Cite as: 40 Cal.App.3d 471
SUPREME COURT OF BRITISH COLUMBIA
WILFRED GARY SUTHERLAND and SHERRYL SARA STEWART SUTHERLAND, Plaintiffs
THE ATTORNEY GENERAL OF CANADA and THE VANCOUVER INTERNATIONAL AIRPORT AUTHORITY, Defendants
Nov. 14, 1997
REASONS FOR JUDGMENT
HONOURABLE MR. JUSTICE K. SMITH
Counsel for the Plaintiffs: Susan A. Griffin, Tracy Wachman
Counsel for the Defendant The Attorney General of Canada: George Carruthers, Laura Wanamaker
Counsel for the Defendant The Vancouver International Airport Authority: Allan P. Seckel, Ward K. Branch
Place and Date of Hearing: Vancouver, B.C., September 15, 16, 17, 18, 1997
 The plaintiffs claim damages for nuisance and compensation for expropriation of their land, both allegedly arising from the use of the recently-opened third runway at the Vancouver International Airport.
 The federal government, represented here by the defendant the Attorney General of Canada, owns the airport. The other defendant, the Vancouver International Airport Authority, operates the airport under a lease from the government through the Minister of Transport.
 The plaintiffs, since 1980, have owned and resided in a home in the Bridgeport area of Richmond, near the airport. By this application, they seek to have their claim in nuisance certified as a class proceeding pursuant to the Class Proceedings Act, R.S.B.C. 1996, c. 50, and to have themselves appointed as representative plaintiffs. Their counsel abandoned their application to certify their claim based on expropriation.
 The plaintiffs' allegations of nuisance are set out in their statement of claim as follows:
16. Particulars of the actionable nuisance created by the Defendants in the operation of the Third Runway include, but are not limited to:
(b) interference with the use of telephones, radio and television;
(c) interference with the performance of daily tasks;
(d) interference with and reduction in the quality of rest and sleep;
(e) creation or aggravation of hypertension;
(f) interference with the reasonable and comfortable use of gardens, patios, yards, and recreational property;
(g) interference in the normal use and enjoyment of community amenities in the Affected Areas;
(h) creation of fear and apprehension; and
(i) expulsion of noxious fumes in the vicinity of residential homes.
17. As a result of the nuisance created by the Defendants as set out in paragraphs 15 - 16, supra, the Plaintiffs and other members of the Class, have suffered substantial and unreasonable interference with the use and enjoyment of their properties and further have suffered reduction in the market value of their properties by rendering such properties undesirable, or significantly less desirable, as residences.
 This action follows a long public process in relation to the third runway, which began in 1976 after it was identified as essential to enable the airport to handle expected increases in air traffic. An Environmental Assessment and Review Panel was formed in 1976 to conduct a public review of the environmental and socio-economic effects of the proposed runway and to consider ways of mitigating its negative effects and of compensating persons affected by them. Ultimately, the Panel reported to the Environment and Transport Ministries in September 1991. The Ministry of Transport accepted and acted on many of the Panel's recommendations. However, it rejected the recommendation that persons adversely affected by increased noise be identified and compensated. The Ministry took the position that it should concentrate on measures to mitigate the effects of noise on surrounding neighbourhoods, rather than to "give the airport a licence to be noisy." This lawsuit is a result of that decision.
 The relevant provisions of the Act are as follows:
(b) there is an identifiable class of 2 or more persons,
(c) the claims of the class members raise common issues, whether or not those common issues predominate over issues affecting only individual members,
(d) a class proceeding would be the preferable procedure for the fair and efficient resolution of the common issues, and
(e) there is a representative plaintiff who
(ii) has produced a plan for the proceeding that sets out a workable method of advancing the proceeding on behalf of the class and of notifying class members of the proceeding, and
(iii) does not have, on the common issues, an interest that is in conflict with the interests of other class members.
(2) In determining whether a class proceeding would be the preferable procedure for the fair and efficient resolution of the common issues, the court must consider all relevant matters including
(b) whether a significant number of the members of the class have a valid interest in individually controlling the prosecution of separate actions,
(c) whether the class proceeding would involve claims that are or have been the subject of any other proceedings,
(d) whether other means of resolving the claims are less practical or less efficient, and
(e) whether the administration of the class proceeding would create greater difficulties than those likely to be experienced if relief were sought by other means.
7. The court must not refuse to certify a proceeding as a class proceeding merely because of one or more of the following:
(b) the relief claimed relates to separate contracts involving different class members;
(c) different remedies are sought for different class members;
(d) the number of class members or the identity of each class member is not known;
(e) the class includes a subclass whose members have claims that raise common issues not shared by all class members.
 The purpose of the Act is described in the following passage in Campbell et al v. Flexwatt Corporation et al (7 November 1997) Victoria CA22124/V02849/V02850/V02852/V02853/ V02856/V02867/V02895 (B.C.C.A.) at para. 25:
Those objectives must inform the consideration of this application.
 The plaintiffs delivered the amended notice of motion after the certification hearing to record their changed positions in response to questions that arose during the hearing. The first set of amendments developed out of and were presented during the plaintiffs' submissions. The final amendments were proposed in the plaintiffs' reply, after the defendants had presented their arguments. For convenience, I will refer to the original proposed issues as issues 1(a) to 1(o), to the first amended set of proposed issues as issues 2(a) to 2(k), and to the final amended set of proposed issues as issues 3(a) to 3(k).
 Issues 1(e) and 1(f) were abandoned during submissions. Issue 1(c) is misconceived; a cause of action in nuisance is not complete without damage, so issue 1(c) is subsumed in issue 1(a).
 The remaining issues can be grouped by their subjects. Issues 1(a), 1(b), 2(a), and 3(a) to 3(d) inclusive ("Group I") are concerned with the plaintiffs' burden of proving the elements of a claim in nuisance. The issue stated in 1(h) and 2(d) ("Group II") is a question of law. Issues 1(g), 1(i), 1(j), 2(c), 2(e), 2(f), 3(g), 3(h), and 3(i) ("Group III") relate to the defences of statutory authority and public nuisance. The issue repeated in 1(k), 2(g), and 3(j) ("Group IV") raises the substantive defence of novus actus interveniens. Issues 1(d), 2(b), and 3(k) ("Group V") deal with quantification of damages. Issues 1(l), 1(m), 1(n), 1(o), 2(h), 2(i), 2(j), 2(k), 3(e), and 3(f) ("Group VI") involve mitigation of the loss by the plaintiffs.
 The analysis must begin with the Group I issues, which relate to proof by the representative plaintiffs of the liability of the defendants to members of the proposed class. As was stated by the Court of Appeal in Campbell et al v. Flexwatt Corporation et al, supra, at para. 52:
 The first step in the analysis is to identify the material facts to be proven by the plaintiffs. They will establish the yardstick against which the significance of the proposed common issues may be measured.
 A material fact is one that is necessary to formulate a complete cause of action: Wyman et al v. Vancouver Real Estate Board (1957), 8 D.L.R. (2d) 724 (B.C.C.A.) at p. 726, Troup v. McPherson (1965), 53 W.W.R. 37 (B.C.S.C.) at p. 39.
 The plaintiffs' cause of action is in nuisance, which is described as follows in J.G. Fleming, The Law of Torts, 8th ed. (Sydney: Law Book, 1992) at p. 416:
At pp. 16-17 Mcintyre J. stated:
2. That the interference with their use and enjoyment of the property is unreasonable in light of all the surrounding circumstances.
 Sound is absorbed and dissipates as it travels. High frequency sound is absorbed over a shorter distance than low frequency sound. The rate and degree of absorption are affected by the topography and type of terrain over which the sound travels and by climatic conditions, such as temperature, wind, humidity, meterological inversions, and cloud-cover. Further, sound may be blocked or deflected by natural objects, like hills, or by artificial structures, like buildings.
 The plaintiffs have characterized the sound of which they complain as "noise". "Noise" is loud or unpleasant or undesired sound: The Concise Oxford Dictionary 8th ed., (Oxford 1990) p. 804. It is inherently subjective: what is noise to one person may not be noise to another. In the present context, the sound of overflying aircraft may not be "noise" to a nearby resident who is employed in a business that is dependent on the airport.
 Liability for each plaintiff in the class will therefore depend on many factors, including, for example:
2. The nature and type of construction of the residential dwelling of the particular plaintiff: whether it is a detached house or a condominium in the centre of a complex, where the sound would be shielded by surrounding structures; whether it is built of wood or brick, or other materials with differing sound-absorption qualities; whether it is insulated, the number of windows it has, etc.;
3. The nature of the immediate neighbourhood of the particular plaintiff: the defined area includes areas zoned for school and public use, light industrial, automobile-oriented commercial, townhouses, agricultural, golf courses, downtown commercial, limited industrial retail, apartments, high-density residential, health care facilities, business district, marina, industrial storage, recreational vehicle parks, two-family and single-family housing, industrial;
4. Sound from other sources: Richmond and Marpole, the areas emphasized by the plaintiffs, include several major automobile traffic arteries, railroads, a major hospital, firehalls, the Fraser River, which is used for marine traffic and floatplanes and has mills and manufacturing plants along its banks, and the airport as it existed before the third runway was constructed;
5. The time of the sound in relation to climatic conditions and to the living patterns of the particular plaintiff: some members of the class will reside in their homes within the affected area, others will not; some will be away from their homes during the day, when noise from the third runway is more prominent, and at home at night, when it is not; some will spend time in their yards and some will not; some will take vacations in winter, some in summer; some will sleep during periods of heightened aircraft sound, others will sleep when the sound is less;
6. The response of the particular plaintiff to sound: some members of the class will be extremely sensitive to sound, others less sensitive; some will be prone to sleep disruption and hypertension, others not; some will have impaired hearing, others not; some will become accustomed to the sound, others not.
 The basic unit of measurement of sound is the decibel (dB), which is essentially a measurement of pressure. The most commonly used measure of sound is the A-weighted decibel (dBA), which de-emphasizes low- and high-frequency sounds to more closely approximate subjective judgments of loudness.
 The defendants monitor sound emanating from operations at the Vancouver International Airport. They presently have twelve "noise monitoring terminals" in operation, two on Sea Island, where the airport is located, five on Lulu Island, immediately west and south of the airport, three in southwest Vancouver adjacent to and north of the airport, and one to the northwest of the airport near the western tip of Point Grey. These stations measure sound levels in dBA. However, they are unable to distinguish aircraft sound from other sounds present.
 It is necessary for the defendants to abstract useful information from the raw data provided by these terminals. Thus, they derive measurements known as "noise metrics", such as SEL ("Sound Exposure Level" or "Single Event Level"), which is a function of the duration and intensity of sound over a short period of time, as occurs in an aircraft overflight; Leq ("Equivalent Sound Level"), which is that level of continuous, steady sound that would, over a given period of time, contain the same acoustic energy as a series of SEL's, including the background noise; Ldn ("Day-Night Noise Level"), which is the average of Leq's for each hour over a twenty-four-hour period, weighted to penalize night-time noise because of an assumption that it is perceived as more annoying; and NEF ("Noise Exposure Forecast"), which is the sum of all sound in a twenty-four-hour period weighted to estimate the annoyance level of sound as opposed to its loudness.
 The defendants use these noise metrics to attempt to predict the general effects of airport sounds in areas subjected to the sounds. For example, Mr. Haboly, an Environmental Specialist employed by the defendant Authority, described the use of NEF as follows:
The NEF is presented as contours of equal noise energy, as plots on maps at and in the vicinity of the airport. NEF contours are best used for comparative purposes, rather than for absolute analysis. That is, NEF calculations provide comparisons between different conditions, so long as consistent assumptions and the same basic data are used for all calculations. A contour drawn on a map through this computer modelling cannot determine that a noise problem exists for any particular individual or population on one side of a line and that no problem exists for any particular individual or population on the other side of a line.
 In the result, no meaningful measurement of sound emanating from the operation of the third runway can be ascertained for the class. To permit inferences to be drawn for all class members on such general findings as are suggested would be unfair to persons in the geographic area who, individually, experience greater adverse effects than the findings would predict, and would be unfair to the defendants in that it would preclude them from defending each individual claim to its fullest.
 Accordingly, in respect of the plaintiffs' burden of proof of liability, there is no material fact or important threshold factual issue that is common to all members of the proposed class or to members of identifiable sub-classes.
 The Group II issue, whether foreseeability of damage is a necessary requisite of a cause of action in nuisance, is a pure question of law that could be determined fairly and efficiently in a test case. It is not an appropriate issue for certification.
 The Group III issues -- the defences of statutory authority and public nuisance -- and the Group IV issue -- the defence of novus actus interveniens -- are, in a sense, liability issues. However, they are subordinate liability issues; that is, it is not necessary to consider them if the plaintiffs do not first prove facts that would otherwise amount to nuisance. Whether or not that necessarily disqualifies them as common issues, I have concluded that they should not be certified here.
 The defence of public nuisance suffers from the same defects for present purposes as the liability issues already discussed. The nature of a public nuisance is summarized in Allen M. Linden, Canadian Tort Law, 5th ed. (Vancouver: Butterworths, 1993) at p. 505 as follows (citations omitted):
Private citizens are entitled to sue for public nuisance by way of civil action in tort, only if it causes "special damage" to them, over and above the general suffering or inconvenience to the public. In other words, individual tort claimants must demonstrate that the injury or damage suffered has placed them in a different position than other members of the public.
 The defence of statutory authority requires the defendants to prove that they were under a statutory duty to construct the third runway and that the nuisance, if any, was an inevitable result of the discharge of that duty: Tock v. St. John's Metropolitan Area Board, supra, at p. 1214. The first proposition, that the statute imposed a mandatory duty to construct the runway, is a question of law that could be fairly and efficiently determined in a test case. The second, that nuisance resulted inevitably, involves the same individual factual inquiry. In the result, the issues raised in this defence are not appropriate for certification.
 The defence of novus actus interveniens requires proof of some intervening act, subsequent in time to the defendants' act or omission, that was the sole legal cause of the harm caused: see Athey v. Leonati,  3 S.C.R. 458 at pp. 466-68, The Dictionary of Canadian Law, 2nd ed. (Carswell: Toronto, 1995), pp. 813-14. Thus, the harm in each individual case is implicated and this issue is disqualified from certification.
 The remaining proposed issues relate to the quantification of damages and mitigation. These are subordinate to and dependent upon the liability issues and are not properly the subject of a class proceeding in their own right. Moreover, they are intrinsically individualistic and would inevitably reduce to discrete adjudications for each plaintiff. Little or no benefit would accrue to class members from a common trial of any of these issues and, in the circumstances, a class proceeding would not be a fair and efficient method for resolving them.
 The application is therefore dismissed.
PLAINTIFFS' PROPOSED COMMON ISSUES
1. (a) Does the operation of the Third Runway (08L/26/R) at Vancouver International Airport cause a nuisance affecting properties owned by members of the Class (the Plaintiffs and other members of the class are hereinafter described together as the "Plaintiffs")?
(c) Have the Plaintiffs suffered damage as a result of the nuisance?
(d) Is the damage measurable and, inter alia, reflected in a loss of market value of the properties owned by the Plaintiffs, and can an aggregate award of damages be made?
(e) Does the operation of the Third Runway (08L-26R) render uninhabitable any properties owned by the Plaintiffs, such that the operation of the Third Runway by the Defendants constitutes an expropriation of those properties?
(f) Does such expropriation give rise to a right of compensation to the Plaintiffs, and if so, does the liability for compensation lie with either one of the Defendants?
(g) If nuisance is established in answer to issues 1 to 3 [sic], is the Vancouver International Airport Authority (the "Authority") or the Attorney General of Canada (the "Crown) or are both liable to the Plaintiffs for damages for the nuisance?
(h) Is it necessary to the establishment of liability for nuisance to establish that the damage is a reasonably foreseeable consequence of the operation of the Third Runway, and if so, is the damage a reasonably foreseeable consequence of the operation of the Third Runway?
(i) Does the defence of "statutory authority" apply as a defence to the nuisance, in particular:
(ii) is the nuisance the inevitable consequence of the Crown discharging the statutory duty identified in the answer to (i);
(iii) is this a defence applicable to both the Crown and the Authority, or only to the Crown?
(j) Does the defence of "public nuisance" apply so as to limit the Plaintiffs' right to sue for private nuisance, as pleaded in the Crown Statement of Defence para. 27 and the Authority Statement of Defence para 10? ie.
(ii) is this actionable without the consent of the Attorney General of British Columbia?
(k) Does the defence of novus actus interveniens apply as a defence to liability of the Crown, as pleaded in the Crown Statement of Defence in para. 26?
(l) Prior to the commencement of operations of the Third Runway on November 4, 1996, was there any duty owed by a prospective purchaser of property to the Defendants to investigate, the failure of which could constitute a defence to nuisance created by the Defendants after the purchase takes place?
(m) In regards to issue (l):
(ii) what information would prospective purchasers have received as a result of these investigations; and,
(iii) what are the legal implications of these facts?
(n) Was there any notice placed on the titles to property of the Plaintiffs which gave rise to a duty on the part of the Plaintiffs owed to the Defendants to "pay sufficient regard" to the notice whereby failure to do so would constitute contributory negligence by the Plaintiffs and would be a defence to nuisance?
(o) Are there any reasonable steps which the Plaintiffs could take which would have the effect of minimizing the effects of the nuisance, and is there an obligation on the Plaintiffs to take such steps, and would failure to do so constitute contributory negligence or failure to mitigate?
2. (a) Does the operation of the Third Runway (08l/26R) at Vancouver International Airport cause a nuisance affecting properties owned by members of the Class (the Plaintiffs and other members of the class are hereinafter described together as the "Plaintiffs")?
(c) If nuisance is established in answer to common issue 1 [sic], is the Vancouver International Airport Authority (the "Authority") or the Attorney General of Canada (the "Crown"), or are both liable to the Plaintiffs for damages for nuisance?
(d) Is it necessary to the establishment of liability for nuisance to establish that the damage is a reasonably foreseeable consequence of the operation of the Third Runway, and if so, is the damage a reasonably foreseeable consequence of the operation of the Third Runway?
(e) Does the defence of "statutory authority" apply as a defence to the nuisance as pleaded in the Crown's Statement of Defence, para. 19 and the Authority's Statement of Defence, para. 9, and is this a defence applicable to both the Crown and the Authority, or only to the Crown?
(f) Does the defence of "public nuisance" apply so as to limit the Plaintiffs' right to sue for private nuisance, as pleaded in the Crown's Statement of Defence, para. 27 and the Authority's Statement of Defence para. 10?
(g) Does the defence of novus actus interveniens apply as a defence to liability of the Crown, as pleaded in the Crown's Statement of Defence para. 26?
(h) Prior to the commencement of operations of the Third Runway on November 4, 1996, was there any obligation on a prospective purchaser of property to investigate, the failure of which could cause contribution to fault, as pleaded in the Crown's Statement of Defence para. 25 and the Authority's Statement of Defence para. 15?
(i) In regards to issue h:
(ii) what information would prospective purchasers have received as a result of those investigations; and
(iii) what are the legal implications of these facts?
(j) Was there any notice placed on the titles to property of the Plaintiffs which gave rise to a duty on the part of the Plaintiffs owed to the Defendants to "pay sufficient regard" to the notice whereby failure to do so would constitute contributory negligence by the Plaintiffs and would be a defence to nuisance as pleaded in the Crown's Statement of Defence, para. 25, and the Authority's Statement of Defence, para. 15?
(k) Are there any reasonable steps which the Plaintiff could take which would have the effect of minimizing the effects of the nuisance, and is there an obligation on the Plaintiffs to take such steps, and would failure to do so constitute contributory negligence or failure to mitigate as pleaded in the Crown's Statement of Defence, para. 25 and the Authority's Statement of Defence, para. 15?
3. (a) Since the Third Runway (08L/26R) at Vancouver International Airport commenced operations on November 4, 1996:
(ii) if so, are there identifiable residential neighbourhoods which have experienced this increase in noise (the "Affected Neighbourhoods")?
(iii) can these increases in noise be measured and the increases identified in a map of the Affected Neighbours, and if so, what method of measurement will best correlate the effect of these noise increases on people living in the Affected Neighbourhoods?
(iv) are the noise increases likely to continue or are they likely to change, and if so, can the changes be reasonably projected and identified on a map using the method of measurement determined in answer to (c), above?
(b) Is the identified increased level of noise caused by the operations of the Third Runway reasonable in the context of the character of each Affected Neighbourhood?
(c) For each Affected Neighbourhood, is there an identifiable level of noise increase which the Court can determine is a higher level than the reasonable person can be expected to bear, if exposed to that noise in the Affected Neighbourhood in the use of their residential property? In this regard, the Court will look at what constitutes reasonable human reactions to the new noise levels in the Affected Neighbourhoods, in the context of each neighbourhood.
(d) Has the increase in noise in the Affected Neighbourhoods caused a general decrease in the value of residential properties in that neighbourhood, and if so, can this effect be measured?
(e) Prior to the commencement of operations of the Third Runway on November 4, 1996, were there any facts on which fault might be attributable to a plaintiff, which fault would affect the amount of damages recoverable by a plaintiff?
(f) Subsequent to the commencement of operations of the Third Runway, is there any action a plaintiff could or should have taken, failure of which could be considered failure to mitigate the nuisance or contributory fault on the part of a plaintiff?
(g) If nuisance is established, is the Vancouver International Airport Authority (the "Authority"), or the Attorney General of Canada (the "Crown"), or both, liable to the Plaintiffs for damages for the nuisance, and is there an apportionment of liability?
(h) Does the defence of "statutory authority" apply as a defence to the nuisance as pleaded in the Crown Statement of Defence para. 19 and the Authority Statement of Defence para. 9, and is this a defence applicable to both the Crown and the Authority, or only to the Crown?
(i) Does the defence of "public nuisance" apply so as to limit the Plaintiffs' right to sue for private nuisance, as pleaded in the Crown Statement of Defence para. 27 and the Authority Statement of Defence para. 10?
(j) Does the defence of novus actus interveniens apply as a defence to liability of the Crown, as pleaded in the Crown statement of Defence para. 26?
(k) After a determination of which plaintiffs have suffered nuisance and which properties have suffered a decrease in market value as a result of the nuisance, and a determination of liability, can an aggregate award of damages be made based on a common formula which measures the aggregate loss of market value of these properties?