It’s been said that the underground fuel storage network in the UK is a ’ticking time bomb’, with thousands of ageing, single-wall steel tanks thought to be hiding under forecourts nationwide. The consequences of a leak can be catastrophic to the environment and bank balance but many retailers are taking a dangerous risk by holding onto ageing tanks longer than they should, because of the prohibitive cost of replacement, according to Vianet Fuel Solutions (VFS). However a relatively inexpensive solution is available.
VFS technical sales manager, Richard Whiting, says: "While the circumstances of each forecourt are different, generally speaking when compared with the cost of installing new tanks, or the potential cost of cleaning up a leak tank lining is usually the best option by far."
To help one customer understand the full financial differences between tank lining and tank replacement, VFS carried out a comparison survey on a real service station and provided the owner with precise figures on single-skin lining, double-skin lining and tank replacement.
While the details of the site must remain confidential, the overall results revealed that the cost of replacing five tanks of varying sizes from 30,000 litres down to 12,400 litres by installing new double-skin tanks, complete with a leak-detection system, using the original tank farm or creating a new tank farm elsewhere on the site, the owner would have to spend in the region of £145,000 to £190,000 plus VAT.
This was set against the cost of double-skin lining, including leak detection, which worked out, for that site, at £62,991 plus VAT. The simpler single-skin lining would have been £32,154 plus VAT. If, as in extreme and unusual cases, all the pipework needs replacing, a further £20,000 would be added to these prices.
"The inescapable conclusion is that tank lining offers a cost-effective alternative to the installation of new underground storage tanks," says Whiting. "In addition, there are other benefits of relining the tanks, such as no requirement for planning permission and minimal site disruption. Wherever possible, the site can remain operational during the lining process."
Meanwhile, it’s not just single-wall tanks retailers should be concerned about, because according to Edward Wheeler, managing director of Eurotank Environmental, the industry has seen its first failures of double-wall steel tanks in the past 12 months, with evidence of leaks springing from the inner and outer skin of underground storage tanks.
"The impact on retailers if the inner skin leaks can be limited to fuel contamination and a patch repair cost, but the impact of the outer skin leaking is very different," warns Wheeler.
He says that an outer-skin leak forces the retailer into one of three courses of action: to stop using the tank and decommission it; to double-skin line the tank because the licensing authority is likely to insist on the tank returning to double skin; or removing the forecourt to expose the tank and either find the leak and repair it or remove the tank and replace it with a new one.
Says Wheeler: "When the European standards for fuel systems were developed, the use of pea gravel as a backfill was judged to be a better material than concrete due to the ease with which it could be removed. However, in a situation where one tank fails, it becomes very difficult to remove it because the pea gravel is ’fluid’ and will move into the void left by the failed tank being removed. To stop this happening, shuttering is required, which is not easy or all tanks have to be replaced."
Wheeler also says there’s a common misconception that double-wall tanks should last a lot longer than single-wall tanks. "Despite the superior corrosion inhibiting coatings applied to double-wall tanks, they may fail faster than single-wall tanks. Even the smallest paint defect in the outer coating will cause accelerated corrosion in that spot and the outer skin will be breached in years, not decades.
"Currently, industry best practice is to remove single-wall tanks and install new double-wall tanks," he adds. "Although technically I would argue that a properly lined, well-installed, single-wall steel tank will outlast a new double-wall steel tank, it is understandable that major retailers have gone down this road when undertaking total knock-down-rebuilds. But the issue now is whether retailers will want to go through the downtime and expense of digging up their sites to replace their double-wall tanks every 20 years? My advice is if you are happy with your tank capacities and your shop, why knock it all down and rebuild it?
"The problem for retailers is selecting the right system and company to carry out the lining works. There is a long list of companies which have carried our tank lining installations and are not around today to honour the warranties. It is better to install a good single-skin system than a bad double-skin system because the single is likely to last a lot longer."
Cleaning fuel tanks is an essential part of forecourt maintenance, whether it be to prepare tanks for biofuels, overcome a contamination problem, get tanks ready for lining, tank testing or just general tank hygiene. But the question is which method for tank cleaning is best?
Nigel Plumb, director of DP Fuel Tank Services, says: "There are two ways the man-entry method or remote cleaning, and both methods have advantages and disadvantages. We use both methods, depending on customer preference and site conditions.
"We prefer getting our safely-gloved hands dirty in order to get a tank thoroughly clean. Personnel going inside tanks always run a minor risk, but providing they are trained and prepared for the job, there is little or no threat.
"Training and safety equipment for manned entry may cost companies money, but is a far cheaper method compared to the cost of pumping gallons of contaminated water, created by jet washing, out of a tank, and then having to dispose of it safely. Understandably some clients prefer remote cleaning and for those we use the Gamma Jet X, a high-pressure water lance that features an innovative two-way swivel nozzle. Using continually recycled water, this cleans without leaving streaks."
To tackle bacterial contamination problems caused by biofuels, Petroman Environmental produces and distributes the Bio-Klenz fuel additive. As Petroman operations manager Phil Lovatt explains: "Bacteria need two things to live: food, which they get from the bio-fuel, and oxygen, which they get from water, which can come from a number of sources. Remove either of these and the bugs die. Bio-Klenz reacts with any water in the fuel and emulsifies it, so it can’t be used by bacteria. Bio-Klenz does not clog pipes, filters or pumps and is burned off harmlessly in engines.
"While other methods and procedures for dealing with the problem, such as fuel polishing and tank cleaning, can be very effective and may be required for severe contamination, these can be expensive, so it is more cost-effective if the problem is caught early enough to carry out preventative maintenance by regularly dosing tanks with BioKlenz," adds Lovatt. "It is also a very practical means of eradicating bacteria from pipework."
The forecourt market was one of the first sectors to embrace the benefits of plastic pipework and has been reaping the rewards for over a decade, according to David Naylor, brand manager for Durapipe PLX.
"Careful consideration should be given to the specification of products," advises Naylor. "Reliability and safety are crucial for forecourts. If any fuel was to leak into the ground or vapours into the atmosphere, it could harm both the environment and the public. With the majority of pipework in a forecourt installed below ground, there is always a threat of ground contamination.
"As a result, it is important that contractors specify secondary contained systems to provide additional pipework protection against damage and to prevent accidental fuel loss into the environment. Secondary-contained pipe systems are becoming compulsory for many pipework applications, and are now the preferred solution for fuel conveyance."
However, there are different options for secondary-contained pipework systems and it is important to ensure the right product is used, adds Naylor. "Within a forecourt, close-fit pipework should be used for below-ground sections and a pipe-in-pipe solution would be the preferred option for above-ground fuel transfer. With such specific requirements, it is essential that a pipework system is selected that is purpose-designed for the specific fuel conveyance application it will be operating in, rather than a product that claims it can cater for multiple applications, as this is when performance can be compromised."
Durapipe UK’s PLX system is purpose-designed for the safe transfer of fuel-based liquids and their vapours. "Manufactured in a robust polyethylene material, PLX provides exceptional resistance to rapid crack propagation and long-term stress cracking," says Naylor. "A protective liner allows increased resistance to all types of fuel blends, ensuring there is no permeation of fuel through to the atmosphere."
Pipework supplier Nupigeco, which offers the Smartflex system, says the trend in plastic pipework is moving towards double-wall piping systems.
Maja Stirrat, area sales manager of Nupigeco, says: "Smartflex offers a full range of double-wall fittings, and the terminating fittings and even some elbows and T-pieces have test port connections on them to allow easy connection to leak detection units or pressure test units."
The installation should be easy but, more importantly, safe for the installer and the environment, stresses Stirrat. "To do that, retailers need to make sure that only trained people are installing the products," she says. "Smartflex’s own welding machine will only operate if the installer holds a smartcard that contains their details and ID number. The Smartflex welding machine also measures temperature and automatically adjusts the welding time so there is no danger of underheating or overheating the weld.
Floods ravaged many areas of the UK last year with some forecourts not escaping rising water levels.
E&S Environmental recommends that retailers with sites in flooded areas check the health of the tank and line fleet.
"When totally submerged in water, tanks try to float as they’re subjected to an up-thrust of 30 tons or more," the company warns. "The worst case is they do float and burst through to above-ground level.
"Less obviously, they can crack the surface, strain connections to lines or suffer structural damage themselves. Most obviously, they may start to take on water either because water is at a level at which a previously unknown flaw becomes covered or because structural damage applies pressure on a previous weak point, causing failure and significant expense.
"A minimum requirement for forecourt retailers is to check for water in the tanks immediately and maintain this at least daily until flooding disappears."
Petroman Environmental is reminding retailers that it’s a legal requirement for forecourts to have their pressure vacuum (PV) and vapour recovery (VR) valves tested at the required intervals.
The company says it can carry out an interactive or static Stage 1B test to check the PV and VR valves, with static testing being without a tanker connected to the system. Inert nitrogen is used to pressurise the tanks to check the PV valve operates at the required pressure and the VR valve is sealing correctly. Using nitrogen as a safe medium for the test gives a lot more flexibility as to when testing can take place, says Petroman.
Pressurising the tanks also allows the testing of the whole system for leaks, from the fill points and vapour recovery pipe work above ground, at the same time.