The First Vacuum Sewerage system in Chile

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A FLOVAC delegation was recently in Chile, in the Llay-Llay commune, where the first vacuum sewerage installation of the country is being built. As this technology is innovative for the Chilean technicians, a conference was organized for everyone interested in FLOVAC’s system, having it coincide with the formation day of the Regional Development Subsecretary (SUBDERE).

His Excellency the Mayor of Llay-Llay, Mr. Mario Marillanca, welcomed FLOVAC’s Commercial Manager, Mr. Bruno Galindo, who introduced the project that is being developed and explained how the system works.

In the audience there were more than 45 engineers from different localities around the country. In the conference room a vacuum pit was installed in order to show the attendees different components  of the system.

“I have great faith that everything works well, and that this project model will serve in other places where there is the same deficit,” said Mayor Mario Marillanca in a welcoming address to regional officials of the Sanitation Clearing of theUndersecretariat Of Regional Development.

For the regional manager of Subdere Valparaíso, Eduardo Pasten, the pioneering and innovative project that is implemented in Llay Llay, can be replicated in other cities of the country. He emphasizes the importance of the presence of representatives from all over Chile, “in order to be able to disseminate, and if applicable in the regions, to implement it,” Pasten said.

A Flovac system was considered in the area due to the difficulty of pipe installation in the rocky area which meant that installation could be carried out quickly and with the least disruption to local residents.

Another important consideration was the low amount of power that is required for the vacuum pump station. With power required only at the vacuum pump station a back up generator can easily be supplied if there is any interruption to local power supplies.

Flovac’s site supervisor on the project Francisco Rodríguez worked very closely with the large local contractor Montec to ensure a correct installation.

 

Largest Vacuum Sewer System in Greece is Completed

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Flovac Greece has just completed the largest vacuum sewerage system ever undertaken in Greece covering the towns of Mitrousi and Skoutari in the Serres Region of northern Greece.

The system which has two large vacuum pump stations, 800 collection pits and 45km of vacuum pipework. The system takes away the sewage of 3,600 residents in Mitrousi and over 4,100 residents in Skoutari. This makes it one of the largest systems ever installed in Europe.

The Serres region is an environmentally important area which won a European sustainable tourism award for aquatourism. A large artificial lake, Lake Kerkini was created nearby to make use of the extensive marshlands in the area. This is also behind the need for vacuum sewers in the villages as the water table is very high and actually visible on the surface in some areas.

As the vacuum sewer pipework can be laid at minimum depth and avoid de-watering is was seen as the only way in which a proper sewer system could be installed.

Vacuum sewer system are also popular in Greece because of the flexibility in the laying of the pipe. On many occasions archaeological artifacts are found during the construction of a system and rather than hold up construction for weeks or months while a site is investigated, the vacuum pipework can be diverted around a sensitive area, thus saving time and money. The Serres region is known for a number of antiquities including important sites from the time of Alexander the Great in 300 BC.

Flovac’s partners in Northern Greece, Environmental Engineering S.A., based in Thessaloniki, are the largest installers and operators of vacuum sewers in Greece and have been involved in a number of important projects since it was founded in 1993. The company principals Miltos Chatziiliou and Spiros Kolovoi have been very involved in engineering design, product development,

construction works, treatment as well as the operations and maintenance of a number of systems. Miltos works very closely With Harry Gerpinis who looks after Flovac’s interests in Southern Greece and has been instrumental in a number of significant projects including many large marina’s.

Flood Affected Sewer Systems

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Vacuum sewerage systems are ideal in areas that are subject to flooding

Nearly all vacuum sewerage systems are found in coastal area’s many of which are subject to flooding from rain/storms or rising sea levels. We all understand the problems that occur if I&I is present, we all know what causes it to occur.

We have operated a number of systems during major floods without the system going down. In one Sydney system major floods occurred every two years (see photo above), our operations contract stated that if any homeowner could not continue to use their plumbing they would be put up at a hotel at our cost. Happily we did not spend a cent on hotel costs.

For the vacuum valve to meet the European standard it must be able to operate under a full 10 inches of water. To meet the Australian standard it must operate without problem under 18 inches of water. By ensuring all hose clips are properly in place and the controller breather is clear of any water , the system will continue to operate.

In area’s where flooding is common we tend to put the controller and controller breather in a pillar besides the pit to ensure that the operator can still fire the valve without trying to access the pit through the flood water which might not always be possible.

Water infiltration from the homeowners property.

We have found that the main source of stormwater entering a system comes from the homeowners property. In some flood areas we have seen that certain sections of the town will regularly go under water. This usually means that residents have to be evacuated and in the past the water inundation from that area could risk the whole system. In this case we would install a remotely controlled division valve that would cut off that section of the town from the vacuum system. It is controlled from the operations base so that operators are not put at risk trying to isolate the area.

In some older towns we find that some houses, or more often camping grounds or caravan parks are set at ground levels

that are blow the legislated 100 year old flood levels that people can build at. If we find houses affected in this way, they must pump into the vacuum system rather than drain into it so that the system is not put at risk.

Candycanes/Gooseneck house breather vents when placed on properties will often be a source of infiltration, usually due them either being cut down by homeowners who object to them being in the middle of their yard or by gardeners knocking them over with their lawn mowers. At times they are placed too low to the ground, under the flood level. In these cases we would install a  Dedicated Pillar or think carefully about where the gooseneck vent is placed. Putting it in the middle of the yard risks it being cut down allowing water to enter the system. Putting it at the roof or garage top or against the house wall will limit water entering the system.

Smart Monitoring

As technology has improved, many asset managers have embraced the ability to locate exactly where and when I&I may be occurring. A sensor on a vacuum valve giving the open/close status will also be able to tell the operator the number of activations in a day. It is very easy for the operator to set up an alert to advise if any particular valve is operating more frequently than the general average, especially during wet weather events.

Once the operator has established which collection pit is activating more frequently than the other valves in the area, they can then troubleshoot the problem. The likely problems are that the homeowner has cut their house vent or inspection point to allow rainwater to enter the system or may have connected up their stormwater system to the sewer system or have a cracked gravity line feeding from the house to the pit. A letter to the homeowner to make the necessary rectifications is required.

There may also be groundwater or stormwater entering the collection pit due to incorrect pipework entering the pit allowing for water to enter. This is usually picked up at commissioning, if not should now be rectified.

You should also make sure that the pit lid is made for area’s that have flooding and has a seal and no holes to allow water to enter. the pit should not be located at a low point in the street.

The monitoring system makes it possible to identify these problems and fix them. this is not possible in a gravity system.

System Design

When designing a gravity sewer consideration must be made for Infiltration and Inflow on the pipes, the pump stations and the treatment plant.

Stormwater cannot enter the vacuum system via the vacuum pipework as it must remain tight for the vacuum pressure to hold tight. If a break occurs in a main it is immediately noticed and repaired.

An allowance is made for I&I but only for a small amount of the network, that being the homeowner gravity lines. So the system is not designed for infiltration and all steps must be taken to ensure that it does not occur. Luckily in a vacuum system the source of any I&I can be located.

If you have any leaks into your system, contact an expert for advice.

Historic Project in France

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Commune De Saint Julien De Concelles

This historic village nestled on the banks of the Loire River near the French city of Nantes on the Atlantic coast of France is the site of the latest Flovac system in Europe.

The site is first mentioned in history books as far back as the year 615 where is started life as a Roman town.  Ruins of a villa and ancient Roman baths can be found in the area. Vacuum sewers have been used in a number of area’s where there is such architectural significance as a way to ensure no damage is done during the construction of the sewer. Often during construction, significant finds may take place which the vacuum system can avoid by going around  at a safe distance without holding up works.

The town is in the heart of an important agricultural area and has very flat and sandy soil, ideal for a vacuum system. It is also known as the town that first developed the beurre blanc sauce, often used in french cuisine. There are also vines on the hills around the town that grow a muscadet wine that is very popular.

The project size is quite small with the Flovac system connecting 168 houses with 100 collection pits and 4 km of vacuum pipework.

It is important when doing installation work into existing townships that there is very little disruption to the way of life for the people in the town. One of the best reasons for utilising a vacuum system is that the trenching for the pipework is very narrow and in an area such as this, there is no need for dewatering as the installation stays above the water table. This ensures that the water table is not changed and so there is no detrimental affect on local agriculture.

The system is able to be installed with only a single vacuum pump station which is also important in an old town like Saint Julien in that space is a precious commodity. It was also important to keep energy use as low as possible, and with a single small vacuum pump station, this is possible.

The Saint Julien project is the first project in France that has incorporated the Flovac wireless monitoring Information about the monitoring systems can be found on our french webpage. https://www.assainissement-sous-vide.fr/

The project is just the latest for Flovac’s partners in France, LSE who have had a long history with vacuum systems.

In June we were finally able to attend the national water and wastewater show in Paris which had unfortunately been delayed due to terrorism in the capital. It was attended by Flovac’s chairman Mr Willem Gooren as well as local Flovac managers Philippe and Nicolas Frasier.

Exfiltration – Why Can’t Vacuum Sewers Leak?

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Gravity sewers have been used for hundreds of years, but they come at a much higher cost than many options reports accurately record. When selecting what type of sewerage system to use, take into account the risks associated with the solution. What happens if a sewer overflows? What happens if a storm or large wet weather event occurs. What will happen if a pipe breaks. What will be the cost and what will be the risk? A vacuum sewer could be far cheaper than you realise.

When you reflect on the damage and the cost of exfiltration from sewer networks the statement that we often hear ‘gravity sewers require no maintenance – we just put them in and leave them be” is wrong and does not reflect the true risks of not only gravity systems, but also low pressure systems as well as old septic tanks and combined sewers.

Sewage leaks can occur for a number of reasons. the most common is leaking sewer pipes (this may be caused by tree roots or ground movement). A break in a gravity line  can remain undetected for months or even years. In a Low Pressure Pump system a break will lead to a surcharging sewer which will be difficult to repair and costly.

With Low pressure systems a pipe break is easier to detect as some local TV news anchor is excitedly showing the 50 foot geyser in the middle of main street.

Overflows can also be caused by the system being inundated with stormwater which overwhelms the entire system allowing polluted stormwater to enter waterways.

A vacuum sewer piping network is leak tight, as it operates under a negative pressure any break cannot allow exfiltration to occur and as the pipe is less than 1/3 full at any time there is no surcharge.

What are the main problems if exfiltration occurs?

Health Issue’s

In the USA the Centres for Disease Control and Prevention (CDC) and the US EPA regularly report on annual deaths due to sanitary sewer overflows.  Sickness is widespread with the most common symptoms being diarrhea and nausea. This can be caused not only by drinking the water but also by swimming and eating shellfish and fish.

Of greatest concern is infectious disease, such as the contamination of Wallis Lake oysters in Australia with the sewage-derived virus hepatitis.

In Baradine a small town in Australia The Department of Health reported a 30{f2ac4d1e1d40dc2e2d9280a1dfa90d854b2d8c80eba743affa37fc4ce2e16def} reduction in student sick days at the local school once a new vacuum system was installed. In far north tropical Queensland the introduction of a vacuum system led to a reduction is diseases caused  by mosquitoes.

Not only is the health of the broader community at risk, there is also a risk for sewer operators needing to deal with overflows and backed up sewers.

Environmental Issue’s

In the nineties nearly 20{f2ac4d1e1d40dc2e2d9280a1dfa90d854b2d8c80eba743affa37fc4ce2e16def} of Florida’s manatee population died due to an algae bloom which had intensified due to sewer overflows.

On average 140 beaches in the US are closed or have warnings due to sewage contamination. KawaKawa Bay in New Zealand which had been a source of shellfish and a place to swim for the indigenous Maori population for hundreds of years was completely closed for ten years due to sewer overflows from a growing seaside community. It was only after a vacuum system was installed that the bay was reopened.

Sewage contamination readily degrades in the environment, but in water it can soak up oxygen from the waterway. Low oxygen levels can kill large numbers of fish and other aquatic life. Sewage also has toxic levels of ammonia that can poison aquatic life, along with many other contaminants.

Overflows contribute nutrients and sediment that encourage the vigorous growth of invasive weeds, such as willows, blackberries and privet, which often choke native species along stream channels and banks.

Aquaculture and Tourism Impact

Owners of Marina’s know the impact of attracting houseboats and tourists if sewage is contaminating the marina area, with bad smells putting off people going to local restaurants.

Dal Lake, one of the most scenic tourist spots in Kashmir has suffered terribly from sewage overflows from nearby towns but even worse from raw sewage entering the lake from houseboats on the lake.

Tourists going to Brazil for the Olympics and the World Cup were told not to go near the beaches. Dr Daniel Becker, founder of the nonprofit Center for Health Promotion in Rio, said: ‘In Rio, if you’re going to the beach, you’re going to sewage.’

“A sewer line clogged with grease caused raw sewage to spill into the Five Mile River , forcing the closure of shellfish beds from Darien’s Long Neck Point to Wilson Point in Norwalk.”  This is a common story, found around the world where sewage overflows can affect not only health but the livelihood of businesses.

Financial and Reputational

In many countries fines are being issued to water authorities if sewage overflows occur. The Environmental Protection Agencies must report any overflows and state and federal reporting is mandatory. If there is a death related to a sewage overflow that could of been prevented then lawsuits and possibly prison could affect senior people within the wastewater industry.

Newport Bay in California had to close its beach to swimmers and divers on one of its busiest weekends due to a large sewage spill that was caused by a sewage pump stopping, flooding the streets and beach. Not only was the beach closed for 4 days, ruining many tourists holidays, it also financially hurt local small businesses including restaurants who are talking about legal action against the Costa Mesa Sanitary District. The District has now been fined $503,000 by the regulators of  The Santa Ana Regional Water Quality Control Board. Sadly it didn’t end there with a smaller spill caused by tree roots blocking a sewer main causing beaches to close for three days the following year.

There are always lots of big fish down at the lake because.

The first problem, is how do you know that you have a leak or overflow.Usually it is because sewage has been spotted at the local playground/beach/street. Or because you know from flow meters at the Treatment Plant that not all the flow is reaching it. In New Delhi it is estimated that only 60{f2ac4d1e1d40dc2e2d9280a1dfa90d854b2d8c80eba743affa37fc4ce2e16def} of all sewage collected is actually reaching the treatment plant.

Even with new technologies it is difficult to find leaks when the pipes are buried 10 metres (40 feet) underground. It is also very expensive to fix that leak. Not only is there potentially a disruption to service, a closing of roads the restoration of the surface, you need to find an allocation in the budget to make those repairs.

Why doesn’t all this happen with a vacuum sewer?

Well admittedly, homeowners can still create overflows at the home and badly maintained systems will always have problems. Modern wireless and cable monitoring systems reduce this risk considerably and is a game changer.

Firstly though, all vacuum mains are fairly small diameter, 125, 160, 200 dia (6,8,10 inches) and laid at a very shallow depth (Under 1.5m or 6 feet) So if there is ever a break it can be reached quickly and repaired without loss of service or expensive restoration. All pipework has to be pressure rated so it is a lot thicker than traditional sewer pipe.

Sewage is transported quickly in the pipe by air. The pipe is full mainly of air and not sewage. Large sections of the pipe are empty with sewage only collecting at lifts in the system. All pipework is under a negative pressure created at the pump station. If a pipe breaks, it sucks in and does not let any water leak out.

Once there is a leak or break in a pipe, the vacuum pump at the vacuum pump station must run longer. This creates an alarm which is transmitted to the operator. He is made aware that a leak is occurring in the system, this may be at the vacuum pump station, at a valve pit or in the pipework. A reticulation monitoring system will automatically notify the operator if there is something blocked in a valve or there is a break in the line. When pressure is monitored at each pit it is easy to detect in which section between two pits a break has occurred.

If a break has occurred, it would usually be due to an outside contractor breaking the pipe, tree roots rarely get into vacuum mains as they are pressure pipes. As a break is at minimum depth it is easy to locate and repair and no sewage would have leaked out.

If a blockage has occurred and sewage is backing up in the pit it cannot overflow through the manhole cover as there is a partition between the sump and cover preventing sewage from flooding at this point. If it starts to back up towards the house a high level alarm in the pit sends an urgent alarm to an operator who attends to the problem. If the problem is hard to solve or an experienced operator is not available a suction truck can be used at this point.

At the Eco Resort near the Barrier Reef in Australia a vacuum system was chosen to ensure that no sewage could affect the local ecology nor leak into the swimming lagoons which would have closed the resort.

As any leak in the pipework, must be repaired immediately, no stormwater can enter the system during wet weather events. This is common in gravity systems where breaks may go unnoticed. This means that the vacuum system can never be inundated with stormwater and wet weather infiltration is not included in design parameters.

Due to the velocity of water in the pipes there is not build up of fats or grease and wet wipes or other objects do not cause blockages at the vacuum valve nor in the pit. See Video for information.

Vacuum Sewers are considered to be the Low Cost of Sewage collection, both in capital costs and also in maintenance costs. Risk is a very important consideration.

Largest Vacuum Sewerage Project in Slovenia has Commenced Operation

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One of Europe’s largest vacuum systems and certainly the largest vacuum sewerage system in Slovenia has commenced operation in the Municipality of Brezovica. The system will have 6 Vacuum Pump Stations and over 1,500 Flovac valves.

The municipality is located just south of the capital  Ljubljana, in central Slovenia. It has a population of about 9,500 people. It is known for its famous marshlands which is why a vacuum system was chosen as the principal form of sewage collection for the region.

As all vacuum pipework is installed in shallow trenches, contractors were able to avoid dewatering to a large extent allowing construction time to be shortened extensively. This meant that there was a lot less impact on local residents who could still go on with their daily chores without disruption. It also meant that when severe cold weather occurred then workers were not impacted for long periods of time.

A gravity system would have required dozens of gravity pump stations due to the high water table while only 6 Vacuum Pump Stations were needed. This has reduced the energy cost of the system and also reduced the maintenance cost. As the area sometimes suffers power outages the ability to have backup generators at each station allowed for unrestricted service for homeowners. The Vacuum Pump Stations have both duty and standby pumps and are fully monitored back to base.

All 6 stations and all 1,500 vacuum valves are also monitored via the Flovac Monitoring System using a cable FLbus system which allows operators to see exactly which valves are operating in the network and if any infiltration is occurring.

Flovac Adria was established in 2006 and is based in  Zalec, Slovenia and has done a number of projects in Slovenia and the region. It is the largest designer and supplier of vacuum systems in the Adriatic region and the groups Managing Director Mr Dejan Pušnik is considered one of the most experienced Vacuum Sewer professionals in Europe.

Frozen Vacuum Sewers and the Lessons from Europe

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Over the Northern winter we read with interest a number of stories related to frozen vacuum systems  which were caused by some of the worst winters seen in 100 years in the North East of America. These stories have increased in recent years with some commentators talking about the reality of climate change and its impact on many types of infrastructure, not just sewerage systems.

To understand some of the problems you need go no further than googling “Plum Island frozen sewers”. The main problems seemed to be related to frozen vacuum valves, water frozen in the pits, gooseneck vents submerged by snow, frozen sewage in the pipework, frozen gate valves and division valves and leaks in the line.

Does this  need to be the case every year that there is a big dump of snow or temperatures fall? Aren’t vacuum system supposed to be resilient?  We don’t have to  look as far afield as the vacuum systems in Alaska or even at the Arctic and Antarctic bases to get some solutions to the problems encountered in America. Germany, France, Poland the UK and some of the Nordic countries like Estonia have experienced very low temperatures and extreme snow falls from time to time with little impact on their vacuum systems.

As an engineering firm we need to be aware of local conditions where ever we install a system whether it is in the arid desert of Australia, tropical conditions in Malaysia, remote islands in the Cocos Islands. All systems should be designed to suit the local conditions..

When dealing in area’s subject to extreme cold we need to take care of how deep the vacuum mains are laid, what type of division valves are used, how the collection pit is designed, where the air intake vent should be for the operation of the valve. Many of these things can be adjusted in existing systems.

One of the important developments in how Flovac vacuum systems are managed is in the use of monitoring systems at the valve and pit. As a standard in cold conditions we monitor the temperature in the pit via our monitoring system.

This would have helped a lot in the Plum island project as any valve failures would have been easily and quickly located due to freezing ensuring no loss of service for residents or sewage overflows into their basements.

The monitoring system also makes it very easy for operators to locate the exact location of collection pits. This is also true in coastal area’s where pits can often be covered by sand during the summer months.

Many communities in the US are fretting over what will happen next winter with their vacuum systems. Will the Fire station chief need to allow residents to use their showers and toilets. Will portable toilets be sold out early, or will everyone just head for Florida.

Maybe one solution is to contact us here at Flovac and we would  bring a team of experts from Europe to look at ways to ensure that your Happy Holiday season is truly Happy.

Flovac Vacuum Sewerage Systems are experts in solving difficult wastewater engineering problems in unique geographic areas with Global Knowledge and Local Solutions.

Santa Pola resolves odours and overflows with a Flovac system

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The Flovac vacuum system is one of the most innovative and longest in Spain – The vacuum system installation, executed over the past 8 years have allowed prevention of salinity problems in the town. With this system, the City of Santa Pola collected wastewater generated for 12,900 homes for later use mainly on irrigation

Vacuum Pump Station

Vacuum Pump Station

Spains largest vacuum system is near completion. It is a technological solution to solve the problems the utility in Santa Pola were suffering as it was built on a cattle farm located on salt marshes , which has a subsoil of sand.

This caused problems of infiltration and unstable ground conditions. Seawater infiltration resulted in increased salinity of the water, which greatly impaired the biological process of purification of the wastewater.

To solve this problem the city has installed a Flovac vacuum sewerage system. Flovac installed pipes up to 315 mm diameter, inside which is a constant vacuum of -0.5 and -0.6 atmosphere is maintained by vacuum pumps.

Vacuum valves are opened by the difference in air pressure automatically and take in  the wastewater from pits. No electricity at the pips is required. The pressure differential allows sewage to flow into the vacuum station and then it is pumped to the Treatment Plant.

There were a number of benefits to the community and to the operators with reduced construction costs and impact on businesses and residents. Operators, who use the monitoring system, note reduced blockages and odours and time at site.

The monitoring system allows operators to know exactly when they are needed and where to go.

A number of other towns with similar problems and now talking to Flovac.

Official Opening of New Smart Vacuum System in Estonia

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Merko, the leading construction company in Estonia has finished construction in Vääna-Jõesuu of Estonia’s second vacuum sewerage system – Flovac’s first system was completed last year in Leppneeme and has performed better than expectations for both the community and the operators.

Both systems were of a similar size about 650 people and near the coast where septic tanks were causing environmental problems.

According to Valdo Liiv of OÜ Strantum, the company that commissioned the work, the use of vacuum sewerage systems in outdoor piping solutions is unjustifiably uncommon in Estonia. “When the work was ordered, the main reason for utilizing a vacuum-based system was the low costs of construction and maintenance, but now that the first customers are hooked up to the system, we also see the system is very convenient to use, particularly with respect to monitoring customers.”

“The work in Vääna-Jõesuu progressed very smoothly and quickly. All four phases of the project were completed before the contractual deadline. We have therefore been able to minimize inconveniences associated with construction work for both residents and holidaymakers in the area,” said Merko Ehitus Eesti AS project manager Peeter Laidma.

“A vacuum station and waste water pumping station were built in the Puraviku tee and Nõmmerohu tee area, as well as 3.8 km of drinking water piping and 4.1 km of sewerage piping, including nearly 3.6 km of vacuum sewerage piping. The benefit of vacuum sewerage is efficiency – the sewerage pumping station does not have to pump excess water, since the watertight vacuum sewerage system takes in significantly less water from rainfall, snowmelt, leaking pipes and wells than ordinary sewerage systems. The vacuum sewerage tanks are waterproof and the tanks’ lids are 10-20 cm above the ground to prevent rainwater from leaking in from the lid,” Laidma explained.

“Additionally, each tank is equipped with sensors to monitor the flow of each client’s waste water. Any increase in flow is automatically picked up by the sensor and notifies a maintenance technician. Ordinary sewerage systems do not have this monitoring capability and major leaks are usually only discovered by chance or when some other problem is being addressed,” added Laidma.

The construction work was carried out by AS Merko Ehitus Eesti and AS Merko Infra, which also built Estonia’s thus far only vacuum sewerage piping system, in the village of Leppneeme in Viimsi municipality.

the official opening was attended by Flovac’s Regional manager Mr Ralph Grüschow

Earthquake Sewer System for Christchurch NZ

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Vacuum Sewers prove to be the best Earthquake sewer system for Christchurch Shirley vacuum sewer a first for the South Island.

SCIRT partner McConnell Dowell is more than halfway through a big project to build a Flovac vacuum wastewater system in the Christchurch residential suburb of Shirley – the first area of the South Island to use such technology.

The catchment includes about 750 houses, with 7km of vacuum main pipes in streets as well as lateral/ side connecting pipes to homes and businesses. About 6km of mains and 150 out of 195 collection chambers have been built, with a pump station and lateral pipes still in progress. It will take just over a year to complete the project, which began April 2013.

The area targeted for the Flovac vacuum system was badly affected by earthquakes with lateral spread and land-level changes. Previously, the city’s wastewater network has relied totally on a gravity system with pipelines at a gradient to support downhill flow.

After the earthquakes, the slope changed in many parts of the city, so wastewater was running in the wrong direction. The Flovac vacuum system will offer much greater resilience if there are further large earthquakes, especially in areas considered prone to liquefaction.

A further reason for using vacuum in Shirley was to keep excavation depths to a minimum because of the high ground water table and running sand. The system allowed McConnell Dowell to lay the pipes mostly at depths between one and 1.5 metres deep.

This is shallow compared to the traditional gravity system which has pipes plunging to several metres deep to maintain the gravity-feedwhich takes a lot longer to access for maintenance or repair work with subsequent traffic and residential disruption.

Wastewater will arrive at the Shirley catchments new pumping station, on Golf Links Road, from small collection chambers, usually located on the grass berm of a street, each serving up to four properties. The only visible parts in most streets will be collection chamber lids and man-holes at ground-level, while vent stacks will sit against property boundaries.

Like in other parts of the city, wastewater from the new pumping station will go via the normal gravity system southeast to the wastewater treatment plant at Bromley.Shirley NZ Flovac Project

Residents will not notice any change

Shirley residents will not notice any difference when they flush their toilets or see their kitchen and bathroom wastewater draining to the collection chamber on the street via the gully trap/ lateral pipe. There is no additional cost to them for becoming part of this modern system.