- 标准号：ASTM D7048-2004(2010)
- 发布日期：2004
- 英文题名：Standard Guide for Applying Statistical Methods for Assessment and Corrective Action Environmental Monitoring Programs
- 英文主题词：assessment monitoring ; confidence limit ; corrective action ; environmental monitoring ; prediction limit ; quantification limit ; statistics ; Corrective action ; Compliance ; Environmental monitoring ; Soil
- 标准状态：现行
- 发布单位：US-ASTM
- 国际标准分类号：13.020.10 (Environmental management)
- 载体形态：17P.;A4
- 中国标准分类号：Z04
- 国别：美国材料与试验协会
The principal use of this standard is in assessment, compliance and corrective action environmental monitoring programs (for example, for any facility that could potentially contaminate ground water). The significance of the guidance is that it presents a statistical method that allows comparison of ground-water data to regulatory and/or health based limits.
Of course, there is considerable USEPA support for statistical methods applied to detection, assessment and corrective action monitoring programs that can be applied to environmental investigations. For example, the 90 % upper confidence limit (UCL) of the mean is used in SW846 (Chapter 9) for determining if a waste is hazardous. If the UCL is less than the criterion for a particular hazardous waste code, then the waste is not a hazardous waste even if certain individual measurements exceed the criterion. Similarly, in the USEPA Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities Addendum to the Interim Final Guidance (1992) (2), confidence intervals for the mean and various upper percentiles of the distribution are advocated for assessment and corrective action. Interestingly, both the 1989 and 1992 USEPA guidance documents (2, 3) suggest use of the lower 95 % confidence limit (LCL) as a tool for determining whether a criterion has been exceeded in assessment monitoring. The latest USEPA guidance in this area (that is, the draft USEPA Unified Statistical Guidance) calls for use of the LCL in assessment monitoring and the UCL in corrective action. In this way, corrective action is only triggered if there is a high degree of confidence that the true concentration has exceeded the criterion or standard, whereas corrective action continues until there is a high degree of confidence that the true concentration is below the criterion or standard. This is the general approach adopted in this guide, as well.
There are several reasons why statistical methods are essential in assessment and corrective action monitoring programs. First, a single measurement indicates very little about the true concentration in the sampling location of interest, and with only one sample there is no way of knowing if the measured concentration is a typical or an extreme value. The objective is to compare the true concentration (or some interval that contains it) to the relevant criterion or standard. Second, in many cases the constituents of interest are naturally occurring (for example, metals) and the naturally existing concentrations may exceed the relevant criteria. In this case, the relevant comparison is to background (for example, off-site soil or upgradient ground water) and not to a fixed criterion. As such, background data must be statistically characterized to obtain a statistical estimate of an upper bound for the naturally occurring concentrations so that it can be confidently determined if onsite concentrations are above background levels. Third, there is often a need to compare numerous potential constituents of concern to criteria or background, at numerous sampling locations. By chance alone there will be exceedances as the number of comparisons becomes large. The statistical approach to this problem can insure that false positive results are minimized.
Statistical methods for detection monitoring have been well studied in recent years (see Gibbons, 1994a, 1996, USEPA 1992 (2, 4, 5) and Practice D6312, formerly PS 64-96 authored by Gibbons, Brown and Cameron, 1996). Although equally important, statistical methods for assessment monitoring, Phase I and II investigations, on-going monitoring and corrective action monitoring have received less attention, (Gibbons and Coleman, 2001) (6).
The guide is summarized in Fig. 1, which provides a f......