SOUTH WOODFORD (SUBSIDENCE) (Hansard, 16 November 1978)

§ Mr. Patrick Jenkin (Wanstead and Woodford)

About five years ago, in 1973, the Department of the Environment, as it then was, began the construction of a major trunk road in South Woodford, in my constituency, the relevant part of which is known as the Grove Road improvement. It involved excavating a cutting running east to west wide enough to take a three-lane dual carriageway, a central reservation and two slip roads, and deep enough to allow the biggest lorries and buses to pass under the roundabout at one end and the road bridge at the other.

At the time the road was being planned and construction was about to begin, there was a public meeting held in an adjacent hall. One of the points made by the Department's spokesman and the engineers was that if, during the process of excavation, any of the residents began to notice any cracks in their houses, they were to draw the matter to the attention of the engineers or contractors as soon as possible.

It did not take long. About two years later the owners of a number of adjacent houses to the south of the cutting began 759 to see signs of subsidence, very slight at first but becoming progressively more serious as the months passed. Cracks began to appear in the walls of their houses; door and window frames began to distort and jam; doorsteps broke away from the walls against which they were fixed; and concrete paths began to fissure. In the silent hours of the night, residents could hear their houses creaking as the subsidence continued, slowly and inexorably.

The evidence over the months mounted. Today there are quite a number of houses in roads in this part of South Woodford —Hillcrest Road, Grove Hill, Craig Gardens, Washington Road, and Grove Crescent—in which the owners are now facing bills running into thousands of pounds in order to stop their houses from falling down.

One of the cases with which I have been most closely concerned is that of Mr. J. F. Turner, of 25 Hillcrest Road, and I have been pressing his case on the Department since he sought my help in July 1976. He first noticed the cracks in the downstairs bathroom of his house in October 1975. It is part of his complaint that, although he wrote four times between October 1975 and July 1976 to the consulting engineers and the Department, no investigation was made into his complaint in that nine months.

This point is important, because by the time I intervened on his behalf and the Department had appointed independent engineers to investigate the complaint we were in the middle of the worst drought of the century. Then, of course, it was too easy for the engineers to take a fairly superficial look and to conclude that what Mr. Turner's house was suffering from was nothing to do with the road works but was due to the drought. That is precisely what they did.

But Mr. Turner, who is a very determined man, did not accept that. Not the least of the reasons for his reluctance to accept it was the fact that by then he had had an estimate for more than £6,000 to underpin his house and repair the damage. He was fortunate, and he was put in touch with an eminent firm of consulting engineers, Crowe Kelsey and Partners, who had been retained by insurers for some other party. They carried 760 out a preliminary survey of 25 Hillcrest Road, and I quote two short passages from that survey: It seems very probable that the damage has been caused by settlement arising from drying shrinkage of the clay subsoil or a major lowering of the ground water table for a gravel subsoil. It goes on to say: If, by digging a cutting 8m deep, the standing water table was lowered by a similar amount locally, this would have a very significant effect on the ground surface level which, in turn, would cause differential settlement to any building that is constructed on this surface. We believe this is what has happened in this case. The preliminary report was shown to the Department, and I am bound to say that the Department was responsive. It suggested a meeting, which was held eventually on 7th February 1977 and was attended by, among others, Messrs Crowe Kelsey, Mr. Turner's surveyors, and the independent firm which had been retained by the Department. The outcome of that meeting was an offer by the Department to pay up to £300 for further investigations. The work suggested was the digging of trial holes around the house to expose the foundations in order to determine what had happened, and also to measure the movement which had taken place in the house.

Meanwhile, the damage continued to increase through the winter of 1976 and 1977, and by January 1977 Mr. Turner had received an estimate for remedial work which was now £12,504. If I tell you, Mr. Deputy Speaker, that this house is a perfectly ordinary four-bedroom semi-detached house, built in 1933, and that until this road cutting was excavated at the end of the garden it had been entirely sound and stable, you can understand the anguish that all this is causing this resident and others in the road.

In March last year, Crowe Kelsey and Partners carried out their full investigation, in two parts. One was on the house itself, and they also used evidence from test boreholes—but, as I shall explain, some hundreds of yards away. I have the report here. As one would expect from that firm, it is a very professionally written and prepared report, full of a mass of measurements, diagrams and figures.

On the house, it says in essence that the cause of the settlement is compaction 761 of the subsoil due to reduction of the natural moisture content. It says that it is unlikely to have been caused by the drought, for a very interesting reason. The drought naturally affects the subsoil nearest the surface, and obviously one would expect more evaporation from the surface of the soil to the south of the house, which receives the sun, than on the shady north side, which is nearest the cutting. If that had happened, one would have expected, and in the normal course of events would have found, the house to be tilting towards the sun.

In fact, the house tilts away from the sun and towards the cutting. There has been more subsidence on the cutting side, to the north, than on the south side. This is the pattern the whole way along the road. Other houses have been surveyed as well. Crowe Kelsey conclude from this evidence that it is the cutting which is the cause of the subsidence, and not the drought, as contended by the Department.

This evidence has been reinforced by the evidence from the boreholes. Perhaps I could digress to describe the geology of the site. The new road cutting cuts across the natural slope of the land, which runs south and west, towards the River Roding and the Thames. The area has long been notorious for springs and ponds, which have always abounded in Epping Forest. The water has always percolated downhill, through the fissures in the clay, towards the bottom of the valleys.

The case which has been examined is that by excavating this new road cutting, across the face of the hill, across the flow, and putting in drains along the bottom of the cutting, as is perfectly proper for the building of the road, that natural percolating flow has been interrupted.

North of the cutting, which I might describe as the uphill side, the water level has been unaffected, and there are no signs of subsidence north of the cutting, because the water continues to flow off the surface of Epping Forest and down into the cutting. But to the south, where lie the roads that I have mentioned and the houses with which I am concerned, it has been cut off. Consequently, the soil has been drying out and it therefore compacts, leading to settlement of the surface.

762 The way to test this is by sinking bore-holes and comparing the moisture content in this land before the road was ever started with the moisture content after the cutting was completed. That is what has been done. The top 2 metres are ignored, because that is affected by climate. It is below that level—from 2 metres down to 7 metres—that is tested. If there were no difference, the answer would be that the cause was the drought and that the Department is right. But if there were a significant difference in the moisture content below the 2 metre level, the conclusion would be that the road cutting was to blame and the Department was liable.

In 1969, as part of the planning of the road, a line of test boreholes was drilled before construction of the trunk road improvement. It included a borehole No. 8 which is quite near 25 Hillcrest Road. But the only test borehole which had been drilled for another investigation—there was, of course, no money for a test borehole for Mr. Turner's house—was about 400 metres away and adjacent to the original test borehole No. 4.

The sum of £300 did not cover a separate borehole, so Messrs. Crowe Kelsey based their comparison on borehole No. 4 and the related adjacent new borehole. But the result was clear. Let me quote a short passage from the report. It states: the clay is now drier than it was in 1969 between these limits. The average moisture content in 1969 between 2 and 7 m was 31.3% and in 1977 this had reduced to 29.4%. This we calculated would reduce the depth of a stratum of saturated clay by 28 mm/m depth. I have made a short calculation, and 28 millimetres per metre depth over a distance of 5 metres provides 140 millimetres contraction. That is almost exactly 6 inches subsidence caused by the reduction of the moisture content. That degree of subsidence at the surface is fully enough to account for the damage that is happening to my constituents' houses.

Armed with this evidence, Mr. Turner returned to the attack, but it was to no avail. The Under-Secretary wrote to me very briefly on 5th September last year: The Department's technical advice is that none of the additional data produced provides evidence to substantiate Mr. Turner's claim that the damage arose as a result of the roadworks. 763 That seems to me, in the face of the evidence that I have quoted, a pretty suprising statement.

However, I was subsequently supplied with a copy of the technical advice by the Department's advisers, a firm called Building Design Partnership, and its comments on Crowe Kelsey's report. The kindest thing that I can say about those comments on Crowe Kelsey's report is that the more I read them the more they sound like the words of a professional man scratching around for arguments to bolster a weak case which he realises has been devastatingly disproved.

What the advice says is most unconvincing. I shall not read it, but a measure of the lack of conviction that it has for me is that it sought to explain the fact that the house had tilted backwards rather than forwards by saying that the roots of the trees at the front had gone right under the house and were draining the moisture away from the back. Of course, there is not a shred of evidence of that. That is totally unconvincing. But the Department, somewhat to my surprise, has continued to rely on this and has continued to deny any liability.

I do not think that that is good enough. The report makes the point that the evidence of the boreholes is quite inconclusive because, it says, they are too far away from the house in question. I therefore asked the Secretary of State why another borehole should not be sunk near to the original borehole No. 8, which is close enough to Mr. Turner's house to provide a much more accurate guide to the loss of moisture. Messrs. Crowe Kelsey believe that a test borehole near borehole No. 8 would establish the case that they have made even more firmly than has been done so far. So also does the borough engineer of the London borough of Redbridge, who knows the area well and, as a professional man, recognises all the difficulties of seeking to establish grounds for proving subsidence.

In a letter to me, the borough engineer wrote: it is very difficult to say that the construction of the under pass has lowered the water table. Without the determination of factual evidence, i.e. a new soil survey taken in the immediate vicinity of the original site investigations to compare moisture contents at present with those previously obtained, then any opinion must be considered speculative. 764 Of course, a new soil survey has been made, 400 metres away. The results are perfectly clear. There has been sufficient loss of moisture to lead to a fall in the surface of up to 6 inches. What is suggested here is that the survey should be done nearer the house.

I have, too, the evidence of the warden of the Epping Forest conservation centre, a noted conservationist, Mr. Paul Moxey, who knows the area well. In a letter to me, he says: the creation of a cutting as deep as that involved here would, in my opinion, be bound to lower the water level and cause movement. When I asked the Secretary of State to support a second test borehole adjacent to the Department's original borehole No. 8, he refused. In his letter he said: I have … obtained further expert advice This advice is, I am afraid, unanimous that further test borings would not help. With the greatest respect to the right hon. Gentleman, that is simply not true. In the report to which I referred earlier, from the Minister's own advisers, Building Design Partnership, there was included in paragraph 6 the following: The evidence of the boreholes is not conclusive, because of the extended distance between them, and the variability of the moisture content of the clay. We do not believe that average moisture content comparisons are relevant unless more accurate data is obtained from bores adjacent to the original ones. This is what I am asking for. The Minister's advisers recognised that more accurate data could be obtained. We could ascertain whether the opinion of Messrs Crowe Kelsey is right. Yet in his letter to me the Secretary of State says that he has had unanimous advice that such a move would not help at all. Which is right—what the Minister's advisers say or what the Secretary of State said in his letter to me?

This issue is too serious for the Secretary of State to take refuge in evasions like that. The issue is intensely serious for my constituents, who are now facing substantial personal losses. Mr. Turner is an elderly man, in his seventies, and is in no way able to get a mortgage on his house for the amount that would be needed to pay for the work that has to be done. He has had some repairs done, some professionally and some by his son-in-law. He has replaced the worst affected window frames at a cost of over £400. He has redecorated the inside of 765 the house, because the wallpaper came away at the corners and round the cornices. But still the damage is going on.

Last Saturday I saw a new crack in Mr. Turner's home, beside the one that had been repaired. This new crack stretches up several feet from the ground, and Mr. Turner says that it is getting wider. Last year he tried to sell his house and was offered almost exactly £10,000 less than the price which could be obtained for a house in the same location but in a state of sound structural repair.

Mr. Turner has already incurred over £400 on professional fees, yet nothing has been done to halt the steady destruction of his home. Many others are similarly affected. But the position may be more serious. As the water level goes down, the subsidence will take place further away from the motorway. Hundreds of houses may be affected. The Minister has recognised this because an official of his Department said at one meeting that the figures could run into millions of pounds.

The cost of this is being borne by my constituents. The Department built this road and if, as Mr. Turner's advisers contend, it is the cause of his woes, the.. Department should pay up. The Department has a clear duty to meet its obligation and its liability. If it is not prepared to do that on the evidence so far available, it should at least be prepared to undertake the drilling of further bore-holes which would be necessary to prove once and for all whether my constituents are entitled to compensation.

§ The Under-Secretary of State for Transport (Mr. John Horam)

I congratulate the right hon. Member for Wanstead and Woodford (Mr. Jenkin) on his success in raising this matter and the vigour with which he has represented his constituents' interests. I have a file full of letters showing the action which he has taken on their behalf. In addition, I appreciate the anguish which this matter causes to those in his constituency who are affected by the scheme.

After the completion of the road works which the right hon. Gentleman described, verbal and written complaints were made by local residents, about damage to 766 houses, which they attributed in general terms to the construction of the new road. About 20 residents have made claims against the Department, and in one case where land slippage has occurred legal proceedings have recently been instituted.

Apart from the case involving land slippage, which is under investigation by the Department, investigations to determine the cause of the damage have been made on a number of occasions by the firm of consulting engineers which designed and supervised the construction of the new road and also by a firm of independent consultants appointed by the Department specially for this purpose in 1976.

Both firms of specialists have visited affected properties and have concluded that the road works are not responsible for the cracking and subsidence but that, in their view, the damage is the result of the natural drying out of the clay subsoil exacerbated by the dry spell which lasted from May 1975 to August 1976. That prolonged period of 16 months of less-than-average rainfall would naturally bring about a gradual decline in the water content of the soil. There is an important additional factor which is relevant to consideration of the problem which the right hon. Gentleman has brought to our attention—namely, that the subsoil in his constituency is largely composed of London clay, a material which is particularly badly affected by problems of alternate drying out and then further wetting.

The general problems associated with London clay were brought out in a debate in this House in 1976, when it was pointed out that, whereas in the country as a whole as a result of the dry spell one in 5,000 houses was affected, in London the proportion was down to one house in 100 and in the South-East one house in 500. This flowed from the fact that London sits on clay. It is fair to say that Woodford is full of houses which have suffered cracks from subsidence caused by the problems of having been built on London clay. That is not only my opinion but is the view of the borough engineer. This is a general problem in the Woodford area.

The right hon. Gentleman referred to the inspections and reports of the Building Design Partnership, which was called 767 in by the Department as a body of independent consultants to examine the problem. We accept that there must be some independent examination of the problems —not simply examination by the consultants advising the right hon. Gentleman's constituents or the consultants involved in the original construction of the road.

The Building Design Partnership reported that the general basis of complaint was that vibration from the road works had caused damage and that the road works by their presence had caused settlement, which in turn had caused damage. The partnership agreed that there was no doubt that settlements—some quite severe—had occurred, and probably were still occurring.

In its report, the partnership said that the grounds for compaint could be separated into four—namely, vibration by itself, settlement by vibration, settlement due to ground slip and settlement due to ground shrinkage.

In its report it ruled out the first three of those causes as having anything to do with the basic problem. The consultants drew attention to the effect of rain in the South of England in 1975–76, which created increasing reductions in groundwater levels and in shrinking clays. The latter problem is exacerbated by trees and shrubs, which draw their moisture from the clays and thus reduce their moisture content very considerably.

Shrinkage of the stiff clays in the London area can be extensive and may, under grass alone, reach 1.5 metres in depth. For this reason, house foundations on clays—even for single-storey construction —are no longer permitted to be shallower than 1 metre without precautions being taken to obviate the effects of differential settlement.

The houses inspected by the consultants had foundations of no more than 0.6 metres deep, and no such precautions. The consultants concluded that the cracking that they had seen was consistent with the type of settlements caused by the drying out of the clay subsoil under very shallow foundations. Also, the consultants' conclusion was that, taking account of the timing and nature of the road works, they did not consider that the 768 road works had caused any damage in the dwellings examined.

If I had had time, I should have liked to go into the various technical points which the right hon. Gentleman quite fairly raised between the various reports, Perhaps I may write to him about them. There is clearly a difference of opinion, but what we are relying upon is the independent consultants' report.

I should add that it is not just one report. After all, as the right hon. Gentleman will agree, there have been six separate reports on six individual cases undertaken by the Building Design Partnership to look into this matter. In all those six cases, they have come to the same conclusions. Again, I shall not go into the details of the exact reasoning because I do not have enough time on this occasion. We can pursue that matter by letter, if the right hon. Gentleman will allow me to write to him.

I come finally to the question of more boreholes. The right hon. Gentleman will remember that he wrote to the borough engineer to ask for his observations on the subsidence which is evident in the area. The borough engineer replied to the effect that within the borough defects had been reported over many years in all kinds of property founded on the band of shrinkable clay on which the borough largely rests. Whilst buildings close to the underpass have suffered serious defects, properties further away have been damaged to an extent which required underpinning. Private claimants have blamed the presence of council-owned trees. The borough engineer said that it might be possible to make further boreholes to determine what change, if any, there had been in the water content of the subsoil. but he entered the caveat that, even if this indicated a difference, it would not pinpoint the reason for the difference.

The right hon. Gentleman then wrote to my right hon. Friend the Secretary of State asking him to consider the taking of further samples of subsoil. As my right hon. Friend has already told the right hon. Gentleman, on the advice of the two firms of consultants and taking account of what the borough engineer said in the caveat which he entered to his general opinion, he came to the conclusion that as the results were bound to be inconclusive there was little further point in making any further borings.

769 None the less, having listened to what the right hon. Gentleman has said tonight —I wanted to do that before coming to any further judgment on this matter—I assure him that I shall study it with care when I have an opportunity of doing so. If I feel that on the arguments that he has advanced in this debate there is a case for taking further borings, I shall consider that most carefully and, again write to him with my final view on that.

I should like to look again at the exact arguments that the right hon. Gentleman 770 has advanced this evening, most of which I have heard before or read before in the file available to me, but which none the less—