The risk of using resin generated (RG) foam to fill redundant tanks on forecourts lies mainly in the assumption that it is risk free.
Resin generated foam, in its many forms – RG22, RG8 and RG30 – is now widely used on fuel sites everywhere. RG30 is used to encase fuel tanks for extra safety and contamination protection. RG8 is used for filling de-gassed tanks on a very temporary basis, as it is claimed that it can be completely broken down with water. RG22 is the most prevalent, as it is widely used for the 'permanent' filling of tanks.
RG22 was first developed at a time when the solid fill material of choice was a 20: 1 sand / cement slurry. To fill every part of the tank successfully with this, contractors needed to open the top of the tank, pour in the slurry and agitate it; otherwise it would settle as a cone with space all around. Sometimes part of the forecourt had to be dug up if the manhole was in the wrong position.
The advantages of RG22 were that it was claimed to be safe, environmentally friendly and could be pumped in through an exiting pipe or a flange on the manhole lid. This made it a big favourite with petroleum officers and oil companies, some of which began to insist on its use.
It was also cheaper than slurry and much lighter, which meant that the eventual excavation of the tank was claimed to be easier and less expensive.
The introduction of foamed concrete has eroded some of these advantages, as it is much lighter than its predecessor and has similar flowing properties. This means that, for most fuel site uses, there is now a viable alternative to RG22 that meets the requirements of oil companies and petroleum officers.
The main reason that we need an alternative to RG foam is that it contains formaldehyde – a probable human carcinogen. In 2002, formaldehyde was placed on the US Report on Carcinogens 11th edition, compiled by the US Department of Health and Human Services, Public Health Service and the National Toxicology Program; something that holds only moral power in the UK and EU.
In Canada Urea-formaldehyde foam, which also uses formaldehyde as a curing aid, was used to insulate homes, particularly timber framed houses, but this has now been banned by the Canadian government after occupants complained of runny noses and sore eyes.
Because formaldehyde is used as a curing agent, while R22 needs to be handled with care at all times, the highest health risk does not occur when the foam is pumped into tanks in its liquid state, but rather when the so called 'permanently' filled tanks have to be excavated and removed, to allow a site to be decommissioned and used for some other purpose.
The concerns are two-fold: handling the foam itself and exposure to the formaldehyde gas that is given off when the tanks are excavated and cut up for disposal.
Because of its alleged properties, we were as interested in using RG22 as anyone else when it first came out. Our doubts began when we started excavating tanks that had been filled with the foam and discovered how difficult and expensive it was to dispose of.
We discovered that RG22 can shrink, letting air get back into the tank, which reduces the safety effects of RG22 and speeds up corrosion. We later also discovered that it gave formaldehyde gas a place to gather.
We have excavated tanks less than three months after they have been filled with RG22 and the foam had already shrunk considerably. On the other hand, we have excavated tanks that were filled with RG22 two years previously and found that some of the foam was still in a liquid state.
When our people opened the tanks they found the fumes were often overpowering and anyone who was unfortunate enough to touch the stuff received an unpleasant and uncomfortable skin rash as a reward. All our people now use an all-over bodysuit and breathing apparatus when dealing with RG22. "
The lightness of the foam was supposed to make excavation easier, allowing the tank containing the foam to be lifted straight from the ground and onto the back of a lorry. Unfortunately we discovered that there are only one or two disposal sites that will accept tanks with RG22 still inside. Even then, they will only accept small tanks, and then only when they can be placed in a deep part of the landfill site.
We will only attempt the all-in-one approach when our client insists, as we prefer the more environmentally friendly approach of sending the metal of the tank for recycling. This means that once it has been removed from the ground, the excavated tank has to be cut away, with the metal taken to one site and the RG22 to another – usually a hazardous waste site.
We are not the only ones to have concerns, another company in our sector told us: "RG foam is fine if the tank was never going to be opened again; the problem is that, these days, eventually, many tanks will need to be removed, if the site is to be sold on for development.
"My concern is, when we cut the tanks open there is a very pungent smell of formaldehyde and often an irritated feeling in the throat and eyes.
"We now use a different technique where we try to use heavy machinery to open the tanks up, keeping personnel away from the excavation.
"It would appear that the problem lies in the fact that during the curing the foam emits a fair amount of formaldehyde gas, which is trapped in the tank, to be released only when it is cut open.
"Our workforce also initially noticed some irritation through exposure to the foam and, indeed, the manufacturers' data sheet says it is a 'light irritant'."
This company believes the main problem is that, as well as being an irritant, the material is light and friable, so, if precautions are not taken, it can get under clothing or even be breathed in.
"However," says the company, "this part of the problem can be dealt with if contractors are properly forewarned. Like any other risk, they can deal with it, if they know exactly what they are facing, by elimination, in the first instance and, where not possible, control techniques such as wearing protective clothing, gloves masks, eye protection etc.
"A bigger problem is that fuel sites undergoing decommissioning are normally bounded by roads and pavements, often in built up areas, so there is a danger that the light friable foam can easily be blown off the site. These days we do not remove these foams on a day when there is any wind at all.
"However, as I said, the problems associated with the foam itself can be dealt with using some simple precautions, our real concern is the formaldehyde gas that is given off when the tanks are cut into, as they must be when a site is decommissioned . "
Experience has shown us that air pockets occur, where the gas tends to concentrate, leading to a burst of gas being released when these pockets are breached.
Proximity is the real problem. Once formaldehyde gas is vented to atmosphere it will disburse to a harmless level, but if you are close to the tank when it is cut it is more worrying.
Environmental and personal monitoring was carried out by a company in our sector, looking at the level of concentration of formaldehyde gas on fuel sites being decommissioned when tanks are cut open.
In one of these tests, formaldehyde sensors were placed at four strategic points on the site. Three produced results of under the recommended level of two parts per million, but the nearest sensor, located 3m from the tank, registered 2.07 parts per million, which exceeds the UK workplace exposure limits (WEL) of 2.0 parts per million, currently listed in HSE publication EH40 / 2005 Workplace Exposure Limits.
This indicates that steps need to be taken to protect anyone going within that distance.
We also believe that the two parts per million limit itself needs examination, as there is, in my opinion, no real evidence for this level, one way or the other. Much more research is needed.
The message is to be aware of the risks and take the right precautions.
The main problem is the respiratory system and the eyes, so we use a helmet, with a visor and a power assisted respirator.
Their message to petroleum officers and oil companies is to not get seduced by the alleged advantages of RG foam, to look at where it is appropriate to use it.
RG foams have their place in the mix, they should not be seen as the first resort.
It may be slightly cheaper to use RG22 to fill the tanks in the first place, but any savings are outweighed by the extra disposal costs and precautions that have to be put in place.
Hierarchy of dealing with hazards.
If the job is hazardous, does it really need doing?
If the job is really necessary, then can the hazardous material be substituted with something more benign, such as slurry, foamed concrete or polyurethane, which is now being sold as a substitute in the US, but not here yet.
3. Change working methods
Using more machinery to reduce direct contact. Paying more attention to the weather on excavation days.
Increased use of personal protection equipment (PPE) and paying more attention to containment within the site.