Factual Report
by a qualified engineer

 

In several important respects the work has conformed to no specification and has been carried out in a careless, irresponsible manner. This is explained below, without going into any more detail than is essential.

 

The pipe is 48” in diameter, made from flat sheets of high quality steel, bent to a circle and welded longitudinally in lengths of approximately 15 metres by German Manufacturers. It has been designed to carry national gas mostly, but not all, methane at a maximum operating pressure (MOP) of 94 BAR (1 BAR =14.5038lb/m2 and 94 BAR =1363lb/m2 or about 3100 feet head of water)

All high pressure gas pipes explode in the end, usually because they become corroded. The rate of corrosion depends almost entirely on the care with which they are laid. Such explosions usually ignite the gas, which forms a fireball, incinerating everything within a few hundred yards and much further down wind. It is therefore important above all to take the utmost care when laying the pipe to preserve the anti-corrosion coating, and to monitor the state of the pipe while in use at frequent interval, if it passes within range of life and/or property.

 

Because the route of the pipe passes close to where I and another civil engineer, still active in the profession, and also a retired metallurgist all live, we have naturally taken what at first was a casual interest in the work in progress. Suspicions were aroused by what was observed , and our MP kindly arranged a meeting with National Grid’s Senior Project Manager which took place on the 22^nd of August 2007.

 

At this meeting certain facts were obtained from National Grid’s Senior Project Manager, but the meeting was unsatisfactory in that no satisfaction was provided by National Grid that the work was being carried out to normal professional standards, despite assurances that this was the case.

 

Much more bas been discovered since, most of it extremely unsatisfactory.

 

A normal procedure for laying the pipe would be as the following:

 

-Soft or boggy ground

- Contaminated ground water, with full chemical analyses

- Underground cavities, either natural or as a result of old mine workings

- Presence of hard rock within the anticipated depth of the trench (usually 8 feet, but more at certain places)

- Nature of all river or stream beds, ie. Whether of soft material, ground, boulders or solid rock

- Approximate length of all tunnels required, with suggestion as to how best to achieve them, ie. By cut and cover, or bored tunnel etc.

- Anything else that could add to or facilitate the work.

 

This is perhaps the most important part of the entire project, which should ensure that no unwelcome surprises are met during the execution and also enable the planning of the work to be carried out effectively.

 

The consultant engineer would proceed with the detailed design and layout, both horizontal and vertical, of the pipe plus ancillary installations. Normally, the consultant engineer would then prepare contract documents and a call for tenders would be advertised. 

 

The consultant would receive the tenders and report on them to the client, with a recommendation.

 

A contract would be signed and work would commence.

 

Throughout the progress of the work the consultant would employ competent supervising engineers and inspectors to check and verify that every stage had been satisfactorily completed on every part of the line before proceeding to the next stage.

 

The consultant would check all accounts submitted monthly for payment by the contractor and after checking and correcting as necessary pass them to the client for payment. This would continue up to the final payment certificate on completion.

 

It has only in the last few days been discovered that the actual procedure followed has been very different from this, prior to the signing of the contract, this will be mentioned later.

 

Deficiencies and shortcomings in the work have been established be eyewitnesses and by photographs. These photographs are particularly important, one of a long length of pipe laid on a bed consisting of rocks, one of the pipe suspended in the air over a large crater full of water, and one showing the pipe emerging from a tunnel through solid rock. Many other photographs are available, most of them showing some irregularity in the work.

 

At the August meeting with N. Grid it was established that the specifications for the pipe was IGE/TD1 edition 4, published in 2001, by the institute of Gas Engineers, for pipes to be used for transmission of gas at high pressure.

 

Following the meeting, a cope of these specification was obtained.

 

The pipe has not been laid throughout in accordance with this specification which requires a bed of fine material 6” or 150mm thick to be provided, and the pipe then to be surrounded with the same minimum thickness of fine material in the course of back filling, up to 6” over the top of the pipe. All sharp objects are to be excluded from this bed and surrounding, stones and such like. This is correctly required in order to preserve intact the anti-corrosion coating provided over the whole outer surface of all the pipes. Wherever this coating is damaged, corrosion will start immediately, and lead to explosions sooner than would otherwise be the case.

 

At no location seen in the Brecon area has the pipe been laid on the specified bed of fine material and many photographs show stones in the proximity of the pipe. N. Grid Senior Project Manager ( based in Leeds) has stated verbally and in writing that the missing bed for the pipe has been provided after the pipe has been laid in the trench, by grading material to fill down the side of the trench. He should be well aware that to provide a bed in this way is a physical impossibility. Some of the photographs confirm this. Many show the pipe deposited on sandbags or sacks containing what is presumably fine material. These do not constitute the specified bed, and if they were an acceptable substitute, the specification would state this. Neither is there any indication in the photographs of a bed being laid in the trench to conform with the tortuous nature of the pipe, deposited in to the trench in long pre-welded lengths up to and over 1200 feet at a time, containing pre-formed horizontal and vertical bends. As the bottom of the trench is not particularly correct, to line or level, the pipe is seen resting in the trench mainly on air, supported at quite long intervals at high points in the trench, or on objects placed in the trench. The pipe with a bed exclusively of rocks is the worst example seen, but there is enough in the photographs to show that nowhere in this neighbourhood has the specified procedure been followed, and there is no reason at all to suppose that it has been followed anywhere else.

 

A typical consequence of the actual, incorrect, procedure, was observed near Trecastle. A pipe was being cut out of the line and replaced because, according to the people working on it, it had been laid on a rock projecting from the bottom of the trench and become deformed. A second similar incident happened not far away. 

 

The impact of pipe on rock, at these locations, was enough to cause deformation which was detected. At many other locations, the pipe, which is immensely strong, would not have been deformed, though the impact would almost certainly have caused damage to the coating.

 

The specification is particularly emphatic on carrying out all necessary repairs to the coating before the pipe is covered up. Once it is in the trench it is impossible to repair damage to its underside without lifting it out again.

 

Since merely lowering the pipe gently onto a rock would not cause deformation, there is a strong suspicion that at this particular location the pipe had been dropped onto the rock, not lowered carefully. A drop of only 3 inches would cause an impact at 4 feet per second, certainly enough to cause deformation if several hundred tons of pipe landed on a single point.

For lowering extremely long lengths of pipe, containing both horizontal and vertical bends, in one lift, it is all the more important that the pipe should descent slowly onto a bed levelled and formed to the correct shape to receive it. 

 

There is no indication at all that this has ever been attempted on this line, anywhere.

 

The sub-contractor’s system of lowering the pipe, suspended from 6 or 7 cranes simultaneously, is controlled by radio telephone, but this still depends on the reaction time of each crew operator and it is difficult to control an operation like this with parts of the pipe out of sight due to bends in the trench. It was surprising to learn from N.Grid’s SRM that there was no upper limit to the length of pipe to be handled in one lift, and that this depended solely on the number of cranes the sub-contractor was able to muster.

 

The photograph of the end of the pipe emerging from a snugly-fitting tunnel in solid rock is also horrifying. The pipe could not have been pulled or pushed through this hole in the rock without causing serious damage to the coating. The sub-contractor has followed the wrong method, and N grid’s inspection system has done nothing to ensure that an acceptable method was used. If this tunnel conceals damage to the pipe coating, at how many other tunnels has damage been similarly caused. In the absence of definite information, only obtainable by digging up the tunnel, it is wiser to assume that all the tunnels contain pipes with damaged coatings.

 

Another breach of the specification is visible in this photograph, which shows mud deposited inside the pipe and muddy water pouring out of it. The specified requirement is for all open ends of pipes which do not have to be open in order to carry on the work, to be closed off with temporary blocks, called “nightcaps”, to prevent ingress of any foreign objects. Water is such an object, but does no lasting harm. The mud it takes with it is quite another matter, almost impossible to get out of a pipe once it is in it, and when dry, it turns to dust, which damages the inside of the pipe. It is easy to exclude muddy water from the uphill end of an open ended pipe, by digging a hole to collect the water and pumping it out well before the level rises to the lip of the pipe. This elementary care requires time and a certain amount of money. Obviously just as from the pipe deformed by a projecting rock, N Grid’s inspection system was absent or useless.

 

An extraordinary situation has arisen over testing the pipe in lengths of about a mile at a time by filling it with water under pressure.

 

N Grid’s SPM stated at the August meeting and has repeated this in correspondence that N Grid are legally obliged to test the pipe at a pressure of 149.5 BAR, 2168lb/in2

 

The legal requirement must be linked to the MOP, as nothing else is logical, so what the SPM means is that he is legally required to test to 159% of the MOP. An odd percentage, but nothing else is logical.

 

The trouble comes over the thickness of the pipes, which are of two nominal thicknesses, of 22.9mm for use near houses and main roads and 15.9mm for general use. Both thicknesses have tolerances between which they are acceptable of +10% and -5%.

 

A thinner pipe at the nominal thickness is stressed by this pressure to 103.4% of the manufacturer’s certified minimum yield stress (CMYS). A pipe of 5% less than the thickness (but still acceptable) is stressed to 108.63% of the certified minimum. If the pipe happens to be on the outside of a bend formed on site, and therefore stretched even thinner, the stress caused by the test can be 110.14% of the CMYS. Thus all pipes of these thicknesses are liable to be overstressed and stretched be the testing procedure. It is absurd to test a pipe or anything else above its yield stress. If the legal requirement is 159% of MOP then the MOP should be lowered from 94 BAR to a value which gives a stress when tested at 159% equal to the CMYS. This reduced MOP comes to, I believe, 84.3 BAR. This muddle is unfortunate but easily understandable if one appreciates that N Grid never worked out what stress would be imposed on the pipes by testing to 149.5BAR.

 

There is also doubt concerning the welds. A United Nation’s Consultant examined welds in the section near Tirley and found a significant number defective. It is not known what action, if any, was taken.

 

This about concludes the incidence of work carried out contrary to specification.

 

It is sufficient to confirm what has been stated above, i.e. a reckless and careless manner of working, totally inappropriate for a pipe of this nature. The pipe cannot be considered as fit for purpose, though a consortium of independent expert engineers might feel justified in verifying operation at a much lower MOP (much lower also than the lower figure of 84.5 BAR mentioned above).

 

Quite a lot has now been discovered about the contract to lay the pipe.

 

First, the route was not chosen by N Grid, but, according to the SPM, by the American oil company Exxon. This seem a very curious procedure, and has certainly not been public knowledge up to 14^th Nov. 2007. Perhaps Exxon have much greater experience gained in Arabia, Alaska and elsewhere of selecting routes for high pressure pipes.

 

Second, there was no call for tenders, and, so far as is known, no consultant engineers have been employed on the pipeline. Instead, N Grid entered into direct negotiations with Land and Marine resulting in a contract on the “Cost Plus” system whereby the contractor submits his accounts and the client pays the full amount of the costs plus an agreed percentage for profit.

 

On this pipeline, N Grid have dispensed with any supervising consultant engineers and have elected to carry out supervisions by their own staff. All that can be said about this, is that it is quite evident that there has been no regular system of inspection and approval of the work, stage by stage, and it is very doubtful from the look of what has been happening, that either N Grid’s supervising staff, or the contractor, or the sub-contractor have even seen the specification. This is no way to lay a pipeline of this critical nature and importance.

 

Other points have been noted. In October 2007 a senior member of the staff of Murphy, the sub-contractor who has done most, in not all, of the work in the area from Neath to Brecon, published an article in the magazine “Contracts Journal”. 

 

In this article it was stated that Murphy had been responsible for the site investigation, which included 300 boreholes and lasted a year. Also that Murphy had been surprised to meet solid rock in parts of their trench excavation.

 

This explains much, a site investigation which did not, in the course of drilling 300 boreholes, discover solid rock within 8 feet of the surface in the hilly country of South Wales, cannot have been much of an “investigation”. It should not, in any case, have been a surprise to find rock when it came to digging the trench.

 

More serious than the failure to anticipate rock in the hills, is the scene shown in the photograph of the pipe suspended over a large crater full of water. The part of the route north of Neath runs over an area which has been extensively mined for coal and is full of old workings. The photograph shows a location where, after the trench was dug, and the pipe placed in it, the floor of the trench subsided into an underground cavity which then became filled with water. This may have been a natural cavity in the limestone but is much more likely to have been something left over from old mining operations. In either case, it is precisely what the site investigation should have been looking for and discovering in advance. 

 

The correct action is either to vary the route to avoid the cavity or to fill it, ahead of laying the pipe, with some form of cementitious material. It is better to avoid such areas altogether when choosing a route for a high pressure pipe, but if this is not feasible, it is then essential to discover all such hazards and deal with them in advance of pipe laying. Now that one has been discovered, too late for proper action, how many more may remain undiscovered by what was evidently an inadequate “site investigation”. Any such will almost certainly cause subsidence during the working life of a pipeline, producing stress in the pipe which it is quite impossible to calculate, and may very well cause fracture.

 

This site investigation should never have been left to Murphy if they were surprised to meet rock in a trench. It would be interesting to see the terms of reference provided for the specialist firm who carried out the investigation, especially the limitations imposed on it’s extend by Murphy. It would be unreasonable to consider the specialist firm responsible for not finding things they were never instructed to look for.

 

It seems also that unexpected obstacles, in the form of rock and boulders, were encountered in some of the tunnels. The short tunnel below the river Usk near Aberyscir took 4 months to complete, and during September 2007 a badly damaged and distorted pipe was seen being removed from the site of the tunnel on a trailer. As is to be expected in an area of glacial melt-down, the tunnel encountered boulders. N Grid have been requested to provide details of Murphy’s tunnelling procedure, without response.  

A pipe, of the thicker kind, is immensely strong. One wonders what Murphy had done to it to damage it in this way. It is certainly no part of a normal tunnelling procedure. Once again, one wonders at how many other tunnels along the route, damage short of actual deformation of the pipe, bet certainly damage to the coating, may have been caused.

 

Mention has been made of the unsatisfactory nature of some of the statement, both verbal and written, made by N Grid’s SPM.

 

Regarding the photograph of the pipe laid on rocks, a written reply to a request for information was so improbable a not to be worth quoting. It was obviously a string of inventions fed to the SPM by a bad contractor, in a state of desperation. A second explanation has been received in which the SPM states that the photograph shows a short length of pipe which was laid in April 2007 and left open on purpose when the rest of the trench was back filled, in order to facilitate the hydro-static test to be carried out later.  The large number of loose rocks visible in the photograph had all fallen down during the 4 months April-August 2007. Something like this may have occurred but the photograph shows quite a long length of trench, not a short length, and the SPM has ignored the specified requirement that pipes should be back filled “soon after laying”. 4 months is not exactly “soon” and the number of loose rocks show exactly why this was written into the specification. The explanation continued to the effect that this length of pipe was then lifted out for repairs to be made to the coating, then replaced, and the bed provided by tipping material down the side of the trench and pushing it under the pipe by hand.

 

This is not an acceptable procedure for providing a bed for a pipe and anything which was done such as carrying out a hydro-static test, lifting the pipe in and out, etc. would have had to be done very quickly as the entire trench was backfilled by 2 days after the photograph was taken.

 

One is left to consider:

One explanation has been received which was clearly invented. A second is subsequently received, not quite as unlikely, but describing procedures in breach of what is specified. Is this second explanation any more likely to be correct than the first one?

 

Certainly one can conclude that N Grid’s SPM is ignorant of the basic procedures for laying pipes, has little knowledge of day to day events on the project of which he is in charge, and has not studied the specification.

 

Further doubts concerning the pipeline arise from the inactivity of the Health and Safety Executive, and their announcements to the press that they monitor all activities on the pipeline and are entirely satisfied that all has been proceeding in accordance with the highest standard of safety. The inactivity is not the fault of the HSE who have not the staff, certainly not the qualified staff, to prowl up and down a line about 122 miles long checking all activities.

 

The press handouts are another matter. Any checking of work in progress has certainly, in the area round Brecon, not been done on site, apart from two occasions, one concerning a dangerous vertical fence in unstable soil, and another when incorrect charges were used for blasting the trench in rock, with dangerous results. The HSE came in response to complaints from the public on these occasions.

 

A letter was sent to HSE, setting out a number of complaints about the contractor’s work, and a polite reply was received from their staff member concerned with all pipeline work, who is based in Norwich, denying none of the points raised and stating they would be looked into.

 

N Grid’s often repeated statements to the press and at meetings (the latest with members of the Welsh Assembly) to the effect that N Grid have an excellent safety record and that all possible care is taken at every stage of the work could well have been recorded several years ago and turned on whenever required.

 

The situation created, regrettably, is due in the first instance to their insufficiently serious approach to the work, which has enabled their contractor and sub-contractor to proceed unchecked in a manner unacceptable by any professional standards.

 

A full enquiry into all of the circumstances, before the pipe is put into operation, is now required, before anyone is killed.

 

It is interesting to report, in conclusion, that within the last 3 days or so a small explosion occurred at Trebanus in an “above ground installation”, followed by a sustained high pitched screech. 

 

On this occasion the HSE were summoned by members of the public and reported that “there was nothing to worry about”.

 

A more balanced view would be, hopefully, that on the contrary, there was everything to worry about, for any mishap concerning high explosive, but that on this occasion the damage had been limited and would not recur. One hopes!