4.1 Use—The standard is intended for use on a voluntary basis by an estimator of costs and liabilities for environmental matters. The user may elect to apply this standard for any or all uses outlined in the Purpose. Application of this standard for one use does not compel application of the standard for all or any other use.

4.2 Principles—The following principles are an integral part of this standard and should be used to resolve ambiguity or dispute regarding the interpretation of estimated costs and liabilities for environmental matters.

4.2.1 Framing the Estimate—It is important to understand and document/disclose the framework in which the estimate is being made, including identification of the requestor, estimator and relevant qualifications, purpose of the estimate, audience/user of the estimate, limitations, assumptions, and a description of what constitutes a reliable estimate.

4.2.2 Caution When Repurposing Estimates—The estimator should exercise care when repurposing an estimate generated for one objective and audience. For example, an estimator may use the expected value approach on a given cost and liability, and find that the “financial assurance estimate” uses unique financial assumptions (inflation, discount rate, time horizon) specified by a state regulator, while a “project controls” or “reserve” forecast – for the very same cost and liability -- will use differing financial factors.

4.2.3 Uncertainty Not Eliminated—Even though an estimate of costs and liabilities for environmental matters is prepared in accordance with this standard, uncertainty remains with regard to, among other things, the resolution of contractual, technological, regulatory, legislative, and judicial issues, which could affect the costs and liabilities. However, inherent uncertainty in estimates should not prevent an estimate from being made.

4.2.4 Periodic Review of Assumptions and Estimates—Assumptions underlying estimates should be reviewed, documented and periodically analyzed for the purpose of incorporating new information. There is a preference for current information over historical assumptions if the current information is comprehensive and comparable. Subsequent improvements in estimates should be made as more information becomes available, or as recognition benchmarks or obligating events occur. For example, for remediation of an individual site, such assumptions include changes to the conceptual site model; contaminant concentration data found in soil, groundwater, air and sediments; the selection of different remedial technologies; the indication of a preferred alternative by the governing agency; the weighting of alternatives; the probability of failure of a remedial technology to achieve the desired outcome in the time anticipated; the probability of accelerated or delayed enforcement; the probability of a compressed remedial construction timetable; the explicit or implied value of impacted drinking water, wetlands, and other natural resources; changes to the default values of fines and penalties and their associated tax consequences; and the ability to pay of PRPs or other counterparties. Changes in available information such as contaminant data, market prices, regulatory requirements, precedential court findings, technology, counterparty ability to pay, dutyholder ability to pay, property use, inflation and discount rates, or other issues may affect the basis for the estimates, therefore necessitating revisions.9

4.2.5 Comparison with Subsequent Estimates—Subsequent estimates based on additional information should not be construed as indicating the prior estimates of costs and liabilities for environmental matters were unreasonable at the time they were made. Estimates should be evaluated on the reasonableness of analyses and judgments made at the time and under the circumstances in which they were made. Subsequent improved estimates should not be considered valid standards on which to measure the reasonableness of a prior estimate based on hindsight, new information, use of developing analytical techniques, or other factors. However, information on trends in estimates over time may be of value to a user of the cost and liability estimates. Any comparison should recognize the reasons the estimates were performed, whether they were accomplished under the standard and any differences in technique in the application of the standard.

4.2.6 Not Exhaustive—Estimation of costs and liabilities for environmental matters does not necessarily require an exhaustive evaluation of all possible outcomes. A point exists at which the cost of obtaining information or the time required to gather it outweighs improvement in the quality of the estimate.

4.2.7 Assessment of Risk—The actual or potential risk to human health and the environment should be considered in assessing environmental matters. The degree of risk should be a factor in developing the cost and liability estimates associated with those matters.

4.2.8 Estimator Selection—An appropriate estimator or group of estimators will consist of those individuals or groups who possess sufficient knowledge, training, and experience to develop appropriate estimates for the costs and liabilities being estimated. It is the responsibility of the entity sponsoring the cost and liability estimates to select an estimator with the appropriate level of knowledge, training, and experience for the parts of the estimation effort for which that estimator is responsible. The estimator should be free of conflicts of interest to provide an objective and reliable estimate.

1.1 Purpose—The purpose of this document is to provide a standard guide for good commercial and customary practice in estimating costs and liabilities for environmental matters.2 Many possible uses for estimates of costs and liabilities for environmental matters exist, including but not limited to business decision making and portfolio optimization, due diligence and communications involving acquisitions and divestitures, regulatory requirements, third-party lawsuits, insurance premium calculation and claim settlement, change of property use, revitalization, compliance planning, construction and project control, analysis of remedial alternatives, budgeting, strategic planning, audit defense, financing, and investment analysis by shareholders. The use of estimated costs and liabilities developed in accordance with this standard may be subject to other standards applicable to the matter involved. For example, it is not intended to supersede accounting and actuarial standards. This standard does not address the establishment of reserves or disclosure requirements.

1.2 Objectives—The objective of this standard is to provide guidance on approaches for estimating costs and liabilities for environmental matters.

1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.