Further oral evidence of the respondent's expert witnesses
56 Cross-examination of the respondent's expert witnesses needs to be dealt with in some detail, as Mr Nock launched a major attack on their respective ability to adopt the degree of independence from the Board as demanded by the Court in its Expert Witness Practice Direction.
57 In answers to questions from Mr McEwen, Professor Galvin distinguished cracks caused by mining using the long wall method as opposed to the cracks identified by and relied upon by Dr Thomas which he says resulted from the subsidence. In long wall mining the excavation is extremely wide and is carried out with a deliberate intention of causing the mine to collapse resulting in maximum subsidence and in turn creating maximum strains and tilts. Cracks in those circumstances can be up to a metre wide. Professor Galvin knows of no example of the mechanism referred to by Dr Thomas in either the textbooks or other literature on the topic of mine subsidence. When asked to assume that the theory put forward by Dr Thomas is correct, Professor Galvin recognised that ultimately the root cause of the subsidence would be the presence of the mine.
58 Early on in the investigation on behalf of the Mine Subsidence Board, Professor Galvin identified the prospect of defective foundations of the structure, the consequence of soil reactivity, the impact of shallow groundwater flows, soil creep and landslip as possible causes of the damage.
59 Subsequently, as experts with more specific qualifications joined in, he ultimately confined his emphasis to an elimination of mine subsidence as the cause of the disturbance and in particular a rebuttal of the theory put forward by Dr Thomas.
60 Professor Galvin maintains uncertainty about the reliability of the so called horizontal vectors demonstrated by the survey results. The vertical components are accepted. Professor Galvin is of the opinion that the way in which the surveyors have indicated the horizontal movement could be wrong. He says there is no evidence to suggest that the structural damage can be attributed to mine subsidence, although a number of further investigations need to be done before he could be absolutely certain. He regards the theories expressed by Dr Thomas as remote. Nevertheless, the reports by Dr Thomas have cause him to give thought to mechanisms that he had not previously considered and should be dealt with as a matter of diligence. He explained that based on his knowledge and extensive experience as well as his own library, the mechanism attributed to the movement which caused the damage, according to Dr Thomas, falls outside that knowledge and experience. He was not prepared to say that the possibility did not exist. He deliberately said that it is remote but he has not eliminated it.
61 Professor Galvin recognises that the soil on the surface at the rear of the house has settled, but relative to when the zero level was established in 1998 that land has risen and fallen. Currently it has settled below the zero that was established in 1998. The graphs developed from the survey records show waves of ground movement coming through. Some of the measurements of the wave motions were only a month apart. At other times there is a gap of up to seven years without any record of what has happened in the intervening period.
62 His answer to a direct question comparing the first survey in 1998 to the last survey carried out in March 2007 he said the following:-
In absolute terms comparing 1998 to March 07 the points are down, they're lower than 1998. In terms of trends the trends are up, down, up, down, and who knows how many more because of the frequency of the surveys.
63 Professor Galvin agreed that at least two points at the rear of the house namely points identified as 23 and 24 show a trend of downward movement between March 2004 and March 2007.
64 Professor Galvin agreed with Mr Nock that the presence of calcium carbonate on the walls of the mine workings and ironstones stains observed on the video suggest that water has been entering the mine. He also agrees that there is evidence of water flowing through the floor. Professor Galvin explained the presence of the water as follows:
Well those workings are down dip on a very large extensive area that's already been mined, and it's common practice particularly in the Lithgow region, that when you get periods of heavy rain, those old workings are all interconnected, and the water makes its way down to the lowest point. And looking at the floor and doing some calculations on the amount of water that must've flowed across that floor, leads me to two opinions. One it's not seepage, couldn't possibly be made all from seepage from the roof. And most likely given that it's connected to the old workings, a bit further up in the hill, it's almost certainly one of the ways of - one of the flow paths for the water when the old workings further up get flooded.
65 He could not agree that the majority of the water found in workings in the Lithgow area came from the surface. However he agreed that the percolation described by Dr Thomas from the surface was a possibility.
66 When challenged in respect of his indication of the prospect that groundwater from a leaking reservoir above Mrs Vervoorn's house had contributed to the damage Professor Galvin acknowledged in cross-examination that he did not know the course the water took and that he was simply indicating that there are signs of groundwater in the area and it is reporting to the surface at some points thereby providing evidence that there is groundwater flow. He could not say whether the water would have made its way to the back of the house. Although in a report in March 2007, Professor Galvin described observations of considerable ongoing water discharge and signs of ground settlement along a line in the road above Mrs Vervoorn's house as elementary and essential to determining and validating if subsidence of mine workings is occurring, he agreed in cross-examination that neither of those factors fitted into that category.
67 He also considered that cracks observed underneath Mrs Vervoorn's house were not approximately coincident with extensive cracking within the house and in the tile pathway to the east of the house. He has not turned his mind to the movement of the house, as his interest has been the movement of the ground. The survey measurements are not taken on the ground but at points on the structure near the ground.
68 He regards the movement of the walls as a separate issue. He noted however, that the eastern and western walls of the house are tilting outwards. He made no observation about the southern wall of the house. He relied on the expertise of others for an explanation of that occurrence. Nevertheless, in a final report prepared in June 2007, he identified the following potential causes for the damage to Mrs Vervoorn's house as follows:-
i. poor footing design and construction practices (by today's standards).
ii. reactive soil.
iii. soil creep.
iv. changes in groundwater regime.
69 He then goes on to make positive remarks about the prospect of each one of the factors being a cause and concludes that a combination of the factors has resulted in the damage to the structure. He sums up his opinions in a conclusion as follows:-
i. The possibility/probability that mine subsidence is cause of damage to Mrs Vervoorn's' house is extremely remote. There is no factual evidence that points to this being the cause of the associated ground movements. The mine subsidence mechanism proposed by Dr Thomas falls outside my subsidence engineering knowledge base and experience.
ii. There is a range of factual evidence that indicates that ground movement is associated with one or more other factors.
iii. A number of these other mechanisms are likely to be active simultaneously, in particular, reactive soil responses, soil creep and changing groundwater regimes.
iv. The damage to Mrs Vervoorn's house has materialised because the design and construction of the footings is inadequate to deal with these mechanisms.
70 It is apparent from the cross-examination by Mr Nock that Professor Galvin independently caused the surveyors to reproduce plans and diagrams of plots that related only to movement at or near the ground level of the building. Some were confined to demonstrating the horizontal shift of the house. When challenged by Mr Nock that he was instructing the surveyors to produce evidence supportive of his case, he protested that he was only interested in the information that he requested the surveyors to specify. He summarised his position as follows:-
The surveyors are registered surveyors. They took out the survey. Their work is surveying. They undertook the surveying. How - what they do with the results and how they plot is up to anyone at all to decide what they wanted. Mr Appleyard wants tops, well he can have tops. If someone else wants bottoms, they can have bottoms it's as simple as that. I did not instruct the surveyors in how to undertake surveying.
71 He nevertheless recognised that the instructions given to the surveyors by him were without direction from the Board. He said "I took them off on my own bat".
72 It is Professor Galvin's position therefore that the readings taken at the top part of the wall of the house are not relevant to his interest in understanding how the ground is moving. He did not interpret the wall movements in response to the ground because, as he explained, in subsidence engineering there are two distinct elements namely the effect of mining on the surface and then the effect of the surface on the structure. The effect of the surface on the structure is a domain of the structural engineers and it is not within his expertise. Nevertheless, in March 2007 he made observations about how the damage to Mrs Vervoorn's house is concentrated and worse in those walls that are orientated down the slope of the hill rather than across of the slope of the hill, including observation about fracture patterns and tilting.
73 Initially he was engaged by the MSB to perform the role of "independent reviewer" in order to ensure that any outcomes were soundly based. Professor Galvin accepts that role was in his capacity as a contractor or servant of the Board where he was being asked to prepare an answer to the claim by Mrs Vervoorn. Subsequently, he said "my role to the Board was to advise them on the merits of the claim". He started off in the role of providing independent advice to the Board and then as the matter progressed his role changed.
74 At one stage Professor Galvin consulted with a Professor Sullivan in relation to soil stability and soil creep but did not obtain a report. Preparations were made for instructions to be given to Professor Sullivan but it was decided not to proceed after he expressed an opinion that he did not consider landslip was occurring. Professor Sullivan made the following observations in an e-mail to Professor Galvin on 5 March 2007.
…..
3. The vectors need to be rotated 30 deg. Counter clockwise on the attached figure. But nevertheless if you believe these vectors they do show the house is mainly moving south and the retaining walls are moving north! If these are correct it is something not related to down slope creep.
4. …..
5. I am wondering if we are dealing with a complex series of factors that have changed or are changing over the life of the structure and now contributing differently to what has been observed over the last few years. These factors could include; poor foundations in extension, movements at the front of the house due to retaining walls and other factors??, poor control of roof runoff affecting house foundations causing some settlement in the old part of the dwelling, poor foundations in the old part of the dwelling, soil creep downhill? And lastly mine subsidence/creep?.
75 Professor Galvin denies that he did not pursue a report from Professor Sullivan because he had expressed the views set out above, particularly as they related to subsidence and the movement to the south.
76 Professor Galvin is unable to agree that the survey data shows a trend for the house to be moving in a southerly direction. When asked what he based that opinion on, his answer was as follows:-
Because it's not showing a trend moving south, it shows that it moves south sometimes and then other periods it moves north.
77 In answer to a further question he answered as follows:-
A trend to me is a long-term thing. I look at a trend and where is it trending, it is not trending south, it is moving south for a while then it's coming back to north again and then it's moving north-east. It's not trending south.
78 After much confusion Professor Galvin agreed that drawings depicting movement between March 2004 and July 2005 showed a horizontal movement of the property to the south. On the other hand, a survey depicting movement between July 2005 and March 2007 showed a movement trending towards the north or northeast. He would not agree that the vertical movement at the rear of the house over the same periods shows the house trending downwards. Rather at the points surveyed the movement is up and down which he says supports his contention that it is probably a combination of factors causing the movement one of which is soil reactivity.
79 He nevertheless agreed in cross-examination that some of the plans show the house moving in an uphill direction and that it would be highly improbable if the cause of the movement was soil creep for the house to move uphill. Between March 2004 and March 2007, five points on the western side of the house are shown as moving uphill. Two points on the eastern side of house are in the same position. Between March 2004 and July 2005 the survey measurements show a 45-degree movement relative to the hill at the rear. Professor Galvin would not be drawn by Mr Nock to agreeing that the movement was uphill, but rather that it shows movement across the hill with an upward component.