# Discharge ports, meters per second, cubic meters per second.

## Discharge ports, meters per second, cubic meters per second.

Dynamo

Could I have some information regarding the discharge ports please?

Am I correct that there are 6 in total, 3 on each side of the vessel?

What is the width of the port at point of discharge?

What is the spacing ( distance) between discharge ports?

Am I correct to assume all  6 discharging ports have to pump continuously over a 24 hour period to purge the proposed 450 million litres of chilled toxic water?

Could you provide a diagram which shows where these ports are located on the FSRU whilst moored at Berth 2?

Could you also provide a diagram which indicates the simutaneous trajectory of discharge of each of the 6 ports as I cannot understand how 3 ports discharging  via 60 meter jets on one side of the vessel and 3 ports discharging via 60 meter jets on the other side of the vessel form one solitary plume?

Am I correct that all 6 ports collectively discharge a volume of 5.2 cubic meters per second (or put easier for everyone to grasp as all AGL's proposal information should be displayed ! ), 312,000 litres per minute or 18,720,000 litres per hour ( EIGHTEEN MILLION SEVEN HUNDRED AND TWENTY THOUSAND LITRES PER HOUR) ?  Or should that be a volume of 5.2 cubic meters discharged per second for each port?

Am I correct that the velocity (speed) of discharge from each port is 5 meters per second- or put easier for everyone to grasp 18 Kilometers an hour?

Is it correct that the mean tidal current for Westernport is 0.3 meters per second, or to put easier for people to grasp 1.08 kilometers per hour?

20 REPLIES 20
AGL Employee

Hi @KerryRainer,

We have sent your queries to the engineers working with the heat exchange process to discuss the particular concerns you have raised. We hope to have an answer for you soon.

Please be aware that we have registered your response and will be in touch soon.

Thanks,

Lachlan

Conductor

Hi @KerryRainer,

I am from CEE Environmental Scientists and Engineers. We are pleased to respond to your questions about the seawater discharge ports on the FSRU.

The design and operation of the FSRU including the locations of intakes and discharge ports and the velocity of discharge flows was based on an understanding of the project at the time of preparing the EES and EPBC referrals.

The seawater discharge ports return seawater used to heat the LNG back to a gas. During the heat-exchange process to warm LNG, up to 450,000 m3/d of seawater will be taken from Western Port by the FSRU, passed through a heat exchanger and  discharged back to Western Port. The circulated seawater discharged from the heat exchanger will be approximately 7oC cooler than ambient seawater.

The present design has six discharge ports, three on each side of the FSRU, with a spacing of about 10 m between the ports.    Each port would be located about 2 m below the surface and has a diameter of 0.45 m (or 450 mm).  The discharge velocity at the port is 5.4 m/s.

The 10 m spacing between the ports, and the separation of three ports on one side and three on the other side, result in six separate plumes that can dilute individually until the reach the seabed or are mixed into the ambient flow.

The number of ports that will be discharging water from the FSRU will depend on the rate of production of gas.  There are three heat exchangers and two ports for each heat exchanger, so either two, four or six ports will be operating.

The environmental assessment includes consideration of the highest discharge case of six ports operating continuously, when the discharge of cooler seawater would be 450 million litres per day.   You are correct in your calculations that flow equals 5.2 m3/s (cubic metres per second) in the highest discharge flow case.

For context, the volume of seawater from Bass Strait entering the Western Arm each day is 0.8 km3 (Westernport Science Review, page 53).   This is 800,000 million litres, equivalent to 1,770 times the daily amount of cooling water used by the FSRU when operating at the highest discharge case.

To use another scale, the flow rate of 5.2 m3/s is equivalent to the propeller discharge of five 40 HP outboard motors on boats travelling at 20 knots.

As a further scale, the flow rate of 5.2 m3/s is equivalent to one-tenth of the propeller discharge of a container vessel travelling at 18 knots.

Just as the propeller wake from a boat dissipates through mixing, the plumes of cooler water mix with the water along the path of the plumes.  The plumes would be discharged horizontally at about 2 m below the surface.  After a travel distance of 9 m from the vessel, the velocity will have reduced to 1 m/s, and the temperature in the plume will then be 1.1oC  cooler than ambient.

After a travel distance of 19 m from the vessel, the velocity will have reduced to 0.5 m/s, and the temperature in the plume will then be 0.6oC cooler than ambient, and after a travel distance of 35 m from the vessel, the velocity will have reduced to 0.3 m/s, and the temperature in the plume will then be 0.3oC  cooler than ambient.

Currents at Crib Point were measured in March-April this year.  Over a day, the current speed ranges from 0.03 m/s (at slack water) to 0.9 m/s (peak tidal current) with a median speed of 0.5 m/s.    Hence after a travel distance of 19 m, the median current will match the plume velocity, and the plume will bend in the direction of the current.   Within a distance averaging about 60 m (and depending on the tidal current), the plume will be travelling at almost the same speed and direction as the tidal current.

For a short period around slack water, the plumes will reach the seabed (with a temperature about 0.3 degrees below ambient).  As the currents increase (with the following ebb or flood tide), the pool of colder water on the seabed in the port around the FSRU will be mixed upward into the passing seawater flow.

Within a few hundred metres, the temperature difference will be under 0.1oC and within a kilometre, the temperature difference will be around 0.01oC.

For context, the temperature of seawater in Westernport varies by about 1oC each day due to solar heating of the mudflats and thin surface layer during the day, and solar cooling of the mudflats and thin surface layer during the night.  There are storms and other weather events that cause the water temperature to rise or fall by more than 2oC in a day.   So the change in water temperature is well within the natural daily variation.

Investigations into the design of the FSRU intake and discharge arrangements as well as the regasification operating modes are ongoing as part of the environment effects statement (EES) process and design development of the project.

The EES will consist of a concise, clear and easy to read main EES report and accompanying technical appendices. The main EES report will use plain English and will define scientific terms and units of measurement to ensure that readers are able to understand the project’s key features as well as potential effects and proposed mitigation.

Consulting Environmental Engineers (CEE) Hydrodynamic Consultant
Connected

I have read this reply and am concerned at some of the statements you have written as slightly misleading, so I will make comment on each of your statements in Blue.

You wrote "The present design has six discharge ports, three on each side of the FSRU, with a spacing of about 10 m between the ports. Each port would be located about 2 m below the surface and has a diameter of 0.45 m (or 450 mm).  The discharge velocity at the port is 5.4 m/s.

The 10 m spacing between the ports, and the separation of three ports on one side and three on the other side, result in six separate plumes that can dilute individually until the reach the seabed or are mixed into the ambient flow."

You say that the plumes can dilute individually until it reaches the seabed or are mixed into the ambient flow. If, as you say the flow is 5.4 metres per second or 10.5 knots. A flow of 10.5 knots will not reach the seabed in a very short time, it is a very fast flow and having a continuous flow from the outlet at 18 million liters an hour the flow will create it's own "tidal" flow and could not reach the seabed. If the normal tidal flow of around the 2.5 knot flow has a 10.5 knot flow added to it then the area north and south of the terminal will be so fast small craft would be in danger, then if there is a northerly wind at 20 knots blowing against this very fast flow the creation of pressure waves would be extremely dangerous for most craft. In a normal fast tide flow on an incoming tide with a strong north quarter wind blowing the pressure waves can be over 2 metres high with a very short pitch {the distance between each wave  and the angle of vertical height} is considered dangerous for boating, so what size pressure waves could be expected with this super fast water.

The word Dilute appears in many articles with the added number of total litres for the north arm, which is a very deliberate misleading piece of information as the North arm is from the shore at stoney point across to the middle spit all the way up past Joes Island which is massive, yet the only part of the North arm affected is the area as wide as the terminal which is 49m a miniscule amount compared to the whole of the north arm, so dilution and your data is completely incorrect.

You stated "For context, the volume of seawater from Bass Strait entering the Western Arm each day is 0.8 km3 (Westernport Science Review, page 53).   This is 800,000 million litres, equivalent to 1,770 times the daily amount of cooling water used by the FSRU when operating at the highest discharge case.

To use another scale, the flow rate of 5.2 m3/s is equivalent to the propeller discharge of five 40 HP outboard motors on boats travelling at 20 knots.

As a further scale, the flow rate of 5.2 m3/s is equivalent to one-tenth of the propeller discharge of a container vessel travelling at 18 knots.

Just as the propeller wake from a boat dissipates through mixing, the plumes of cooler water mix with the water along the path of the plumes.  The plumes would be discharged horizontally at about 2 m below the surface.  After a travel distance of 9 m from the vessel, the velocity will have reduced to 1 m/s, and the temperature in the plume will then be 1.1oC  cooler than ambient."

Spoiler
I am astounded that you could even this of using this as examples with the aim to have the readers believe the flow is minimal and just like an outboard motor. The use of 800,000 million litres of seawater and compare it with 1,770 times the usage at the terminal is in this case a use of figures to deliberately mislead the readers of your statement into believing it is very minimal. How could you possibly say that the total amount of water entering the Western entrance has anything to do with the amount of seawater flowing past the 49m wide Terminal, has nothing at all with the amount of water used in the terminal to even be considered. The water flowing into westernport via the western entrance divides into the eastern arm and the northern arm, then in the northern arm splits into the eastern and north arm. The North arm has much less water than your 800,000 million litres, the only area affected is around the terminal north and south and around the width of the terminal of 49m, so anyone reading this reply would now consider your figures as bordering on a misuse of figures to conceal the actual facts.
Now we look at the most ridiculous comparison between 4 outboard motors flow at 20 knots.
Each propeller is about 10" or 25.4cm, your outlet of 6 ports of 45cm has a much greater volume of flow.
The statement where you say the 10.3 knot flow will dissipate after 9m is completely untrue as that is absolutely impossible. If it was on a slack tide with very little tide flow it is defying all physic law, if the tide is flowing then I would say you need a new calculator or glasses, it is physically impossible.

You wrote: "After a travel distance of 19 m from the vessel, the velocity will have reduced to 0.5 m/s, and the temperature in the plume will then be 0.6oC cooler than ambient, and after a travel distance of 35 m from the vessel, the velocity will have reduced to 0.3 m/s, and the temperature in the plume will then be 0.3oC  cooler than ambient"
On the speed of the flow, I am trying to understand how you came to this figure. Lets say the tide is a slow incoming tide of 1.6 knots and you are telling us the flow from the outlet will reduce to 0.5 or 0.97 knots, or on a fast tide of 3 knots your outlet flow will slow to 0.97 knots, do you actually realise what you are asking us to believe ?
On the temperature. are these figure based on the absurd total number of litres entering the Western entrance or the total number of litres for the North arm or the area around the terminal, I ask this because your figures are rubbery at best. to calculate the 19m from the terminal did you consider the tide phase and at what speed the flow is? what the slack water time on the dead or very slow tides are ? A flow of 18 million litres in one hour of chilled water that is 7 deg colder than the ambient temperature travelling in a plume is going to  dissipate within 19m of the terminal! The flow is in a plume so how can it mix if you say the flow almost stops after travelling 9m ?

You wrote: "For a short period around slack water, the plumes will reach the seabed (with a temperature about 0.3 degrees below ambient).  As the currents increase (with the following ebb or flood tide), the pool of colder water on the seabed in the port around the FSRU will be mixed upward into the passing seawater flow.Within a few hundred metres, the temperature difference will be under 0.1oC and within a kilometre, the temperature difference will be around 0.01oC."

The words"for a short period of time" depends on what you consider short, a few minutes an hour 2 hours or more, you do not explain that small piece of critical data. You also claim all the discharged water will go straight to the seabed because it is cold, but being pumped out at 18 million litres an hour 2m below the surface has a couple of problems, the first it is being pumped out at 10.3 knots which at that speed could not go the the bottom, second it has about 17 m to get to the bottom, so how fast does water 7 deg less than the surrounding water take to get to the bottom. an example I can use is with fishing which a lot of people will understand. In a fast flowing tide in 17m of water I sometimes have to use a 10 oz sinker, if I use a one ounce sinker it will not reach the bottom for a very long distance.

There is another problem you have that for some reason is missing in all of this, if the discharge is 18 million litres an hour then the intake is the same, you intake is 5m off the bottom the outlet 2m below the surface, so that would create a huge turbulence with the ports only 49m apart, a 10.3 knot suction which will create currents around the area of intake, the same as it will on the outflow so it would not be unreasonable to believe that the area around the Terminal will be extremely turbulent causing some of the discharged chilled water to be sucked in and chilled again. On the "slack" tide flow this water will be chilled over and over, worse if your assumption the outflow water will go to the bottom only to be sucked up by the intake. If there is no tide flow and on certain moon phases this slack tide flow can be for 2 hours creating a massive plume of super chilled water. As the tide flows this super chilled and highly chlorinated water will travel in a massive plume and as it will travel at the same speed as the tide flow, then how does it mix, it can't catch up to the water in front of it nor the water behind can catch it. So your statement of " Within a few hundred metres, the temperature difference will be under 0.1oC and within a kilometre, the temperature difference will be around 0.01oC." is very misleading because you claim it mixes, how can it mix if it travels at the same tide flow speed with all the water in and around travelling at the same speed.? Are these figures based on the misleading total amount of litres of water in westernport, or the north arm or just around the terminal?

You wrote: "Investigations into the design of the FSRU intake and discharge arrangements as well as the regasification operating modes are ongoing as part of the environment effects statement (EES) process and design development of the project."

Is the design taking into account of the huge amount of floating weed that is in the water column, weed in such density that sometimes boats have trouble pulling up their anchors due to the enormous amount of weed on the chain ? The picture of the grill filter would take about 5 minutes to be completely clogged up, so then what happens?

You wrote: "The EES will consist of a concise, clear and easy to read main EES report and accompanying technical appendices. The main EES report will use plain English and will define scientific terms and units of measurement to ensure that readers are able to understand the project’s key features as well as potential effects and proposed mitigation."

After reading many AGL responses to questions in this forum, after reading your brochures and posters is the EES going to use the misleading figures AGL keeps using to assist in their efforts to give the impression of how minor the discharge of super chilled water and chlorine concentration will be?

Sparky

A further simple question in relation to this water issue is why can't the ship simply recycle fresh water and use some of the gas on board to heat it up and just keep re-using the same water?  There is already a recycled water line running right past the gate from Somers to Hastings, seems madness to put chlorinated sea water back into the bay at such incredible volumes.

Connected

Russell, you will probably find AGL will either not reply or take many weeks to do so.

The enormous amount of water needed to heat the gas in enormous, 450 million L per day or 18 million L an hour. The amount of water passing through the system could be a burden on our freshwater supplies and the cost of reheating this water would be a major task. It will be interesting to see what AGL say in their reply to you. I am still waiting for any form of reply to my pulling apart their response to my previous questions.

Sparky

Rob, thanks for getting back to me but you have missed part of my point.

There is already a recycled water line coming from the Somers treatment plant to Hastings which can fill the vessel with water and rather than offload and onload every day, just reheat it.  This is NOT a potable water supply but recycled treated sewage which otherwise, as in the case at Gunnamatta, gets dumped at sea at the rate of 350 million litres every single day.

AGL mentioned at one of their sessions that it is possible to reheat and reuse the water and contain it to the ship but that there is a cost issue for them.

My view is so what? If we have an environmental asset worth protecting then the cost of reheating recycled water is simply a cost of doing business in this location and if we pay a couple of cents extra for the gas then so be it.

Connected

Hi Russell, it is an interesting point you have raised. The Sommers recycle plant supplies just over 300 million litres per year for about 24  customers to reuse.

How much AGL would need on top of that would have to be determined and have a back up storage container tank for evaporation and emergency in case of line breakage. The problem for AGL is that has not been a proposal, they chose the cheaper version and would delay the project if they altered it now.

Sparky

Understood they chose the cheaper version but for the government and community to decide if there is more value in paying a little bit more for the gas or potentially destroying the marine environment of this RAMSAR site then I think we need to be able to quantify this cost.  Just saying it is a cheaper option is meaningless, how much cheaper and how does this stack up against the environmental value of Westernport Bay as an environmental asset.  We need to deal in actual numbers here.

Dynamo

AGL chose the 'we will make most profit ' version Russell Joseph and they will continue to do so if they think their proposal will get the green light.  Regardless of the form it may take- this proposal does not substantiate a shortage need, cannot justify the site location given the environmental importance and sensitivity of the area, and cannot guarantee that a negative impact will not occur- either on land or the sea.