Raedel v Shahin

[2019] SASCFC 141

SUPREME COURT OF SOUTH AUSTRALIA

(Full Court)

RAEDEL & ANOR v SHAHIN

[2019] SASCFC 141

Judgment of The Full Court

(The Honourable Justice Kelly, The Honourable Justice Stanley and The Honourable Justice Hinton)

14 November 2019

APPEAL AND NEW TRIAL - APPEAL - GENERAL PRINCIPLES - INTERFERENCE WITH JUDGE'S FINDINGS OF FACT - FUNCTIONS OF APPELLATE COURT - WHERE CONFLICT OF EVIDENCE

APPEAL AND NEW TRIAL - APPEAL - GENERAL PRINCIPLES - INTERFERENCE WITH DISCRETION OF COURT BELOW - IN GENERAL

Appeal against the judgments of the District Court and the Environment, Resources and Development Court (ERD Court).

These two appeals concern a dispute between neighbours.  The appellants, the Raedels, live next-door to the respondent, Mr Shahin, in Ifould Drive, Burnside.    A dispute arose between Mr Shahin and the Raedels over a retaining wall constructed on the Raedels’ property.  The adequacy of the retaining wall was the key issue in dispute.  Mr Shahin commenced two actions complaining of the construction of the retaining wall.

Mr Shahin brought an action in nuisance in the District Court and enforcement proceedings in the ERD Court for an order for reconstruction of a retaining wall constructed by the Raedels pursuant to s 85(1) of the Development Act 1983 (SA) (Development Act).

The two actions were heard together. The judge heard expert engineering evidence from Dr Mitchell and Mr John. The judge delivered reasons and made consequential orders in the nuisance action and delivered reasons and made consequential orders in the Development Act action.

In the nuisance action, the Court found, inter alia, that there were horizontal gaps in the pavers forming a path alongside Mr Shahin’s house which was attributable to a lack of support caused by the excavation from the Raedels’ side in the construction of the retaining wall. Further, that the retaining wall was unacceptably over-stressed, inadequate to retain the Shahin land and in need of rectification. The defect could be rectified by the erection of six new piers and posts in the retaining wall at equal intervals between the existing posts. The Court awarded Mr Shahin damages of $2,604 in nuisance to re-lay the pavers.

In the ERD Court proceedings, the ERD Court found, inter alia, that the retaining wall was constructed in breach of the Development Act having regard to the relevant retrospective approval of 4 March 2014. Mr Shahin had commenced proceedings within three years of the breach, which occurred on and after 4 March 2014, therefore no extension of time was required. The ERD Court made orders for the rectification of the retaining wall and installation of a safety fence affixed to the top of the wall, to be effected at the Raedels’ cost, and after obtaining development approval from the City of Burnside (the Council).

The Raedels appealed both judgments. The grounds of appeal are that the judge erred in preferring the evidence of the expert Dr Mitchell over Mr John; that the finding that the height of the retaining wall is inadequate to retain the Shahin land by between 200 and 400 mm is contrary to the evidence and the weight of the evidence; that the judge erred in excluding the evidence in Exhibit D162 which had been admitted de bene esse; that the Development Act action was brought out of time and the proceedings should have been found to have been incompetent; and that in any event the exercise of the judge’s discretion miscarried in ordering remediation.

Held, per Stanley J (Kelly and Hinton JJ agreeing):

1.  It was open to the judge to prefer the expert evidence of Dr Mitchell over Mr John where it conflicted.  There was no error in the judge doing so.

2.  There was no error in the judge’s finding that the retaining was inadequate to retain the Shahin land.

3.  There was no error in the judge ruling that Exhibit D162 should not be admitted in evidence.

4.  The judge erred in finding that the Raedels were in breach of the Development Act 1983 (SA) on and from 4 March 2014 and therefore the proceedings were commenced within time.

5.  The interests of justice warrant the grant of an extension of time to 8 December 2016 within which to bring the enforcement proceedings.

6.  There was no error in the judge’s exercise of discretion to make orders for rectification. 

7.  Appeals dismissed.

8.  Parties are to be heard as to costs.

Development Act 1983 (SA) s 30, s 32, s 85; Limitation of Actions Act 1936 (SA) s 48(1); Environmental Planning and Assessment Act 1979 (NSW) s 124, referred to.
Sotiroulis v Kosac (1978) 80 LSJS 112; Casley-Smith & Ors v FS Evans & Sons Pty Ltd and the District Council of Stirling (No. 10) Unreported, Olsson J, delivered 23 May 1989; Warringah Shire Council v Sedevcic (1987) 10 NSWLR 335; ACR Trading Pty Ltd v Fat-Sel Pty Ltd (1987) 11 NSWLR 67, applied.
Jemena Gas Networks (NSW) Ltd v Mine Subsidence Board (2011) 243 CLR 558; CSR v Della Maddalena (2006) 80 ALJR 458; Minister of Immigration and Border Protection v SZVFW (2018) 92 ALJR 713; Skorpos & Anor v United Petroleum Pty Ltd [2013] SASCFC 117; Holtman v Sampson [1985] 2 Qd R 472; Flemming v Gibson [2001] QCA 244; Ahmedi v Ahmedi (1991) 23 NSWLR 288; University of Wollongong v Metwally (No. 2) (1985) 59 ALJR 481; Braunack v Goers (1979) 23 SASR 1, discussed.
Dalton v Henry Angus & Co (1881) 6 App Cas 740; Pantalone v Alaouie (1989) 18 NSWLR 119; Walker v Corporation of the City of Adelaide (2004) 88 SASR 225; S J Weir Ltd v Bijok (2011) 112 SASR 127; Shahin v Raedel & Anor [2017] SADC 92; Monroe Australia v Campbell (1995) 65 SASR 16; Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588; Housing Commission of NSW v Tatmar Pastoral Co Pty Ltd [1983] 3 NSWLR 378; Wainhou v New South Wales (2011) 243 CLR 181; Soulemezis v Dudley (Holdings) Pty Ltd (1987) 10 NSWLR 247; Segal v Waverley Council (2005) 64 NSWLR 117; Beale v Government Insurance Office of New South Wales (1997) 48 NSWLR 430; Lucke v Cleary & Ors (2011) 111 SASR 134; Chilcotin Pty Ltd v Cenelage Pty Ltd [1999] NSWCA 11; Stunzi Sons Ltd v House of Youth Pty Ltd (1960) SR (NSW) 220; Paric v John Holland (1985) 59 ALJR 844; Makita (Aust) Pty Ltd v Sprowles (2001) 52 NSWLR 705; Ulowski v Miller [1968] SASR 277; Shahin v Raedel & Anor [2017] SAERDC 90; Athens v Randwick City Council [2002] NSWCA 83, considered.

RAEDEL & ANOR v SHAHIN
[2019] SASCFC 141

Full Court:      Kelly, Stanley and Hinton JJ

1. KELLY J:             I agree with Stanley J.

   STANLEY J

   Introduction

2. These two appeals concern a dispute between neighbours.  The appellants, the Raedels, live next-door to the respondent, Mr Shahin, in Ifould Drive, Burnside.    A dispute arose between Mr Shahin and the Raedels over a retaining wall constructed on the Raedels’ property.  The adequacy of the retaining wall was the key issue in dispute.  Mr Shahin commenced two actions complaining of the construction of the retaining wall.

3. Mr Shahin brought an action in nuisance in the District Court and enforcement proceedings in the Environment Resources and Development Court (ERD Court) for an order for reconstruction of a retaining wall constructed by the Raedels pursuant to s 85(1) of the Development Act 1983 (SA) (Development Act).

4. The two actions were heard together. The judge heard expert engineering evidence from Dr Mitchell and Mr John. The judge delivered reasons and made consequential orders in the nuisance action and delivered reasons and made consequential orders in the Development Act action. The Raedels appealed both judgments.

   The action in nuisance

5. A person commits the tort of nuisance when he or she is responsible for an act indirectly causing physical injury to land or substantially interfering with the use and enjoyment of land or of an interest in land, where, in the light of all the surrounding circumstances, the injury or interference is unreasonable.[1]

   [1]    Dalton v Henry Angus & Co (1881) 6 App Cas 740; Pantalone v Alaouie(1989) 18 NSWLR 119 at 129; Walker v Corporation of the City of Adelaide (2004) 88 SASR 225 at 254-255; S J Weir Ltd v Bijok (2011) 112 SASR 127 at 135.

6. In Jemena Gas Networks (NSW) Ltd v Mine Subsidence Board[2] the High Court said that at common law a land owner is liable in nuisance for a withdrawal of support creating subsidence which causes actual damage.  This is because an owner of land has a right to the support of that land in its natural state from adjacent and subjacent land of neighbouring owners.  The right is a natural incident of the ownership.  Although the remedy of damages is not available until the subsidence has caused injury to a land owner’s property, equity will grant a negative injunction against conduct causing subsidence in the future, whether or not there has been any injury caused by subsidence.  And a land owner may apply for a mandatory injunction compelling a defendant to take positive steps to prevent subsidence causing injury. 

   [2] [2011] HCA 19 at [32]-[33]; (2011) 243 CLR 558 at 569-570.

7. If support is withdrawn so as to cause the land to subside, the owner of the land is entitled to succeed in an action in nuisance.  The withdrawal of lateral support from land is an actionable nuisance for which strict liability attaches without proof of any negligence.[3]

   [3]    Sutherland Shire Council v Becker [2006] NSWCA 344 at [1] and [4].

   The approach on appeal

8. In CSR v Della Maddalena[4] Kirby J, with whom Gleeson CJ agreed, explained the appellate function to be followed by this Court[5] hearing an appeal by way of rehearing from a single judge sitting without a jury.  The appeal by way of rehearing is a procedure for the correction of error.  In Minister of Immigration and Border Protection v SZVFW[6] Gageler J[7] described this approach to the performance of that appellate function as the application of the correctness standard.  The issue on appeal is whether the judgment under appeal is vitiated by error.[8] 

   [4] [2006] HCA 1, (2006) 80 ALJR 458.

   [5] [2006] HCA 1 at [13]-[23], (2006) 80 ALJR 458 at 464-466.

   [6] [2018] HCA 30, (2018) 92 ALJR 713.

   [7] [2018] HCA 30 at [29]-[33], [41], [48]-[49], (2018) 92 ALJR 713 at 722-723, 725, 727.

   [8]    Skorpos & Anor v United Petroleum Pty Ltd [2013] SASCFC 117 at [33].

   The retaining wall

9. The judge found that the Raedels’ property is immediately to the west of Mr Shahin’s property.  Mr Shahin’s property is on the high side of the Raedels’ property.  The Raedel land falls away from the front south-west corner to the rear north-west corner.  In 2009 the Raedels undertook an excavation of their land adjacent to the Shahin property.  In about October 2009 the Raedels erected a retaining wall in the excavation made on their property.  The distance between the face of the retaining wall, the face consisting of concrete sleepers, and the boundary between the Raedel and the Shahin property is approximately 500-600 millimetres.[9]  The space between the cut of the excavation and the inside of the sleepers has been filled with gravel topped with soil and plants in the uppermost section.  The judge found the retaining wall is constructed of 10 cantilever steel posts cast into pre-bored concrete piers supporting 200 millimetre wide concrete sleepers placed horizontally between the vertical steel posts.  Its maximum height is four metres at the southern end dropping in height to just under two metres at the northern end.  The wall steps down one concrete sleeper, or 200 millimetres, approximately every two metres.  There are three raised garden beds at the base of three of the vertical steel posts. 

   [9]    T 1434-1435.

10. There is a brush fence constructed along the boundary between the two properties which sits behind or to the east of the retaining wall as far as it extends.  The brush fence runs from the rear of the properties and terminates shortly past the front of the house on the Shahin property.  A path made of pavers has been laid on the Shahin property adjacent to the side of the house.  Also erected on the Shahin property, but effectively on the boundary, is a low stone retaining wall extending from the end of the brush fence to the street front of Mr Shahin’s property, planted over with bushes and shrubs.  At some point after the construction of the retaining wall, the stone retaining wall on the Shahin property was replaced with a retaining wall made of interlocking concrete blocks occupying approximately the same position. 

11. In the nuisance action, the judge made the following key findings:

    ·The retaining wall was too low by between 200 to 400 millimetres to retain the pre‑existing natural ground surface;

    ·There may have been some small movement of the brush fence on the common boundary, but it had stabilised and was of no further consequence;

    ·There were horizontal gaps in the pavers forming a path alongside Mr Shahin’s house which was attributable to a lack of support caused by the excavation from the Raedels’ side in the construction of the retaining wall;

    ·The deficiency in the retaining wall could be cured by adding an extra sleeper to each panel of the retaining wall to increase its height;

    ·The extra sleeper would operate as a “catch” to catch any material which might fall from the Shahin land and prevent it falling over the external side of the retaining wall;

    ·The retaining wall was unacceptably over-stressed, inadequate to retain the Shahin land and in need of rectification;

    ·The defect could be rectified by the erection of six new piers and posts in the retaining wall at equal intervals between the existing posts.

12. The Court awarded Mr Shahin damages of $2,604 in nuisance to re-lay the pavers.

13. The judge made the following key findings in the Development Act action:

    ·At the time the retaining wall was constructed there was no relevant Development Act approval;

    ·Retrospective development approval was purportedly granted, which included purported approval of the retaining wall on 4 March 2014, but based upon the original application’s supporting materials submitted on 4 September 2009, which materials did not represent the wall as built. The wall as built did not comply with the retrospective approval; 

    ·The retaining wall was constructed in breach of the Development Act having regard to the relevant approval because it is four metres high (in places) rather than three metres high and there is no fence on top (whether 3.6 metres or otherwise);

    ·The breach was a breach of the retrospective approval of 4 March 2014. Mr Shahin had commenced proceedings within three years of the breach for the purposes of s 85(18) of the Development Act and no extension of time was required;

    ·The discretion to order relief should be exercised having regard, inter alia, to the findings that:

    -    Mr Shahin’s land is not adequately retained by the height of the wall and the retaining wall is structurally inadequate and unacceptably over-stressed; and

    -    The rectification proposal is appropriate and proportionate to the risk of harm should the wall fail.

14. Accordingly, the ERD Court made orders for the rectification of the retaining wall and installation of a safety fence affixed to the top of the wall, to be effected at the Raedels’ cost, and after obtaining development approval from the City of Burnside (the Council). 

    Grounds of appeal

15. The appellants submit that the judge erred in preferring the evidence of the expert Dr Mitchell over Mr John; that the finding that the height of the retaining wall is inadequate to retain the Shahin land by between 200 and 400 mm is contrary to the evidence and the weight of the evidence; that the judge erred in excluding the evidence in Exhibit D162 which had been admitted de bene esse; that the Development Act action was brought out of time and the proceedings should have been found to have been incompetent; and that in any event the exercise of the judge’s discretion miscarried in ordering remediation.

    The judge’s preference for the expert evidence of Dr Mitchell over Mr John

16. Critical to the outcome of both actions was the judge’s finding that the retaining wall does not adequately retain Mr Shahin’s land and is unacceptably overstressed.  That finding is based in the judge’s preference for the expert opinion of Dr Mitchell where it conflicted with the evidence of Mr John.  The Raedels submit that the judge erred in doing so or failed to provide reasons for doing so that demonstrated the judge actually understood the expert evidence to enable her to make correct findings on the evidence she heard.

17. The judge explained her conclusion in the following terms:[10]

    I have carefully considered the evidence and the parties’ submissions as to the structural adequacy of the Raedel Retaining wall.  Neither the soil composition nor the construction details are known.  The only method of ascertaining the wall’s structural adequacy is by engineering back calculations.  Mr John’s method of calculation is not a recognised method.  I accept Dr Mitchell’s evidence concerning the flaws in Mr John’s assumptions and equation.  The assumptions that Dr Mitchell made were conservative but, in my view warranted, by reason of the dearth of available information.  Likewise I accept that Dr Mitchell’s use of the safety factor of 1.5 was, in all of the circumstances, appropriate.  I accept and prefer Dr Mitchell’s method of calculation to that of Mr John.  I accept the evidence of Dr Mitchell that the Raedel retaining wall is unacceptably overstressed and in need of rectification. 

    [10] [2017] SADC 92 at [198].

18. The basis for that conclusion was set out in the preceding reasons of the judge.[11]  I will return to these reasons.

    [11] [2017] SADC 92 at [140]-[197].

19. In Sotiroulis v Kosac[12] Wells J explained the correct approach to resolving a conflict of expert evidence as follows:

    1.The issue will not be resolved by counting witnesses:  The maxim tests ponderantur, non numerantur is one of the few latin maxims that has an almost universal validity.

    2.If it is open to the trial judge to prefer one body of evidence to the other on grounds fairly discerned, he should express his reasoned preference; he should not readily abandon the task of trying to find such grounds.  Distinctions may be drawn on the basis of demeanour – a limited ground, where experts are under consideration (see also in this regard the decision of King CJ in Wiechmann v Lovering (1992) 59 SASR 203; qualifications; impressiveness and cogency of reasoning and exposition – not always a decisive ground, by any means; preparation for, and application to, the problem in hand; and the extent to which the witness had a correct grasp of basic, objective, facts relevant to that problem. I do not, of course, purport to be exhaustive. Resolution of conflict is desirable if it can conscientiously be achieved, but resolution is not to be achieved at any cost.

    3.If a trial judge is faced with two authoritative opinions, and is unable conscientiously to find grounds for preferring one to the other, he is not on that account to regard himself as having reached an impasse.  What he has before him are, in effect, two objective facts, the bearing and implications of which he must determine in light of the facts as a whole: Pipikos v W Brown & Sons Pty Ltd [1970] SASR 508, especially at pages 520 and 521.

    [12] (1978) 80 LSJS 112 at 115.

20. This approach was approved by the Full Court in Monroe Australia v Campbell[13] and by Heydon J in Dasreef Pty Ltd v Hawchar.[14] 

    [13] (1995) 65 SASR 16 at 27.

    [14] [2011] HCA 21 at [92], (2011) 243 CLR 588 at 623.

1. In Monroe Australia v Campbell[15] Bollen J, with whom Doyle CJ and Debelle J agreed, held that on appeal from a judgment based on the acceptance of the evidence of one expert over another the appeal Court must give due weight to the advantage the trial judge had in assessing the respective expertise and learned authority of one expert over another.  Bollen J cited with approval the reasoning of the Full Court of the Supreme Court of Queensland in Holtman v Sampson[16] as follows:

   In cases where the experts differ, the lay tribunal will apply logic and commonsense to the best of its ability in deciding which view is to be preferred or which parts of the evidence are to be accepted. The initial question here is whether the trial judge’s acceptance of Dr German’s evidence and his finding that the plaintiff suffered from frontal lobe dysfunction is “an inference” or a “primary fact” according to the usage of those terms in Warren v. Coombes above. There is no doubt that the finding of frontal lobe dysfunction was a finding of a disputed fact which was “established by the findings of the trial judge” (vide p. 551), and one of the “primary facts found by the learned trial judge” (vide p. 553). Whilst it is true that any diagnosis is the product of inference that is not to say that the diagnosis may not be one of the primary facts in issue at the trial.  The finding could also be described as one based on the court’s view of credibility of witnesses. Commonly the acceptance of the evidence of an expert witness, particularly one who is a member of a profession, does not involve the same approach on questions of credit and credibility as that of an ordinary witness. But it would be wrong to say that questions of credit and credibility are not applicable in the evaluation of an expert’s evidence. In Joyce v. Yeomans, Brandon L.J., dealt with a submission that the trial judge has no significant advantage over the appellate court in forming a correct judgment between conflicting views of expert witnesses. His Lordship said:

   “In my judgment, even when dealing with expert witnesses, a trial judge has an advantage over an appellate court in assessing the value, the reliability and impressiveness of the evidence given by experts called on either side.

   There are various aspects of such evidence in respect of which the trial judge can get the ‘feeling’ of a case in a way in which an appellate court, reading the transcript cannot. Sometimes expert witnesses display signs of partisanship in a witness box or lack of objectivity. This may or may not be obvious from the transcript, yet it may be quite plain to the trial judge. Sometimes an expert witness may refuse to make what a more wise witness would make, namely, proper concessions to the viewpoint of the other side. Here again this may or may not be apparent to an appellate court but plain to the trial judge. I mention only two aspects of the matter, but there are others.

   I do not think that the authorities on the right of an appellate court to interfere with the findings of fact of a trial judge based on witnesses of simple fact are entirely applicable to cases where the finding is based on expert evidence, but I certainly would not go to the other extreme and say that the trial judge has no advantage over an appellate court because the witnesses are expert. I think he  has certain advantages, not perhaps so great as those applicable where witnesses are witnesses of fact, but nevertheless significant advantages which an appellate court ought not to ignore.”

   [Citation omitted].

   [15] (1995) 65 SASR 16.

   [16] (1985) 2 Qd R 472 at 474-475.

2. Holtman v Sampson[17] was followed by the Queensland Court of Appeal in Flemming v Gibson[18] where the Court said:[19]

   The present appeal challenges the rejection by a trial judge of one expert in the acceptance of another.  That seems to have followed a process of rational inference upon examination of the whole of the evidence than upon any particular matter of credit discerned in the giving of evidence.  The high qualifications of Professor James were an objective fact to which regard might properly be had.  Some difference of approach may be found in the cases on the question whether appellate intervention is more readily available in relation to findings based on expert witnesses than in relation to other types of witness.  It may be taken that the primary tribunal must look beyond the expertise of the expert witness and examine the substance of the opinion expressed and "apply logic and common sense to the best of its ability in deciding which view is to be preferred or which parts of the evidence are to be accepted". But in the end, in order to set aside a finding of fact based totally or partly on the evidence of an expert witness it is still necessary to show some error or omission of the kinds recognized in the cases that deal with the setting aside of primary findings of fact by the primary tribunal. 

   [Citations omitted].

   [17] [1985] 2 Qd R 472.

   [18] [2001] QCA 244.

   [19] [2001] QCA 244 at [14].

3. In Ahmedi v Ahmedi,[20] a judgment of the New South Wales Court of Appeal, Clarke JA, with whom Handley JA agreed, said:[21]

   It has been contended that the principle which requires the Court to accord appropriate weight to the trial judge's assessment of the witnesses he has seen and heard does not apply in the case of expert witnesses. I do not think that the cases support the submission. In Chambers v Jobling, Mahoney JA concluded that the principle applied with appropriate limitations to the evidence of experts. In support of that view his Honour cited Maynard v West Midlands Regional Health Authority, a decision of the House of Lords. Although his Honour's judgment was a dissenting one, and to that extent his remarks must be regarded as obiter dicta, I find them persuasive particularly as they have been supported by later authority. In Abalos, for instance, the evidence of at least one of the witnesses was that of an expert. Again in Wilsher v Essex Area Health Authority, Lord Bridge, clearly indicated that the general principles relating to the power of an appellate court to interfere with a trial judge's findings as to which witnesses should be accepted applied equally in the area of expert evidence. His Lordship said:

   “¼ Where expert witnesses are radically at issue about complex technical questions within their own field and are examined and cross-examined at length about their conflicting theories, I believe that the judge's advantage in seeing them and hearing them is scarcely less important than when he has to resolve some conflict of primary fact between lay witnesses in purely mundane matters.”

   (See, also, X and Y (by her Tutor X) v Pal).

   [Citations omitted].

   [20] (1991) 23 NSWLR 288.

   [21] (1991) 23 NSWLR 288 at 299-300.

4. As was observed in Housing Commission of NSW v Tatmar Pastoral Co Pty Ltd[22] by Hutley JA, with whom Samuels JA agreed, the choice between conflicting experts may have to be a matter of judgment not of detailed reasoning. 

   [22] [1983] 3 NSWLR 378 at 381.

5. The provision of adequate reasons is an incident of the judicial process.[23]  The reasons should demonstrate that the judge has addressed the evidence critical to the issues in the case and that the basis of critical findings is apparent.  The judge is obliged to state generally and briefly the grounds which have led him or her to the conclusions reached concerning disputed factual questions.[24]   The reasons must be sufficient to enable an appeal court to perform its function and to provide the litigants with an understanding of why they won or lost.[25]

   [23]   Wainhou v New South Wales [2011] HCA 24 at [54]-[56], (2011) 243 CLR 181 at 213-215.

   [24]   Soulemezis v Dudley (Holdings) Pty Ltd (1987) 10 NSWLR 247 at 259 and 281.

   [25]   Beale v Government Insurance Office of New South Wales (1997) 48 NSWLR 430 at 441.

6. A judge is not obliged to give lengthy or elaborate reasons or reasons for every finding of fact leading or relevant to the ultimate decision or the detailed chain of reasoning to be set out.[26]   It is not the duty of a judge to decide every matter which is raised in argument.  It will ordinarily be sufficient if a judge apprises the parties of the broad outline and constituent facts of the reasoning on which he or she has acted.[27]  A trial judge is not required to conduct a tedious examination of detailed evidence or a minute explanation of every step in the reasoning process that leads to the judge’s conclusion. 

   [26]   Soulemezis v Dudley (Holdings) Pty Ltd (1987) 10 NSWLR 247 at 271, 280.

   [27]   Segal v Waverley Council [2005] NSWCA 310 at [71], (2005) 64 NSWLR 117 at 196.

7. In the course of the appeal the Raedels disavowed any submission that the judge failed to provide adequate reasons for preferring the expert evidence of Dr Mitchell over Mr John where it conflicted.  However, they developed a submission that without proper articulation by the judge of the expert evidence this Court could not be satisfied that the judge actually apprehended the evidence and made correct findings.  This submission reflects the absence of a ground of appeal complaining of inadequate reasons.   

8. I do not accept this submission.  The argument put on appeal represents a distinction without a difference.  It was open to the judge to prefer the evidence of Dr Mitchell over the evidence of Mr John where it conflicted.  The Raedels have failed to demonstrate any error on the part of the judge in doing so. 

   The judge’s reasons for accepting Dr Mitchell’s evidence where it conflicted with Mr John’s evidence

9. The judge commenced her consideration of whether the retaining wall was structurally adequate by observing that there was limited evidence as to the construction of the wall.   This was a significant factor in the judge’s reasons for finding that the retaining wall was structurally inadequate. 

10. The judge found that the retaining wall’s construction was not supervised by an engineer.  The judge accepted the evidence of Dr Mitchell that it would have been necessary for a geotechnical engineer or an engineering geologist to inspect and map the defects within the rock and soil after the excavation cut was made.  The judge found there was no evidence that this occurred.  The judge noted Dr Mitchell’s evidence that from his observations of photographs of the excavation it was unlikely that the natural ground behind the retaining wall was made of solid rock.  The judge found that Mr John did not disagree with the premise that the excavation ought to have been supervised by an engineer.  The judge found there was limited information about the geotechnical properties of the soil profile exposed by the excavation.  This was significant in determining the structural integrity of the wall.

11. The judge found there was uncertainty about materials used in the construction of the retaining wall.  The judge noted that Dr Mitchell gave evidence he was unable to confirm that the steel posts used in the retaining wall were constructed of Australian steel.  He considered this could affect the yield strength of the steel.

12. The judge observed that both Dr Mitchell and Mr John agreed that the diameter and depth of the holes bored for the posts were of critical importance to the adequacy of the retaining wall.  The judge found that the evidence did not reveal how deep or how wide the pier holes were drilled at the site.  The judge rejected the assertion that it was reasonable to assume that the retaining wall was constructed in accordance with engineering plans prepared by FMG Engineering Pty Ltd (FMG).  The judge came to this conclusion on the basis that FMG prepared two sets of calculations, the first in July 2009 and the second in September 2009, which provided for different maximum heights of the wall.  As the wall was not constructed in relation to its height in accordance with either plan, the judge was not prepared to infer that the wall was constructed in accordance with those designs in other respects.  The judge further held that it was not possible to ascertain what, if any, drainage was installed; what, if any, aggregate was used; how deep or wide the concrete piers were; what quality of steel posts was used and what quality of concrete sleepers was used.  While the judge came to the conclusion that Forticon sheeting was used in the construction, it was not clear if it was installed in accordance with the design prepared by FMG. 

13. The judge found that even if the assumption was made that the retaining wall was constructed in accordance with the FMG design for a three metre wall, it was common ground that the engineering for a three metre wall differs significantly from the engineering required for a four metre wall.  The judge accepted Dr Mitchell’s evidence that the bending stressors from lateral earth pressure increase in proportion to the depth cubed.  The judge accepted Dr Mitchell’s evidence that the bending moment in a retaining wall of four metres is nearly double that of a three metre high wall.  The judge noted Mr John did not dispute this.  The judge held that a three metre wall design is under designed for four metres by about half.  The judge adopted Dr Mitchell’s characterisation of this as a very serious departure.  Dr Mitchell was also critical of the FMG calculations for the three metre wall because they assumed there would be no water pressure behind the wall.  While the FMG calculations for the three metre wall assumed it would be fully drained, there was no evidence as to whether drainage was installed in the retaining wall as it was constructed.  The judge accepted Dr Mitchell’s evidence that the absence of, or failure of, drainage behind the retaining wall would influence the soil pressure behind the wall. 

14. Dr Mitchell also gave evidence that the FMG drawings incorrectly assumed a ground slope at the top of the retaining wall of zero when in fact there was a six degree slope which should have been factored into the design as this would increase pressure on the wall. 

15. A significant aspect of the evidence of Dr Mitchell was the change in his opinion as to the adequacy of the strength of the retaining wall following the meeting of an expert conclave attended, inter alia, by him and Mr John.  Prior to the conclave Dr Mitchell had undertaken some calculations for a four metre wall on the assumption that the wall was constructed on the basis of the FMG design and specifications of 4 September 2009.  The only variables Dr Mitchell amended were the height of the wall, which he altered from three metres to four metres, and the slope which he calculated to be 0.6 degrees.  Dr Mitchell considered the results of two verticality surveys that had been undertaken in respect of the steel posts by Alexander & Symonds of 26 August 2016 and State Surveys of 13 September 2016.  He undertook calculations which led him to conclude that some of the measured movements were close to that considered to be near the upper limit of tolerability and that although the wall was functioning as a retaining wall, it was significantly stressed so that no additional surcharge loads should be applied to the wall. 

16. The judge found that prior to the expert conclave being convened Dr Mitchell was not recommending strengthening the wall, although he considered no additional load should be placed on it.

17. The judge found that prior to the conclave Mr John had not undertaken any calculations as to the structural adequacy of the wall.  Prior to the conclave he was unable to express an opinion as to whether the wall was structurally adequate and required further information in order to do so.

18. The judge found that the participants in the conclave were unable to quantify the performance of the retaining wall.  Given the uncertainty over the design and construction of the wall it was necessary to undertake a process of back calculation from survey measurements of the wall in order to ascertain its structural adequacy.  It was agreed that Mr Lindsay Ames of FMG would undertake some specified back analysis calculations which were to be based on the following assumptions:

    ·the steel posts comprise 310 UB 32 members, which are 4 m high and at 2.08 m centres;

    ·the steel post acts as a cantilever (with no rotation or deflection at the base) with a lateral deflection of 28 mm at the top;

    ·the ground surface behind the wall is inclined upwards at 6 degrees;

    ·no ground surcharge or fence wind loading are to be considered;

    ·the bulk density of the retained soil/rock is 18 kNm²;  

    ·the bond piles are 600 mm in diameter and 2.5 m deep;

    ·the pile embedment shall be assessed using the Rutledge Formula (as used in the original FMG calculations;

    ·the required lateral bearing pressure of the ground around the bored piles is to be assess [sic] for an assumed bored pile length of 2.5 m.

19. Following the conclave Dr Mitchell prepared a further report based on the additional information he had received from Mr Ames that the wall had not been supervised during construction and details of the below-ground concrete piles and the soil bearing capacity.  Utilising Mr Ames’ calculations Dr Mitchell undertook his own calculations using that additional information.  This resulted in him concluding that the wall was unacceptably overstressed.  As a result, he considered it required strengthening.  Dr Mitchell concluded that the bending stresses in the steel posts should not exceed 211 MPa[28] (being two-thirds of the guaranteed 320 MPa yield strength of the steel beams) in order to give the 1.5 safety factor required by the Australian Loading Code (the Code).  Dr Mitchell considered that a safety factor of 1.5 resulted in a designed bending yield strength of 211 MPa.  Dr Mitchell said that Mr Ames’ calculations indicated that the stresses in the beams were greater than was permitted in accordance with the Australian Standards. 

    [28]   Megapascals.

20. The judge rejected the Raedels’ criticism of Dr Mitchell for this change in his position.  The judge considered it reasonable for him to revisit his calculations on the basis of receipt of further information.

21. In response Mr John undertook his own calculations.  He concluded that the wall was fit for purpose, structurally adequate and did not require any remediation.  The judge noted that during the course of the trial both Dr Mitchell and Mr John prepared additional calculations and materials to illustrate their respective positions. 

22. The judge found that the conflict in the opinions of Dr Mitchell and Mr John was the result of differences in the assumptions used in the back calculation, the methodology used in the back calculation and the safety factor each applied. 

    The assumptions

23. The judge heard evidence that the posts of the retaining wall were measured by three surveys undertaken at different times.  Alexander & Symonds undertook two surveys; one on 26 August 2016 and another on 7 December 2016.  State Survey undertook an assessment on 13 September 2016. 

24. The judge found that Dr Mitchell concluded on the basis of the survey results that all the posts, with the exception of post 1BH, which could not move due to it being buttressed against the front retaining wall, sloped towards the Raedel property.  Dr Mitchell said that the measurements by all surveyors showed that the displacement of the posts exceeded the normally accepted out of verticality for posts of one horizontal to one-fifty vertical.  The judge indicated that she did not understand Mr John to disagree with this conclusion but rather differed from Dr Mitchell as to the cause.

25. The judge found that Dr Mitchell made an assumption that the steel posts were vertical to start with as their position at the time of construction was unknown.  On the other hand, Mr John assumed that the steel posts were installed out of vertical.  Dr Mitchell agreed that it was unlikely that all of the posts were installed completely vertically but said that he did not consider it likely that the out of vertical construction was substantial.  This was critical because even though Dr Mitchell accepted that there was a degree of out of vertical construction in the wall, by averaging out for all the posts he arrived at an approximate value of Ka.  He found that by doing that, the average value of Ka of 0.539 was nearly double that which was originally adopted in the FMG design.  That was the basis of his conclusion that the wall required strengthening. 

1. The judge observed that Mr John considered that footing rotation was a cause of the displacement of the steel posts.  But the judge noted that Dr Mitchell did not believe any footing rotation had occurred.  The judge considered that the evidence did not support a finding that there had been footing rotation.  On the other hand, the judge considered that if it was the case that there was footing rotation it further supported the conclusion that the retaining wall was structurally inadequate. 

2. The judge found that Mr John assumed that the steel posts and concrete acted as a composite for the purpose of his calculations.  Mr John considered the maximum bending moment of the steel post was at the top of the pier or footing.  By contrast, Dr Mitchell considered it was below the top of the pier or below ground.  Dr Mitchell gave evidence that to enable composite action to occur the steel post is made to interlock with the concrete to avoid the steel post slipping.  Dr Mitchell’s evidence was that in the absence of any indication that steps were taken in construction to ensure that there was composite action, it was safer to assume that the posts and the concrete did not act in a composite manner.  The judge preferred Dr Mitchell’s approach in this regard.

   The methodologies

3. Dr Mitchell gave evidence that he determined the steel stresses in the posts using the measured displacements from the State Survey report.  He checked those calculations against the safety factor of 1.5 required by the Code.  The judge found that Mr John disagreed with the use of that safety factor.  Further, Mr John maintained that Dr Mitchell assessed the Ka as 0.287.  The judge found that Dr Mitchell did so not for the purpose of the back calculations as Mr John thought, but only for his calculations for rectification.  The judge found that Mr Mitchell identified two bench marks against which he assessed the posts.  First an acceptable yield stress giving a safety factor of 1.5 being 211 MPa, and second, the yield strength for the steel being 320 MPa.  He found that the bending stresses were in the order of .92 times the yield strength of the steel and that the stress was greater than the Code requirement of less than .66 times the yield strength.  He concluded that where the wall was unacceptably overstressed (being the posts 2BH, 5BH and 6BH) the wall did not have an acceptable factor of safety against failure in accordance with current design standards.  Further, where the steel stress was greater than the yield strength (being the posts 3BH and 4BH) the wall only remained vertical because its stability was reliant on the yield strength of the steel being greater than the minimum guaranteed value of 320 MPa.  Dr Mitchell gave evidence that this was not in accordance with current design standards.  He concluded that as a result the wall was under engineered.  The judge noted that Dr Mitchell was concerned by the expansion and contraction of clay behind the wall.  The Code required the design life of a domestic wall should be at least 60 years but the Raedels’ retaining wall had only been constructed seven years earlier and he was already concerned about its long term stability.  If there was deficient drainage of water behind the wall, hydrostatic pressures could develop increasing the bending stresses in the posts.  He considered there was potential, over the 60-year lifetime of the wall, for it to undergo major deformation.  When that would occur was difficult to predict, but because the wall was significantly overstressed there existed potential for significant damage to the wall. 

4. Dr Mitchell also gave evidence that an earthquake can impose horizontal inertial forces on the soil mass behind the retaining wall.  The design of a retaining wall in Adelaide needs to consider this risk as it can cause additional force to be exerted increasing the stress acting on the wall.  While Dr Mitchell did not consider the effect of an earthquake in carrying out his calculations, because those calculations had already demonstrated the wall was overstressed, he did consider earthquake issues in his calculations for the rectification work. 

5. The judge found that Mr John’s methodology was based on the premise that the posts were installed out of vertical.  This was a key difference between the opinions reached by Mr John and Dr Mitchell.  The effect of Mr John’s method was to reduce the amount of displacement or deflection measured by the surveyors attributable to soil pressure.

6. The judge found that Mr John did not know what the starting out of construction position was and used a formula to calculate this.  Mr John said that it did not matter how much his calculated out of verticality was due to construction non-verticality and how much from footing rotation.  The judge held that it became apparent during his evidence that his formula required an assumed Ka and that he assumed a Ka of 0.287 for the purpose of his calculations.  Dr Mitchell gave evidence that he had never seen Mr John’s formula used by engineers.  Mr John said his formula was founded on engineering principles but agreed that he could not identify any code, text or other publication utilising his formula.  Dr Mitchell gave evidence that the final value of Ka calculated using Mr John’s formula depended on the initial assumption of the Ka value.  Dr Mitchell criticised the formula on the basis that using it, you could obtain any value of Ka depending on what was assumed as the initial input. 

7. The judge found that Mr John further calculated from the lowest points of the posts rather than the measurements of the upper point of the posts.  Dr Mitchell gave evidence that the lower readings were subject to the most inaccuracies and that using the top measured values was a much more sensible approach. 

8. Mr John said that a Ka had to be assumed as a starting point and that his formula merely produced a conservative result.  He contended that the validity of his method was demonstrated by comparing the results of his formula for each post on a graph using lines of best fit for the measured points and for his own calculated theoretical points.  He said that these lines were relatively coincident and that this indicated that the majority of the deflection was caused by initial verticality or footing rotation and very little by soil pressure. 

9. The judge found that Dr Mitchell’s calculations showed that the effect of Mr John’s equation was always to provide a lower factor of Ka at the end than was originally assumed for the purposes of the formula and that the analysis was dependent upon the assumed starting Ka value.  Dr Mitchell said that the flaw in Mr John’s equation was that it had the effect of always giving a line of best fit between the measured points from which he calculated his Ka and further because it was dependent upon the assumption as to the starting point.  While Mr John did not agree with the criticism based on the line of best fit, he conceded that Dr Mitchell’s graph in Exhibit P158 illustrated that if you assumed a different Ka as your starting point using his formula you would always get a different result. 

   The safety factor

10. The judge found that Dr Mitchell and Mr John did not agree on the appropriate safety factor to be used in the calculations.  Initially Mr John undertook his calculations using a soil load only factor of 1.35 and a soil load when surcharge applied factor of 1.20.  Dr Mitchell gave evidence that these were too low and should be 1.5 in each case under the relevant Codes.  In light of Dr Mitchell’s opinion Mr John reconsidered the load factors and revised the load factor for soil only load downwards to 1.25 based on the Australian Standard 4678-2002 for Earth-Retaining Structures.  Dr Mitchell disagreed with this approach asserting that the terms of the relevant Standard did not support the use of the lower safety factor adopted by Mr John.  The Standard required an adjustment of the load factors depending upon the soil properties.  Section 4.1(a)(iii) of the Standard provided:

    for the strength and stability limit states the requirement in AS1170.1 for a load factor of 1.5 to be applied to earth pressures is deemed to be met by applying a load factor of 1.25 on the dead loads (including soil weight) and 1.5 on the live loads in combination with the material factors specified in Clause 5.2 of this Standard.

11. Dr Mitchell gave evidence that the use of a load factor of 1.25 on dead loads requires steps which reduce the strength of the soil properties behind the retaining wall.  As no one knew the soil properties in this case, Dr Mitchell considered it was inappropriate to use the lower figure. 

12. For these reasons, as explained above, the judge accepted Dr Mitchell’s evidence that Mr John’s equation was not a recognised methodology; that his assumptions were flawed; that Dr Mitchell’s assumptions were warranted given the dearth of available information; and Dr Mitchell’s use of the safety factor of 1.5 was appropriate.  On that basis the judge accepted Dr Mitchell’s opinion that the retaining wall was unacceptably over stressed and in need of rectification. 

13. On appeal, the Raedels undertook a sustained critique of the evidence of Dr Mitchell.  For the reasons that follow, I do not consider that critique demonstrates that the judge erred in preferring his evidence over Mr John’s evidence.  Further, the judge’s reasons adequately explain the basis for her acceptance of Dr Mitchell’s evidence. 

    No error in accepting Dr Mitchell’s evidence where it conflicted with Mr John’s evidence

14. Dr Mitchell is a highly qualified and experienced expert in his field.  He is an adjunct professor of civil, environmental and mining engineering at the University of Adelaide and involved with the University of South Australia in the geotechnical area.  He lectures at those institutions, inter alia, on concrete sleeper retaining walls, their design and construction and soil and rock engineering issues.  He is qualified as a civil engineer and has 46 years of experience.  He specialised in geotechnical engineering and obtained his doctorate in that field.  He attended the site on a number of occasions. 

15. On the other hand, Mr John is a structural engineer.  He does not have the same qualifications or experience as Dr Mitchell in geotechnical engineering.  He did not visit the site. 

16. Further, much of the critique of the evidence of Dr Mitchell on appeal constituted a reframing of the Raedels’ case on appeal from that run at trial, particularly by taking issue with aspects of the evidence of Dr Mitchell which were not challenged at trial.  In this context on appeal the Raedels put submissions couched in engineering principles relating to horizontal force calculation and the effect of soil pressure on a post that were not the subject of cross-examination of Dr Mitchell at trial.  These submissions were not obviously referable to any ground of appeal other than the general complaint that the judge erred by preferring the evidence of Dr Mitchell over Mr John.  

17. In University of Wollongong v Metwally (No. 2)[29] the High Court said that it is elementary that on appeal a party is bound by the conduct of its case at trial.  While this principle does not preclude an appeal court from considering a point on appeal which was not taken at trial where the interests of justice require it, the appeal court will not entertain the argument other than in exceptional circumstances.[30]

    [29] (1985) 59 ALJR 481 at 483.

    [30]   Lucke v Cleary & Ors [2011] SASCFC 118 at [44]-[47], (2011) 111 SASR 134 at 146-147.

18. In Chilcotin Pty Ltd v Cenelage Pty Ltd[31] Giles JA, with whom Mason P and Priestley JA agreed, held that even where no other evidence would have been adduced at trial bearing on an issue sought to be raised for the first time on appeal, a party might still be bound by the conduct of his or her case at trial.  This approach reflected the principle of public policy favouring the finality of litigation.  The judicial determination of an action at trial is a final, not preliminary, resolution of the legal controversy.  Appeal proceedings are not a continuation or extension of the trial.[32] 

    [31] [1999] NSWCA 11.

    [32]   Skorpos & Anor v United Petroleum Pty Ltd [2013] SASCFC 117 at [33].

19. At trial extensive evidence was adduced from the engineering experts Dr Mitchell and Mr John.  Much of that evidence was directed to the issue of the adequacy of the strength of the retaining wall.  The structural adequacy of the wall to resist stress was calculated by reference to the capacity of the steel posts to restrain the soil pressure load applied to the wall.  That pressure was measured by a calculation of the Ka which permits a calculation of the stress on the wall by the lateral pressure applied by the soil. 

20. The assessment of the strength of the retaining wall focused attention on the verticality of the 10 steel posts, the extent to which they were inclined or out of vertical, the extent to which any such displacement from vertical occurred in construction and the extent to which it may have been caused by the load behind the wall. 

21. It was Dr Mitchell’s opinion, accepted by the judge, that the retaining wall lacks structural integrity on the basis of the displacement of the wall from the vertical in the direction of the Raedel land, which is a response to the pressure of the material behind the retaining wall. 

22. A significant aspect of the expert evidence was that neither expert knew the specifics of the actual soil, clay and rock, if any, at the site. 

23. Contrary to the submission of the Raedels there was no evidence that their excavation exposed a vertical rock face[33] except the reference in the conclave report to the natural soil and weathered rock profile exposed in the excavation for the retaining wall.  This observation was based solely on photographs.[34]  The court heard evidence that it is not possible to identify the composition of the exposed face from a photograph.[35]  The judge accepted this evidence.[36] It was open to the judge to do so. The composition was unknown.  Dr Mitchell inferred from the absence of rock breaking equipment and a geotechnical engineer that the exposed face was not made of rock.  The judge’s acceptance of this opinion is not demonstrably wrong.  There was no evidence before the judge of the total depth of soil at the face of the excavation.  In considering its yield strength Dr Mitchell assumed the steel for the posts met the Australian Standard.  In doing so the approach he took favoured the Raedels.  The evidence from the conclave was that there were no detailed construction records available for the retaining wall or a construction certificate from FMG Engineering.  In particular the depth and diameter of the bored piles used in the wall and the embedment depth of the steel posts in the piles was unknown.[37]  Further, there was no evidence as to the width or depth of any of the concrete piers supporting the steel posts.[38]  There was no evidence that there was drainage installed.[39] 

    [33]   T 435.1-436.27.

    [34]   T 428.25-429.15.

    [35]   T 435.1-436.27, 487.37-488.38, 667.12-33.

    [36] [2017] SADC 92 at [149].

    [37]   ACB 31/1379 at 2.1.3.

    [38]   ACB 110/2405 at 2445; T 438.11-29.

    [39]   ACB 110/2405 at 2445; T 428.20-24, 446.3-9 and 462.31-463.10.

24. The absence of data was one of the reasons that Dr Mitchell and Mr John differed because it led each of them to make assumptions about a number of variables, including the nature of the soil and its effect on Ka.  Having made certain assumptions, the experts used formulae to calculate the Ka.  On the other hand, both Dr Mitchell and Mr John assumed that aggregate was used and exerted a force on the retaining wall.[40]  In addition, each made the same assumptions concerning the concrete sleepers and Forticon sheeting.  Accordingly, these latter assumptions made no difference to their conclusions or the judge’s preference for the evidence of Dr Mitchell where it conflicted with the evidence of Mr John. 

    [40]   ACB 31/1379 at 2.1.6.

25. The evidence was that Ka is the ratio of horizontal pressure to vertical pressure.[41]  Ka is calculated to identify the pressure acting on a retaining wall and the ratio of horizontal to vertical pressure that the wall is resisting, or is designed to resist, by reason of the pressures of soil, rock or water behind the retaining wall.  Ka is a co-efficient or ratio of pressure.[42]  Ka is site specific.[43]  The force at the bottom of the steel posts was unknown and unsurprisingly not explored at trial.  On the other hand the function of steel posts in retaining walls was considered.  Dr Mitchell gave evidence that a post transfers the pressure acting against the wall down the post into the pier and concrete foundation.[44]  Contrary to the submission of the Raedels, Dr Mitchell did not give evidence that force is greatest at the base of the post.  His evidence was that pressure against the wall is resisted by the sleepers, steel posts and the concrete pier.[45]  By reference to the relevant Australian Standard he said the wall must be able to resist at least 1.5 times the pressure placed upon it.[46]  Further, in this context, he gave evidence that it was only in the context of calculating the bending moment of a steel post that the concept of force is used.   The equation is force multiplied by the length of the post.[47]  Neither factor was known.  Further, the width and depth of the footing in which the post is embedded also is important because the design engineer needs to know that in order to assess the ability of the wall to resist the pressure exerted upon it.  Dr Mitchell said that the whole of the surface area of the pier is designed to resist the pressure from the land behind the wall.[48] 

    [41]   T 424.37-425.20.

    [42]   T 424.37-425.36.

    [43]   T 426.3.

    [44]   T 406.15-26 and 437.19-29.

    [45]   T 424.27-31, 438.30-440.6.

    [46]   Exhibit P152.

    [47]   T 472.6-24.

    [48]   T 439.2-29.

26. The judge accepted this evidence.  It has not been demonstrated that she erred in doing so. 

27. On appeal the Raedels made submissions concerning the effect of the equation used by Dr Mitchell to back calculate Ka which was neither challenged nor criticised by them at trial.  At trial Dr Mitchell gave evidence that the calculated value of Ka varied from 0.849 to 0.214 and, with one exception, the results were all above the predicted Ka of 0.287.[49]  In cross-examination Dr Mitchell was taken to his calculated average of the Ka values of 0.539.  Dr Mitchell’s conclusions were not challenged at trial except in relation to the proposition that force is proportional to the height of the post squared.  Dr Mitchell accepted this proposition.[50]  But the evidence is that force is only relevant in calculating the pressure a retaining wall can resist when using the force by length calculation for the bending moment of a steel post.[51] 

    [49]   Exhibit P40, ACB 26/1248 at 1253, T 555.5-8.

    [50]   T 693.

    [51]   T 472.6-24.

28. On appeal the Raedels criticise Dr Mitchell’s purported reliance upon the following assumptions in relation to the issue of verticality:

    1.The Alexander & Symonds surveys were not the best evidence of the vertical position of the posts given the State Surveys data indicating maximum displacement of 28 millimetres;

    2.The displacement of posts 8BH, 9BH and 10BH measured by Alexander & Symonds at two millimetres, four millimetres and zero millimetres respectively could be ignored in any calculation of the average displacement of the retaining wall as they could not be correct; and

    3.The posts were precisely vertical when constructed and all of the observed displacement from vertical could be attributed to pressure on the post.

29. The Raedels also challenge the evidence of Dr Mitchell about the use of the surveyors’ measurements from the top of the garden bed and the plotting of results. 

    Dr Mitchell’s assumption that the Alexander & Symonds surveys were not the best evidence of the vertical position of the posts 

1. In addressing these criticisms it is convenient first to deal with the Raedels’ complaint about Dr Mitchell’s reliance upon the survey data gathered by State Surveys.  The State Surveys data identified the steel posts had a lateral deflection of 28 millimetres at the top.  I do not accept that Dr Mitchell’s evidence reliant upon this data was inadmissible on the basis that the State Survey results were not in evidence.  This objection was not taken at trial.  On the hearing of the appeal there was a dispute concerning whether at trial counsel had agreed the data from State Surveys could be relied upon.  I need not decide that question.  At trial the State Survey results were tendered by the Raedels as part of their case as Exhibit D69, being the Rule 160 working papers of Dr Mitchell.  In this case, once admitted that evidence was admitted for all purposes, the purpose of its tender not having been expressly limited.[52]  In any event, for the purpose of the assumption identification rule the law is that complete precision in proof of facts intended to support the assumptions of an expert is not required.  It is sufficient if the case proved is enough like the case assumed to render the expert’s opinion valuable.[53]  The report of the expert conclave assumed lateral deflection of the steel posts of 28 millimetres at the top.[54]  Dr Mitchell relied on this evidence in forming his opinion.  Moreover, no objection was taken at trial and it is not raised as a ground of appeal. 

   [52]   Stunzi Sons Ltd v House of Youth Pty Ltd (1960) SR (NSW) 220 at 225-226.

   [53]   Paric v John Holland (1985) 59 ALJR 844 at 846; Makita (Aust) Pty Ltd v Sprowles [2001] NSWCA 305 at [38], (2001) 52 NSWLR 705 at 722; Dasreef Pty Ltd v Hawchar [2011] HCA 1 at [64]-[66], (2011) 243 CLR 588 at 612-614.

   [54]   ACB 31/1379 at 1381.

2. Dr Mitchell said that caution had to be exercised in forming an opinion in reliance on some of the survey data.  Dr Mitchell’s evidence was that he reviewed the survey data and identified an inconsistency within the Alexander & Symonds data and an inconsistency between the Alexander & Symonds data and the State Survey data.  For example, Alexander & Symonds’ measurements for post 1BH, a post that could not move, recorded it as being eight millimetres towards the Shahin land on one occasion when measured and five millimetres on the next occasion.[55]  Alexander & Symonds also measured 8BH showing the post bowed outwards to three millimetres then came back to two millimetres along its height[56] and measurements of 2BH and 9BH which purported to show kinks in each post.[57]  But steel posts do not have kinks.[58] 

   [55]   Exhibit P40 ACB 26/1248 at 1249.

   [56]   Exhibit D50 ACB 29/1296 at 1327.

   [57]   Exhibit P158 ACB 94/2198 at 2228 and Exhibit D50 ACB 29/1296 at 1327.

   [58]   T 1320.23-24.

3. Dr Mitchell attempted to calculate the resulting likely errors arising from the techniques used by the respective surveyors.[59]  From his review of the three sets of survey measurements by Alexander & Symonds and State Surveys, Dr Mitchell concluded that the survey measurements obtained using the theodolite method were only accurate to five millimetres by comparing the degree of displacement measured by the three surveys.[60]  At trial this observation was unchallenged. 

   [59]   T 537.14-539.4.

   [60]   T 478.14-35.

   Dr Mitchell’s assumption that the displacement of posts 8BH, 9BH and 10BH could be ignored

4. Dr Mitchell considered the measurements of the posts 8BH, 9BH and 10BH could be ignored because they could not be correct.  Dr Mitchell ignored posts 8BH and 9BH because of the uncertainty with the measurements.[61]  That uncertainty can be seen in the difference in measurements between the surveyors as shown in Dr Mitchell’s comparison table contained in his report dated 13 January 2017.[62]  There was no comparison for 10BH which was not surveyed by State Surveys.[63]  In any event, the displacement of the posts 8BH, 9BH and 10BH further north along the wall were not relevant.[64]  The average was taken over 2HBH to 7BH.  The retaining wall was purportedly constructed for a maximum design height of three metres.  8BH and 9BH are less than three metres in height. 

   Dr Mitchell’s assumption that the posts were vertical when constructed and all displacement is attributable to pressure on the posts

   [61]   T 554.37-555.8.

   [62]   Exhibit P40 ACB 26/1248 at 1249.

   [63]   T 511.12-13.

   [64]   T 555.3-11.

5. It is true that Dr Mitchell assumed that the steel posts were constructed vertically in circumstances where the position at the time of construction of the retaining wall was unknown.[65]  That was not a baseless assumption.  If the posts had not been installed plumb and in alignment, the sleepers would have been difficult to install and there may have been an aesthetic issue.  Dr Mitchell said there was no evidence of either of these problems.  On the contrary, Dr Mitchell had observed from photographs that the contractor had been using a spirit level.  That was consistent with the contractor endeavouring to install the posts plumb. 

   [65]   ACB 110/2405 at 2449-2450; T 477.28-478.13.

6. However, it is not correct that Dr Mitchell did not take the possibility of an initial out of verticality into account.  He gave evidence that all of the posts, excluding post 1BH,[66] sloped towards the Raedel property[67] and he assumed that a contractor would construct vertically and not sloping in the direction of the fall of the land away from the proposed wall.[68]   Nonetheless, Dr Mitchell accepted that there could have been a degree of out of verticality at the time of construction, but that it was more probable that any out of verticality would be randomly out of vertical distributed towards both the Shahin land and the Raedel land, but this was not the case.[69]  In this case all the posts were deflected towards the Raedel land[70] i.e. in the direction of the pressure on the retaining wall. 

   [66]   Both Dr Mitchell and Mr John ignored post 1BH because it was a corner post welded to a wall at the front of the property. 

   [67]   ACB 110/2405 at 2449; T 480.1-21.

   [68]   T 441.17-442.34.

   [69]   T 550.37-551.11, 713.31-714.6, 727.21-718.8.

   [70]   Except 1BH.

7. Dr Mitchell did not illogically disregard evidence of displacement.  Using an established formula recognised in the engineering profession he back calculated the Ka that would have been exerted on all of the steel posts by using the actual measured displacement of the retaining wall.  Then he averaged the Ka values obtained for 2BH to 7BH, being the posts at the southern end of the retaining wall, based on the measured displacement. 

8. In any event, Dr Mitchell relied on more than simple displacement.  He took into account a degree of out of verticality by averaging the Kas measures on each relevant post so as to find an average Ka for the wall.[71]  Averaging took into account any out of verticality construction for the posts because, in the event that the steel was out of vertical towards the Shahin land at construction, there was likely a higher pressure on that post so as to move it back to vertical and beyond into the Raedel land.[72] 

   [71] [2017] SADC 92 at [170]; T 551.23-32.

   [72] [2017] SADC 92 at [170]; T 554.26-33.

9. There was no evidentiary basis for this critique of Dr Mitchell’s evidence.  It was not put to Dr Mitchell at trial.  The judge was entitled to accept Dr Mitchell’s methodology.[73] 

   [73] [2017] SADC 92 at [170].

10. Furthermore, even if there was a degree of out of verticality in the posts at the time of construction, as the judge found, there is no avoiding the fact that the FMG design was for a three metre wall not a four metre wall, with the result that a four metre wall would have been under strength by half.[74] 

    [74] [2017] SADC 92 at [154].

    The use of the surveyors’ measurements from the top of the garden bed

11. The Raedels submit that taking a measurement from the top of the garden bed would result in the overstatement of Ka.  Again, this is another matter not put to Dr Mitchell at trial.  Moreover, this submission does not reflect the effect the length of the post has in the calculation of Ka.  Dr Mitchell’s evidence was that he used the measurements that could be measured by the surveyors.[75]  There were no measurements of the extent of the posts in the garden bed, only on top of the garden bed.  Even if the post could have been measured below the garden bed the net result would not have been affected because the total movement with respect to that depth of measurement would have been greater so the overall result on the value of Ka would not have been that significant.[76]  Dr Mitchell’s graph of the lateral movement of post 6BH, which was not behind the garden bed, demonstrates that there was only a minor difference between using the horizontal displacement from the base of the post to the top of the post and using the displacement from the measurement of 0.39 metres, being the height of the garden bed, to the top of the post.  Contrary to the Raedels’ submission that the effect of Dr Mitchell’s approach was to treat the post as starting to bend or deflect at the top of the garden bed, Dr Mitchell did not assume the bending moment of the post would be at the top of the garden bed.[77] 

    [75]   T 546.12-16.

    [76]   Exhibit P158 ACB 94/2198 at 2242 and T 546.25-28.

    [77]   T 510.9-510.22.

12. This is another example of a criticism made of Dr Mitchell’s evidence on appeal that was not put at trial. 

    The plotting of results

13. On appeal the Raedels submit that Dr Mitchell used a line of best fit.  I do not accept this submission. 

14. Dr Mitchell’s graphs record the displacements measured by the surveyors and, at the same heights, the theoretical displacement of the posts caused by the Ka calculated by Dr Mitchell.  The theoretical displacements are connected by a line passing through each point, as are the measurements taken by the surveyors.  Dr Mitchell then compared the lines.  This is not a line of best fit but rather the plotting of actual data and his calculations for the purpose of comparison and analysis.   

15. In contrast, Mr John did use a line of best fit that, by his own admission, did not pass through any of the other points either measured by the surveyors or calculated by him.   Mr John did not plot the actual measurements taken by the surveyors on his graphs.[78]  Accordingly, it was Mr John who used an averaging process, by creating a line of best fit, which was not a plot of actual data or calculated results, but the outcome of his invented formula which had the effect of minimising the amount of deflection and the value of Ka. 

    [78]   T 1824.1-5.

16. A comparison of Dr Mitchell’s results with Mr John’s results is difficult because of the different assumptions made and the different methodologies used.  Dr Mitchell followed an approach recognised and accepted within the engineering profession.  Mr John did not.  Dr Mitchell was recalled and gave further evidence to assist the court.  Dr Mitchell plotted more graphs, for the purpose of illustrating that Mr John’s approach was untenable.  The judge accepted Dr Mitchell’s approach.  No error has been demonstrated in her doing so.

17. Dr Mitchell did not use any displacements measured by the surveyors along the posts in his calculation of Ka.  He did use the measurements when plotting his graph so he could compare the plotted graph to the measurements.  The Raedels submit that Ka may be treated as a constant in a given body of soil.  Contrary to that submission the Ka does not change along the depth of the retaining wall, the pressure exerted on the wall does, but the Ka does not.  The formula for calculation of Ka, well recognised and understood in the engineering profession is called the deflection of a cantilever subject to a triangular pressure.  It requires the use of the differential deflection at the top of the cantilever versus the deflection at the bottom to calculate Ka.[79]  That enabled Dr Mitchell to calculate the horizontal pressures acting on the posts.  Those calculations are for the purpose of determining the bending stressors in each post.  Dr Mitchell gave evidence the bending stressors are a function of the magnitude of horizontal earth pressure acting on the retaining wall.  Dr Mitchell undertook this exercise to determine whether the bending stressors met the applicable safety factor of 1.5 in the relevant Australian Standard AS1170.1.  He found they did not. 

    [79]   T 504.6-505.21, 705.29-706.10.

18. Given the above, the intermediate measurements of deflection along the posts, made by Mr John, were of minimal, if any, assistance in the calculation of Ka and were only of assistance as a means of comparing the theoretical measurements calculated by him as against the actual measurements of the surveyors.

19. This is a further example of a criticism made of Dr Mitchell’s evidence on appeal that was not put at trial. 

    Mr John’s evidence

20. Finally, it is necessary to address the critical features of Mr John’s evidence.  

21. First, Mr John, purporting to apply AS4678-2002, applied a safety factor lower than that required by the Standard.  Mr John gave evidence that the load factor is similar to a safety factor.  He applied a load factor of 1.25 on the dead loads.  As Dr Mitchell pointed out, that approach omitted to take account of the full terms of the relevant portion of the Standard[80] which required a safety factor of 1.5.[81]

    [80] [2017] SADC 92 at [196].

    [81]   T 424.13-31 and 600.38-601.18; P152 at 2084.

22. Second, Mr John assumed that the steel posts were not vertical at the time of construction or that their footings rotated thereafter.  The judge found, consistent with the accepted position amongst all experts,[82] that there was no evidence of the construction and accordingly that assumption was mere speculation.[83]  Further, the judge found that there was no evidence to support the hypothesis that there had been footing rotation.[84] 

    [82] [2017] SADC 92 at [161]-[162]; ACB 31-1379; T 477.28-30.

    [83]   T 1508.15-28, 1367.36-1377.6, 1510.2-7.

    [84] [2017] SADC 92 at [171]-[173].

23. Third, Mr John purported to apply a formula of his own making not generally accepted or recognised within the engineering profession.[85]  Dr Mitchell gave evidence that Mr John’s formula would always give a lower Ka than the assumed Ka applied at the beginning of Mr John’s formula.  The formula used theoretical numbers and averages calculated from the accumulation of those theoretical numbers to plot lines of best fit of both measured points and the results produced by the adoption of Mr John’s formula.  Mr John’s formula, unlike the analysis conducted by Dr Mitchell, did not involve a comparison of the actual measurements to the calculated pressure exerted on the retaining wall to determine the extent to which a calculated pressure is likely to be the actual pressure exerted on the wall. 

    [85]   T 1535.26-37 and 1531.27-31.

24. This can be demonstrated by analysis of the process followed by Mr John employing his formula.  This involved a nine-step process.  He commenced by calculating the deflection of the posts that would be caused by an assumed Ka of 0.287 exerted on the posts of a theoretical wall at the points on the posts measured by the surveyors (step 1).[86]  He deducted from the displacements of the posts actually measured by the surveyors, the assumed deflections.[87]   He then assumed that the resulting differences were attributable to an initial out of verticality installation of each post (step 2). He applied a weighted average to the sum of the assumed differences at the two lowest points of each post.[88]  He described this as the “calculated non-verticality at the base”[89] and used it as the “slope rate” for inferring a theoretical straight line.[90]  He plotted the results in an Excel table (step 3).[91]  He then repeated the process in step 2 using the result obtained and assumed that the outcome represented the actual non-verticality of the posts at the time of construction.[92]  He further assumed that the difference between the results obtained by employing his formula and the actual measurements obtained by the surveyors were the true displacement of the posts caused by soil pressure on the retaining wall (step 4).  He then used an Excel tool “Goal Seek” to undertake a calculation relying upon the results which he assumed represented the actual non-verticality of the posts at the time of construction to imagine what the Ka value should be for the hypothetical displacement at points along a post.[93]  This gave a different Ka value at different points along the same post (step 5).  To accommodate the difficulty presented by multiple Kas along a single post, he created a weighted average of the Kas along each post (step 6).[94]  He then repeated the initial calculation of deflection to be caused by an assumed Ka of 0.287 in step 1 using that weighted average to derive a hypothetical displacement of each post.  He attributed this hypothetical displacement to soil pressure alone (step 7).[95]  He then accumulated these results from step 7 with the earlier results from step 4 representing his assumption of the actual non-verticality of the posts at the time of construction.  He suggested this showed the notional total displacement for each post measured using his formula (step 8).  Finally, he plotted a graph of these results against the actual displacements measured by the surveyors (step 9). 

    [86]   T 1485.10-25, 1489.26-29 and 1491.14-20. 

    [87]   T 1491.29-33.

    [88]   T 1491.21-1492.28.

    [89]   T 1523.35-38.

    [90]   T 1493.32-1494.9.

    [91]   T 1320.2-11.

    [92]   T 1508.24-28.

    [93]   T 1505.4-15.

    [94]   T 1519.19-1520.2 and 1639.5-7.

    [95]   T 1285.28-35.

25. Mr John’s process involved taking the average of the bottom two measurements of the posts to plot a slope of the posts at construction;  using Goal Seek to calculate multiple Kas for each post, then averaging these Kas, using a weighted average, to derive an individual Ka for each post;  then averaging the Kas of the average Kas for each post to obtain an average Ka for the retaining wall, then using a line of best fit of both the actual measurements made by the surveyors and the displacement implied by the average Ka his formula had calculated.  It was on this basis that Mr John concluded that the retaining wall structure was sufficient to support the soil behind it.  Dr Mitchell criticised this methodology as unrecognised by the engineering profession and illogical.[96]

    [96]   T 1727.5-1728.16, 1755.27-1755.32.

26. It was open to the judge to reject Mr John’s approach.  It has not been demonstrated that the judge erred in doing so. 

27. In preference to Mr John’s evidence the judge accepted the evidence of Dr Mitchell that the retaining wall is unacceptably overstressed and in need of rectification.  The judge accepted Dr Mitchell’s evidence that because the Australian Standard AS1170.1 prescribed a safety factor of 1.5 it required that the yield stress on the posts should be less than 66 per cent of the steel’s tolerance.  For the three metre wall FMG had designed, FMG had prescribed steel having a yield strength of 320MPa.[97]  Therefore, the Standard required a yield stress of 211 MPa.  The evidence was that the bending stresses from lateral earth pressure increase in proportion to depth cubed. Therefore, the pressure exerted upon a retaining wall of four metres is nearly double the pressure exerted on a three metre high wall.[98]  Accordingly, Dr Mitchell calculated that the load was in the order of 92 per cent of the steel’s tolerance and therefore the stress on the four metre high posts was in excess of the Australian Standard and approaching the guaranteed tolerance of the steel.[99]  That created an unacceptable risk of failure of the steel posts with the consequent risk of collapse of the retaining wall.  The assumptions made by Dr Mitchell in his evidence were conservative but warranted in the circumstances where relevant information was unavailable; the photographs of the excavation showed that it was unlikely that the natural ground behind the retaining wall was made of solid rock; there was no evidence that a geotechnical engineer had inspected the cut after it was made to map any defects within the soil and (if relevant) rock; there was uncertainty that the steel used in the construction of the retaining wall was Australian, and therefore whether it met the Australian Standard; there was no evidence that drainage had been installed in the retaining wall; and as there was no evidence of the construction of the retaining wall, it was safer to assume the posts and concrete do not act in a composite manner.  The appellant has not demonstrated that the judge erred in preferring the evidence of Dr Mitchell in this regard.  

    [97] [2017] SADC 92 at [180].

    [98] [2017] SADC 92 at [154]; T 400.16-24.

    [99]   Exhibit P38, p 3, ACB 24/1194 at 1196;  T 502-505.

1. Accordingly, I would not interfere with the judge’s conclusion that Mr Shahin had proved his claim in nuisance.

2. The nuisance was the Raedels’ failure to support the Shahin land having excavated and erected a four metre high unapproved retaining wall which was overstressed and inadequate to retain the Shahin land. The evidence of the nuisance is the displacement of the retaining wall and the erosion of soil from Mr Shahin’s property falling into the Raedels’ property when it rained.  The fact that the wall has not yet collapsed does not disprove the judge’s ultimate conclusion.

3. The judge rejected the Raedels’ submission that the Shahin land was not in its natural state[100] because of the use of fill behind the Shahin stone retaining wall.[101]  The Raedels have not demonstrated any error in this conclusion.  The evidence is that there was only modest use of fill and some cultivation of the existing soil.[102]   This did not result in any significant interference with the natural state of the Shahin land. 

   [100] The judge referred to “natural ground” but plainly is referring to the issue of whether the Shahin land was in its natural state. 

   [101] [2017] SADC 92 at [138].

   [102] [2017] SADC 92 at [130], [134]-[136] and [138] and [2019] SASCFC 141 at [108].

4. In the circumstances it is unnecessary to address at length Mr Shahin’s notice of contention that if he did not succeed on appeal in upholding the judge’s finding that his claim in nuisance was made out, nonetheless he is entitled to a judgment in negligence against the Raedels.   However, I am satisfied that the Raedels owed Mr Shahin a duty of care not to damage, endanger or affect the Shahin land when excavating and constructing the retaining wall.  Such duty is non-delegable.  The Raedels breached that duty by constructing the retaining wall in a manner that removed support from, or endangered the support of, the Shahin land thereby causing damage to the land by reason of the need to provide adequate support for the land.

   The height of the retaining wall is inadequate to retain the Shahin land

5. There is no error in the judge accepting Mr Shahin’s evidence that the soil on his land was unsupported due to it being eroded and falling into the Raedel land when it rained.[103]  Acceptance of that evidence was consistent with the judge’s finding that the retaining wall was too low to retain the pre-existing natural ground surface of the Shahin land by between 200 and 400 millimetres.[104]  That finding was supported by the evidence of Dr Mitchell. 

   [103] [2017] SADC 92 at [113], T 153.1-11 and T 156.1-25.

   [104] [2017] SADC 92 at [139].

6. Dr Mitchell gave evidence that the slope of the ground on the Shahin land prior to excavation was six degrees.[105]  This was accepted by all the conclave experts, including Mr John.[106]  The conclave agreed that the top of the steel posts were up to 400 millimetres below the pre-construction ground surface of the Shahin land.[107]  It was Dr Mitchell’s evidence, accepted by the judge, that because of that six degree slope above the wall on the Shahin land a properly designed wall would have taken this into account to cater for potential erosion of soil and garden debris and rainfall runoff at the top of the retaining wall running over the top into the Raedel land.  He considered this could be prevented by adding an extra sleeper to the wall as a “catch”, giving the wall a height of 4.2 metres. Given that there is no error demonstrated in the judge’s preference for the evidence of Dr Mitchell, there is no reason to interfere with the judge’s finding as to the adequacy of the height of the retaining wall based on his evidence. 

   [105] T 468.7-22 and T 531.19-26, [2017] SADC 92 at [120]-[121] and [208].

   [106] [2017] SADC 92 at [161], ACB 31/1379 at 1381.

   [107] ACB 31/1379 at 1380.

7. Dr Mitchell’s opinion concerning the natural ground level of the Shahin land is supported by the evidence of the contour plans of the Raedel land predating 2008 and the site plan of the Shahin land dated 20 May 1991, being before the construction of the house on the Shahin land.[108]  That was at least 200 to 400 millimetres above the height of the retaining wall.[109]  Further support for his opinion was found in the bore logs.[110] 

   [108] Exhibit P37, ACB 23/1150 at 1152.

   [109] [2017] SADC 92 at [122]-[123], [127], [134] and [139], ACB 31/1379 at 1380; T 480.36-481-14, T 530.18-38 and T 532.1-12.

   [110] [2017] SADC 92 at [119], Exhibit P68, ACB 37/1465.

8. Mr John’s opinion that the Shahin land had been built up with fill was correctly rejected by the judge.[111]  There was no fill behind panels A, B and C of the retaining wall,[112] being the highest panels commencing from the Ifould Drive end of the retaining wall.  The rest of the Shahin land immediately above the southern-most section of the retaining wall was found to be re-worked topsoil.[113] 

   [111] [2017] SADC 92 at [134].

   [112] T 1147.18-1448.9.

   [113] [2017] SADC 92 at [119]-[120], Exhibit D69, ACB 38/1474-1479, T 1438-1446.

9. Accordingly, there was no error in the judge’s finding that the retaining wall was too low by between 200 and 400 millimetres. 

   The exclusion of D162 

10. D162 is a number of spreadsheets and graphs prepared by Mr John after his cross-examination.[114]  The judge admitted it de bene esse during re-examination of Mr John over the objection of counsel for Mr Shahin.  It can be inferred the judge deferred ruling on the admissibility of the evidence as a matter of convenience.  There were other instances during the course of the trial where the judge admitted evidence de bene esse on the basis she would consider the arguments of counsel subsequently.   Ultimately the judge ruled that D162 should not be admitted because, after considering the material, she held it was not of assistance or irrelevant.  The judge did so on two bases:  first, some of the material was already in evidence and second, the material which was not, was entirely new and not raised in response to matters the subject of cross-examination.[115] 

    [114] [2017] SADC 92 at [30].

    [115] [2017] SADC 92 at [30].

11. The purpose of admitting evidence de bene esse is to afford a judge sitting alone the opportunity to consider the relevance and admissibility of the evidence sought to be adduced and to afford the parties the opportunity to address those questions subsequent to the time when the evidence is tendered. 

12. In Casley-Smith & Ors v FS Evans & Sons Pty Ltd and the District Council of Stirling (No. 10)[116] Olsson J considered the admission of evidence de bene esse.  He said:

    [I]t has become the practice of courts, not infrequently, to receive evidence in oral or written form in the course of a trial, sometimes, but not always, de bene esse, where it has, for various reasons, proved difficult – at the time of reception – finally to rule on admissibility… The expression “de bene esse”, as employed in its more modern idiom, has variously been defined in the legal dictionaries.  The majority of them treat the expression as meaning that evidence is received provisionally (or “for what it is worth”), subject to future exception or challenge – at which time it must then stand or fall according to its intrinsic merit and validity… In essence, when evidence has been tendered and then admitted de bene esse, it has been admitted in evidence conditionally upon it being found, in due course, to be proper evidence, in the sense that it is both relevant and admissible. 

    [116] Unreported, Olsson J delivered 23 May 1989.

13. The Raedels failed to demonstrate any error in the judge’s ruling.  The Raedels had the opportunity to address the judge on the admissibility of D162.  Contrary to their submission on appeal, there was no obligation on the judge to identify the material that was already in evidence.  The material in D162 that was new did not arise out of Mr John’s cross-examination.  It did not properly arise in re-examination.  That was the objection taken by counsel for Mr Shahin.[117]  That Dr Mitchell was later recalled to give evidence during which he was asked about D162 does not alter the position.[118]  It is in the nature of evidence admitted de bene esse that the other party be afforded a subsequent opportunity to address it.  The fact that Dr Mitchell did so did not render D162 admissible. 

    [117] T 1649.38-1650.34, 1657.17-33, 1658.8-18 and 1658.34-36.

    [118] T 1748-1752.

    The Development Act action

14. Section 32 of the Development Act 1993 (SA) (the DA) provides that no development may be undertaken unless it is approved.

15. The judge found that the Raedels’ retaining wall was constructed without approval.  The judge further found that the retaining wall was not adequate structurally to retain the Shahins’ land and was unacceptably overstressed.  The judge made declarations to this effect.  The Raedels challenge each of these declarations. 

16. In or around September to October 2009 the Raedels excavated along the eastern boundary of their land to a depth of up to 4.2 metres.  They constructed a retaining wall the face of which was approximately 500-600 millimetres from the boundary with the Shahin land.  The retaining wall is 4 metres high at its maximum point and is constructed from concrete sleepers and steel posts.  The retaining wall is unfenced at its top despite there being a drop of in excess of 4.2 metres from the Shahin property to the Raedel property.

17. At the time of the construction of the retaining wall there was no development approval.  Development approval was granted on 4 March 2014 but it was not for the wall which had been constructed in 2009. 

18. The judge found the Raedels made applications to the City of Burnside as follows:[119]

    [119] [2017] SAERDC 90 at [8].

    1.Development Application 180\0495\09 was lodged with the City of Burnside (the council) on or about 9 June 2009.[120]  That application related to the whole of the building project on the Raedel land but did not include a retaining wall at the southern end of the boundary between the Shahin property and the Raedel property. 

    [120] Exhibit P28 (ANB1) & P86.

    2.Development plan consent was granted on 3 July 2009.

    3.Building rules consent was granted on 17 August 2009.[121] That consent was certified for compliance based on a report from FMG Engineering Pty Ltd (FMG) dated 27 July 2009 (FMG’s July 2009 calculations) which includes calculations for a concrete sleeper retaining wall to a maximum height of 2.7 metres.[122] The calculations also contemplated a fence of 3.6 metres on top of the retaining wall.  It is not clear why a fence of that height was thought necessary.  It is however plainly incorporated in the design and the calculations. 

    [121] Exhibit P28 (ANB2).

    [122] Exhibit P62.

    4.Development Approval was granted on 20 August 2009.[123] 

    5.In around September 2009 the respondents’ builder applied for and obtained a variation to the development plan consent relating to a rainwater tank. (The first variation)[124]

    6.The respondents’ builder obtained a second set of calculations from FMG dated 4 September 2009 for concrete sleeper retaining wall to a maximum height of 3 metres.[125] (FMG’s September 2009 calculations)  Again, for reasons that are not clear, the calculations contemplated a 3.6 metre fence on top of the retaining wall.

    7.The Raedel retaining wall was constructed in or around October 2009.  It is uncontentious that the wall was built to a maximum of four metres and that there is no fence on top of the retaining wall. 

    8.In early November 2009 the defendants’ builder lodged a development application with the council for further variations to the development approval including a lower ground floor room, front staircase, courtyard and a retaining wall at the southern end of the boundary between the Raedel and Shahin properties.  The plans did not nominate a height for that retaining wall. (The second variation)[126]

    9.Development plan consent was granted for the second variation on 10 November 2009.[127] 

    10.The council wrote to the respondents on 14 November 2013 advising that, although development plan consent was granted, no building rules documentation was lodged with council and thus development approval had not been granted for the second variation.[128]  

    11.On 26 November 2013 the respondents applied for a retrospective extension of the development plan consent for the second variation.  A four year retrospective extension was granted by the council on 12 December 2013.[129]

    12.On 19 December 2013 building rules consent was granted for the second variation based on the FMG September 2009 calculations which included the calculations for a 3 metre wall with a 3.6 metre fence.[130]  

    13.On 4 March 2014 the council granted retrospective development approval for the second variation.[131]  

    [123] Exhibit P28 (ANB4) & P88.

    [124] Exhibit P28 (ANB5).

    [125] Exhibit P64.

    [126] Exhibit P28 (ANB8).

    [127] Exhibit P8 (ANB9) and Exhibit P92.

    [128] Exhibit P103.

    [129] Exhibit P28 (ANB11 & ANB12).

    [130] Exhibit P28 (ANB13).

    [131] Exhibit P28 (ANB19).

19. The judge found the Raedels had breached sections 44(4), 45(1) and 45(2) of the DA and that the breaches arose from and after 4 March 2014.

20. Section 44(4) of the DA provides:

    (4) A person must not contravene, or fail to comply with, a condition imposed under this Division.

21. Sections 45(1) and (2) of the DA provide:

    (1) A person must not perform building work, or cause it to be performed, except in accordance with technical details, particulars, plans, drawings and specifications approved in accordance with this Division.

    (2) A person must, in performing any building work, comply with the Building Rules (unless modified under this Part), and any other requirements imposed by or under this Division in respect of that work.

22. The judge found the retaining wall was constructed in breach of the development approval of 4 March 2014 and the conditions of that approval.  The approval of 4 March 2014 was for a wall constructed to a maximum height of 3 metres.  It was further a condition of that approval that a safety fence was constructed on top of the wall.  No such fence was constructed.  On that basis the judge found the Raedels breached the conditions of the approval of 4 March 2014 on and from that date, contrary to s 44(4) of the DA, and they failed to build the retaining wall in accordance with the approved plans, drawings and technical details contrary to s 45(1) and (2) of the DA. 

23. At trial the Raedels argued that they had an approval in 2014 for the retaining wall that was constructed and denied that they lacked development approval.  That submission was not pressed on appeal. 

24. Mr Shahin issued proceedings against the Raedels pursuant to s 85(1) of the DA applying for an order to remedy a breach of the DA by reconstructing the retaining wall (civil enforcement proceedings). On appeal the Raedels contend, as they did at trial, that Mr Shahin did not issue the civil enforcement proceedings under s 85 of the DA within the three-year time limit prescribed by s 85(18) of the DA. On that basis they submit that the proceedings were incompetent. They contend the judge erred in finding that the breaches arose on and after 4 March 2014.

25. Mr Shahin contends that there was no error in the judge’s finding that the proceedings were commenced within time. In the alternative, by notice of cross-contention, he submits that he should be granted an extension of time to institute the enforcement proceedings pursuant to s 48(1) of the Limitation of Actions Act 1936 (SA) (Limitation Act).

26. Central to the Raedels’ submission is the contention that any alleged breach of the DA occurred when the retaining wall was constructed in September and October 2009.  The enforcement proceedings were commenced on 5 December 2016.  Accordingly, the Raedels submit the enforcement proceedings were considerably out of time. 

27. The judge proceeded on the basis that the purpose of the application for approval which was granted on 4 March 2014 was to obtain approval of what had been constructed in 2009.  However, the approval obtained in March 2014 was ineffective for this purpose.  That was because the approval was for the construction of a 3-metre high retaining wall with a safety fence on top of the wall when what had been constructed was a 4-metre high retaining wall with no safety fence.  As a result, the judge held that the Raedels were in breach of the DA from the time the approval was granted on 4 March 2014.  Consequently, the judge found the enforcement proceedings were within time. 

28. The Raedels submit that the judge erred because the March 2014 development approval was nugatory as the purported approval was approval of something which had not been constructed.  Furthermore, the judge held that the retaining wall as constructed could not be approved unless it was rectified.  Accordingly, there could be no breach in reliance upon the March 2014 approval. 

29. I accept this submission. 

30. In my view the judge erred in finding that the Raedels were in breach of the DA on and from the date of the approval of 4 March 2014.  The approval granted was not an approval for a proposed development.[132]  The Raedels accept that the intention of the “retrospective approval” application may have been to obtain approval of the retaining wall as built as from the date of its construction.[133]   Development approval could have been granted in March 2014 for the retaining wall as constructed in 2009, but that did not occur.  The approval of 4 March 2014 was not retrospective.  It operated from that date.  The Raedels failed to act on that approval.  This is unsurprising as the approval was not effective in achieving their purpose.   It follows that the judge fell into error in finding there was a breach of the DA by the Raedels on and from 4 March 2014 as a result of the approval granted on that date. 

    [132] See s 33(2) of the DA. 

    [133] Appellants’ written submissions [93].

31. The Raedels breached the DA in 2009 when they constructed the retaining wall without approval.  Braunack v Goers[134] is authority for the proposition that the carrying out of building work is a once and for all offence.  Once a building has been constructed without approval the offence is complete.  As a result, enforcement proceedings in relation to that breach had to be issued within three years, namely, by October 2012.[135]  Accordingly, Mr Shahin’s enforcement proceedings are out of time.  The judge erred in finding to the contrary. 

    [134] (1979) 23 SASR 1 at 23-24.

    [135] Subject to any grant of an extension of time. 

32. In those circumstances it is necessary to consider Mr Shahin’s application for an extension of time.  He brings an application for an extension of time by notice of cross-contention. 

33. The Raedels constructed a retaining wall without approval.  This was a breach of the DA.  This breach occurred in late 2009.  Proceedings had to be commenced within three years of the breach.  Proceedings were not commenced until 5 December 2016. 

34. The Court is conferred with power to grant an extension of time pursuant to s 48 of the Limitation Act.  The four principal matters to be considered when deciding an application for an extension of time are the length of the delay, the reason for the delay, whether there is an arguable case and the extent of any prejudice to the respondent to the application.[136]

    [136] Ulowski v Miller [1968] SASR 277 at 280 and 282.

35. The length of the delay is four years and two months.  It was not until 17 November 2016 that Mr Shahin understood that the retaining wall was not constructed in accordance with a development authorisation and it was overstressed and unsafe.[137]  The proceedings were issued within a month.  The delay was in part due to the obfuscation of the Council, also partly due to the denials of the Raedels and the associated lack of documentary evidence available, or made available, to Mr Shahin by the Council and the Raedels.[138]  In the circumstances, Mr Shahin acted with reasonable diligence.  In any event, given the conduct of the Raedels and the lack of co-operation from the Council, it is doubtful that any greater diligence on the part of Mr Shahin would have elicited any more or better information concerning the absence of approval by the Council of the construction of the retaining wall.  The hardship to Mr Shahin if the action is dismissed and the cause of action is left statute barred is self‑evident.  He will be left with insufficient support of his property from an unacceptably overstressed and unsafe retaining wall.  As the judge found, the retaining wall requires rectification in order to avoid the risk it currently poses.  None of that risk was precipitated by Mr Shahin.  On the other hand, the prejudice to the Raedels if the action is allowed to proceed is that they will be obliged to comply with the DA and obtain the legal authorisation applicable and construct the retaining wall in accordance with it.  While this will occasion further expenditure, it is the natural consequence of their own non-compliance and failure to accept that non-compliance until ordered by the judge.  In any event, their conduct in the litigation has been unmeritorious.  They have without explanation persisted in maintaining that they had a valid development authorisation when they did not.  They resisted the production of documents that would have disclosed that they had neither development authorisation nor a compliant development.  At trial they contended that they had an approval for the retaining wall that was constructed and denied they lacked development approval. 

    [137] Exhibit P60, ACB 31/1379.

    [138] Exhibits P22, P25, T 238.13-16, Exhibits P99, P101, T 240.9-10, Exhibits P29, P177, P125, P37, Affidavit of Andrew Bullock of 5 December 2016.

1. For all these reasons, the interests of justice warrant the grant of an extension of time.  I would grant Mr Shahin an extension of time to 8 December 2016[139] within which to bring the enforcement proceedings.

   [139] This is the date the ERD Court granted leave to issue the summons. 

   The discretion to order rectification

2. The Raedels complain that the judge’s reasons fail to disclose the grounds upon which she exercised the discretion to make orders for rectification pursuant to s 85(6) of the DA.

3. I do not accept that submission.

4. The judge set out her reasons for ordering rectification as follows:[140]

   The power to order relief is discretionary. It is expressed in wide terms.  There are a number of guidelines articulated in the case law concerning the exercise of such discretion.  These are usefully summarised in Warringah Shire Council v Sedevcic. Applying those guidelines to the facts of this case it is my view that the discretion ought to be exercised in favour of the applicant Mr Shahin.  I note in particular Mr Raedel’s evidence concerning the letter from his solicitors to the Burnside Council dated 9 January 2017 relating to the question of retrospective approval for the retaining wall as built. Given my findings concerning the structural adequacy of the wall this does not persuade me to a contrary view. 

   The breaches of the Act have resulted in significant consequences for Mr Shahin. First his land is not adequately retained and second the wall is unacceptably overstressed.  This affects Mr Shahin’s enjoyment of his property together with that of his family.  It would affect any subsequent owners of Mr Shahin’s property.  The role of the planning system is to prevent such situations arising. 

   The rectification proposed by Dr Mitchell is appropriate and proportionate to the risk of harm should the wall fail. It facilitates the objects of the Act. Accordingly I consider it appropriate to make orders for rectification under section 85. As I observe in the civil judgment however there are two methods for approaching this rectification; one is from the Shahin property and the other is from the Raedel property. There is insufficient evidence to ascertain which method is preferable. Further, Dr Mitchell’s recommendation of the installation of a “catch” will likely mean that there is no necessity for a safety fence on top of the wall. In view of this, I will hear the parties as to the precise terms of the orders.

   [Citations omitted].

   [140] [2017] SAERDC 90 at [21]-[24].

5. The judge correctly recognised that the power to order relief pursuant to s 85(6)(d) is discretionary. The judge had regard to the reasons of Kirby P, as he then was, in Warringah Shire Council v Sedevcic[141] who identified guidelines applicable to the exercise of a comparable discretion conferred by s 124 of the Environmental Planning and Assessment Act 1979 (NSW). Those guidelines are:

   [141] (1987) 10 NSWLR 335 at 339-340.

   ·The discretionary power is wide.

   ·It is undesirable to attempt to catalogue or classify all of the circumstances which will enliven the exercise of the discretion.  The discretion is not fettered.  Nonetheless it is instructive to consider the variety of circumstances in which the discretion has been exercised.  Relevant factors would include the fact that the breach complained of was a purely technical breach which was unnoticeable other than to a person well versed in the relevant law; or the fact that the local authority had delayed the bringing of its action, or the fact that, far from having an adverse effect on the environment or the amenity of the locality, the breach, in reality, had been shown to have a beneficial effect. 

   ·In exercising the discretion it must be kept in mind that the restraint sought is not the enforcement of a private right but of a public duty imposed by a statute in the protection of the public interest in the orderly development and use of the environment.  Because the Act permits any person to bring proceedings for an order to remedy or restrain a breach, there is indicated a legislative purpose of upholding the integrated and coordinated nature of planning law.  Unless this is done equal justice may not be secured.  Private advantage may be won by a particular individual which others cannot enjoy.

   ·It is only in this sense that special circumstances need to be established to secure a favourable exercise of the discretion.  The obvious intention of the statute is that those concerned in development will comply with the terms of the legislation.  Otherwise if unlawful exceptions and exemptions are frequently condoned by a refusal to enforce the statute through the exercise of the discretion, the equal and orderly development which the statute enforces would be undermined. 

   ·Where the application for the enforcement of the Act is made by the Attorney-General or a council a court may be less likely to deny equitable relief than it would in litigation between private citizens.

   ·Where the relief is sought against a static development i.e. the erection of a building which, once having occurred can only be remedied at great cost or inconvenience, the discretion may, in the normal case, be more readily exercised than where what is involved is a continuing breach by conduct which could quite easily be modified to bring it into compliance with the law.  But this observation is simply a reflection of the judicial perception in balancing, on the one hand, the public interest in equal compliance with the law and, on the other, the degree of irremediability occasioned by the breach and the expense or inconvenience which would follow the law’s enforcement.  It does not amount to a hard and fast exception to the discretion.  Nor is it a reason to refuse relief where no “static” development can be proved.

   ·The discretion permits the court to soften, according to the justice of particular circumstances, the application of rules which, though right in the general, may produce an unjust result in the particular case. 

   ·On appeal due regard will be had to the exercise by a judge of the ERD Court of his or her discretion to decline or grant an injunction.  Restraint is called for because what is being reviewed is the exercise of a discretion by a specialist court.

6. The Raedels complain that the judge appears only to have given real consideration to two potentially relevant factors, namely, the height of the wall relative to its capacity to retain the Shahin land and the structural integrity of the wall.

7. Clearly the judge had regard to those two factors.  I am satisfied that they are relevant considerations in deciding whether, in the exercise of the discretion, to make orders for remediation of the found breaches.  But, it is also apparent, that the judge must have had regard to other considerations identified by Kirby P in Sedevic.  It was not necessary that the judge expressly refer to every consideration indicating whether it was relevant and the weight she gave each relevant consideration.[142]  In the circumstances I do not consider that the judge’s exercise of her discretion miscarried.  Further, I do not accept that the judge failed to adequately explain the basis upon which she exercised her discretion.  Mr Shahin contends that the Raedels’ grounds of appeal do not include a ground that the judge’s reasons for the exercise of her discretion are not adequately explained.  The Raedels’ riposte is that they do not complain of inadequate reasons but of a House v King error.  They contend that it is not apparent how the judge reached her decision in the exercise of her discretion to order remediation.  In my view that submission is untenable.  The basis upon which the judge exercised her discretion is adequately explained to the extent that this Court can identify how the judge reached the impugned conclusion. 

   [142] Athens v Randwick City Council [2002] NSWCA 83 at [16].

8. In any event, if this Court is to exercise the discretion afresh, I consider that there are additional cogent reasons in favour of the exercise of the discretion in the way undertaken by the judge.  First, the obvious necessity of obviating the risk the wall presently poses.  Second, the importance of ensuring compliance with the DA.  Third, the consideration that the breach is not merely technical.  Fourth, that there has been no actual lack of diligence on the part of Mr Shahin in bringing enforcement proceedings.  Fifth, that while the proceedings are concerned with enforcing a private right, there is an underlying public interest in the integrity of the development approval process.  Sixth, that while the retaining wall might be considered a static development, the expense and inconvenience which would result from the law’s enforcement is adequately justified for the reasons set out above.  Seventh, the restraint and deference which this Court ordinarily extends to decisions of specialist courts discourages interference with the exercise of the discretion which necessarily is informed by the specialist court’s understanding and experience of its jurisdiction. 

9. The conferral of a discretion is not a warrant to set aside the complicated and sensitively balanced provisions of the DA.[143] 

   [143] ACR Trading Pty Ltd v Fat-Sel Pty Ltd (1987) 11 NSWLR 67 at 82.

   Permission to appeal

10. Pursuant to s 30(2) of the Environment, Resources and Development Court Act 1993 (SA) an appeal lies as of right to this Court on a question of law but permission is required to appeal a question of fact. In the circumstances I would grant permission.

    Conclusion

11. I would dismiss the appeals.  I would hear the parties as to costs.

12. HINTON J:           I agree with the orders proposed by Stanley J for the reasons his Honour gives.