It’s easy to let something that’s out of sight be out of mind, but the consequences of neglecting underground fuel storage systems could put a fuel retailer out of business. Ground contamination from a leak can not only cost tens of thousands of pounds to sort out, but it could also reduce the value of the forecourt.

And with more than half of the UK’s petrol stations estimated to have single-skin tanks, much of the forecourt network is sitting on a constant threat of ground contamination, according to Brian Humm, chairman of the Association for Petroleum and Explosives Administration.

"Whenever fuel is kept below ground in single-skin steel tanks, there is the continuous threat of the tank corroding and leaking," says Humm. "From a ground contamination point of view, the worst case scenario is a leak finding its way to a groundwater extraction point, where water is pumped from the water table to provide drinking water. But even a leak that remains within the sub soil below the site will devalue the site if it ever comes to be sold; in some cases it renders the site worthless.

"The only method of completely addressing this risk is for the tanks to be double skinned and for the interstitial space to be monitored," adds Humm. "This can be achieved either by installing new double-skin tanks, or by employing a company to line the existing tanks with a second skin. Both new tanks and double-skin linings must be to the appropriate European Standard."

Tank lining

As of April 1 this year, the London Fire and Emergency Planning Authority requires all double-skin tank linings to meet European standard EN13160-7 certification, which addresses issues with past double-skin linings such as the weight of fuel compressing the interstitial space.

But while this new European standard aims to raise the standard of double-skin linings, some retailers are understandably reluctant to pay for a costly service where the results are hidden underground. After all, any tank lining system is only as good as the installation. In a bid to give retailers peace of mind about the service they’re receiving, Eurotank Environmental has developed an explosion-proof CCTV system for watching the tank-lining process.

Eurotank managing director Edward Wheeler says: "It is now possible for the retailer to see exactly what they are paying for, rather than having made a significant investment in something that they cannot ever touch or see.

"From Eurotank’s safety point of view, the ’top man’ outside the tank a legal requirement for confined space entry can also see the installation crew in the tanks carrying out the works."

Eurotank is the UK and Ireland applicator for the ZCL Phoenix system, which is certified as being compatible with a Class 1 pressure leak-detection system said to be the best-practice method for monitoring underground storage tanks and comes with a 30-year guarantee. "The benefit of a Class 1 pressure system is that if there is a leak, the pressure ensures that only air leaks out, rather than letting fuel leak in, which ensures product cannot get into the ground," explains Wheeler. The Phoenix system uses a structural three-dimensional glass fabric called Parabeam which, combined with resin, goes hard and creates a structural space between the two skins, as well as bonding the outer skin to the inner skin. The system uses ultra-violet curing, which fully cures the Parabeam in 15 minutes.

Less disruption

Eurotank has also invested in making tank lining safer and less disruptive for the retailer with the introduction of a tank entry container, which is placed over the tanks being relined. This is said to allow forecourts to continue trading with minimal disruption while the work is being done.

Brulines Fuel Solutions’ ELS tank lining system has also achieved full approval for double-skin lining. Phil Prow, sales & marketing director, says tank lining is the logical choice over tank replacement: "It requires no deep excavations, minimal site disruption and wherever possible the site can remain operational," he says. "Given the size of tanks we think that each site should be done in consecutive phases of five or six tanks at a time."

The ELS system has two interstitial spaces and does not rely on the existing outer skin for structural strength. It is compatible with all blends of fuel and comes with a 10-year guarantee.

While the authorities in some areas will insist on double-skin lining with the added bonus that the tanks are constantly monitored many independents are choosing single-skin lining over double-skin. Bob Taylor, general manager of King Tanktechnic, says: "Single-skin lining can be completed more quickly and is usually less expensive. Tank lining uses the steel shell of an old tank as a mould to create a new totally chemically-resistant tank within a tank. Our lining is not only impervious to the secretions of micro organisms but also all fuels and, if necessary, 100% ethanol."

Good housekeeping

Since the introduction of biofuels, fuel storage system housekeeping has become critical for retailers.

The two main problems associated with biofuel are both linked to water: microbial contamination in diesel the much publicised ’diesel bug’. This clogs pump filters, causes nozzles not to cut off and so spills fuel, and can also cause premature tank failure if sulphate-reducing bacteria, which excrete sulphuric acid that can burn its way through steel tanks, are present. Phase separation is the main cause of concern with petrol. If enough free water enters the tank, the water mixes with the ethanol part of the fuel and drags it down to the bottom of the tank.

King Tanktechnic’s Taylor says retailers are not doing enough to look after their fuel storage systems.

"They are very concerned with how customers are spending their money in the shop but often only worry a little that the customer could complain that the fuel they have sold them is of poor quality or has damaged their car. It’s only a passing thought though."

Taylor says it’s important that retailers regularly dip or otherwise check for the presence of water and, if found, remove it. "Contaminated fuel can cause blocked filters and customers’ cars to break down," he says. "Complaints are not good for a retailer’s reputation and they will be unable to sell product if it’s contaminated. Fuel polishing can return contaminated fuel to usable product, and this is one of our services."

Alan Scrafton, group sales and marketing manager at Adler and Allan, says the common causes of water entering tanks are leaking tanks and supply, vent and offset fill pipeline systems. "Another issue may be leaking fittings and gaskets inside the man chamber, and most sites in the UK have issues with high water tables increasing the potential issue of water ingress." Scrafton explains. "The typical sign of a problem is slow-running pumps as a result of blocked fuel filters. Most modern tank-gauging systems do not react quickly enough to give ample warning of any potential water ingress in both diesel and petrol, so it’s very important to look at preventative measures rather than reactive. The best recommendation is to dip all tanks on a regular basis with an approved water-detection paste.

"Precision tank and line testing will identify any potential issues with water entering a tank. A good precision tank- testing system will also identify and confirm that all fittings and gaskets inside the man chamber are liquid and gas tight."

Eurotank’s Edward Wheeler also stresses that retailers should not ignore any water alarms in petrol tanks. "If phase separation occurs, the tank gauge water alarm will not detect the water/ethanol mix in the bottom of the tank as the float is only designed to lift in pure water, not wet ethanol," he explains. "Phase separation generally only occurs if a significant amount of water is mixed into the fuel.

The tanker delivery is the perfect method of mixing water into fuel as it drops around 1,000 litres of petrol per minute, a few inches off the bottom of the tank where the free water settles.

"If a retailer gets a water alarm on their tank gauge, it is critical that they do not take any more deliveries until the stuck water float which is the issue 95% of the time or the water, has been removed," adds Wheeler.

"By doing this, the retailer can be saved tens of thousands of pounds in lost product costs and vehicle damage caused by phase separation."

In addition, Eurotank recommends that retailers conduct annual water checks and periodic tank cleaning as a minimum. "As a rough estimate, £1,000 per tank, per year would be an appropriate figure to budget for if a retailer wants to protect itself from problems," says Wheeler.

"This figure is likely to raise eyebrows, but if you consider the cost of fixing one vehicle, which is generally equal to or in excess of £1,000, then the cost benefit can be seen."

Meanwhile, DP Fuel Tank Services (DP FTS) is helping retailers deal with problems associated with biofuels with a 10-point advice sheet.

The document approaches the problems step by step, starting with symptoms and simple actions, and progressing to tank cleaning and fuel polishing as a last resort.

Best practice

The advice sheet also looks at how to keep biofuel problems at bay through regular testing, whether there is an apparent problem or not. Nigel Plumb, director of DP FTS, says: "Sometimes problems are not obvious by eye alone. A test will show just what problems there are and their extent. It will also establish a base line against which to judge the effectiveness of any remedial work that may have to be carried out.

"As well as testing for particles and bio-contamination, it is worth testing the specific gravity of the fuel," continues Plumb. "Normally, water in the fuel is reasonably obvious, but biofuel absorbs water and masks the problem. Often, the only indication is a change in the density of the fuel. Water in the fuel helps the growth of bacteria and algae. There is also the question of where the water is coming from; the water absorbent biofuel could be masking a leak."

All the advice from the US and Australia, where they have had biofuels longer than the UK, is that it is vital to have a clean tank when dealing with biofuel, adds Plumb.

"Our experience has shown that removing the fuel and thoroughly cleaning all sediment from the tank will cure a clogging problem caused by sediment. It will also remove bacterial colonies and algae clinging to the inside of the tank or in the residual sludge."

system that saves you money

Save £3.60 for every 1,000l sold with Petroman

The Petroman Environmental Services Total Vapour Solutions system is said to let forecourt operators keep hold of petrol they would otherwise lose to delivery tankers equipped for Stage 1B vapour recovery.

Roger Bailey, sales manager of Petroman Environmental Services, says: "The system pays for itself and begins to actually make money in a remarkably short time, simply by retaining petrol that would otherwise go back to the depot or refinery."

When a tank is ready to accept a new delivery, it is normally low on liquid and high on ullage filled with petrol vapour. When the tanker attaches its delivery hose to the fill pipe and begins the delivery, that vapour is taken back into the tanker.

By using the Petroman system, with an OPW Vapour Saver processor at its heart, a forecourt can recover two to four litres of petrol on which the duty has already been paid from this vapour for every 1,000 litres sold. According to Petroman, this is equivalent to £3.60.

Says Bailey: "Not recovering this vapour is equivalent to having seven Mars bars stolen for every 1,000l of petrol sold. If you sell 3mlpa, this rises to around 30 Mars bars every day. If that much confectionery was going missing every day, there isn’t a garage owner in the country who wouldn’t invest in extra security to prevent it, yet this is the equivalent of what is happening to every forecourt operator who is not taking vapour management seriously."

Steel versus fibreglass

While steel tanks are still the preferred material for tanks, fibreglass or glass reinforced plastic (GRP) is seen as best practice in the majority of countries around the world, according to Edward Wheeler, managing director of Eurotank Environmental.

"The UK industry is fearful of GRP tanks because of past failures, but the reality is that these failures were primarily down to companies not building them and installing them correctly the technology itself is sound," he claims.

The primary benefit of GRP is that it doesn’t corrode. "Steel has inherent problems with corrosion," explains Wheeler. "In many countries, cathodic protection of steel tanks is mandatory as it is technically accepted that without cathodic protection, steel tanks will corrode.

"New coatings have been developed and used to protect the outside of tanks, but these are less than 1mm thick and totally reliant on the coatings not getting damaged during installation or degraded by ground-water contamination.

"Internal corrosion is also a serious problem with wet ethanol blended fuel, and premature failure is technically likely over the next decade," adds Wheeler. "However, despite all of this, double-wall, coated, steel tanks are likely to be the only option for retailers going forward in the UK because GRP’s reputation has been tainted unfortunately."

Strategic alliance

To address all the fuel-related challenges of a modern forecourt, tank cleaning specialist DP Fuel Tank Services has completed a series of strategic alliances with other specialist companies.

The alliances concluded so far are with pipework specialist Thames Valley Petroleum, tank-lining specialist RPM and the TankCare division of OTS, which specialises in the implementation of planned preventative maintenance to help customers reduce the risks associated with fuel contamination.

This includes comprehensive measures for testing and monitoring microbial bacteria, particulates contamination and excessive water.

DP Fuel Tank Services director Nigel Plumb comments: "Many of the projects we are called in for these days require a multi-disciplinary approach, with all the tasks requiring a high level of experience and expertise if they are to be carried out efficiently and, above all, safely. Rather than trying to become a jack-of-all-trades, we decided to conclude joint working agreements with companies we know have the right level of training, expertise and experience and will give our customers the high level of service they have come to expect from us."