today we will begin a continual release from the dam of 50 megalitres a day to maintain that refresh as we bring in a dredge to draw the salty water from the bottom and pump it out directly over the weir wall.

“However, the salty water already within the reticulation system is going to spread beyond Murwillumbah today and over the coming days.”

Tides up to 380mm higher than predicted pushed over the weir wall on Monday night.

“Since Saturday, all the high tides have been greater than predicted but the last of these occurred overnight. While the spectacular solar eclipse in the northern hemisphere played a major role in Monday night’s overtopping, the fact is that with the effects of climate change and rising sea levels these events are going to become more frequent and of higher intensity.

“This current incident brings into clear focus the need to raise the wall of the weir and Council will be working hard to get the approvals and licences in place to get this important project off the drawing board and into construction.”

The Australian Drinking Guidelines advise that the salt levels are not harmful to human health. Residents are advised to use bottled water for drinking if the taste of the water is too unpalatable.

The water at Uki and Tyalgum is not affected and no restrictions apply in those villages.

Thursday 24 August, 8.30am:

Council last night managed to reduce the salt concentrations in the drinking water treated at the Bray Park Treatment Plant but has been unable to produce enough ‘good’ water to fully satisfy demand today.

Actions taken yesterday afternoon to bring in a small surface pump to draw the ‘good’ water from the top strata of the dam, avoiding as much as possible any draw of the heavier salty waters from the bottom levels, worked. The amount of total dissolved solids in the treated supply fell to within the ‘good’ range.

However, a number of reservoirs need to be recharged today and Council is again urging residents to use as little water as possible while it works to get more ‘good’ water into the system.

The treatment plant operated all night to treat the water intake but with inflow rates of ‘good’ surface water at just 128 litres per second, Council does not yet have the 20 megalitres of ‘good’ water it will need today to recharge the reservoirs.

Consequently it will start the main intake pump and run it at minimal capacity to limit the draw of salty water and, together, both pumps should draw a greater volume of a suitable ‘shandy’ of ‘good to fair’ quality water to boost production.

The dredge pumping the salty water from the bottom of the weir is now drawing very salty water from a depth of 8.5 metres at about 160 litres a second and releasing it downstream.

“If we can minimise the amount of water consumed and maintain a higher production level of ‘fair’ quality water, the situation will gradually improve from here on,” Manager Water and Wastewater Anthony Burnham said.

“But, if the demand for water is not contained, we will have to draw more salty water into the system to guarantee supply.”

The Australian Drinking Water Guidelines rule <600mg/litre of dissolved solids is ‘good’ quality; 600-900mg/litre is ‘fair quality; and, >1200mg/litre is of ‘unacceptable’ quality. Water produced last night had a dissolved solids concentration of 204mg/litre. By bringing the main pump online Council expects that to rise to about 500mg/litre today. Normally the water produced at the plant has a dissolved solids concentration of 160mg/litre.

The Australian Drinking Guidelines advise that the current salt levels are not harmful to human health. However, residents are advised to use bottled water for drinking if the taste of the water is too unpalatable.

The water at Uki and Tyalgum is not affected and no restrictions apply in those villages.

Wednesday 23 August 2017, 5pm:

A dredge has arrived on site at Bray Park Weir and will be working until late tonight to pump salty water from the bottom of the pool and release it back into the river system downstream.

Meanwhile a smaller floating surface pump has been set up and will be working at maximum capacity all night to push as much ‘good’ water into the Bray Park Water Treatment Plant so several reservoirs can be recharged.

“Our reservoir network is holding up very well given the circumstances but we do need to add water to Hospital Hill, Tumbulgum and Banora Point reservoirs tonight,” Manager Water and Wastewater Anthony Burnham said.

“We are hoping this smaller surface pump will draw a sufficient volume of the fresh water into the treatment plant, avoiding as much draw from the saltier bottom levels of the weir as possible. If we have to switch the main weir pump on to meet demand we will run it at minimum capacity to limit the salty water intake.

“We’ve had a continual release of water from Clarrie Hall Dam today and that water will now be sitting at the top of the weir so the small surface pump intake should be relatively good.”

Council will test tonight’s water intake tomorrow morning to refine its remediation plan.

Council would like to thank residents for their cooperation in minimising their water use during this event.

“Our reservoirs are holding up because people are using less water and this will help us recovery from this event sooner, so we thank everyone for their ongoing efforts.”

The Australian Drinking Guidelines advise that the salt levels in the system are not harmful to human health. Residents are advised to use bottled water for drinking if the taste of the water is too unpalatable.

The water at Uki and Tyalgum is not affected and no restrictions apply in those villages.

Thursday 24 August 2017, 2pm:

The salty water situation at Bray Park Weir is now under control. However, residents are asked to continue to minimise water use as it will take another four to five days for the situation to return to normal.

Council is now producing 440 litres a second of good quality water with a dissolved solids concentration of 279mg/litre. Normal operations produce water at 160mg/litre and Australian Drinking Guidelines state that anything below 600mg/litre is ‘good’ quality.

“Every hour we can produce 1.5 megalitres of good water so we will be in a position shortly to recharge the shire’s reservoirs without the risk of pushing more salt into the system,” Manager Water and Wastewater Anthony Burnham said. “We need 20 megalitres a day to meet demand.

“Gold Coast City Council also has very generously allowed us to open the connection between Coolangatta and Tweed Heads and we are receiving 31 litres a second of quality water from them, equating to about 2.7 megalitres a day.

“We should be in a position to close that connection by mid-morning tomorrow.”

Council will continue to release 90 megalitres a day from Clarrie Hall Dam for the next few days to continue to top up the good supplies in the top strata of the weir pool as the dredge works to draw the heavier salty water from depths of about 8.5 metres and discharge it downstream.

“The dissolved solids concentration at the bottom depths has been measured at 3700mg/litre so we are very appreciative of the huge effort of our staff and the assistance of external agencies, contractors and the Gold Coast City Council who have worked to control this situation.”

Tuesday 29 August 2017

The voluntary water restrictions have been lifted on outdoor uses for Tweed town water, after Council has taken a number of measures to address the effects of salt water entering Bray Park Weir.

Manager Water and Wastewater Anthony Burnham said dredging at the weir, steps to modify how water was drawn from the weir and scouring of mains pipes had succeeded in producing town water supplies with lower salt contents over the weekend.

The improved water quality has assisted Council to refill reservoirs throughout Tweed Shire. However, the ongoing presence of elevated salt levels means this salty taste is now affecting more consumers than last week.

Immediate water restrictions were put in place in Tweed Shire on 22 August after a combination of climatic conditions caused salt water in Tweed River to surge over the weir wall: a run of higher-than-expected tides up to 420mm above predicted levels, higher salinity levels offshore and warmer ocean temperatures.

Mr Burnham thanked the community for minimising water use while Council worked to bring salt levels down.

“The community response bought us time to drain the worst affected parts of the system before demand for water forced us to release water with higher than normal salt levels into the system,” he said.

“Ninety megalitres of water has been released from Clarrie Hall Dam each day to top up the good supplies, while dredging works drew the heavier salty water from the depths of the weir pool and discharged it back downstream.

“Salt levels again marginally improved at Bray Park Weir during the weekend as a result.”

Mr Burnham emphasised the water has remained safe to drink in line with Australian Drinking Water Guidelines.

He said the water is also suitable for outdoor use, such as washing cars but some care should be taken when watering salt-intolerant plants or for use in freshwater fish tanks.

“Dredging is ongoing and we are continuing to release water from Clarrie Hall Dam. We expect water quality in the weir will continue to improve during the next three to five days,” he said.

The Uki and Tyalgum villages have a separate water treatment system and are not affected.

Tuesday 29 August 2017

Council has now got two dredges working to pump salty water from the lower depths of the Bray Park Weir.

Together they are pumping about 380 litres a second out from depths up to 12 metres and discharging it over the weir wall and downstream.

The dissolved solids content from 12 metres is just shy of 3000mg/litre.

Tweed’s normal dissolved solids content for the drinking water it treats at Bray Park Water Treatment Plant is 160mg/litre. Levels currently in the mains pipes are at about 360mg/litre, indicating residents may still taste the salt for a few days’ yet. However, water treated at the plant and due for release in the next few days is at near-normal levels of 250gm/litre.

The weir is 19 metres at its deepest point and salt concentrations at the bottom of that hole are likely to be very high as they have been built up over many years with heavier salty waters sinking. It is not known yet whether the current dredging operation will manage to pull water from that depth.

Meanwhile Council is continuing to harvest water from the weir up to about two metres deep and refresh it with a continual release of 50 megalitres a day from Clarrie Hall Dam.

“We are continuing to get good quality water into the Bray Park Water Treatment Plant but it will still be several days before the salty water has been removed through household taps with normal water consumption,” Manager Water and Wastewater Anthony Burnham said.

The water is good to drink but should not be used on salt-sensitive plants or in freshwater fish tanks.

Meanwhile the Bureau of Meteorology has confirmed that a number of climatic factors came together in a rare event resulting in the overtopping of the weir wall on the night of Monday 21 August.

First, there was a run of high tides up to 420mm higher than predicted. Second, sea waters were saltier than normal. Third, ocean temperatures were higher than normal. And fourth, a ‘trapped’ wave travelled north up the coastline to the Tweed.

“Under normal operating procedures, Council uses tidal information together with downstream river flows to manage the risk of the weir wall overtopping during high tides,” Mr Burnham said. “If the information indicates overtopping is likely, we raise the weir wall with sandbags. However, that data failed us this time given the ocean anomalies that were in play.”

Dredging of the lower depths of the weir will continue for the remainder of the week.

Monday 4 September 2017

Council is continuing to dredge salty water from Bray Park Weir to return the Tweed water supply to normal.

Two dredges are working to pull water from the depths of two deep holes; one very close to the intake tower. The water the dredges are discharging downstream over the wall of the weir has a dissolved solids content of 3100mg/litre.

The water now being produced at the Bray Park Water Treatment Plant has a dissolved solids content of 198mg/litre, which is very near Council’s normal high-quality water standard of 160mg/litre.

Chlorine dosing levels at the plant have been reset to normal.

“Over the coming week or so there may still be elevated salt levels in our tap water as it does take some time for our reticulated water network to completely refresh,” Manager Water and Wastewater Anthony Burnham said. “But the water is not harmful to human health and the salt levels have remained well within the ‘good’ range as set by the Australian Drinking Water Guidelines.”

Meanwhile, Council workers are today filling sandbags in readiness for sandbagging the wall to protect the weir from another predicted high tide in coming days.

“It’s going to be difficult to sandbag the wall yet maintain the current daily release of fresh water from Clarrie Hall Dam,” Mr Burnham said.

Meanwhile, Council has had some reports of dirty water in parts of Murwillumbah. This was a result of Hospital Hill reservoir empting on Saturday evening and air getting into the mains, leading to a scouring action in the pipes and the water becoming discoloured.

“This is a separate issue and has nothing to do with the salt water issue,” Mr Burnham said. “We will respond individually to these calls and flush the pipes at affected properties. We have had a total of 24 calls to 11am this morning.”