Full opinion text
Opinion LUCAS, C. J. In Prudential-LMI Com. Insurance v. Superior Court (1990) 51 Cal.3d 674 [274 Cal.Rptr. 387, 798 P.2d 1230] (Prudential-LMI), we examined the issue of allocation of indemnity among insurers in a first party property insurance case, where a loss had occurred over several policy periods but was not discovered until several years after it commenced. We found the “manifestation of loss rule” applicable, holding that the insurer insuring the property at the time appreciable property damage becomes manifest is solely responsible for indemnifying the insured once coverage is established. (Id. at p. 699.) We expressly reserved the question of what rules should apply in third party liability insurance cases involving continuous or progressively deteriorating damage or injury. We recognized there are substantial analytical differences between first party property and third party liability policies, and cautioned that we were intimating no view as to the application of our decision in either the third party liability or commercial liability (including toxic tort) context. (Prudential-LMI, supra, 51 Cal.3d at pp. 679, 694; see also Garvey v. State Farm Fire & Casualty Co. (1989) 48 Cal.3d 395, 405-408 [257 Cal.Rptr. 292, 770 P.2d 704] (Garvey).) In this case we address the issue reserved in Prudential-LMI. Specifically, we must determine whether four comprehensive general liability (CGL) policies issued by defendant and respondent Admiral Insurance Company (Admiral) to plaintiff and appellant Montrose Chemical Corporation of California (Montrose) obligate Admiral to defend Montrose in lawsuits seeking damages for continuous or progressively deteriorating bodily injury and property damage that occurred during the successive policy periods. These losses, it is alleged, were caused by Montrose’s disposal of hazardous wastes at times predating the commencement of Admiral’s policy periods. As explained below, we conclude that the standard CGL policy language, such as was incorporated into Admiral’s policies in issue in this case, provides coverage for bodily injury and property damage that occurs during the policy period. In the case of successive policies, bodily injury and property damage that is continuous or progressively deteriorating throughout several policy periods is potentially covered by all policies in effect during those periods. Stated in the insurance industry’s parlance, we conclude the “continuous injury” trigger of coverage should be adopted for third party liability insurance cases involving continuous or progressively deteriorating losses. In this case, because the potential of coverage arose under Admiral’s policies, so too did its duty to defend Montrose in the underlying lawsuits. As will further be explained, we also conclude, with respect to the “loss-in-progress” rule codified in Insurance Code sections 22 and 250, that in the context of continuous or progressively deteriorating property or bodily injury losses insurable under a third party CGL policy, as long as there remains uncertainty about damage or injury that may occur during the policy period and the imposition of liability upon the insured, and no legal obligation to pay third party claims has been established, there is an insurable risk within the meaning of sections 22 and 250 for which coverage may be sought under such a policy. We shall therefore affirm the judgment of the Court of Appeal reversing the summary judgment granted in favor of Admiral. I Facts and Procedural Background From 1947 until 1982, Montrose manufactured the pesticide dichlorodiphenyl-trichlorethane (DDT) at its plant in Torrance, California. In 1972, the federal government prohibited all domestic use of DDT. Montrose continued to manufacture the chemical for export at the Torrance facility until the plant closed in 1982. Between January 1960 and March 1986, seven different carriers, ending with Admiral, furnished CGL policies to Montrose. Admiral issued four policies to Montrose, covering the period from October 13, 1982, to March 20, 1986. The remaining six CGL insurers involved in this litigation are not parties to this appeal. Admiral’s policies obligate it to “pay on behalf of the insured all sums which the insured shall become legally obligated to pay as damages because of . . . bodily injury, or . . . property damage to which this insurance applies, caused by an occurrence. . . “Occurrence” is defined as “an accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage neither expected nor intended from the standpoint of the insured.” The broad issue before the trial court was whether any of the seven CGL carriers, including Admiral, were obligated to defend Montrose in five actions pending against it in connection with Montrose’s disposal of toxic or hazardous wastes at several locations in California. Admiral joined in an interim defense agreement to provisionally fund Montrose’s defense (to this date the parties apparently still disagree as to whether such agreement was entered into subject to a complete reservation of rights, a matter of no direct concern in this appeal). When Montrose filed its declaratory relief action, Admiral moved for summary judgment on the issue of its duty to defend given the effective dates and terms of coverage of its policies. The trial court found there was no potential for coverage under Admiral’s policies, and thus that Admiral had no duty to defend the liability actions. We next briefly summarize the facts of the underlying actions as established by the evidence submitted in support of, and in opposition to, Admiral’s summary judgment motion. 1. The Stringfellow cases. In an action initiated in 1983—United States v. J.B. Stringfellow (U.S. Dist. Ct. (C.D.Cal.)) No. C-83-2501 HLH—the United States and the State of California sued Montrose and numerous other businesses under the Comprehensive Environmental Response, Compensation, and Liability Act (42 U.S.C. § 9601 et seq.; hereafter CERCLA), as well as various state environmental law provisions, seeking reimbursement for response costs incurred pursuant to the investigation, removal, and remediation of toxic waste contamination at and near the state-licensed class I hazardous waste disposal site known as the Stringfellow acid pits in Riverside County. The government also seeks damages for injury to natural resources, abatement of conditions, and cleanup at and near the Stringfellow site. The basis for the federal law claim against Montrose is strict liability under CERCLA for generating toxic waste shipped to the site. The Stringfellow waste disposal site opened in 1956 and closed in 1972. Chemical wastes generated by Montrose were deposited there between 1968 and 1972, when Montrose paid a hauling company to transport byproducts of its DDT manufacturing process to the state-approved and licensed disposal facility. As early as 1970, toxic wastes were detected seeping from the site, and in 1975 the Santa Ana Regional Water Quality Control Board declared the site a public nuisance. It is noteworthy that the Stringfellow site was selected and designed as a hazardous waste disposal facility by the State of California, and that the site was used for that purpose by many defense contractors. In 1989, the State of California was found jointly and severally liable for the cleanup, both on strict liability and various fault-based common law grounds, due to its actions in designing, licensing and supervising the facility. According to the allegations of the CERCLA complaint, the property damage commenced in 1956 and continued throughout the periods when Admiral’s CGL policies issued to Montrose were in effect. No bodily injury is alleged in the CERCLA action. In a second lawsuit, a consolidated private party toxic tort action— Newman v. J.B. Stringfellow (Super. Ct. Riverside County, No. 165994MF) —numerous plaintiffs seek damages from Montrose and other defendants for bodily injury and property damage alleged to have resulted from the release of contaminants at the Stringfellow site. Plaintiffs allege that the bodily injury and property damage occurred on a continuous basis, commencing in 1956 and extending to the present. Specifically, plaintiffs allege that 27 wrongful deaths occurred between 1982 and 1986 (the period Admiral’s policies were in effect), and that property damage was continuous throughout that same period. Although both Stringfellow cases involve allegations of progressively deteriorating property damage caused by contaminants being released into, or migrating through, soil, groundwater, and surface water, only Newman v. Stringfellow additionally seeks damages for bodily injuries. According to the plaintiffs in both Stringfellow cases, between February 1982 and February 1983, the concentration of trichloroethylene (a suspected human carcinogen) tripled in the groundwater located between the Stringfellow site and the town of Glen Avon. On August 31, 1982, six weeks prior to commencement of the policy term under the first of Admiral’s policies issued to Montrose, Montrose was notified by the federal Environmental Protection Agency (EPA) that it considered Montrose a potentially responsible party (PRP) for money expended for response activities at the Stringfellow site. At about the same time, Montrose notified its environmental impairment liability (EIL) carrier, International Insurance Company, about the Stringfellow allegations, but did not notify Admiral. 2. The Levin Metals Cases. The three remaining actions—Parr-Richmond Terminal Co. v. Levin Metals Corp. (U.S. Dist. Ct. (N.D.Cal.)) No. C-85-4776 SC, Levin Metals Corp. v. Parr-Richmond Terminal Co. (U.S. Dist. Ct. (N.D.Cal.)) Nos. C-84-6273 SC and 84-6324 SC, and Levin Metals Corp. v. Parr-Richmond Terminal Co. (Super. Ct. Contra Costa County, No. 255836)—are all interrelated. Each arises out of a state court action brought by Levin Metals against Parr-Richmond, alleging that real property sold by Parr-Richmond to Levin Metals in Contra Costa County in 1981 was contaminated by hazardous waste. The suits allege both on-site and off-site contamination of soil, groundwater, and surface water, and seek damages for fraud based on Parr-Richmond’s failure to disclose the alleged contamination. All chemical processing at the Parr-Richmond Terminal site ceased in 1964 or 1965; the basis of Montrose’s alleged CERCLA liability is that it shipped chemicals to the site prior to that time, which chemicals were then formulated into chemical products by an independent company, and that the formulator’s disposal of chemical waste byproducts in turn caused or contributed to the contamination. According to the plaintiffs in the Levin Metals cases, the environmental contamination at the Parr-Richmond site was discovered by them no later than August 1982. After the lawsuits were filed, Parr-Richmond cross-complained against Montrose and others for contribution and indemnity. Although the Levin Metals cases were further complicated by Parr-Richmond’s efforts to avoid CERCLA liability and other related federal actions, for purposes of this appeal we need focus only on the lawsuits filed against Montrose for indemnity and contribution for allegedly contaminating the property in question in Contra Costa County during a period beginning in 1947, and continuing through the effective dates of Admiral’s policy periods. 3. Proceedings on Summary Judgment. Montrose tendered defense of these actions to its seven CGL insurers, including Admiral. In 1986, Montrose sued the carriers in a declaratory relief action, seeking a declaration that the insurers had a duty to both defend and indemnify Montrose in all five underlying actions. All the carriers except Admiral agreed to defend subject to a reservation of rights. In 1989, Admiral moved for summary judgment and summary adjudication of issues, urging the trial court to find (i) that it had no duty to defend or indemnify Montrose in the Levin Metals cases because the circumstances which trigger coverage, within the meaning of the coverage clauses and definitions in its policies, did not occur during the policy periods, and (ii) that it had no duty to defend or indemnify Montrose in the Stringfellow cases because the contamination alleged in those actions was an uninsurable loss-in-progress prior to the effective date of the first policy issued by Admiral (Oct. 13, 1982). The trial court granted summary judgment in favor of Admiral on each ground. First, with respect to the Levin Metals cases, the court held that coverage for third party claims of progressive property damage under a CGL policy is “triggered” when the damage is first discovered; in essence, an application of the “manifestation” or “manifestation of loss” rule we later adopted in Prudential-LMI, supra, 51 Cal.3d 674, for progressive losses in first party property insurance cases. The trial court reasoned there was no possibility of coverage under Admiral’s policies because the third party Levins Metal claimants (although not Montrose, the insured) allegedly discovered contamination at the Parr-Richmond site no later than August 1982, before the start of Admiral’s first policy term. Second, with respect to the Stringfellow cases, the trial court found that coverage was further barred under the “loss-in-progress” rule codified in sections 22 and 250. Those statutory provisions will be examined in greater detail below; for present purposes it will suffice to note the rule provides that insurance is a contract that indemnifies against a loss or losses arising from contingent or unknown events (§ 22), and that any such contingent or unknown event may be insured against subject to the limitations of the Insurance Code (§ 250). Relying on the PRP letter that Montrose received from the EPA in August 1982, informing Montrose it might be responsible for response and other cleanup costs at the Stringfellow site, the trial court concluded coverage was barred for all claims relating to the site because, prior to the commencement of Admiral’s policies issued to Montrose, Montrose knew its liability for property damage and/or bodily injury stemming from contamination at the site was “likely.” Montrose appealed, and the Court of Appeal reversed the summary judgment order. The appellate court rejected a “manifestation of loss” or “discovery” trigger of coverage analysis (as employed in the first party insurance context), finding it incompatible with the language of Admiral’s third party CGL policies. It held that, because the underlying Levin Metals actions allege that continuous or progressively deteriorating property damage “occurred” throughout the period Admiral’s policies were in effect, potential coverage under those policies was triggered, at least for purposes of the duty to defend. The court further held that the loss-in-progress rule did not bar coverage in the Stringfellow cases. It reasoned that Montrose’s potential liability to third parties for the progressive property damage alleged to have “occurred” throughout the period of Admiral’s policies was still “contingent,” and thus insurable, under section 250, even if damage as defined in the Admiral policies was inevitable, and notwithstanding Montrose’s earlier receipt of the PRP letter. The Court of Appeal remanded Admiral’s affirmative defense—that Montrose had concealed material facts prior to purchasing the CGL policies from Admiral—and further declined to address the insurer’s argument, not raised in the trial court, that coverage for progressive damage at the Stringfellow site is also barred under specific policy exclusions because Montrose “expected or intended” the progressive damage that occurred during Admiral’s policy periods. (§ 22.) We granted Admiral’s petition for review to consider the complex and important issue of when potential coverage is triggered under a CGL policy where the underlying third party claims involve continuous or progressively deteriorating damage or injury, and how the loss-in-progress rule applies to such policies. II Trigger of Coverage in Third Party Progressive Loss Cases As noted, Admiral moved for summary judgment in the trial court on grounds that it had no duty to defend or indemnify Montrose in the Levin Metals cases because the circumstances which trigger coverage, within the meaning of the coverage clauses in its policies, did not occur during the policy periods, and that it had no duty to defend or indemnify Montrose in the Stringfellow cases because the contamination alleged in those actions was an uninsurable loss-in-progress prior to the effective date of the first policy it issued to Montrose. Having convinced the trial court, but not the Court of Appeal, Admiral seeks to renew these claims. Admiral asserts in its brief on the merits that “the fact that the Stringfellow CERCLA action alleges continuing or progressive contamination does not establish there was an occurrence while Admiral’s policies were in effect.” Admiral submits that “all damage was caused by a single occurrence outside (i.e., prior to commencement of) Admiral’s policy period,” and urges that any determination that continuous or progressive damage or injury occurring during its ensuing policy periods can itself trigger coverage, “ignore[s] the policy language and confuse[s] the consequences of the occurrence with the occurrence itself, i.e., the event that ‘resulted’ in damage.” 1. Preliminary considerations: distinguishing third party liability insurance from first party property insurance. To properly analyze the trigger of coverage issues presented in this case, it is necessary to first clearly distinguish between third party liability insurance, the type of coverage here at issue, and coverage under a first party property insurance policy, such as the standardized homeowners policy in issue in Prudential-LMI, supra, 51 Cal.3d 674. As we observed in both Garvey, supra, 48 Cal.3d at page 399, footnote 2, and Prudential-LMI, supra, 51 Cal.3d at pages 698-699, a first party insurance policy provides coverage for loss or damage sustained directly by the insured (e.g., life, disability, health, fire, theft and casualty insurance). A third party liability policy, in contrast, provides coverage for liability of the insured to a “third party” (e.g., a CGL policy, a directors and officers liability policy, or an errors and omissions policy). In the usual first party policy, the insurer promises to pay money to the insured upon the happening of an event, the risk of which has been insured against. In the typical third party liability policy, the carrier assumes a contractual duty to pay judgments the insured becomes legally obligated to pay as damages because of bodily injury or property damage caused by the insured. (Garvey, supra, 48 Cal.3d at p. 407.) The difference in the nature of the risks insured against under first party property policies and third party liability policies is also reflected in the differing causation analyses that must be undertaken to determine coverage under each type of policy. (Garvey, supra, 48 Cal.3d at p. 406.) “ ‘Property insurance ... is an agreement, a contract, in which the insurer agrees to indemnify the insured in the event that the insured property suffers a covered loss. Coverage, in turn, is commonly provided by reference to causation, e.g., “loss caused by . . .” certain enumerated perils. [¶] The term “perils” in traditional property insurance parlance refers to fortuitous, active, physical forces such as lightning, wind, and explosion, which bring about the loss.’ ” (Ibid., quoting Bragg, Concurrent Causation and the Art of Policy Drafting: New Perils for Property Insurers (1985) 20 Forum 385, 386-387.) In contrast, “ 'the “cause” of loss in the context of a property insurance contract is totally different from that in a liability policy.'" (Garvey, supra, 48 Cal.3d at p. 406, italics in original.) “[T]he right to coverage in the third party liability insurance context draws on traditional tort concepts of fault, proximate cause and duty. This liability analysis differs substantially from the coverage analysis in the property insurance context, which draws on the relationship between perils that are either covered or excluded in the contract. In liability insurance, by insuring for personal liability, and agreeing to cover the insured for his own negligence, the insurer agrees to cover the insured for a broader spectrum of risks.'' (Id. at p. 407, italics added.) The parties’ expectations may also differ depending upon the type of coverage sought. First party property coverage is typically purchased in an amount sufficient to cover the insured’s maximum potential loss (e.g., fire insurance typically covers the value of the property insured). Hence, there is no reason for a first party insured to look to more than one policy in the event of loss (the policy in effect at the time of the fire). (See Garvey, supra, 48 Cal.3d at p. 406.) Third party liability coverage differs substantially. As the Court of Appeal below observed, “[a]t best, the insured makes an educated guess about its potential exposure to third parties. At worst, the insured’s best guess falls far short of the mark.” Yet another distinction between the two types of insurance coverage is that third party CGL policies do not impose, as a condition of coverage, a requirement that the damage or injury be discovered at any particular point in time. Instead, they provide coverage for injuries and damage caused by an “occurrence,” and typically define “occurrence” as an accident (or sometimes a “loss”), including a “continuous or repeated exposure to conditions,” that results in bodily injury or property damage during the policy period. The standardized CGL policy language (like the language in Admiral’s policies) will be reviewed in greater detail below. As will be seen, nothing about this language suggests a manifestation or discovery requirement as a prerequisite for triggering coverage. (See, e.g., Trizec Properties v. Biltmore Const. Co. (11th Cir. 1985) 767 F.2d 810, 813 [no requirement in standard CGL policy that damages “manifest” themselves during the policy period].) Another important difference between first and third party policies is that first party insurance policies require the insured to bring any action against the insurer within 12 months after “inception of the loss.” (Prudential-LMI, supra, 51 Cal.3d at pp. 682-687.) Before an action is filed under such a policy, there must be a dispute between the insured and insurer. Before there can be a dispute, the insured must (or reasonably should) know it has suffered a “loss.” (Id. at pp. 686-687.) By contrast, third party liability policies do not include a 12-month limitations period in which the insured must bring an action against the insurer (although the policies may contain express notification requirements). It is the damaged or injured third party who initiates the action against the insured. If coverage is ultimately established, it is the insurer that in turn must indemnify the insured for “all sums which the insured shall become legally obligated to pay.” Hence, there is no “inception of the loss” language in a standard CGL policy, and, as will become apparent, no corollary need to apply the definition of “inception of the loss” that this court articulated in Prudential-LMI, supra, 51 Cal.3d at pp. 682, 699. (Cf. § 2071 [standard form fire insurance policy].) Unfortunately, some courts have failed to draw these critical distinctions when discussing coverage issues under first and third party insurance policies. In the third party liability insurance context, some reported cases have muddied the waters by seemingly failing to distinguish between disputes arising between an insured and insurer, and actions among several CGL carriers that seek a judicial declaration allocating a loss already paid out to the insured under one or more such policies. In suits between an insured and an insurer to determine coverage, interpretation of the policy language and, in the case of ambiguous policy language, the expectations of the parties, will typically take precedence. The existence of excess or “secondary insurance” policies, “other insurance” clauses, or similar policy language decreeing the manner of apportionment of liability under multiple policies may also factor into the coverage analysis. In contrast, where two or more CGL carriers turn to the courts to allocate the cost of indemnity for a paid loss, different contractual and policy considerations may come into play in the effort to apportion such costs among the insurers. The task may require allocation of contribution amongst all insurers on the risk in proportion to their respective policies’ liability limits (such as deductibles and ceilings) or the time periods covered under each such policy. Reported cases whose analyses fail to take these distinctions into account, although purporting to clarify or settle an underlying “trigger of coverage” issue, may shed more darkness than light on the matter. The proper analysis and resolution of a trigger of coverage issue may also depend on whether the CGL policy in issue insures against liability to third parties for bodily injury, property damage, or both. As will be shown, the coverage clauses in Admiral’s policies do not distinguish between the nature of the underlying harm (bodily injury or property damage) that triggers the insured’s liability coverage. Accordingly, Montrose and Admiral appear to agree that under a plain reading of that unambiguous aspect of the policy language, whatever be the circumstances (or timing of the circumstances) that will potentially trigger liability coverage under the policies, coverage will apply uniformly under such circumstances whether the claims be for bodily injury, or property damage, alleged in the underlying third party lawsuits. Finally, the proper resolution of a trigger of coverage issue in any given case may turn on whether the court is addressing underlying facts involving a single event resulting in immediate injury (e.g., an explosion causing instantaneous bodily injuries and destruction of property), a single event resulting in delayed or progressively deteriorating injury (e.g., a chemical spill), or a continuing event (referred to in CGL policies as “continuous or repeated exposure to conditions”) resulting in single or multiple injuries (e.g., exposure to toxic wastes or asbestos over time). Significantly, in the present case we are dealing both with claims of continuous or progressively deteriorating bodily injury (the Newman v. Stringfellow lawsuit), and progressively deteriorating property damage (the Stringfellow and Levin Metals cases), all arising from continuous or repeated exposure to hazardous waste contamination over time, allegedly including the periods when Admiral’s policies were in effect. With these considerations in mind, we turn next to the express language of the contracts of insurance here in issue, looking first to the relevant principles of insurance policy interpretation that must govern our construction of the contested provisions. 2. Admiral’s policy language and the applicable rules of interpretation. Insurance policies are contracts and, therefore, are governed in the first instance by the rules of construction applicable to contracts. Under statutory rules of contract interpretation, the mutual intention of the parties at the time the contract is formed governs its interpretation. (Civ. Code, § 1636.) Such intent is to be inferred, if possible, solely from the written provisions of the contract. (Id., § 1639.) The “clear and explicit” meaning of these provisions, interpreted in their “ordinary and popular sense,” controls judicial interpretation unless “used by the parties in a technical sense, or unless a special meaning is given to them by usage.” (Id., §§ 1638, 1644.) If the meaning a layperson would ascribe to the language of a contract of insurance is clear and unambiguous, a court will apply that meaning. (See AIU Ins. Co. v. Superior Court (1990) 51 Cal.3d 807, 822 [274 Cal.Rptr. 820, 799 P.2d 1253] (AIU); Reserve Insurance Co. v. Pisciotta (1982) 30 Cal.3d 800, 807 [180 Cal.Rptr. 628, 640 P.2d 764]; Crane v. State Farm Fire & Cas. Co. (1971) 5 Cal.3d 112, 115 [95 Cal.Rptr. 513, 485 P.2d 1129, 48 A.L.R.3d 1089].) In contrast, “[i]f there is ambiguity . . . it is resolved by interpreting the ambiguous provisions in the sense the promisor (i.e., the insurer) believed the promisee understood them at the time of formation. (Civ. Code, § 1649.) If application of this rule does not eliminate the ambiguity, ambiguous language is construed against the party who caused the uncertainty to exist. (Id., § 1654.)” (AIU, supra, 51 Cal.3d at p. 822.) “This rule, as applied to a promise of coverage in an insurance policy, protects not the subjective beliefs of the insurer but, rather, ‘the objectively reasonable expectations of the insured.’ (AIU, supra, at p. 822.) Only if this rule does not resolve the ambiguity do we then resolve it against the insurer. (See AIU, supra, at p. 822.)” (Bank of the West v. Superior Court (1992) 2 Cal.4th 1254, 1265 [10 Cal.Rptr.2d 538, 833 P.2d 545]; see also Cooper Companies v. Transcontinental Ins. Co. (1995) 31 Cal.App.4th 1094, 1101-1102 [37 Cal.Rptr.2d 508].) We explained further in AIU, supra, 51 Cal.3d at page 822, that “[i]n the insurance context, we generally resolve ambiguities in favor of coverage. (See, e.g., State Farm Mut. Auto. Ins. Co. v. Jacober (1973) 10 Cal.3d 193, 197 [110 Cal.Rptr. 1, 514 P.2d 953]; Bareno v. Employers Life Ins. Co. (1972) 7 Cal.3d 875, 878 [103 Cal.Rptr. 865, 500 P.2d 889]; Continental Casualty Co. v. Phoenix Constr. Co. (1956) 46 Cal.2d 423, 437 [296 P.2d 801, 57 A.L.R.2d 914].) Similarly, we generally interpret the coverage clauses of insurance policies broadly, [in order to protect] the objectively reasonable expectations of the insured. (See, e.g., Garvey v. State Farm Fire & Casualty Co.[, supra,) 48 Cal.3d 395, 406; Reserve Insurance Co. v. Pisciotta, supra, 30 Cal.3d at p. 808.) These rules stem from the fact that the insurer typically drafts policy language, leaving the insured little or no meaningful opportunity or ability to bargain for modifications. (See, e.g., Garcia v. Truck Ins. Exchange (1984) 36 Cal.3d 426, 438 [204 Cal.Rptr. 435, 682 P.2d 1100]; Bareno, supra, 7 Cal.3d at p. 878.) Because the insurer writes the policy, it is held ‘responsible’ for ambiguous policy language, which is therefore construed in favor of coverage.” (Fn. omitted; see also Mehr et al., Principles of Insurance (8th ed. 1985) p. 137.) Is the language of Admiral’s contracts of insurance here in issue “clear and explicit,” and thus controlling (Civ. Code, §§ 1638, 1644)—or is it ambiguous, requiring us to interpret the coverage clauses broadly in order to protect the objectively reasonable expectations of Montrose, the insured? Some courts, including the Court of Appeal below, have concluded that the varying judicial constructions placed on the definition of occurrence in the standard form CGL policy themselves attest to the inherent ambiguity in that definition. (See California Union Ins. Co. v. Landmark Ins. Co. (1983) 145 Cal.App.3d 462, 472 [193 Cal.Rptr. 461].) One commentator has gone so far as to suggest that “[t]he word ‘occurrence’ itself is ambiguous because the injury process is not a definite, discrete event.” (Note, Developments in the Law—Toxic Waste Litigation (1986) 99 Harv. L.Rev. 1458, 1579.) Although any such ambiguity would ultimately have to be resolved in favor of the reasonable expectations of the insured (Bank of the West v. Superior Court, supra, 2 Cal.4th at p. 1265; AIU, supra, 51 Cal.3d at p. 822; Garvey, supra, 48 Cal.3d at p. 406), we find that the express language of Admiral’s policies of insurance, when read as a whole, unambiguously provides potential coverage for the continuous and progressively deteriorating bodily injury and property damage alleged to have occurred during Admiral’s policy periods. Turning to the express policy language, Admiral contracted with Montrose to “pay on behalf of the insured all sums which the insured shall become legally obligated to pay as damages because of . . . bodily injury, or .. . property damage to which this insurance applies, caused by an occurrence. . . .” (Italics added.) “[Pjroperty damage to which this insurance applies” is defined in Admiral’s policies as “(1) physical injury to or destruction of tangible property which occurs during the policy period, including the loss of use thereof at any time resulting thereform . . . .” (Italics added.) “Bodily injury” to which the insurance applies is defined as “bodily injury, sickness or disease sustained by any person which occurs during the policy period, including death at any time resulting therefrom.” (Italics added.) We find no ambiguity in this language; it clearly and explicitly provides that the occurrence of bodily injury or property damage during the policy period is the operative event that triggers coverage. Furthermore, “occurrence” is defined in Admiral’s policies as “an accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage neither expected nor intended from the standpoint of the insured.” (Italics added.) When read together with the aforementioned clauses defining covered bodily injury and property damage, this policy language unambiguously distinguishes between the causative event—an accident or “continuous and repeated exposure to conditions”— and the resulting “bodily injury or property damage.” It is the latter injury or damage that must “occur” during the policy period, and “which results” from the accident or “continuous and repeated exposure to conditions.” In this case, it is the third party litigants’ bodily injuries and property damage, which are alleged to have been continuous or progressively deteriorating throughout Admiral’s policy periods, and which allegedly resulted from the continuous and repeated exposure to toxic chemicals for which the insured, Montrose, is an allegedly responsible party, that triggers potential coverage under the policies in question. 3. Settled case law and the drafting history of the standardized CGL policy language confirm that coverage is triggered by damage or injury occurring during the policy period. Admiral contends that to read its CGL policies as providing that coverage is triggered when damage or injury occurs within the policy periods as a result of an “occurrence” is to “ignore[] the policy language and confuse[] the consequences of the occurrence with the occurrence itself, i.e., the event that ‘resulted’ in damage.” (Ante, at p. 663.) Admiral in essence urges that coverage under a CGL policy is established at the time the “occurrence” (i.e., the precipitating act or event) first gives rise to appreciable damage or injury, and that policies that commence after an “occurrence” and some consequent appreciable damage or injury cannot be on the risk for progressive damage or injury that occurs during such subsequent policy periods. The relevant cases and interpretative authorities which have construed the industry-standardized CGL policy language lend no support to Admiral’s position. California courts have long recognized that coverage in the context of a liability insurance policy is established at the time the complaining party was actually damaged. In Remmer v. Glens Falls Indem. Co. (1956) 140 Cal.App.2d 84 [295 P.2d 19, 57 A.L.R.2d 1379] (Remmer), the court was asked to interpret the definition of “occurrence” as that term was used in a CGL policy. The precise issue in Remmer was whether the act of defectively grading and filling a lot constituted the sole occurrence giving rise to coverage under the policy’s “one occurrence” provision, or whether subsequent injury (an alleged maintenance of a nuisance on the graded lot adjoining the third party claimants’ property) also triggered liability coverage under the policy. Relying on cases from California and other jurisdictions, the Remmer court formulated the following rule: “The general rule is that the time of the occurrence of an accident within the meaning of an indemnity policy is not the time the wrongful act was committed, but the time when the complaining party was actually damaged.” (Id. at p. 88.) The Remmer formulation, which distinguishes between a wrongful act and the injurious result of that act, and holds that the triggering of liability coverage under a CGL policy is established at the time the complaining third party was actually damaged, has been embraced by such noted experts as Appleman (7A Appleman, Insurance Law & Practice (1979 rev.) § 4501.03, p. 256) and Couch (11 Couch, Insurance (2d ed. 1982) § 44:8, p. 194.) It can be found in American Jurisprudence Second (43 Am.Jur.2d (1982 rev.) Insurance, § 243, p. 324), has been accepted by the courts of many other states, and has been cited by federal courts interpreting the law of still other states. (See Annot., Event Triggering Liability Insurance Coverage as Occurring Within Period of Time Covered by Liability Insurance Policy Where Injury or Damage is Delayed—Modem Cases (1993) 14 A.L.R.5th 695, § 6 and cases cited therein.) Indeed, as stated by the Idaho Supreme Court, “This rule is followed in every jurisdiction that has considered the issue except Louisiana.” (Millers Mut. Fire Ins., etc. v. Ed Bailey, Inc. (1982) 103 Idaho 377 [647 P.2d 1249, 1251].) Although the Court of Appeal concluded that potential coverage was triggered under Admiral’s policies by damage or injury occurring during the policy periods, the court did not trace this long-standing interpretation of how liability coverage is triggered under a CGL policy to the rule formulated in Remmer. Instead, the court independently looked to the drafting history of the standard CGL policy language for support for its conclusion that no reasonable construction, other than that described above, could be placed on the insurance industry’s use of such policy language. Admiral contends that evidence of the drafting history of the standardized CGL policy provisions and definitions, and available interpretative materials, are irrelevant and should not have been considered by the Court of Appeal in construing the language of its CGL policies issued to Montrose. Most courts and commentators have recognized, however, that the presence of standardized industry provisions and the availability of interpretative literature are of considerable assistance in determining coverage issues. (See, e.g., Maryland Casualty Co. v. Reeder (1990) 221 Cal.App.3d 961, 968 [270 Cal.Rptr. 719].) Such interpretative materials have been widely cited and relied on in the relevant case law and authorities construing standardized insurance policy language. As one court has suggested, “where two insurers dispute the meaning of identical standard form policy language—the meaning attached to the provisions by the insurance industry is, at minimum, relevant.” (Fireman’s Fund Ins. Co. v. Aetna Casualty & Surety Co. (1990) 223 Cal.App.3d 1621, 1629 [273 Cal.Rptr. 431].) On the other hand, as another court has observed, “[w]hile insurance industry publications are helpful in understanding the scope of coverage insurers are trying to delineate in any given policy, they are by no means dispositive.” (American Star Ins. Co. v. Insurance Co. of the West (1991) 232 Cal.App.3d 1320, 1330 [284 Cal.Rptr. 45], italics in original.) In this case, we find the drafting history relevant in evaluating Admiral’s argument that, from a public policy standpoint, the insurance industry will be harmed by the adoption of a continuous injury trigger that the industry assertedly never anticipated would be applied to these policies. Standard CGL policy language was revised by insurance industry drafters in several important respects starting in 1966. Prior to that year, third party general liability policies covered bodily injuries and damages caused by “accidents.” (American Home Prod. v. Liberty Mut. Ins. Co. (S.D.N.Y. 1983) 565 F.Supp. 1485, 1501, affd. as mod. (2d Cir. 1984) 748 F.2d 760.) In 1966, the National Bureau of Casualty Underwriters and the Mutual Insurance Rating Board, the predecessor organizations to the Insurance Services Office (ISO), changed the standard form policy from an “accident-based” to an “occurrence-based” format. (Ibid., see also New Castle County v. Hartford Acc. and Indem. Co., supra, 933 F.2d at p. 1181; Pasich, Insurance Coverage for Environmental Claims (Jan. 1989) L.A.Law., p. 23, fn. 12; 3 Cal. Insurance Law & Practice, supra, Property and Liability Insurance, § 49.04, at p. 49-10.) It is reasonable to infer that the insurance industry knew precisely what the change entailed. In comments addressing the question of coverage under the new CGL policies for progressive personal injury or property damage resulting over an extended period of time, one of the drafters explained that “[i]n some exposure type cases involving cumulative injuries it is possible that more than one policy will afford coverage.” (Elliott, The New Comprehensive General Liability Policy, in Liability Insurance Disputes (PLI, Schreiber edit. 1968), pp. 12-3 to 12-5; see also Obrist, The New Comprehensive General Liability Insurance Policy—A Coverage Analysis (Defense Research Inst. Monograph 1966) p. 6 [same]; Nachman, The New Policy Provisions for General Liability Insurance (1965) 18 CPU Annals 197, 200 [same].) By 1966, the insurance industry was also demonstrating its awareness of potential coverage issues involving continuous or progressively deteriorating bodily injury and property damage. Richard H. Elliott, then secretary of the National Bureau of Casualty Underwriters, wrote the following regarding the adoption of the occurrence-based CGL policy, which standard form policy retained the term “accident” within its definition of occurrence: “The new policy will afford coverage on an ‘occurrence’ basis. ‘Occurrence’ is defined as ‘an accident, including injurious exposure to conditions, which results, during the policy period, in bodily injury and property damage neither expected nor intended from the standpoint of the insured.’ Note that this definition includes the word ‘accident.’ This has been done in order to clarify the intent with respect to time of coverage and application of policy limits, particularly in situations involving a related series of events attributable to the same factor. Under such circumstances only one accident or occurrence is intended as far as the application of policy limits is concerned. For example, the liability of a contractor arising out of the derailment of ten or twelve freight cars as a result of a collision with a piece of his equipment is intended to be subject to one application of the occurrence limit of the policy. Retention of the word ‘accident’ is limiting in this sense and no other.” (Elliott, The New Comprehensive General Liability Policy, in Liability Insurance Disputes, supra, at p. 12-5, italics added.) Secretary Elliot’s comments leave little doubt that the definition of “occurrence” in the newly drafted standard form CGL policy was intended to provide coverage when damage or injury resulting from an accident or “injurious exposure to conditions” occurs during the policy period. The term “accident” was left in the definition of occurrence for the purpose of circumscribing the policy limits applicable to each occurrence. The drafters did not intend to require that an “accident” in the literal sense, e.g., a sudden precipitating event, occur during the policy period in order to trigger potential coverage for ensuing damage or injury. “The reference to ‘injurious exposure to conditions [resulting in] . . . bodily injury [or property damage]’ eliminates any requirement that the injury result from a sudden event. Although it is most common that an injury takes place simultaneously with the exposure, there are many instances of injuries taking place over an extended period of time before they become evident [for example, the slow ingestion of foreign substances or the inhalation of noxious fumes]. In these and similar cases, the definition of ‘occurrence’ identifies the time of loss for purposes of applying coverage—the injury must take place during the policy period.” (3 Cal. Insurance Law & Practice, supra, Property and Liability Insurance, § 49.12, at pp. 49-20-49-21, fns. omitted.) As these materials demonstrate, the drafters of the standard occurrence-based CGL policy, and the experts advising the industry regarding its interpretation when formulated in 1966, contemplated that the policy would afford liability coverage for all property damage or injury occurring during the policy period resulting from an accident, or from injurious exposure to conditions. Nothing in the policy language purports to exclude damage or injury of a continuous or progressively deteriorating nature, as long as it occurs during the policy period. Nor is there any basis for inferring that an insured’s understanding and reasonable expectations regarding the scope of coverage for damage or injury occasioned during the effective period of an occurrence-based CGL policy would have been otherwise. We have shown how the clear and explicit language of Admiral’s policies supports the conclusion that potential coverage is triggered by the occurrence of bodily injury or property damage during the policy periods, as a result of an accident or the “continuous or repeated exposure to conditions.” We next review the relevant reported decisions, from California, the federal courts, and other state courts, that have sought to construe the industry-standardized CGL policy language to determine how continuous injury or damage triggers potential coverage under such policies. As will be seen, the weight of authority, consistent with our own interpretation of Admiral’s express policy language, is that bodily injury and property damage that is continuous or progressively deteriorating throughout successive CGL policy periods, is potentially covered by all policies in effect during those periods. 4. Survey of case law and authorities discussing triggering of coverage under CGL policies where injury or damage is continuous over successive policy periods. The issue of trigger of coverage in continuous injury or damage cases has been explored by many courts. (See Annot. (1993) 14 A.L.R. 5th 695.) Courts have recognized several “triggers” as a means of identifying the nature and timing of damage or injury that will give rise to liability coverage under an occurrence-based CGL policy. The courts have generally viewed the timing of damage or injury under occurrence-based CGL policies in four ways: at the date of exposure to the injurious or damage-causing event or conditions; at the date of the first occurrence of “injury in fact”; at the date of manifestation or discovery of the damage or injury; and over the continuous period from exposure through manifestation and beyond, where the damage or injury is ongoing, continuous, or progressively deteriorating throughout a policy period or successive policy periods. At this point it will be helpful to briefly outline the various trigger theories formulated by the courts. The exposure (or continuous exposure) trigger. This trigger of coverage theory, first applied in cases involving asbestos-related bodily injuries, focuses on the date on which the injury-producing agent first contacts the body. The exposure theory apportions the cost of indemnity among those insurers whose policies were in effect from that point in time onward. In effect, under this theory, damage or injury is deemed to commence from the first contact of the injury-producing agent with the injured party. The leading case espousing this trigger of coverage analysis is the Sixth Circuit’s decision in Ins. Co. North America v. Forty-Eight Insulations (6th Cir. 1980) 633 F.2d 1212, clarified 657 F.2d 814, cert. den. (1981) 454 U.S. 1109 [70 L.Ed.2d 650, 102 S.Ct. 686] (Forty-Eight Insulations). The court in FortyEight Insulations found that the covered occurrence of injury commenced with the immediate contact of an asbestos fiber with the lungs, even though the progressive disease typically took some 20 years to develop. (633 F.2d at pp. 1215, 1218-1220.) The court reasoned that because of the cumulative and progressively deteriorating nature of the disease, it had to be distinguished from the ordinary accident or injury situation, and further, that because the injury is a continuing one, the insurers who furnished comprehensive general liability policies would expect the scope of their policies’ coverage to parallel the applicable theory of liability. The manifestation (or manifestation of loss) trigger. This trigger of coverage, which, as already explained, was adopted by this court in the first party property insurance context in Prudential-LMI, supra, 51 Cal.3d 674, holds the insurer insuring the property at the time appreciable property damage first becomes manifest solely responsible for indemnification to the insured. For purposes of applying the rule, the time at which the property damage becomes manifest (also the point of “inception of the loss”) is “that point in time when appreciable damage occurs and is or should be known to the insured, such that a reasonable insured would be aware that his notification duty under the policy had been triggered.” (Id. at p. 699.) In Prudential-LMI, supra, 51 Cal.3d 674, we identified three reasons supporting the application of the manifestation theory in the first party property insurance context. First, application of that trigger of coverage meets the reasonable expectations of the insureds who, in seeking to insure against perils to their property, would normally look to their present carrier for coverage. (Id. at p. 699.) Second, “the underwriting practices of the insurer can be made predictable because the insurer is not liable for a loss once its contract with the insured ends unless the manifestation of loss occurred during its contract term.” (Ibid.) Third, since the insured is required under a standard first party property insurance policy to file suit against the insurer within 12 months after “inception of the loss,” and since inception of the loss is the date on which appreciable damage occurs and is or should be known to the insured, the definition of manifestation of loss and inception of the loss must be one and the same, that is to say, “that point in time when appreciable damage occurs and is or should be known to the insured, such that a reasonable insured would be aware that his notification duty under the policy had been triggered.” (Prudential-LMI, supra, 51 Cal.3d at pp. 686-687, 699.) These policy reasons led us to conclude, “in conformity with the loss-in-progress rule, [that first party property] insurers whose policy terms commence after initial manifestation of the loss are not responsible for any potential claim . . . .” (Id. at p. 699.) The continuous injury (or multiple) trigger. Under this trigger of coverage theory, bodily injuries and property damage that are continuous or progressively deteriorating throughout successive policy periods are covered by all policies in effect during those periods. The timing of the accident, event, or conditions causing the bodily injury or property damage, e.g., an insured’s negligent act, is largely immaterial to establishing coverage; it can occur before or during the policy period. Neither is the date of discovery of the damage or injury controlling: it might or might not be contemporaneous with the causal event. It is only the effect—the occurrence of bodily injury or property damage during the policy period, resulting from a sudden accidental event or the “continuous or repeated exposure to conditions”—that triggers potential liability coverage. The appellate cases in which this trigger of coverage was developed are discussed in greater detail below. The injury-in-fact trigger. Under an injury-in-fact trigger, coverage is first triggered at that point in time at which an actual injury can be shown, retrospectively, to have been first suffered. This rationale places the injury-in-fact somewhere between the exposure, which is considered the initiating cause of the disease or bodily injury, and the manifestation of symptoms, which, logically, is only possible when an injury already exists. (See Abex Corp. v. Maryland Cas. Co. (D.C. Cir. 1986) 790 F.2d 119 [252 App.D.C. 297] [asbestos]; American Home Products Corp. v. Liberty Mut. Ins. (2d Cir. 1984) 748 F.2d 760 [pharmaceuticals].) In the context of continuous or progressively deteriorating injuries, the injury-in-fact trigger, like the continuous injury trigger, affords coverage for continuing or progressive injuries occurring during successive policy periods subsequent to the established date of the initial injury-in-fact. However, the injury-in-fact trigger, unlike the exposure trigger, when applied in asbestos cases excludes from coverage the period from initial exposure to the date on which the injury-in-fact was first suffered. As already indicated, in the case before us, Montrose urges our adoption of a continuous injury trigger of coverage. Admiral in turn, in its briefs, urges us to apply a manifestation trigger of coverage. At oral argument, however, counsel for Admiral appeared to deviate from this position, arguing instead that an injury-in-fact trigger, and not a manifestation trigger, should be applied. We shall give Admiral the benefit of the doubt and consider which, if any, of the recognized trigger of coverage theories should be applied here. The precise question, of course, is what result follows under the language of the policies of insurance to which the parties agreed, including the standardized definitions that were incorporated into those policies. As will be seen, most courts that have analyzed the issue have found the continuous injury trigger of coverage applicable to the standard occurrence-based CGL policy. One of the first cases to apply a continuing injury theory of loss allocation in the context of progressive property damage was Gruol Construction Co. v. Insurance Co. of North America (1974) 11 Wn.App. 632 [524 P.2d 427] (Gruol). In that case, a contractor prevailed in an action against his insurer who had failed to defend him under his general liability policy in a third party construction defect suit for recovery of dry rot damage to a building. The contractor’s improper piling of dirt against the building had caused the dry rot. The court held that the injury was a continuous process which began at the time of the negligent construction and continued through the manifestation of the dry rot damage, “ ‘even though there [was] a lapse of time between the initial negligent act and the occurrence of the ultimate damage (Id. at p. 636 [524 P.2d at p. 430].) Thus the holding of Gruol was that, when warranted by the facts, property damage should be deemed to occur over the entire process of the continuing injury. An insurer would become liable at any point in the process for the entire loss up to the policy limits, even though the continuing injury or progressively deteriorating damage may extend over several policy periods. The first reported California case to discuss the triggering of potential coverage under third party liability insurance policies, where continuous or progressively deteriorating property damage was involved, was California Union Ins. Co. v. Landmark Ins. Co., supra, 145 Cal.App.3d 462 (California Union). That case involved a gradual leak of water from a swimming pool which caused damage to adjoining property. The parties stipulated that the pool began to leak in June 1979, and that a crack in the pool was the sole cause of the ensuing property damage. Damage to the adjoining property occurred between July 1979 and November 1980. Landmark Insurance Company (Landmark) was on the risk from July 1978 to July 1980. California Union Insurance Company (Cal Union) provided liability coverage from July 1980 to July 1981. (Id. at pp. 467-469.) The source of the leakage damage in California Union was discovered during an inspection of the pool in October 1980, at a point in time following expiration of the Landmark policy and during the term of the successive Cal Union policy. At trial, the two carriers contested liability for the damage that occurred between October 1980 (discovery of the leak) and November 1980 (repair of the source of the damage). Landmark had undertaken repairs prior to the expiration of its policy in July 1980, but apparently repaired only the damage to the slopes of the adjoining property, and not the as-yet undiscovered source of the damage: the leaking pool. Landmark contended that the postdiscovery damage (that which occurred after October 1980) constituted a separate occurrence within the definition of that term in the Cal Union policy, and was therefore Cal Union’s sole responsibility. Cal Union in turn argued the damage was a continuation of a single occurrence that began during the period of coverage provided by the Landmark policies, and was thus the sole responsibility of Landmark. (California Union, supra, 145 Cal.App.3d at p. 468.) The trial court held that each manifestation of damage should be treated as a separate occurrence under the policies, rejecting Cal Union’s position that separate incidents of manifestation of damage which are attributable to the same underlying cause are merely manifestations of the same continuous “occurrence” of damage. (California Union, supra, 145 Cal.App.3d at p. 469.) The Court of Appeal reversed, concluding that the trial court’s ruling contravened the express language of each insurer’s policies. (Ibid.) On appeal, both insurers in California Union readily acknowledged that under the rule of Remmer, supra, 140 Cal.App.2d 84 (ante, at pp. 669-670), a coverable “occurrence” arose under their policy language at the point at which the complaining party was actually damaged, not the time at which the initial damage-causing act or conditions transpired. (California Union, supra, 145 Cal.App.3d at p. 470.) The California Union court agreed, pointing out that the precise facts of Remmer were distinguishable from those in the case before it. Observing that the dangerous condition in Remmer (a defectively graded lot) had failed to manifest any damage for a period of five years, the California Union court noted that in the case before it the leaking pool was a “continuous active force at work” during the eighteen months between the time of the “wrongful act” (the crack in the pool that first gave rise to the water damage to the adjoining property) and the manifestation of the actual loss. (Id. at p. 473.) Focusing on the identical “one occurrence” language in Cal Union’s and Landmark’s CGL policies (“ ‘all . . . property damage arising out of continuous or repeated exposure to substantially the same general conditions shall be considered as arising out of one occurrence’ ”), the California Union court concluded that, given the continuing and progressively deteriorating nature of the pool leakage damage, the trial court’s determination that each manifestation of damage was a separate occurrence conflicted with the “one occurrence” policy language in each insurer’s policies. (Id. at p. 469.) The California Union court next surveyed several California appellate decisions which, up to that time, had attempted to set, for definitional purposes, the timing of occurrences of damage or injury transpiri