ASTM D7048-04
(Guide)Standard Guide for Applying Statistical Methods for Assessment and Corrective Action Environmental Monitoring Programs
Standard Guide for Applying Statistical Methods for Assessment and Corrective Action Environmental Monitoring Programs
SCOPE
1.1 The scope and purpose of this guidance is to present a variety of statistical approaches for assessment, compliance and corrective action environmental monitoring programs. Although the methods provided here are appropriate and often optimal for many environmental monitoring problems, they do not preclude use of other statistical approaches that may be equally or even more useful for certain site-specific applications.
1.2 In the following sections, complete details of select statistical procedures used in assessment and corrective action programs for environmental monitoring (soil, ground water, air, surface water, and waste streams) are presented.
1.3 The statistical methodology described in the following sections should be used as guidance. Other methods may also be appropriate based on site-specific conditions or for monitoring situations or media that are not presented in this document.
1.4 This practice offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education, experience and professional judgements. Not all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged without consideration of a project's many unique aspects. The word Standard in the title of this document only means that the document has been approved through the ASTM consensus process.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.
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Designation:D7048–04
Standard Guide for
Applying Statistical Methods for Assessment and Corrective
Action Environmental Monitoring Programs
This standard is issued under the fixed designation D7048; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 The scope and purpose of this guidance is to present a 2.1 ASTM Standards:
variety of statistical approaches for assessment, compliance D5092 PracticeforDesignandInstallationofGroundWater
and corrective action environmental monitoring programs. Monitoring Wells
Although the methods provided here are appropriate and often D5792 Practice for Generation of Environmental Data Re-
optimalformanyenvironmentalmonitoringproblems,theydo lated to Waste Management Activities: Development of
not preclude use of other statistical approaches that may be Data Quality Objectives
equally or even more useful for certain site-specific applica- D6250 Practice for Derivation of Decision Point and Con-
tions. fidenceLimitforStatisticalTestingofMeanConcentration
1.2 In the following sections, complete details of select in Waste Management Decisions
statistical procedures used in assessment and corrective action D6312 Guide for Developing Appropriate Statistical Ap-
programs for environmental monitoring (soil, ground water, proaches for Ground-Water Detection Monitoring Pro-
air, surface water, and waste streams) are presented. grams
1.3 The statistical methodology described in the following
3. Terminology
sections should be used as guidance. Other methods may also
be appropriate based on site-specific conditions or for moni- 3.1 Definitions:
3.1.1 assessment monitoring—investigative monitoring that
toring situations or media that are not presented in this
document. is initiated after the presence of a contaminant has been
detected in ground water above a relevant criterion at one or
1.4 This practice offers an organized collection of informa-
morelocations.Theobjectiveoftheprogramistodetermineif
tion or a series of options and does not recommend a specific
course of action. This document cannot replace education, there is a statistical exceedance of a standard or criteria at a
Potential Area of Concern (PAOC) or at the ground water
experienceandprofessionaljudgements.Notallaspectsofthis
practice may be applicable in all circumstances. This ASTM discharging to surface water interface, and/or to quantify the
rate and extent of migration of constituents detected in ground
standard is not intended to represent or replace the standard of
care by which the adequacy of a given professional service water above applicable criteria.
3.1.2 compliance monitoring—as specified under 40 CFR
must be judged without consideration of a project’s many
uniqueaspects.ThewordStandardinthetitleofthisdocument 264.99, compliance monitoring is instituted when hazardous
constituents have been detected above a relevant criterion at
only means that the document has been approved through the
ASTM consensus process. the compliance point during RCRA detection monitoring.
Ground-water samples are collected at the compliance point,
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the facilitypropertyboundary,andupgradientmonitoringwellsfor
analysis of hazardous constituents to determine if they are
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- leaving the regulated unit at statistically significant concentra-
tions above background.
bility of regulatory requirements prior to use.
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
and is the direct responsibility of Subcommittee D18.21 on Ground Water and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Vadose Zone Investigations. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved May 1, 2004. Published June 2004. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D7048-04. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7048–04
3.1.3 corrective action monitoring—under RCRA, correc- 3.1.13 nonparametric prediction limit—the largest (or sec-
tive action monitoring is instituted when hazardous constitu- ond largest) of n background samples. The confidence level
associatedwiththenonparametricpredictionlimitisafunction
ents from a RCRA regulated unit have been detected at
of n, m and k.
statistically significant concentrations between the compliance
point and the downgradient facility property boundary as 3.1.14 normal distribution—a frequency distribution whose
plot is a continuous, infinite, bell-shaped curve that is sym-
specified under 40 CFR 264.100. Corrective action monitoring
metrical about its arithmetic mean, mode and median (which
is conducted throughout a corrective action program that is
are numerically equivalent). The normal distribution has two
implemented to address ground-water contamination. At non-
parameters, the mean and variance.
RCRA sites, corrective action monitoring is conducted
3.1.15 outlier—a measurement that is statistically inconsis-
throughout the active period of corrective action to determine
tent with the distribution of other measurements from which it
the progress of remediation and to identify statistically signifi-
was drawn.
cant trends in ground-water contaminant concentrations.
3.1.16 parametric—a term referring to a statistical tech-
3.1.4 detection limit, DL—the true concentration at which
nique in which the distribution of the constituent in the
there is a specified level of confidence (for example, 99%
population is assumed to be known.
confidence) that the true concentration is greater than zero.
3.1.17 quantification limit, QL—a lower limit on the con-
3.1.5 detection monitoring—a program of monitoring for
centration at which quantitative determinations of an analyte’s
the express purpose of determining whether or not there has
concentration in the sample can be reliably made during
beenareleaseofacontaminanttogroundwater.UnderRCRA,
routine laboratory operating conditions. The QL is typically
Detection Monitoring involves collection of ground-water
described quantitatively as the true concentration at which the
samples from compliance point and upgradient monitoring
signal to noise ratio of measured concentration or instrument
wells on a semi-annual basis for analysis of hazardous con-
response is 10:1. The signal to noise ratio is often determined
stituentsofconcern,asspecifiedunder40CFR264.98.Results
by a percent relative standard deviation of 10%.
are evaluated to determine if there is a statistically significant
3.1.18 potential area of concern—areas with a documented
exceedance of the ground-water protection criterion and/or
release or likely presence of a hazardous substance that could
background.At non-RCRAsites, monitoring is conducted in a
pose an unacceptable risk to human health or the environment.
similar manner and results are compared to criteria to deter-
3.1.19 phase I environmental site assessment—non-
mine if there is a statistically significant exceedance.
intrusive investigation that identifies PAOCs which may re-
3.1.6 direct push sampling—ground-water sampling con-
quire further investigation in subsequent phases of work.
ductedwithadevicethatistemporarilypushedintotheground
3.1.20 phase II environmental site assessment, ESI—
with a hydraulic system or with a hammer.After ground-water
intrusive survey to confirm or deny existence of a release into
sample collection, the device is removed from the ground.
the environment at a PAOC at levels which may adversely
Examples include Geoprobet, Hydropuncht direct push, and
impact public health or the environment.
environmental soil probe.
3.1.21 upperconfidencelimit,UCL—anupperlimitthathas
a specified probability (for example, 95%) of including the
3.1.7 false negative rate—the rate at which the statistical
true concentration (or other parameter). Taken together with
procedure does not indicate contamination when contamina-
the lower confidence limit, the UCL forms a confidence
tion is present.
intervalthatwillincludethetrueconcentrationwithconfidence
3.1.8 false positive rate—the rate at which the statistical
level that accounts for both tail areas.
procedure indates contamination when contamination is not
3.1.22 upperpredictionlimit,UPL—astatisticalestimateof
present.
the maximum concentration that will not be exceeded by the
3.1.9 lognormal distribution—a frequency distribution
next series of k measurements from that distribution, or the
whose logarithm follows a normal distribution.
meanofmnewmeasurementsforeachofksamplinglocations,
3.1.10 lowerconfidencelimit,LCL—alowerlimitthathasa
with specified level of confidence (for example, 95%) based
specified probability (for example, 95%) of including the true
on a sample of n background measurements.
concentration (or other parameter). Taken together with the
3.2 Symbols:
upper confidence limit, forms a confidence interval that will
µ=the true population mean of a constituent
include the true concentration with confidence level that
–
x =the sample-based mean or average concentration of a
accounts for both tail areas (for example, 90%).
constituentcomputedfromnbackgroundmeasurementswhich
3.1.11 lower prediction limit, LPL—a statistical estimate of
differs from µ because of sampling variability, and other error
theminimumconcentrationthatwillprovidealowerboundfor
s =the true population variance of a constituent
thenextseriesof kmeasurementsfromthatdistribution,orthe
s =the sample-based variance of a constituent computed
meanofmnewmeasurementsforeachofksamplinglocations,
from n background measurements
with specified level of confidence (for example, 95%).
s=the sample-based standard deviation of a constituent
3.1.12 nonparametric—atermreferringtoastatisticaltech-
computed from n background measurements
nique in which the distribution of the constituent in the
–
populationisunknownandisnotrestrictedtobeofaspecified
y =the mean of the natural log transformed data (also the
form. natural log of the geometric mean)
D7048–04
s =the standard deviation of the natural log transformed Statistical Guidance) calls for use of the LCL in assessment
y
data monitoring and the UCL in corrective action. In this way,
n=the number of background (offsite or upgradient) mea- corrective action is only triggered if there is a high degree of
surements confidence that the true concentration has exceeded the crite-
k=the number of future comparisons for a single monitor- rion or standard, whereas corrective action continues until
ing event (for example, the number of downgradient monitor- there is a high degree of confidence that the true concentration
ing wells multiplied by the number of constituents to be is below the criterion or standard.This is the general approach
monitored) for which statistics are to be computed adopted in this guide, as well.
a=the false positive rate for an individual comparison (that 5.3 There are several reasons why statistical methods are
is, one sampling location and constituent) essential in assessment and corrective action monitoring pro-
m=the number of onsite or downgradient measurements grams. First, a single measurement indicates very little about
used in computing the onsite mean concentration the true concentration in the sampling location of interest, and
a*=the site-wide false positive rate covering all sampling with only one sample there is no way of knowing if the
locations and constituents measured concentration is a typical or an extreme value. The
t = the 100(1 − a) percentage point of Student’s objectiveistocomparethetrueconcentration(orsomeinterval
t-distribution on n − 1 degrees of freedom thatcontainsit)totherelevantcriterionorstandard.Second,in
H =the factor developed by Land (1971) (1) to obtain the many cases the constituents of interest are naturally occurring
L
lower 100(a)% confidence limit for the mean of a lognormal (for example, metals) and the naturally existing concentrations
distribution may exceed the relevant criteria. In this case, the relevant
H =the factor developed by Land (1971) (1) to obtain the comparison is to background (for example, off-site soil or
U
upper 100(a)% confidence limit for the mean of a lognormal upgradient ground water) and not to a fixed criterion.As such,
distribution background data must be statistically characterized to obtain a
statistical estimate of an upper bound for the naturally occur-
4. Summary of Guide
ring concentrations so that it can be confidently determined if
onsiteconcentrationsareabovebackgroundlevels.Third,there
4.1 The guide is summarized as Figs. 1-7. These figures
is often a need to compare numerous potential constituents of
provides a flow-chart illustrating the steps used in computing
concern to criteria or background, at numerous sampling
the comparisons to regulatory or health based ground-water
locations. By chance alone there will be exceedances as the
protection standard (GWPS) in assessment and corrective
numberofcomparisonsbecomeslarge.Thestatisticalapproach
action environmental monitoring programs.
to this problem can insure that false positive results are
5. Significance and Use
minimized.
5.4 Statistical methods for detection monitoring have been
5.1 The principal use of this standard is in assessment,
wellstudiedinrecentyears(seeGibbons,1994a,1996,USEPA
compliance and corrective action environmental monitoring
1992 (2, 4, 5)andPracticeD6312,formerlyPS64-96authored
programs (for example, for any facility that could potentially
by Gibbons, Brown and Cameron, 1996). Although equally
contaminategroundwater).Thesignificanceoftheguidanceis
important, statistical methods for assessment monitoring,
that it presents a statistical method that allows comparison of
Phase I and II investigations, on-going monitoring and correc-
ground-water data to regulatory and/or health based limits.
tive action monitoring have received less attention, (Gibbons
5.2 Of course, there is considerable USEPA support for
and Coleman, 2001) (6).
statistical methods applied to detection, assessment and cor-
5.5 The guide is summarized in Fig. 1, which provides a
rective action monitoring programs that can be applied to
flow-chart illustrating the steps in developing a statistica
...
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