Radionuclide Rule Compliance · Radionuclide Rule Compliance: ... approved analytical methods for radionuclides such as gross alpha ... set requirements for bid documents to ensure

1

Copyright ©2015 American Water Works Association

Radionuclide Rule Compliance: Utility Guidance on Analytical Methods

Dr. Andrew Eaton and Mr. Robert Shannon


Acknowledgements This guidance was developed and prepared using a collaborative workshop process to elicit the

expertise and experience of utility, laboratory, and state/federal agency professionals. This

guidance builds on analytical examinations and utility compliance observations associated with

the application of the radionuclide methods.

Dr. Andrew Eaton, Eurofins Eaton Analytical

Robert Shannon, Quality Radioanalytical Support, LLC

Dr. Kevin M. Morley, American Water Works Association

Joe Drago, Kennedy Jenks

Kevin Dixon, CH2M

Michella Karapondo, USEPA

Dan Hauptman, USEPA

Bernie Lucey, New Hampshire Department of Health (Retired)

Dr. Bob Read, Tennessee Department of Health

Robert Rosson, Georgia Tech Research Institute

Glynda Smith, USEPA

Carol Storms, Aqua New Jersey

Zoltan Szabo, USGS

Steve Wendelken, USEPA

Larry Umbaugh, CSC

Project Funding

This project was funded by the American Water Works Association (AWWA), utilizing the Water

Industry Technical Action Fund (WITAF), Project # 327.

3


Contents Executive Summary ....................................................................................................................................... 4

Acronyms, Abbreviations and Units.............................................................................................................. 6

Radionuclide Methods and Compliance Challenges ..................................................................................... 8

Obtaining Reliable Data for Decision Making about SDWA Compliance .................................................... 15

Utility guidance to Enhance Data Reliability ............................................................................................... 16

Method Proficiency Testing ........................................................................................................................ 22

Recommendations for review and action based on analytical results ....................................................... 29

Appendix A: Discussion of ERA Proficiency Testing (PT) Data .................................................................... 32

Appendix B: Calculations Used to Assess Method Performance ................................................................ 42

Appendix C: How Does Measurement Uncertainty Impact Compliance Decisions? .................................. 43

References .................................................................................................................................................. 47

4


Executive Summary Utilities in many parts of the country are challenged by compliance issues associated with the

Radionuclide Rule, in large part due to the performance limitations associated with the existing

approved analytical methods for radionuclides such as gross alpha activity, radium-226 (226Ra),

and radium-228 (228Ra). When utilities are supplying water that is low in radium and/or gross

alpha, the method limitations do not typically affect compliance. However, when source waters

contain these analytes near decision levels (e.g. 5 pCi/L as a trigger for 226Ra or 15 pCi/L for

adjusted gross alpha (alpha activity minus uranium and radon, but including radium) or 5 pCi/L

for 226Ra, 228Ra or combined radium), selection of appropriate analytical methods and ensuring

that laboratories are performing those methods in a manner to minimize uncertainty is critical.

This guidance document is limited to 226Ra and 228Ra, with discussion of gross alpha as it

relates to 226Ra, but also points out the general issues with the current gross alpha analytical

methods. It provides background on the relevant radionuclide methods that are commonly

used for compliance monitoring for these constituents. It provides criteria by which utilities can

a) evaluate performance of laboratories as pre-qualifications for bids when maximum accuracy

is important; b) set requirements for bid documents to ensure that labs understand the

requirements; and c) let utilities evaluate the data upon receipt to ensure that the laboratory met

the requirements.

The document does not suggest options for utilities which have high adjusted gross alpha

results that cannot be explained by either 226Ra alone or uranium. The document assumes that

uranium measurements are not as problematic as the gross alpha and radium methods. The

guidance document also provides recommendations for selection of the most appropriate

methods and sample handling techniques for compliance monitoring, to assist utilities in

specifying methods that are most likely to provide higher quality results.

To ensure maximum accuracy for gross alpha measurements, in situations where 224Ra

is not a consideration, the document recommends that utilities hold samples for 2-3

weeks before submittal to the laboratory to allow short lived radionuclides such as 224Ra

to decay, and then have the lab count gross alpha immediately (ideally within 24-48

hours) after sample preparation to minimize ingrowth.

For selection of methods, EPA is currently revising Method 900.0, but as it is currently

written it does not result in the most accurate measurements, in part due to the

requirement that samples be held for at least 72 hours after preparation and before

counting.

Specifically, this guidance document recommends that gross alpha measurements be

conducted using the Standard Methods 7110 B protocol with counting immediately after

preparation to minimize ingrowth of radium.

The co-precipitation method (7110 C) is recommended for samples with high dissolved

solids.

5


For radium isotopes, the document strongly recommends the use of the gamma

counting methods developed by Georgia Tech, as they demonstrate better precision and

accuracy in proficiency testing (PT) studies.

The document provides flow charts and tables that should assist utilities in obtaining the best

quality data, given limitations of existing methods, when radionuclide activity is near various

compliance points.

Note that actual compliance with the Safe Drinking Water Act (SDWA) adjusted gross alpha

Maximum Contaminant Level (MCL) is based on a running quarterly annual average, but

individual gross alpha measurements may be highly inaccurate and impact this compliance

decision, whereas the major focus of this document is on the radium measurements and the

gross alpha measurement itself. A utility should keep both issues in mind when evaluating

data.

Appendices to the document provide information on the performance of various methods in PT

studies, examples of relevant calculations for accuracy and precision, and a demonstration of

the issues involved in compliance determinations due to method uncertainty.

6


Acronyms, Abbreviations and Units %RSD .............. relative standard deviation 133Ba ................. barium-133 210Po ................. polonium-210 212Po ................. polonium-212 214Bi .................. polonium-216 214Pb ................. polonium-212 216Po ................. polonium-216 220Rn ................ radon-222 222Rn ................ radon-222 223Ra ................ radium-223 224Ra ................ radium-224 226Ra ................ radium-226 228Ra ................ radium-228 228Th ................. thorium-228 228Ac ................. actinium-228 230Th ................. thorium-230 235U .................. uranium-235 AAL .................. analytical action level Cert Manual .... Manual for the Certification of Laboratories Analyzing Drinking Water

Criteria and Procedures Quality Assurance (5th Edition, 2005) USEPA CFR ................. Code of Federal Regulations DL .................... Safe Drinking Water Act Detection Limit EPA .................. Environmental Protection Agency ERA ................. Environmental Resource Associates GA Tech ........... Georgia Tech GPC ................. gas-flow proportional counting HPGe ............... high purity germanium ID ..................... identifier L ....................... liter LCS .................. laboratory control sample LFB .................. laboratory fortified blank max .................. maximum min. .................. minimum MCL ................. Maximum Contaminant Level mg .................... milligram mg/L ................. milligram per liter MS ................... matrix spike MSD ................. matrix spike duplicate NJ .................... New Jersey pCi/L ................ picocurie per liter ppm .................. part per million (mg/L) PT .................... proficiency testing QC ................... quality control Ra .................... radium RB .................... reagent blank RDL .................. required detection limit (RDL) RER ................. replicate error ratio RPD ................. relative percent difference σ ...................... sigma (standard deviation)

7


SDWA .............. Safe Drinking Water Act SM ................... Standard Methods (for the Examination of Water and Wastewater) Stnd. Dev. ....... standard deviation TDS. ................. total dissolved solids USEPA. ............ United States Environmental Protection Agency USDHS. ........... United States Department of Homeland Security

8


Radionuclide Methods and Compliance Challenges Utility Challenges The current Radionuclide Rule, coupled with the precision and accuracy of existing approved radioanalytical methods, and inherent variability in the way individual laboratories perform the testing, present potential compliance challenges to utilities. This is particularly true for utilities which have 226Ra and/or 228Ra present in their source waters. The method variability noted above impacts the reported gross alpha activity, possibly more even than it does the test results for 226Ra or 228Ra. Examples of this variability are shown below. The purpose of this guidance document is to assist utilities in maintaining compliance with the Radionuclide Rule by minimizing method inaccuracies and imprecision and selecting labs based on performance capabilities that support these concepts. Some of the variability seen by utilities is attributable to a lack of specific guidance to laboratories that would help them navigate the complexity and options available when performing commonly used approved methods. This would range from the selection of methods, and the size of samples being processed, to decisions about the timing of sample counts. This all ultimately impacts the uncertainty in radioanalytical measurement results. Failure to minimize uncertainty can significantly increase the rate of incorrect decisions about whether drinking water is determined to be compliant with Safe Drinking Water Act (SDWA) regulations. Decision errors about compliance can have quite significant consequences. They may result in potential public health issues associated with failing to identify water with levels of radionuclides that are above compliance limits. Alternatively, incorrectly deciding that a water system is out of compliance may result in costly treatment. Either example can result in a concern that is nearly as serious, loss of public confidence in the water supply. Background Information about SDWA Approved Methods Some background about the methods follows that should help put the challenges into perspective. These observations focus on the most commonly performed methods based on the relative numbers of proficiency testing results submitted as a laboratory certification / accreditation requirement. Gross Alpha – Relevant Background Information and Testing Concerns Under the SDWA, the primary concern for alpha emitters is long-lived 226Ra, with a half-life of 1600 years, (and to a lesser extent other medium-lived, non-uranium alpha emitters such as 210Po, with a half-life of 138 days). Gross alpha is a non-specific screening method for alpha emitters. It is relatively inexpensive but the non-specific nature of the analytical determination can lead to down-stream compliance risks and costs. Gross alpha methods should be designed to reliably identify waters that could contain 226Ra in excess of an amount that would be compliant with the SDWA maximum contaminant level (MCL) for combined radium (226Ra + 228Ra). The SDWA allows gross alpha results to be substituted for 226Ra to demonstrate compliance with the combined radium MCL if the sum of the gross alpha and 228Ra is less than or equal to 5 pCi/L. When the sum of the gross alpha and 228Ra exceeds the combined radium MCL, a utility is not automatically out of compliance. Rather a radionuclide-specific method for 226Ra is run that presumably will not overestimate the 226Ra activity (see further discussion of 226Ra methods below). The results of this analysis are then used to determine compliance with the combined radium MCL. These results may be used to determine compliance with the combined radium MCL and may increase the frequency of required testing. Both cases will result in higher overall costs for radioanalytical testing.

9


EPA has also established an MCL for alpha particle emitters (including 226Ra but excluding radon and uranium), referred to as adjusted gross alpha. When the gross alpha result (“adjusted” by subtracting the uranium activity) exceeds the MCL of 15 pCi/L, the drinking water is determined to be out of compliance. This can have consequences that range from additional testing to implementation of treatment. Approved methods for gross alpha involve concentrating the sample by evaporation or co-precipitation, followed by analysis of alpha emissions from the test source in a low-background gas flow proportional counter. Although turn-around times as rapid as 1-3 days are possible, depending on regulatory requirements, as will be discussed later, the most accurate screening results for 226Ra will be obtained by delaying preparation of the sample for 2-3 weeks after collection. Water utilities should be careful in their interpretation of gross alpha results. It is crucial to keep in mind that this method is a screen and that it is not specific for 226Ra. It also assumes that the utility has measured the uranium level, which is also a source of alpha, but is subtracted in determining the adjusted gross alpha. If alpha emitters other than 226Ra are present, the result protectively overestimates the activity of 226Ra present. In addition to the presence of alpha emitters not related to 226Ra, other uncontrolled factors associated with approved methods can artificially increase the bias and uncertainty associated with measurements of alpha activity. When 226Ra is present in a sample, the length of time between the preparation and the counting will dramatically impact the sample result. Radium-226 decays into a noble gas familiar to many as a radionuclide of concern for indoor air, radon-222 (222Rn), with a half-life of 3.8 days. Since the evaporation used to prepare samples drives off any dissolved gases, including 222Rn, the concentration of radon (and its decay progeny) upon completion of sample preparation, will essentially be zero. The sample at this point has been converted by the preparation process to a thin layer of solid salts on a 2-inch planchet. From this point, 226Ra continues to decay forming new atoms of 222Rn. The newly generated radon has limited capability to escape from the solid salt matrix, which allows it to build up over time. As 222Rn and its short-lived alpha-emitting decay products, polonium-218 and polonium-214, build up in the sample, the alpha activity in the sample actually increases. The activity doubles in the first three to four days after preparation and continues to increase until it reaches a maximum of four times the initial concentration of 226Ra (See Figure 1) after about four weeks. For example, if a sample containing 4 pCi/L of 226Ra (as the sole contaminant) is counted immediately after evaporation, the alpha activity will be approximately 4 pCi/L (less than 1/3 the gross alpha MCL), whereas if the sample count occurs three weeks after evaporation, the activity could be as high as 16 pCi/L which would be out of compliance with the MCL for adjusted gross alpha. However, bear in mind that compliance is determined by the running average of quarterly samples, so even under these circumstances, a sampling point may or may not be out of compliance based on an individual result.

10


Figure 1: Four-fold Increase in Alpha Activity after Sample Preparation due to 226Ra Decay Products

SDWA-approved gross alpha methods have different requirements regarding the minimum time that must elapse between the preparation and counting of samples. One of the major sources of interlaboratory variability is associated with labs counting samples containing short-lived radionuclides at different points after sample collection. For example, the most commonly used method, EPA Method 900.0, requires delay of the sample count for 72 hours after evaporation whereas SM 7110B or SM 7110C allow the sample to be counted immediately following preparation. Depending on the choices made about when the sample is counted, a Method 900.0 result could arbitrarily be 2-4 times that of a Method 7110B or 7110C result. It should be noted that there are no method restrictions that require samples to be counted more quickly than is needed to meet holding time restrictions1. In contrast to 226Ra, 224Ra has a very short half-life of 3.7 days. Although 224Ra is produced through decay of its parent, thorium-228 (228Th), the solubility of thorium in water is extremely low and 228Th is rarely present in drinking water. Lacking a radioactive parent, 224Ra begins to decay as soon as the sample is collected. Following preparation, the alpha emitters in the decay chain below 224Ra (220Rn, 216Po and 212Po) very quickly reach equilibrium (minutes to hours). After this point these radionuclides decay as a group over the next several weeks following the half-life characteristic of 224Ra (see Figure 2).

1 A regulatory hold-time restriction for gross alpha of 180 days from collection to analysis is the upper limit for delay of the count of a sample. Note that this hold-time is not protective when medium-lived radionuclides such as 210Po with its 138 day half-life, since it could allow considerable decay of these radionuclides prior to analysis. The State of New Jersey has implemented much more stringent requirements than the EPA and has prescribed specific methods gross alpha and radium. Two counts of each sample are required, one quickly (within 24 hours if possible) to capture the activity of short-lived 224Ra plus unsupported 212Po from unsupported 212Pb (in addition to 226Ra), and one after 48 hours to protectively capture the activity of short-lived 224Ra plus supported 212Po while accepting that this will introduce a positive bias in the screening estimate is 226Ra is present in the sample. If the gross alpha activity exceeds 5 pCi/L, specific 226Ra analysis is required.

0

0.5

1

1.5

2

2.5

3

3.5

4

0.0 3.8 7.6 11.4 15.2 19.0 22.8 26.6

Alp

has

Em

itte

d p

er

De

cay

of

22

6 Ra

Days Elapsed Since Evaporation

Total Alpha Activity

Ra-226 Activity

11


Figure 2: Rapid Decay after Sample Collection of Alpha Activity from 224Ra and Decay Progeny

Analogous to 226Ra, when 224Ra is present in a sample, the timing of the count will have a substantial impact on gross alpha results. Since radium is not lost during preparation of the sample (as was radon with 226Ra), it is the length of time between sample collection and the count that matters. Inspection of Figure 2 shows that, in contrast to 226Ra, the sooner the sample is counted, the higher the result will be. The ingrowth of progeny from 224Ra detectable by the gross alpha test takes place on the order of minutes, hence the very sharp increase in gross alpha immediately after sample collection. If 224Ra is of regulatory concern, such as is the case in New Jersey, the sample must be counted as quickly following collection as possible, but not longer than 72 hours. In NJ, on the basis of the prevalence of 224Ra in major aquifers, gross alpha is used as a conservative test to capture elevated levels of 224Ra that are considered to be of regulatory concern. If 224Ra is not of regulatory concern, however, the presence of this short-lived radionuclide will be detected by the gross alpha measurement and increase the risk of non-compliance. In such cases, delaying the count of the sample will minimize the likelihood that the gross alpha MCL will be exceeded. Another limitation of all approved gross alpha evaporation methods2 relates to interference from sample solids. High sample solids is a recognized interference to evaporation methods. Most methods require that laboratories limit the size of sample that can be measured to that which will produce less than one-hundred milligrams of dried solids. As sample solids concentrations increase, the size of the sample that can be counted decreases and the uncertainty of results increases. If solids concentrations are too high, it may not be possible for a laboratory to meet the SDWA Required Detection Limits (RDL) for gross alpha of 3 pCi/L. While there is no formally enforced limit, Standard Methods and EPA methods recommend using a co-precipitation method instead of the evaporation method for samples containing more than 500 mg/L of total dissolved solids.3 Although laboratories must adhere to the 100 mg limit on solids, and some laboratories extend counting times to meet Required Detection Limits, these measures may not always produce results that are compliant with SDWA requirements for sensitivity. It may be difficult or impossible for data users (or even laboratories) to identify non-compliant data unless the laboratory

2 All methods except SM 7110C and EPA 00-02 rely on evaporation of the sample to prepare the test source. 3 SDWA-approved methods, SM 7110C and EPA 00-02, use the principle of co-precipitation to chemically isolate

alpha emitters from sample solids which can usually produce SDWA compliant results for samples containing elevated solids above 500 mg/L.

0

0.5

1

1.5

2

2.5

3

3.5

0 3.7 7.4 11.1 14.8 18.5 22.2 25.9 29.6 33.3 37

Alp

has

Emit

ted

pe

r D

eca

y o

f 22

4 Ra

Days Elapsed Since Sample Collection

Total Alpha Activity

Ra-224 Activity


12


calculates and reports the actual (a posteriori) SDWA Detection Limit achieved for each sample result using information specifically associated with that sample. This sample-specific information allows utilities to more readily identify non-compliant results that are not of sufficient quality to be used to make compliance decisions.4 Another source of interlaboratory variability for the evaporation methods results from counting sample planchets with unevenly distributed solids residues. While this is in part an intrinsic weakness of a method that requires evaporation of a wide variety of types of waters, weak laboratory technique can exacerbate the issue. Finally, an EPA Method 900.0 requirement specifies that laboratories calibrate the instrument using solid residues obtained by evaporating their tap water. This may result in calibration standards that are both poorly intercomparable with other laboratories and poorly representative of samples being analyzed5, and thus introduce varying degrees of bias into gross alpha measurements. The impact of these two issues on the utilities’ results are best controlled by ensuring that results for internal quality control (QC) data (laboratory control samples (LCS) and matrix spikes (MS)), and for proficiency testing (PT) show results that are consistent with minimum requirements presented later in this document (i.e., Table 4). Radium 226 (226Ra) - Relevant Background Information and Testing Concerns Three general analytical approaches are used by SDWA-approved methods for 226Ra determinations: gas-flow proportional counting (GPC)6, radon emanation methods, and gamma spectrometry. The cost and reliability of these methods varies. In general, higher cost tends to be positively correlated with better performance and reliability. Precipitation and Gas Flow Proportional Counting Methods Most 226Ra methods rely on the measurement of alpha emissions. The least costly of the methods tend to be precipitation methods of which EPA Method 903.0 and SM 7500-Ra B7 are the most widely used. Although the methods are generally described as screening techniques for 226Ra, they can be run in a manner that eliminates interference from 224Ra producing results that will provide accurate measurements of the true 226Ra concentration in the sample. These approaches all combine chemical complexation with co-precipitation to produce a test source of purified radium in a barium sulfate precipitate. Alpha emissions from the test source are analyzed using low-background gas flow proportional counting 8 with corrections applied for detection efficiency, ingrowth, and in the case of SM 7110 B (but not EPA 903.0), chemical yield. The turn-around time for this method can be as quick as 24 hours, although, as will be discussed below, higher quality results can be obtained by delaying the counting of the sample after preparation for up to three weeks. These methods measure alpha-emitting isotopes of radium and are commonly given the misleading name of “Total Radium” or “Total Alpha-Emitting Radium Isotopes”. Since isotopes of a given element cannot be chemically separated from one another, the test source will contain any radium isotopes present in the sample, including 228Ra, 226Ra, 224Ra, and 223Ra. While 228Ra

4 See the Generic SDWA Detection Limit Calculation in Appendix B. 5 since the chemical composition of dissolved solids in the calibration matrix differ from than that of samples being

analyzed 6 Alpha scintillation of the evaporated test source is permissible but is only infrequently performed. Alpha spectral

methods are available but not approved. 7 SM 7500-Ra D may optionally incorporate the precipitation approach used in SM 7500-Ra B. 8 Other alpha detection methods may be used but this is rare. The alpha spectral method is more sensitive but

requires more detailed wet chemistry preparation.

13


is of regulatory concern, it is a low-energy beta emitter and will not be detected using these methods that are sensitive only to alpha emitters9. The other three radium isotopes are all alpha emitters that will be detected if they are present in the test source at the time of the count. 226Ra is the analyte of concern. 224Ra is an interference to the determination of the methods meant to screen for 226Ra.10 While 224Ra is often present in freshly collected samples at levels similar to 228Ra, it decays away in the first 2-3 weeks after sample collection (see discussion and Figure 2 above). 223Ra is a member of the naturally-occurring 235U decay chain that may be present in samples at the time of collection at approximately five percent the concentration of 226Ra so it does not contribute very significantly to the overall activity. This precipitation / GPC method is generally described as a screening technique for 226Ra. The largest weakness of this method regards interference from 224Ra. Similar to the approach discussed for gross alpha above, delaying the sample count until at least 2-3 weeks after collection allows time for 224Ra to decay away (see Figure 2). During this time, 222Rn and its progeny continue to ingrow (see Figure 1) and effectively amplify the signal from 226Ra. This further overwhelms any interference remaining from 224Ra to the point where its impact is equivalent to less than about 2% of its original activity. One difference between the two most commonly used approaches is that EPA 903.0 does not apply a chemical yield correction, whereas SM 7110 B does. Radiochemical methods routinely correct results for losses occurring during chemical separation based on the recovery of carriers/tracers that are added to the sample prior to processing. Failure to account for such losses could result in significantly low results and failure to properly identify water as being out of compliance with SDWA requirements. Interlaboratory proficiency testing data for 226Ra precipitation / gas flow proportional counting methods (Appendix A) show positive bias and high relative uncertainties. The skew toward high results may be evidence that at least some laboratories are counting ERA Proficiency Testing samples (PTs) that contain ingrown 224Ra promptly after separation. EPA 903.0 shows a mean recovery of 107% and a relative standard deviation (%RSD) of 44% with the average recovery and %RSD rising to 120% and 70%, respectively, at concentrations in the 3-10 pCi/L range where compliance decisions are made. A high %RSD for proficiency testing results, especially when there are data from large numbers of laboratories, usually indicates that a method is inherently variable. SM 7500-Ra B shows a mean recovery of 100% with a %RSD of 16%. Although there is no change in average recovery, the %RSD rises to 20% at concentrations in the 3 -10 pCi/L range where compliance decisions are made. While the reason for the difference in performance of the two similar methods cannot be determined with certainty, the extended discussion in Method SM 7500-Ra B of the impact of 224Ra on measurements may prompt laboratories to delay counting of sample to address the interference. Radon-Emanation Methods In contrast to the precipitation methods above, which are often described as screening methods, radon emanation methods are generally considered to be definitive or confirmatory methods capable of very accurate and precise measurements. The cost for these methods tends to be higher than the precipitation GPC approach. Radium in the sample is first chemically separated using the complexation approach common to the precipitation methods above. The precipitate is dissolved and the liquid transferred to a bubbler apparatus, purged of radon, and sealed and stored for a period of time to allow 222Rn to

9 See below for further discussion of 228Ra methods. 10 Except in New Jersey.

14


ingrow (see Figure 1). The radon gas is then carefully flushed into an alpha scintillation cell for counting on a photomultiplier tube device. This is an old, but tried -and-true method. When run reliably, it can deliver accurate and precise measurements. In practice, however, it is very time intensive and technique dependent. It requires complex glassware and a skilled analyst. The most commonly run method, EPA Method 903.1, does not correct results for losses during processing (chemical yield). Unknown losses of radon can also occur during the transfer of radon gas. While in the hands of a capable analyst, these losses are generally, on average, minimal, but more significant issues may occur with individual samples and the problem will never be detected. Frequent analysis of standards can help identify recurring leakage and weak technique, but the additional quality control is time consuming and costly. Turn-around times for this method vary from 1 - 4 weeks depending on the length of the ingrowth period used by the laboratory, with 3-4 weeks being typical to achieve the best sensitivity levels. Interlaboratory proficiency testing data for EPA Method 903.1 (Appendix A) show an average recovery of 97% with a %RSD of 18%. Gamma Spectrometry Methods With gamma spectrometry methods, radium in the sample is co-precipitated with barium sulfate. The crystalline precipitate, which does not allow ingrowing radon to escape, is stored for a period of time (generally 2-4 weeks) to allow 222Rn and its decay progeny, 214Bi and 214Pb, to come to radioactive equilibrium. During this time, 228Ac, the decay product of 228Ra also comes to equilibrium with 228Ra. The precipitate is then measured on an HPGe gamma ray spectrometer and the activity of 226Ra and 228Ra calculated from ingrown progeny activity. This is a newer option for drinking water analysis. High Purity Germanium (HPGe) gamma-ray spectrometry, however, has been used for at least two decades to produce highly accurate and precise determinations of 226Ra and 228Ra in water samples. While the sensitivity of this approach may not quite match that of the precipitation or de-emanation approaches, this is more than compensated for by the reliability and specificity possible using gamma-ray spectrometry, and the relative ease and robustness of sample preparation and analysis. While the cost of this method tends to be somewhat higher than for the precipitation and de-emanation methods (due to the high cost of the detection system), it does allow both 226Ra and 228Ra to be determined in a single measurement. To increase the sensitivity at low levels, however, large sample sizes (e.g., 3-4 liters) and / or a considerable increase in counting time is needed. Given that this is a method has only been more recently approved for use with SDWA, the interlaboratory proficiency testing data (Appendix A) are sparse; however results are generally tighter than for the other types of methods. The most frequently performed method is the Georgia Tech (GA Tech) method. Average recovery for 226Ra is 99% with a %RSD of 12%. Radium 228 (228Ra) - Relevant Background Information and Testing Concerns Two general analytical approaches, gas-flow proportional counting (GPC) of beta emissions and gamma spectrometry, are used by SDWA-approved methods for 228Ra determinations. Both of these involve measurement of 228Ac, the short-lived decay progeny of 228Ra. The cost and reliability of these methods varies. In general, higher cost tends to be positively correlated with better performance and reliability. Chemical Separation of 228Ac Followed by Gas Flow Proportional Counting Most 228Ra methods, including EPA Methods 904.0, Ra-05, SM 7500 Ra-D and several older EPA methods, rely on the measurement of the beta emissions from purified actinium-228 (228Ac)

15


progeny in a low-background gas-flow proportional counter. The 228Ac measurement follows extended and complex chemical separation schemes involving complexation, co-precipitation/precipitation, and in some cases, liquid-liquid extractions. Calculation of the final result involves applying correction factors to the count results. These correction factors include instrument response (efficiency), decay and ingrowth of the radionuclides, and chemical yield, each of which can introduce significant uncertainty and bias into the final result. For these methods, however, the combined uncertainty associated with the correction factors can be significant. Because SDWA specifications for uncertainty currently only consider counting statistics (“count uncertainty”), the uncertainty reported in association with results is likely to significantly underestimate overall uncertainty. Interlaboratory proficiency testing data (Appendix A) for approved 228Ra methods that employ gas flow proportional counting show average recoveries ranging from 97-108% (overall average 100%), with %RSDs ranging from 20-26% (overall 24%). It is noted that the acceptance range for PT samples containing 228Ra at the 5 pCi/L MCL is 41% to 153% and for PT samples containing 228Ra at 15 pCi/L where counting uncertainty is lower, would be 53% - 135%. EPA’s Drinking Water Certification Manual specifies that recoveries for control samples (LCS/LFB) which can be spiked at the higher activity, should fall in the range of 100 ± 20% (1σ = 8.3%). Gamma Spectrometry Methods The general gamma spectrometry method was described previously in the 226Ra discussion and is not repeated here. Given that this is a newer method, the interlaboratory proficiency testing data (Appendix A) is sparse. The most frequently performed method is the Georgia Tech (GA Tech) method. Average recovery for 228Ra is 102% with a %RSD of 16%, significantly more precise than the other methods.

Obtaining Reliable Data for Decision Making about SDWA Compliance

At present, there are insufficient criteria in the existing methods to ensure that utilities will consistently get reliable results from multiple labs, even while the labs are following approved methods. The purpose of this section is to provide a framework for utilities to use in contracting with laboratories that, if followed, will allow them to improve the precision and accuracy of measurements. Ultimately, EPA needs to update the SDWA radionuclide methods, but that is not a short term solution. In the meantime utilities need to know that before they invest significant capital on treatment systems, that they truly have verified a compliance problem. PT acceptance ranges are established based on a statistical evaluation of historical PT results. These acceptance criteria reflect actual laboratory performance, using available approved methods, as written, as opposed to being driven by an evaluation of the quality of results needed to maintain decision errors about compliance at low and tolerable levels. At the low end of the PT acceptance range, counting uncertainty is by far the largest contributor to overall uncertainty of the result. This error-source identification is positive since counting uncertainty is generally the most predictable and easily managed component of uncertainty. The effect on the results can be minimized by processing larger amounts of sample and by extending sample count times. Neither of these measures requires that methods be modified so they can be done within the bounds of approved methods. As larger sample sizes are processed and count times are extended and measurement uncertainties approach a minimum, the uncertainty is controlled by uncertainties associated with the core efficacy/reliability of the analytical approach itself, factors such as the uncertainty associated with yield determinations and detector calibrations.

16


For this reason, EPA’s Drinking Water Certification Manual specifies that the recovery for control samples (LCS/LFB), which can be spiked at higher activities, should fall within the range of 100 ± 20%. This ensures that relative uncertainties be maintained at approximately 8.3% (1σ) and forces laboratories to ensure that they have control of core analytical process (as opposed to relying on counting uncertainty to explain anomalous results). Once laboratories have control over the core integrity of their analytical method, they and the utility are in a position to obtain data optimized to make reliable decisions. By using performance data such as QC and PT sample results, water utilities can identify reliable and well qualified laboratories to perform analysis. They can make ongoing decisions that balance the need for high precision, accuracy and reliability against cost based on what they do (or do not) know about water samples. For example, if they expect results to be close to key decision points (e.g., MCLs or levels that impact the frequency of required testing) or if they just do not know what levels of contaminant may be in a sample, they can instruct the laboratory to minimize result uncertainty by implementing more costly measures. Such measures might include using the most reliable, accurate and precise methods, processing larger samples, and/or extending count times. In contrast, when results are expected to be well below key decision points and the need for precision is lower, they can allow the laboratory to use less costly analytical approaches. This requires extensive communication with the laboratory that should be considered as part of the original contracting process between the lab and the utility.

Utility guidance to Enhance Data Reliability

Flow Charts to Assist Utilities in Lab Evaluation and Contracting Default analytical methods will not necessarily produce results that ensure reliable decisions about whether water samples actually comply with SDWA requirements. These two sets of flow charts (Figures 3 and 4), along with Tables 1 through 3, will help utilities select the analytical methods and contractual terms that will help them maximize the likelihood of correct compliance decisions by selecting reliable and capable laboratories, and using more optimal methods and analytical parameters. The recommendations also consider some key characteristics of samples and should result in minimizing uncertainty and bias and producing data that will help minimize the risk of costly incorrect compliance decisions. These are presented in two steps. The first flow chart addresses the process that can be used to identify laboratories that are qualified and capable of meeting and exceeding minimum requirements specified in EPA’s Manual for the Certification of Laboratories Analyzing Drinking Water Criteria and Procedures Quality Assurance (5th Edition, 2005).

17


Figure 3: Procurement of Radiological Laboratory Services for Reliable Drinking Water Compliance Measurements

Req

ues

t q

ual

ific

atio

ns

fro

m e

ach

po

ten

tial

lab

Co

nsu

lt li

st o

f ap

pro

ved

lab

s fo

r re

qu

ired

par

amet

ers

Yes

No

Isla

b in

go

od

st

and

ing

(cer

tifi

cati

on

/ ac

cred

itat

ion

) fo

r al

l p

aram

eter

s?

Yes

Yes

No

Is

his

tori

cal P

T p

erfo

rman

ce

sati

sfac

tory

fo

r ea

ch

par

amet

er?

Rev

iew

PT

resu

lts

and

co

rrec

tive

ac

tio

ns

for

eac

h p

aram

ete

r

Re

view

inte

rnal

QC

res

ult

in

form

atio

n

Eval

uat

e b

ids

an

d c

on

firm

ca

pab

iliti

es a

nd

aw

ard

to

o

ne

or

mo

re o

f th

e b

est

qu

alif

ied

lab

s.

Sen

d c

om

plia

nce

sam

ple

s fo

r an

alys

is.

Co

nsi

der

wh

eth

er la

b c

an

fun

ctio

n a

s b

ack-

up

fo

r p

aram

eter

s fo

r w

hic

h t

hey

ar

e ce

rtif

ied

.

Wri

te r

equ

est

for

bid

Incl

ud

ing

req

uir

emen

ts t

o im

ple

men

t re

com

men

dat

ion

s o

f th

is

rep

ort

.

Eval

uat

e q

ual

ific

atio

ns

fro

m e

ach

lab

Seek

an

oth

er

lab

fo

r th

is

par

ame

ter

Seek

an

oth

er

lab

fo

r th

is

par

ame

ter

Yes

No

Acc

epta

nce

ra

nge

s fo

r b

atch

Q

Cs

for

each

p

aram

eter

per

C

ert

Man

ual

sp

ecif

icat

ion

s(s

ee T

able

s 1

-3)

Yes

Ensu

re o

n a

n o

ngo

ing

bas

is t

hat

rep

ort

ed r

esu

lts

are

adeq

uat

e to

su

pp

ort

co

mp

lian

ce d

ecis

ion

s.

Ve

rify

RD

L h

as b

een

met

, th

at u

nce

rtai

nti

es w

ere

op

tim

ally

man

aged

usi

ng

aliq

uo

t si

ze, c

ou

nt

du

rati

on

, an

d

tim

ing

of

the

cou

nt

rela

tive

to

co

llect

ion

an

d p

rep

arat

ion

.

No

18


The second flow chart addresses selection of methods and analytical parameters for required parameters. This flow chart assumes that the laboratory selected to do the work has been chosen using a process similar to that proposed in the first flow chart. Figure 4: Election of Optimal Methods and Analytical Parameters for Reliable Drinking

Water Compliance Measurements for gross alpha.

Flo

w c

har

t fo

r se

lect

ion

of

met

ho

d a

nd

op

tim

al

anal

ytic

al p

aram

ete

rs f

or

gro

ss a

lph

a

No

Yes

Is 2

24R

a a

con

cern

fo

r co

mp

lian

ce

(Sta

te o

f N

J)

?

Yes

No

Will

sa

mp

les

con

tain

>5

00

m

g/L

solid

s?

Use

Sta

te o

f N

ew

Je

rsey

ap

pro

ved

lab

an

d m

eth

od

s.(4

8-h

ou

r h

old

-tim

e fo

r 2

co

un

ts)

An

y EP

A-a

pp

rove

d

gro

ss a

lph

a m

eth

od

m

ay b

e u

sed

Use

a

cop

reci

pit

atio

n

met

ho

d

(e.g

., S

M 7

11

0C

or

EPA

00

-02

)

Use

ap

pro

ved

ev

apo

rati

on

or

co

pre

cip

itat

ion

m

eth

od

Yes

No

Pas

t ra

dio

logi

cal

test

ing

resu

lts

avai

lab

le?

Take

mea

sure

s to

min

imiz

e u

nce

rtai

nty

(i

.e.,

use

mo

re r

elia

ble

/sen

siti

ve m

eth

od

, in

crea

se a

liqu

ot,

incr

ease

co

un

t d

ura

tio

n, a

dju

st

tim

ing

of

pre

pa

rati

on

an

d c

ou

nt

to a

dd

ress

d

eca

y p

rog

eny

Yes

No

Is

co

mb

ined

ra

diu

m

>2 p

Ci/

L

Yes

No

Gro

ss

alp

ha

> ½

MC

L (7

.5

pC

i/L)

Take

mea

sure

s to

min

imiz

e u

nce

rtai

nty

un

til

the

tru

e al

ph

a ac

tivi

ty o

f th

e w

ater

is k

no

wn

(i

.e.,

incr

ease

aliq

uo

t a

nd

co

un

t d

ura

tio

n, d

ela

y p

rep

ara

tio

n u

nti

l 2-3

wee

ks a

fter

co

llect

ion

, a

nd

sp

ecif

y m

eth

od

th

at

allo

ws

cou

nt

of

pre

pa

red

sa

mp

le w

ith

in 2

4 h

ou

rs o

f p

rep

) a

nd

re

qu

ire

pro

mp

t co

un

tin

g a

fter

pre

pa

rati

on

.

An

alyz

e u

sin

g d

efau

lt m

eth

od

p

aram

ete

rs t

o m

eet

RD

L

19


Sample Scope of Work – Background and Rationale The EPA has indicated that it intends to make improvements in approved EPA methods or to push for changes in methods from other organizations such as Standard Methods (as well as potentially withdrawing methods that do not meet performance or expectations for QC, etc.). Until changes for compliance monitoring are made and codified through rulemaking and other processes, there are limits to what utilities can do to improve data quality. We suggest that utilities who may have potential radionuclide concerns consider incorporating this scope of work into requests for pricing and laboratory contracts. An explanation of the rationale for each step is shown. Note that some states may have requirements that supersede this guidance, in which case the state requirements must be satisfied. Some of the recommendations go beyond literal requirements of the SDWA program – but following these requirements will improve the accuracy and precision of results and can minimize the rate of decision errors about compliance with SDWA requirements. Gross alpha analysis

Gross alpha is meant to screen for longer-lived radionuclides, principally 226Ra and uranium, and for medium-lived nuclides such as 210Po. In cases where short-lived nuclides such as 224Ra or other short-lived nuclides are not of regulatory concern11, delaying analysis of the sample will minimize interference of short-lived radionuclides and produce results that most accurately estimate of the activity of longer-lived radionuclides in the sample. Interference from 224Ra can best be minimized by holding samples for several weeks after collection before submittal to the laboratory (or by having the laboratory delay initiating analysis of samples for the same time). This ensures that by the time the sample is counted, short half-lived nuclides such as 224Ra have decayed.12 This consistency in hold time will also minimize interlaboratory variability associated with labs counting samples containing short-lived radionuclides at different points after sample collection. It is important, however, to minimize the time period before analysis to ensure that moderately-lived nuclides that can be of concern (e.g. 210Po, with a half-life of 138 days) will still be reliably detected. Since alpha activity from 210Po is of regulatory concern, holding the sample for the maximum permissible time of 180 days is neither protective nor advisable because more than half the 210Po will have decayed during the holding time.

For all samples: o Ensure that the laboratory meets all requirements defined in 40 CFR 141 and that the

laboratory uses a validated method that satisfies the batch quality control requirements summarized in Table 4 below. Many laboratories do not currently adhere to the specifications for batch quality controls presented in EPA’s Laboratory Certification Manual. Although it is considered to be guidance in some states, EPA requires that state primacy laboratories meet the requirements. Incorporating its requirements into scopes of work will help minimize the

11 New Jersey regulates 224Ra. NJ’s required methods require initial and second counting of the sample within 48

hours of collection which will help ensure that samples containing significantly elevated levels of 224Ra will be reliably identified. If the gross alpha at that point is elevated above 5 pCi/L, testing for 226Ra directly is indicated. This approach conservatively presumes uniform strong association among the Ra radionuclide occurrences, which is true for many (but not all) aquifers. The additional alpha count of the sample approximately three weeks after preparation with amplifed signal from 226Ra, is not required although it is advisable. Exceeding the 15 pCi/L MCL for Combined Gross Alpha after the counts are completed within 48 hours necessitates action by the utility on the basis of the prevalence of 224Ra in aquifers of the State of New Jersey.

12 For example, only 7% and 2%, respectively, of the amount of 224Ra initially present will remain 14 and 21 days after sample collection (Figure 2).

20


uncertainty of results and improve the reliability of decisions about SDWA compliance.

o Count gross alpha samples as soon as possible after evaporation or co-precipitation. 226Ra decay progeny ingrow over time and the longer one waits after preparation the higher the apparent gross alpha may become. Even 96 hours may increase the gross alpha due to 226Ra by up to two times, but method 900.0 currently requires a minimum 72-hour holding time after evaporation.

If using EPA Method 900.0, count the sample as soon as possible after the required 72-hour holding time between preparation and the count.

If using a method such as SM 7110 B, EPA 00-02, or SM 7110 C, there is no hold-time, so the sample may be counted as soon as possible after preparation.

o Ensure that the SDWA Required Detection Limit (RDL) of 3 pCi/L has been met for each sample by optimizing the sample aliquot and count time.

Optimize the volume of sample taken for analysis – There are multiple sources of uncertainty in the gross alpha analysis, but the dominant source in low-activity samples is the counting uncertainty, which is inversely proportional to the square root of the number of counts. Processing larger sample aliquots will provide higher signal-to-noise and decrease the counting uncertainty. Beyond practical limitations (available equipment, bounds of validated methods), the maximum size of sample that can be processed is limited by methods to that which will produce ≤ 100 mg of solid residue in a 2” planchet.

If sample TDS concentration is known, process enough sample to ensure that the RDL will be met in the count time planned for samples. Gross alpha counting efficiency is highly impacted by the solids present in the sample. Lower counting efficiencies result in lower count rates and much greater uncertainty.

If solids concentrations in samples are unknown, estimate the TDS (using conductivity of an unpreserved portion of multiplied by 0.6). Alternatively a small portion of sample may be evaporated and used to estimate the solids in the sample. Once an estimate of the solid content is obtained, this can be used to calculate the amount of sample needed to produce residues that approach but do not exceed 100 mg in a 2” diameter planchet

If the TDS concentration is known to exceed 500 ppm, analyze the sample using a coprecipitation method (e.g., SM 7110 C) rather than an evaporation method (e.g., EPA 900.0 or 7110 B).

Clearly, there is a practical limit to how long a sample can be counted. Count samples to meet a SDWA detection limit of 3 pCi/L, or to result in a relative counting uncertainty of less than or equal to 16% (1.96σ) assuming 15 pCi/L is present in each sample, whichever is longer.

The laboratory should calculate the actual SDWA DL13 achieved for each sample and QC sample analyzed and verify that they have at least met the RDL of 3 pCi/L for gross alpha. Require that the laboratory report, for each result, the DL achieved in the laboratory report to the utility and to regulators (see Appendix B for a generic calculation). If the

13 A generic calculation for the SDWA Detection limit is presented in Appendix B. Note that the SDWA DL is specific

to the SDWA and should not be confused with other detection concepts such as: LLD, MDA, MDC, RL, or Lc. The SDWA DL should be calculated and reported for each sample result.

21


detection limit is not met, consider reprocessing the sample using more optimal conditions to obtain the required sensitivity.

If sample gross alpha concentrations are unknown, may be variable, or are known or are expected to be within 5 pCi/L of the 15 pCi/L MCL, proceed as follows, and as price permits:

o Use the most reliable method for analysis. Based on PT data analyzed in this paper, we would recommend that SM 7110 C be used (regardless of solids content) since it allows use of a significantly larger aliquot while producing a much more reproducible test source;

o Follow recommendations from above regarding delay of processing samples until 2-3 weeks after collection;

o Minimize the time between the preparation and counting; o Maximize the sample aliquot. If possible process up to 1 L of sample to minimize

uncertainty; o Increase the counting time to target 1σ counting uncertainties of 5-8% (or better); o Ensure that requirements for batch QC samples summarized in Table 4 are met or

exceeded. o Review all results to ensure that only results that are compliant with SDWA

requirements are used to make compliance decisions.

228Ra analysis

Ensure that the laboratory meets all requirements defined in 40 CFR 141 and that the laboratory uses a validated method that satisfies the batch quality control requirements summarized in Table 6 below.

o Preferably specify the use of the GA-Tech method in lieu of EPA Method 904.0. The specificity of the spectrometric method and the ability to more easily process much larger samples produces more precise and accurate results. Interlaboratory study results indicate that the GA Tech method yields results with a relative standard deviation of 16% (1σ), as compared to 26% for EPA Method 904.0 (see discussion above and data in Appendix A)

o If using Methods 904.0 or 7500 Ra-D which require determination of yield using gravimetric methods, the laboratory’s LCS and MS recoveries should be inspected. These methods have numerous chemical separation steps and measurement of the barium and yttrium yield can be inaccurate. This can be exacerbated if samples contain more than a few mg of barium to begin with. (In theory elevated levels of barium should not occur in finished drinking waters, as the barium MCL is 2 mg/L but some source waters may contain high levels.)

If mean/median values significantly less than 100% are observed, we recommend that yield measurements be confirmed by monitoring barium with either ICP-AES or ICP-MS analysis or by using 133Ba as a tracer. If gravimetric yield and confirmation method differ by more than 10% absolute, repeat sample preparation with a fresh aliquot as the non-gravimetric techniques are not currently allowed for compliance measurements until new versions of the methods are approved (Consider whether re-precipitation (i.e., repeating BaSO4, or Y2(C2O4)3 precipitation steps) may be used to purify precipitates)14. Alternatively, use a more reliable method (e.g., GA Tech).

14 This may require involving the regulator to obtain concurrence on the approach to be used.

22


Optimize the sample aliquot and count samples to meet a SDWA detection limit of 1 pCi/L, or to result in a relative counting uncertainty of 16% (1.96σ) assuming 5 pCi/L is present in each sample, whichever is more restrictive.

o The laboratory should calculate the actual SDWA DL achieved for each sample and QC sample analyzed (see Appendix B for a generic DL calculation) and verify that they have at least met the RDL of 1 pCi/L for 228Ra. Require that the laboratory report, for each result, the DL achieved in the laboratory report to the utility and to regulators (if the regulatory reporting system allows that). If the detection limit is not met, consider whether reprocessing the sample using more optimal conditions will result in meeting the required sensitivity.

Method Proficiency Testing Method-Specific PT studies support these recommendations

Appendix A contains a detailed summary and analysis of proficiency testing results by analyte and method that indicate performance for different methods for all drinking water laboratories. The data also show differences between methods as shown in the following proficiency testing data review. Overall Performance of Approved Gross Alpha Methods Based on Proficiency Testing Results Laboratory performance for proficiency testing samples run as an ongoing requirement for laboratory certification / accreditation for gross alpha is summarized in Table 1. 15 Table 1: Summary of Gross Alpha Proficiency Testing Results from ERA PT

Studies 55-99

Method

Data Points Average

Stnd. Dev. Min.

2.5 percentile Median

97.5

percentile Max

Gross Alpha

EPA 900.0 1537 95% 24% 27% 52% 93% 148% 246%

EPA 00-02 223 91% 20% 40% 49% 93% 130% 195%

SM 7110 C 198 92% 16% 7.5% 62% 92% 124% 133%

SM 7110 B 162 97% 22% 7.2% 54% 98% 137% 174%

All Methods 2119 94% 23% 7.2% 52% 93% 143% 246%

Interlaboratory proficiency testing samples contained activities ranging from 7 pCi/L to 70 pCi/L. The NELAC FOPT table acceptance ranges for Gross Alpha (230Th) PT samples at 7 pCi/L, 15 pCi/L (the MCL for Corrected Gross Alpha), and 25 pCi/L are 10%-204%, 25%-167%, and 38%-154%, respectively. The result that ranges for recovery converge towards 100% with increasing activity is consistent with findings of other such tabulations. Although the distribution of results is largely normal, long tails reflect intermittent extreme results. It is not clear whether this reflects method performance or the fact that data contain results from more and less reliable laboratories. PT results for gross alpha evaporation methods showed an average recovery of 95% and a %RSD of 23% (1σ). At concentrations close to the MCL of 15 pCi/L where compliance decisions are made, the %RSD for Method 900.0 was somewhat higher at 29% (1σ) with SM 7110 B largely

15 See Appendix A for detailed analysis of drinking water laboratory proficiency testing results.

23


unchanged at 22% (1σ). PT results for Gross Alpha co-precipitation methods showed an average recovery of 92% with an %RSD of 18% (1σ). For method SM 7110 C, at concentrations close to the MCL of 15 pCi/L, where compliance decisions are made, the average recovery was 91% with a %RSD of 15% (1σ). At concentrations around the MCL, EPA co-precipitation Method 00-02 showed average recovery of 96% and %RSD of 26% (1σ). For the four approved methods for which there were a significant number of results provided, there were notable differences in the quality of results. While the range of average recoveries among the methods was relatively small (91%-97%), the most commonly used method, EPA 900.0, showed the poorest precision with a standard deviation of 24% (1σ). In contrast, co-precipitation method SM 7110 C, showed a relative standard deviation of 16% (1σ) which is 20-33% lower than the other methods, likely a result of the nearly uniform planchet matrix and mass generated by the technique. For 7110 C, 95% of reported results fell between 62% and 124%, a range that, although slightly skewed low, is close to the ideal range targeted for internal quality control sample results (LCS/LFB) in the Drinking Water Certification Manual. As such, SM 7110 C would appear to be the best method available for samples with unknown activities, or samples with true activities close to a trigger point.

It is important to note that the alpha emitter in gross alpha PT samples is 230Th, which does not exhibit the time-sensitive changes in activity discussed for 226Ra and 224Ra. Thus, PT statistics provide a false sense of security about the quality of results that will be obtained when analyzing real samples. As described above, and depending on individual laboratory practices, time-sensitive effects may introduce additional bias and uncertainty into actual test results in excess of 400% of the activity of radium isotopes present. Especially as the sample activity approaches the MCLs, the uncertainty apparent in the PT results will combine with uncertainty associated with the timing of the count and significantly increase the risk that measurement conditions may result in arbitrary compliance decisions. If gross alpha were used only as a screening technique for radium, and if exceedances were always followed by confirmation using more reliable testing methods (such as is the case for 226Ra or beta emitters), elevated uncertainties might be tolerable. This is not the case for adjusted gross alpha, however, where the result obtained is compared directly to the gross alpha MCL to make a final compliance decision. Thus, uncontrolled uncertainty (and bias) in the gross alpha measurement can have quite a large and arbitrary effect on compliance decisions. Further discussion of the impact of measurement uncertainty and measures that might be taken to minimize its negative impact on compliance decisions follows below.

24


Overall Performance for 226Ra Methods Based on Proficiency Testing Results Laboratory performance for proficiency testing samples run as an ongoing requirement for laboratory certification / accreditation for 228Ra is summarized in Table 2.16 Table 2: Summary of 226Ra Proficiency Testing Results from ERA PT Studies 55-99

Method

Data Points Average

Stnd. Dev. Min.


97.5

percentile Max

Radium 226

EPA 903.0 534 107% 44% 16% 80% 103% 321% 619%

EPA 903.1 312 97% 18% 23% 61% 97% 125% 223%

SM 7500-Ra-B

150 100% 16% 55% 70% 99% 133% 171%

Ga. Tech 33 99% 12% 77% 85% 99% 125% 143%

All Methods 1029 103% 34% 16% 68% 99% 146% 619%

Interlaboratory proficiency testing samples contained with activities ranging from 3 pCi/L to 20 pCi/L. PT acceptance ranges for samples containing 226Ra at 5 pCi/L (Ra MCL) and 15 pCi/L are 65%-133% and 64% - 125%, respectively. Convergence in the ranges of recovery is not as noticeable with increasing concentration as it is for increasing gross alpha activity because the specific isotope analyses for 226Ra uses more elaborate preparation techniques and instrumentation that produce results considerably more accurate and precise than the gross alpha measurement (the exception being use of GPC for Method 903.0). Among the four approved methods for which there were a significant number of results provided, there were notable differences in the quality of results. While the difference in average recoveries among the methods was relatively small (99-107%), the most commonly used method, EPA 903.0, demonstrably showed the poorest precision with a standard deviation of 44% (1σ). In contrast, the least commonly used method, the gamma spectrometry method from Georgia Tech, showed a standard deviation of 12% (1σ) which was 25-73% better than the other methods. Consistent with this observation, 95% of reported results for the Georgia Tech method fell between 85% and 125%, a range that is very close to the ideal range 80%-120% targeted in the Drinking Water Certification Manual for internal quality control sample results (LCS/LFB). As such, the Georgia Tech gamma spectrometry method would appear to be the best method available for samples with unknown activities, or samples with true activities close to a trigger point.17 Overall Performance for 228Ra Methods Based on Proficiency Testing Results Laboratory performance for proficiency testing samples run as an ongoing requirement for laboratory certification / accreditation for 228Ra is summarized in Table 3.18

16 See Appendix A for detailed analysis of drinking water laboratory proficiency testing results. 17 It is noted that the number of data points available for the GA Tech method was small, but the statistics are

consistent with method performance that would be expected using much more modern spectrometric instrumentation. There is a possibility of inadvertent sample compilation bias with regards to this method – if only experienced labs offering high level of sample care from expert analytical staff use it. Investigation may be warranted to further characterize the performance of this method as more data become available. The authors do note gradual movement at laboratories away from de-emanation while gamma spectrometry appears to be

25


Table 3: Summary of 228Ra Proficiency Testing Results from ERA PT Studies 55-99

Method Data

Points Average Stnd. Dev. Min.


97.5

percentile Max

Radium 228

EPA 904.0 689 99% 26% 10% 58% 97% 161% 295%

EPA Ra-05 334 102% 24% 26% 63% 99% 150% 274%

SM 7500 Ra-D

74 97% 20% 49% 79% 106% 158% 216%

Brooks & Blanchard

45 108% 22% 35% 79% 106% 158% 178%

Ga Tech 40 102% 16% 70% 72% 101% 137% 155%

All Methods 1182 100% 24% 10% 59% 98% 154% 295%

The PT samples contained activities that range from 3 pCi/L to 20 pCi/L. PT acceptance ranges for samples containing 228Ra at 5 pCi/L (Ra MCL) and 15 pCi/L are 41% - 153% and 53% - 135%, respectively. Among the five approved methods for which there were a significant number of results provided, there were notable differences in the quality of results. While the difference in average recoveries among the methods was relatively small, the most commonly used method, EPA 904.0, showed the poorest precision with a standard deviation of 26% (1σ). In contrast, the least commonly used method, the gamma spectrometry method from Georgia Tech, showed a standard deviation of 16% (1σ) which was 20-40% lower than the other methods. Consistent with this observation, 95% of reported results for the Georgia Tech method fell between 72% and 137%, a range that is close to the ideal range targeted in the Drinking Water Certification Manual for internal quality control sample results (LCS/LFB). As such, the Georgia Tech gamma spectrometry method would appear to be the best method available for samples with unknown activities, or samples with true activities close to a trigger point.19 There are no comparable approaches that provide better sensitivity of even comparable accuracy and precision as was the case for the de-emanation method for 226Ra. Key performance characteristics that can help in lab selection Ultimately it is incumbent upon the utility to do an adequate job of reviewing a laboratory’s capabilities to achieve reliable data on an ongoing basis. It is NOT sufficient to assume that because a laboratory is EPA or state certified, that you can expect data of sufficient quality for appropriate decision making, in the same way that having a driver’s license does not automatically make one a good driver. Listed here are some lab performance characteristics that should help in evaluation of a lab’s ability to meet requirements.

gaining in popularity. While the de-emanation method offers similar (and better performance at the lowest detection levels (i.e., <<0.5 pCi/L where detection capability of the gamma spectral method diminishes). As far as 228Ra is concerned, the absolute sensitivity of the gamma measurement is not as good as for 226Ra, but in relative terms, it is at least comparable to that provided by GPC with significantly better performance as far as bias, precision, specificity, and robustness and reliability are concerned.

18 See Appendix A for detailed analysis of drinking water laboratory proficiency testing results. 19 It is noted that the number of data points available for the GA Tech method was small, but the statistics are very

consistent with method performance that would be expected using much more modern spectrometric instrumentation. See footnote 15.

26


Gross alpha/beta

Method selection o Commitment and ability to use a method that does not delay the count of samples

for 72-hours after preparation as documented by an SOP that states that samples shall be counted as quickly as possible but which establishes a holding time between sample preparation and counting of 48 hours (and preferably sooner). At present this would eliminate Method 900.0 as an option, but it is expected that EPA’s newer version of 900.0 will eliminate the 72-hour delay (in upcoming revisions).

o Commitment and ability to use co-precipitation for any samples with TDS >500 ppm, and for samples that are deemed to require higher precision results (i.e., results that are very close to decision or trigger points).

Maximum RDL of 3 pCi/L o The laboratory determines compliance with SDWA on a sample-by-sample basis

and re-prepares any samples for which sensitivity requirements are not met.

LCS spikes are high enough to minimize counting uncertainty. Current LCS control charts are provided to demonstrate that the QC limits for LCS fall within the range of 100 ± 20% (3σ), and that the laboratory is consistently able to meet these requirements.

Matrix spikes (MS) are at approximately 10 times the lab’s default detection limit (or 10 times the expected sample activity, whichever is higher), which under the SDWA must be at or below 3 pCi/L for alpha, so ~30 pCi/L. Current MS control charts are provided to demonstrate that the QC limits for MS fall within the range of 100 ± 30% (3σ), and that the laboratory is consistently able to meet these requirements.

PT results indicate good performance with the method at the laboratory o The laboratory runs PT samples using the same method and approach as it uses

for samples. If the laboratory uses more than one approach, it submits PT results accordingly. If it extends count times, it may submit PT samples at the lower and upper range of count times it plans to use.

o Four out of the five most recent PT rounds show results for gross alpha that meet acceptance limits.

o Any results at or above 15 pCi/L should fall within ± 25% of assigned value (unless there was a problem with the study documented by the PT provider).

o If results fail to meet these requirements, prompt corrective action is performed, and documented to show that the root cause was identified and the problem eliminated.

Agreement to follow the requirements of the Lab Certification Manual for radiochemistry and the batch QC requirements presented in Table 4.

Ability to report elapsed time between prep and counting and the SDWA detection limit achieved for each sample.

Radium 226 (226Ra)

Method selection – o Preferred labs would use the Georgia Tech method (gamma spectrometry) or

equivalent. o If the laboratory uses EPA 903.0 or SM 7500-Ra B, it is able to and commits to

prepare sample promptly when received, and to hold the sample for 2-3 weeks prior to counting to minimize positive bias and uncertainty.

27


Maximum DL of 1 pCi/L o The laboratory determines compliance with SDWA on a sample-by-sample basis

and reprepares any samples for which sensitivity requirements are not met..

LCS spikes are high enough to minimize counting uncertainty (e.g., 15 pCi/L) o Current LCS control charts are provided to demonstrate that the QC limits for LCS

fall within the range of 100 ± 10% (3σ), and that the laboratory is consistently able to meet these requirements.

Matrix spikes are at approximately 10 times the lab’s default detection limit (which must be at or below 1 pCi/L under the SDWA), or 10 times the sample activity, whichever is higher); so ~10 pCi/L, depending on sample activity.

o Current MS control charts are provided to demonstrate that the QC limits for MS fall within the range of 100 ± 20% (3σ), and that the laboratory is consistently able to meet these requirements.



o Four out of the five most recent PT rounds show results for 226Ra that meet acceptance limits.




Ability to report elapsed time between prep and counting and the SDWA achieved for each sample.

Radium 228 (228Ra)

Method selection – o Preferred labs would use the Georgia Tech method (gamma spectrometry) or

equivalent. o Commitment and ability to process larger sample sizes (e.g., 4 L) for any samples

that are deemed to require higher precision results (i.e., results that are very close to decision or trigger points)

Maximum DL of 1 pCi/L o The laboratory determines compliance with SDWA on a sample-by-sample basis

and reprepares any samples for which sensitivity requirements are not met.

LCS spikes are high enough to minimize counting uncertainty (e.g., 15 pCi/L) o Current LCS control charts are provided to demonstrate that the QC limits for LCS

fall within the range of 100 ± 20% (3σ), and that the laboratory is consistently able to meet these requirements.

28


Matrix spikes are at approximately 10 times the lab’s default detection limit (which must be at or below 1 pCi/L under the SDWA), or 10 times the sample activity, whichever is higher); so ~10 pCi/L, depending on sample activity.

o Current MS control charts are provided to demonstrate that the QC limits for MS fall within the range of 100 ± 30% (3σ), and that the laboratory is consistently able to meet these requirements.



o Four of the five most recent PT rounds show results for 228Ra that meet acceptance limits.




Ability to report elapsed time between prep and counting and the SDWA achieved for each sample. Control chart of gravimetric barium yield available.

29


Recommendations for review and action based on analytical results The recommendations in these tables could also be incorporated into a scope of work. Note that these are only CRITICAL for utilities that have radionuclide levels near compliance limits. Table 4: Recommended QC Sample Requirements for Gross Alpha Analyses

QC Parameter Frequency

Acceptance Criteria and Considerations Action / Comment

Required Detection

Limit

each compliance

sample

The sample specific DL for each compliance sample must be less than or equal to the RDL for gross alpha of 3 pCi/L. The DL will vary by sample since solids determine the maximum sample size and the count is often adjusted to meet the RDL.

If the SDWA RDL is not met, 1) recount affected samples longer or on lower background detectors to achieve RDLs**, 2) If a recount cannot meet the RDL, where possible re-prepare samples using a larger aliquot (to improve sensitivity), or 3) analyze samples using a more sensitive method (e.g., co-precipitation).

Reagent Blank (RB)

one per preparation batch of up to twenty samples&

The RB activity must be less than the 1.96σ counting uncertainty.@ The reagent blank must be counted at least as long as the longest sample in the batch. Duplicates are counted the same duration.

If RB result is unacceptable; 1) check for errors – samples may be recounted once ** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy all requirements and produce unqualified results

Matrix Spike

Sample (MS)


MS recovery must fall within the range of historical MS results (mean ± 3 sd) where this range must fall within the range of 70-130%.#

Spike MS at ~30 pCi/L (~10×RDL) or 10 times the expected sample activity; If MS recovery is unacceptable, 1) check for errors – samples may be recounted once. 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

Matrix Spike

Duplicate (MSD)

exception

The certification manual allows MSDs to be run in lieu of sample duplicates when results are frequently below the DL.

MSDs must be evaluated both as matrix spikes (i.e., recovery) and as duplicates (RPD/RER).

Laboratory Control Sample (LCS)++


LCS recovery must fall within the range of historical MS results (mean ± 3 sd) but the acceptance range may not extend outside 80-120%.

Spike LCS at a minimum of 30 pCi/L (~10×RDL); If LCS recovery is unacceptable, 1) check for errors – samples may be recounted once. 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

Sample Duplicate

(SD) or MSD


and at least one

per ten samples&

If the mean activity of the duplicate pair is greater than 5 × RDL, the Relative Percent Difference (RPD) must be ≤20%.

If RPD is unacceptable, 1) check for errors – samples may be recounted once. 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

If the RPD >20% and the mean activity of the duplicate pair is ≤5 × DL, the Replicate Error Ratio (RER) must be ≤ 2.

If RER is unacceptable 1) check for errors – samples may be recounted once. 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

@ Sample size varies within the batch depending on the solids content of samples. Requiring that the count duration of the

blank is at least as long as that of the longest sample improves the probability that the blank will detect contamination that could impact samples.

# The Drinking Water Certification Manual permits acceptance limits as wide as low as 70% - 130% but wider limits allow larger uncertainties and increase the risk of incorrect compliance decisions.

& Ten and twenty sample limits do not include quality control samples. ** Within limits, extending the duration of a sample count can lower uncertainty. Sample counts, however, should not be

extended beyond the duration of the routine background subtraction counts since the laboratory cannot demonstrate statistical control over longer counts.

++ The LCS is also referred to as the Laboratory Fortified Blank (LFB).

30


Table 5: Recommended QC Sample Requirements for 226Ra Analyses



Required Detection

Limit

each compliance

sample and QC sample

The sample specific DL for each compliance sample and QC sample must be ≤ 1 pCi/L (i.e., ≤ RDL for 226Ra). Note: Batch QC samples should be prepared and processed using the same sample size and count durations as samples in the batch.

If the SDWA RDL is not met, 1) recount affected samples longer or on lower background detectors to achieve RDLs** 2) re-prepare samples to obtain lower uncertainty (e.g., using a larger aliquot, obtain better yield), or 3) analyze samples using a more sensitive method.

Reagent Blank (RB)


The activity and the 1.96σ counting uncertainty must both be less than the 1 pCi/L (i.e., the RDL must be satisfied and the activity for 226Ra less than the 1.96σ counting uncertainty).

If RB result is unacceptable; 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy all requirements and produce unqualified results.

Matrix Spike

Sample (MS)


MS recovery must fall within the range of historical MS results (mean ± 3σ) where this range may not fall outside the range of 80-120%.

Spike the MS at a minimum of 10 pCi/L (~10×RDL) or ~10 times expected sample activity; If MS recovery is unacceptable, 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results).

Matrix Spike

Duplicate (MSD)

exception

The certification manual allows MSDs to be run in lieu of sample duplicates when results are frequently below the DL.




LCS recovery must fall within the range of historical MS results (mean ± 3 sd) but the acceptance range should not extend outside 90-110%

Spike LCS at a minimum of 10 pCi/L (~10×RDL); If LCS recovery is unacceptable, 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

Sample Duplicate

(SD) or MSD


and at least

one per ten samples&


If RPD is unacceptable, 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in prep batch to obtain QC results that satisfy requirements (i.e., unqualified results)


If RER is unacceptable 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

& Ten and twenty sample limits do not include quality control samples. ** Although extending the duration of a sample count can lower uncertainty, for methods that measure 222Rn following separation

from 226Ra, recounting must be conducted promptly to be a viable option due to the short half-life of the analyte. For methods that measure gamma spectrometry methods, extending counts will help achieve lower uncertainty. Sample counts should not be extended beyond the duration if the routine background subtraction count since the laboratory cannot demonstrate statistical control over longer counts.


31


Table 6: Recommended QC Sample Requirements for 228Ra Analyses



Required Detection

Limit

each compliance

sample and QC sample

The sample specific DL for each compliance sample and QC sample must be ≤ 1 pCi/L (≤ RDL for 228Ra). Note: Batch QC samples should be prepared and processed using the same sample size and count durations as samples in the batch.

If the SDWA RDL is not met, 1) recount affected samples longer or on lower background detectors to achieve RDLs** 2) re-prepare samples to obtain lower uncertainty (e.g., using a larger aliquot, obtain better yield), or 3) analyze samples using a more sensitive method.

Reagent Blank (RB)


The activity and the 1.96σ counting uncertainty must both be less than the 1 pCi/L (i.e., the RDL must be satisfied and the activity for 228Ra less than the 1.96σ counting uncertainty).

If RB result is unacceptable; 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy all requirements and produce unqualified results.

Matrix Spike

Sample (MS)


MS recovery must fall within the range of historical MS results (mean ± 3σ) where this range may not fall outside the range of 70-130%.#

Spike the MS at ~10 pCi/L (~10×RDL) or ~10 times expected sample activity; If MS recovery is unacceptable, 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results).

Matrix Spike

Duplicate (MSD)

exception The certification manual allows MSDs to be run in lieu of sample duplicates when results are frequently below the DL.




LCS recovery must fall within the range of historical MS results (mean ± 3 sd) but the acceptance range should not extend

outside 80-120%

Spike LCS at ~10 pCi/L (~10×RDL); If LCS recovery is unacceptable, 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

Sample Duplicate

(SD) or MSD


and at least

one per ten samples&


If RPD is unacceptable, 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)


If RER is unacceptable 1) check for errors – samples may be recounted once.** 2) If recounting fails to produce acceptable results, re-prepare all samples in preparation batch to obtain QC results that satisfy requirements (i.e., unqualified results)

# The Drinking Water Certification Manual permits acceptance limits as wide as 70% - 130% but wider limits allow larger uncertainties and increase the risk of incorrect compliance decisions especially when the true activity of 226Ra or 228Ra may be present above RDLs.

& Ten and twenty sample limits do not include quality control samples. ** Although extending the duration of a sample count can lower uncertainty, for methods that measure 228Ac following separation

from 228Ra the short half-life of the analyte eliminates recounting as a viable option. For gamma spectrometry methods, extending the count will help achieve lower uncertainty but counts should not be extended beyond the duration for routine background subtraction counts since the laboratory cannot demonstrate statistical control for longer counts.


32


Appendix A: Discussion of ERA Proficiency Testing (PT) Data

Over 7,000 data points for gross alpha, Gross Beta, 226Ra and 228Ra from studies Rad-55 – Rad 99 were obtained from ERA, the sole provider of radiochemistry proficiency testing for drinking water. The information in Excel spreadsheet format included: study ID; analyte; laboratory reported method IDs; laboratory reported result; ERA assigned true value. All laboratory identifiers had been removed by ERA, which prevented an assessment of single laboratory versus overall performance. It is also noted that measurement uncertainty and detection limits are not captured by the PT data reporting program, and that ERA does not report uncertainties for its assigned values. This prevents rapid assessment of whether individual results had been run with sufficient precision to meet EPA assigned measurement quality objectives for SDWA. Since ERA allows laboratories to manually enter method identifiers, a large number of variants of methods were present in the data. The data had to be manually reviewed to eliminate records where the laboratory supplied method identifier could not unambiguously be correlated to EPA-approved methods. The remaining data were then collated. Methods for which fewer than 30 data points were reported were eliminated. The percent recovery (the reported value divided by the true value times 100) was evaluated for the three critical analytes (gross alpha, 226Ra, and 228Ra), and any method for which the minimum of 30 data points was available. A normal probability plot was prepared for all methods and for each of the methods to qualitatively assess the normality of results. The vast majority of results appear to be normally distributed, and thus appear to be consistent with likely true output from the method as opposed to spurious data points attributable to non-method-related occurrences in the lab, such as data entry errors. Descriptive statistics were calculated on the remaining data set, and again on smaller subsets of results close to the Maximum Contaminant Level. For gross alpha methods, the distribution of recoveries generally conforms to a normal distribution with a small number of apparent outlying data points. EPA Method 900.0 is the exception with a positive skew and fat high tail. This implies that the standard deviation underestimates the number of points in the high tail of the distribution. For 226Ra, the analyte recovery distribution is largely normal. Methods EPA 903.0 and SM 7110 B show a heavier high-side tail than do the isotope specific methods. A high tail would be consistent with results impacted by 224Ra present as an accumulated decay product of 228Ra in the test samples20. While the distribution of results for the GA Tech method appears to conform well to a normal distribution, the number of points available is too small to make firm conclusions. Continued data collection is needed to develop a more robust characterization of the performance of this method. For 228Ra, methods EPA 904.0, and to a lesser extent EPA Ra-05, show a heavy high-side tail, likely due to bias associated with yttrium yield correction. The distribution of analyte recovery for methods SM 7500-Ra D and the Brooks and Blanchard Method appear to conform well to a normal distribution. The distribution of results for the GA Tech method appears to conform to a normal distribution, but the number of points available is too small to make any firm conclusions. Similar to 226Ra, continued data collection is needed to develop a more robust characterization of the performance of this method.

20 While some labs delay counting of the test source until 2-3 weeks after preparation to allow for 224Ra to decay,

other labs do not which would result in high bias for results counted more promptly after preparation.

33


Summary of Method Performance Data for ERA Gross Alpha PT Studies 55-99 Results

Method

Data Points Average

Stnd. Dev. Min.


97.5

percentile Max

Gross Alpha

EPA 900.0 1537 95% 24% 27% 52% 93% 148% 246%

EPA 00-02 223 91% 20% 40% 49% 93% 130% 195%

SM 7110 C 198 92% 16% 7.5% 62% 92% 124% 133%

SM 7110 B 161 97% 22% 7.2% 54% 98% 137% 174%

All Methods 2119 94% 23% 7.2% 52% 93% 143% 246%

All Approved Gross Alpha Methods – Gross Alpha Recovery

Activity pCi/L number average

Stnd. dev. minimum


97.5 percentile Maximum

All results 2119 94% 23% 7.2% 52% 93% 143% 246%

9-25 451 98% 27% 35% 54% 95% 165% 246%

25-70 1668 93% 21% 7.2% 51% 93% 138% 202%

y = 0.8901x + 1.7477

0102030405060708090

100110120130

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

All Methods All Gross Alpha Results

1:1 Line

Alpha MCL

y = 1.0178x - 0.6348

0

10

20

30

40

50

60

0 5 10 15 20 25 30

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

All Methods Gross Alpha Results < 25 pCi/L

1:1 Line

Alpha MCL

34


EPA Method 900.0 – Gross Alpha Recovery

Activity pCi/L number average

Stnd. dev. minimum

2.5 percentile median


All results 1537 95% 24% 27% 52% 93% 148% 246%

9-25 327 99% 29% 35% 54% 95% 167% 246%

25-70 1210 93% 22% 27% 52% 92% 143% 202%

EPA Method 00-02 – Gross Alpha Recovery

Activity (pCi/L) number average

Stnd. dev. minimum



All results 223 91% 20% 40% 49% 93% 130% 195%

9-25 46 96% 26% 58% 59% 94% 146% 195%

25-70 177 90% 18% 40% 48% 93% 117% 144%

y = 0.8759x + 2.363

0102030405060708090

100110120130

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method 900.0 All Gross Alpha Results

1:1 Line

Alpha MCL

y = 1.0419x - 0.8523

0

5

10

15

20

25

30

35

40

45

50

55

0 5 10 15 20 25 30

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method 900.0 Gross Alpha Results < 25 pCi/L

1:1 Line

Alpha MCL

y = 0.8925x + 0.5624

05

101520253035404550556065707580

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA 00-02All Gross Alpha Results

1:1 Line

Alpha MCL

y = 0.7199x + 3.7413

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA 00-02Gross Alpha Results < 25 pCi/L

1:1 Line

Alpha MCL

35


SM Method 7110 C – Gross Alpha Recovery


Stnd. dev. minimum



All results 198 92% 16% 7.5% 62% 92% 124% 133%

9-25 46 91% 15% 39% 57% 92% 119% 124%

25-70 152 92% 17% 7.5% 63% 92% 125% 133%

EPA Method 7110 B – Gross Alpha Recovery


Stnd. dev. minimum



All results 161 97% 22% 7.2% 54% 98% 137% 174%

9-25 32 93% 20% 48% 52% 97% 126% 128%

25-70 129 97% 22% 7.2% 54% 98% 137% 174%

y = 1.0681x + 1.9004

05

1015202530354045505560657075808590

0 5 10 15 20 25 30 35 40 45 50 55 60

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM Method 7110CAll Gross Alpha Results

1:1 Line

Alpha MCL

y = 0.8066x + 1.5089

0

5

10

15

20

25

30

0 5 10 15 20 25 30R

ep

ort

ed

Val

ue

(p

Ci/

L)

Known Value (pCi/L)

SM Method 7110CGross Alpha Results < 25 pCi/L

1:1 Line

Alpha MCL

y = 0.9316x + 1.46

05

1015202530354045505560657075808590

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM Method 7110BAll Gross Alpha Results

1:1 Line

Alpha MCL

y = 0.9365x - 0.0211

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM Method 7110BGross Alpha Results < 25 pCi/L

1:1 Line

Alpha MCL

36


Summary of Method Performance Data for ERA 226Ra PT Studies 55-99 Results

Method

Data Points Average

Stnd. Dev. Min.


97.5

percentile Max

Radium226

EPA 903.0 534 107% 44% 16% 80% 103% 321% 619%

EPA 903.1 312 97% 18% 23% 61% 97% 125% 223%

SM 7500-Ra-B

150 100% 16% 55% 70% 99% 133% 171%

Ga. Tech 33 99% 12% 77% 85% 99% 125% 143%

All Methods 1029 103% 34% 16% 68% 99% 146% 619%

All Ra-226 Methods – Ra-226 Recovery


Stnd. dev. minimum



All results 1029 103% 34% 16% 68% 99% 146% 619%

3-10 408 110% 50% 44% 72% 101% 204% 619%

10-20 621 98% 16% 16% 67% 98% 128% 239%

Method 903.0 – Ra-226 Recovery


Stnd. dev. minimum



All results 534 107% 44% 16% 73% 101% 177% 619%

3-10 186 120% 70% 67% 80% 103% 321% 619%

10-20 348 100% 17% 16% 70% 99% 133% 239%

y = 0.8983x + 1.2025

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

All Ra-226 Methods

1:1 Line

5 pCi/L MCL

y = 0.8458x + 1.5511

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

Ra-226 - All Methods3-10 pC/L

1:1 Line

5 pCi/L MCL

y = 0.8835x + 1.782

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method 903.0 Ra-226 Results

1:1 Line

5 pCi/L MCL

y = 0.6663x + 3.4049

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method 903.0 Ra-226 Results from 3-10 pCi/L

1:1 Line

5 pCi/L MCL

37


Method 903.1 – Ra-226 Recovery


Stnd. dev. minimum



All results 312 97% 18% 23% 61% 97% 125% 223%

3-10 55 99% 15% 72% 75% 96% 124% 160%

10-20 257 96% 19% 23% 57% 97% 126% 223%

SM Method 7500-Ra B – Ra-226 Recovery


Stnd. dev. minimum



All results 150 100% 16% 55% 70% 99% 133% 171%

3-10 57 103% 20% 56% 63% 101% 152% 171%

10-20 93 99% 12% 55% 78% 99% 119% 120%

y = 0.8645x + 0.9235

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)


1:1 Line

5 pCi/L MCL

y = 0.9509x + 0.3089

0

5

10

15

20

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method 903.1 Ra-226 Results from 3-10 pCi/L

1:1 Line

5 pCi/L MCL

y = 0.9479x + 0.5376

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM 7500 Ra-BRa-226 Results

1:1 Line

5 pCi/L MCL

y = 0.9552x + 0.4886

0

5

10

15

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM 7500 Ra-BRa-226 Results from 3-10 pCi/L

1:1 Line

5 pCi/L MCL

38


GA Tech Method – Ra-226 Recovery


Stnd. dev. minimum



All results 33 99% 12% 77% 85% 99% 125% 143%

3-10 10 98% 13% 77% 79% 98% 119% 120%

10-20 23 100% 11% 87% 88% 101% 125% 143%

Summary of Method Performance Data for ERA 228Ra PT Studies 55-99 Results

Method Data

Points Average Stnd. Dev. Min.


97.5

percentile Max

Radium

228

EPA 904.0 689 99% 26% 10% 58% 97% 161% 295%

EPA Ra-05 334 102% 24% 26% 63% 99% 150% 274%

SM 7500 Ra-D

74 97% 20% 49% 79% 106% 158% 216%

Brooks & Blanchard

45 108% 22% 35% 79% 106% 158% 178%

Ga. Tech 40 102% 16% 70% 72% 101% 137% 155%

All Methods 1182 100% 24% 10% 59% 98% 154% 295%

y = 0.912x + 1.0185

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

GA Tech MethodAll Ra-226 Results

1:1 Line

5 pCi/L MCL

39


All Methods - Ra-228 Recovery

Activity (pCi/L) number

Average

Stnd. dev.

minimum

2.5 percentil

e median

97.5 percentil

e Maximu

m

All results 1182 100% 24% 10% 59% 98% 154% 295%

3-10 588 104% 28% 35% 63% 99% 178% 295%

10-20 595 96% 19% 10% 57% 97% 137% 241%

EPA Method 904.0 - Ra-228 Recovery

Activity number Average Stnd. dev. minimum


97.5 percentile maximum

All results 689 99% 26% 10% 58% 97% 161% 295%

3-10 343 103% 29% 40% 65% 98% 180% 295%

10-20 346 94% 21% 10% 55% 96% 137% 241%

y = 0.9215x + 0.6052

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

All Ra-228 Methods

1:1 Line

5 pCi/L MCL

y = 0.9491x + 0.4696

0

5

10

15

20

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

All Ra-228 Methods 3-10 pCi/L

1:1 Line

5 pCi/L MCL

y = 0.9019x + 0.6623

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)


1:1 Line

5 pCi/L MCL

y = 0.9688x + 0.3317

0

5

10

15

20

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method 904.0 Ra-228 - 3-10 pCi/L

1:1 Line

5 pCi/L MCL

40


EPA Method Ra-05 - Ra-228 Recovery


Stnd. dev. Minimum



All results 334 102% 24% 26% 63% 99% 150% 274%

3-10 161 106% 29% 42% 62% 103% 178% 274%

10-20 173 97% 16% 26% 67% 98% 131% 148%

SM 7500 Ra-D - Ra-228 Recovery

Activity (pCi/L) Number average

Stnd. dev. minimum



All results 74 97% 20% 49% 72% 97% 124% 216%

3-10 38 100% 25% 49% 75% 100% 148% 216%

10-20 36 94% 12% 71% 72% 94% 114% 119%

y = 0.928x + 0.6882

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method Ra-05Ra-228 Results

1:1 Line

5 pCi/L MCL

y = 0.928x + 0.6882

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

EPA Method Ra-05Ra-228 - 3-10 pCi/L

1:1 Line

5 pCi/L MCL

y = 0.9196x + 0.4135

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM 7500-Ra D Ra-228 Results

1:1 Line

5 pCi/L MCL

y = 0.9524x + 0.2732

0

5

10

15

0 1 2 3 4 5 6 7 8 9 10

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

SM 7500-Ra DRa-228 Results from 3-10 pCi/L

1:1 Line

5 pCi/L MCL

41


Brooks and Blanchard Method - Ra-228 Recovery

Activity (pCi/L) number Average

Stnd. dev. minimum



All results 45 108% 22% 35% 79% 106% 158% 178%

3-10 18 103% 22% 35% 54% 104% 132% 139%

10-20 27 111% 23% 86% 87% 109% 332% 178%

Ra-228 - GA Tech

Activity (pCi/L) number Average

Stnd.

dev. minimum

2.5

percentile median

97.5

percentile Maximum

All results 40 102% 16% 70% 72% 101% 137% 155%

3-10 28 101% 16% 70% 71% 102% 136% 155%

10-20 12 104% 17% 85% 86% 97% 133% 136%

y = 1.1199x - 0.2974

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

Brooks and Blanchard MethodRa-228 Results

1:1 Line

5 pCi/L MCL

y = 1.298x - 1.6332

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

Brooks and Blanchard MethodRa-228 - 3-10 pCi/L

1:1 Line

5 pCi/L MCL

y = 1.0039x + 0.1035

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Re

po

rte

d V

alu

e (

pC

i/L)

Known Value (pCi/L)

GA Tech Ra-228 Results

1:1 Line

5 pCi/L MCL

42


Appendix B: Calculations Used to Assess Method Performance

Replicate Error Ratio (RER) The replicate error ratio, RER, assesses statistical agreement between duplicate results. The test compares the magnitude of the difference between two results to the expected uncertainty of that difference at the 95% confidence interval. To be acceptable, the EPA Laboratory Certification Manual specifies that the RER ≤ 2. It is important to be sure that replicate error ratio (RER) is properly calculated by the laboratory. RER is calculated as follows:

RER = |A − B|

√sa2 + sb

2

where; A = Activity of the first measurement (in pCi/L) B = Activity of the second measurement made from a different aliquot from the same

sample (in pCi/L) sa = 1-sigma counting uncertainty of the first measurement (in pCi/L) sb = 1-sigma counting uncertainty of the second measurement (in pCi/L)

Note that this formulation requires that the terms sa and sb be 1-sigma uncertainties. Inputting 1.96σ uncertainty, as has occurred at some laboratories, will result in the failure to properly identify problematic precision for samples containing activity near the maximum contaminant level (MCL) and can result in elevated rates of compliance decision errors for radium.

Generic SDWA Detection Limit Calculation

Note that this is a default calculation. The actual calculation should incorporate factors used in the laboratory’s calculation of the sample activity

VAε2.22

11

96.1

4 11

296.1

=

B2

22

YID

ttR

t

t

DLBs

s

s

DL = Safe Drinking Water Detection Limit ts = sample count time ts = background count time RB = background count rate for subtraction 2.22 = conversion from dpm to pCi, (dpm/pCi)

ε = calibrated efficiency (corrected for attenuation) D = Factor to correct for sample decay I = Factor to correct for sample Ingrowth Y = Factor to correct for chemical yield A = Factor to correct for abundance (decay particles/disintegration) V = volume of sample

43


Appendix C: How Does Measurement Uncertainty Impact Compliance

Decisions? In evaluating data for radionuclides, particularly if results are very close to compliance points (e.g. gross alpha substitution near the trigger level for 226Ra monitoring, 226Ra or 228Ra near the MCL, gross alpha near the MCL), it is important to understand how the uncertainty of the measurement may affect results. Even though uncertainty is not considered in most states as part of the compliance decision (California is an exception, where gross alpha substitution for combined radium compliance and adjusted gross alpha compliance is based on adding the error to the measured value to be more conservative), minimizing measurement uncertainty is critical in maximizing the likelihood of correct compliance decisions. This appendix demonstrates how uncertainty of radionuclide measurements may influence those decisions. For any measurement there is a finite possibility that results will generate a false positive or a false negative. Figure 5 demonstrates that phenomenon. Figure 5: Distribution of Possible Results for Samples Containing No Activity and Activity

at the MCL

Measurement uncertainty is associated with and intrinsic to every measurement. Measurement uncertainty will unavoidably lead to making incorrect decisions.

The curve delineated by the dark red line shows the distribution of measurements we would get if we were to measure a sample many, many times.

Although each measurement would produce a slightly different result, those results presumably group around the most likely result for analyte in the sample which is the highest point in the curve.

This distribution of measurements is bell-shaped, or Gaussian. Most results would fall closer to the analytical action level with fewer and fewer as we move further from the true value in the sample.

A less precise measurement technique will produce wider distributions, and a more precise technique, narrower ones.

In this example, the average measured concentration of analyte in the sample is equal to the analytical action level. For SDWA analysis, the AAL might be the MCL (even though compliance is based on the running annual average of quarterly samples, a utility would want to be assured that no single measurement could drive it out of compliance.

Concentration Relative to Action Level

44


Half of our measurement results will fall above the average and half below.

If we compare the results of each measurement directly to the action level, we will:

Incorrectly decide that the sample is in compliance (i.e., true value is less than the action level) approximately 50% of the time (red shaded area).

Correctly decide that our sample is out of compliance (i.e., true value is equal to or greater than the action level) approximately 50% of the time.

The blue curve emphasizes why it is so important to ensure that we control the uncertainty / sensitivity of our measurements.

The blue curve shows the distribution of measurements of a sample that contains no analyte (i.e., a blank sample).

In this case, the measurement uncertainty is large enough that a certain portion of our measurements will produce results that are greater than the action level such that we will incorrectly decide that there is activity above the AAL when lower levels of activity are present (blue shaded area).

The next figure (Figure 6) shows a generic power curve, which relates the likelihood of decision errors to the analyte concentration and allows one to assess the impact of incorrect decisions. So how much uncertainty can we accept and achieve acceptable decision error rates?

Decision makers use power curves to graphically show the rate of decision errors relative to analyte concentration in the sample.

While we can minimize measurement uncertainty, this costs time and money.

Decision makers try to balance the cost of making incorrect decisions against the cost of minimizing measurement uncertainty that make their decisions more reliable.

The gray region is the area on either side of the action level.

Its width is controlled by decision makers’ confidence about their tolerance to making incorrect decisions.

The rate of decision errors outside of the gray region is controlled at low rates that are deemed to be acceptable by decision makers.

Within the gray region, the concentration approaches the action limit and measurement uncertainty will limit project planners’ ability to control decision errors at the low rate possible outside the grey region.

Ideally, the gray region should kept be as small as possible, but higher precision measurements cost time and money.

45


Figure 6: The Gray Region - Activity near the Action Level 21

An example of how uncertainty impacts our gross alpha measurement is shown in Figure 7.

Figure 7: Comparison of distributions of results for a sample with a given activity.

21 Figure 6 is from US EPA Office of Environmental Information, EPA-QA/G4 - Guidance on Systematic Planning

Using the Data Quality Objectives Process, EPA/240/B-06/001 February 2006, Washington, DC.

0 1

Measurement Results in

Shaded Area Result in Incorrect

Compliance Decision

Distribution of Measurements

at the MCL

Upper 95th Percentile of Sample

Measurements(5% of measurementsfall above this value)

True Sample Activity MCL

Distribution of Measurements

of Sample Activity

46


We want to determine whether a sample contains activity that is in compliance with the MCL for gross alpha.

The laboratory successfully follows the approved method and obtains an SDWA DL of 3 pCi/L.

The width of results distribution is a function of measurement uncertainty which results when a measurement satisfies the SDWA required detection limit (RDL).

About 5% of our distribution of measurements falls to the right of the action level. Compare the measured result to the MCL for adjusted gross alpha to determine compliance

Since 5% of our measurement results will fall above the MCL, one in twenty measurements will incorrectly produce a result that indicates that the water is not in compliance with SDWA regulations.

What can we do???

Minimize the uncertainty of the measurement.

The closer the true result is to the MCL, however, the less uncertainty can be tolerated and the more expensive the measurement.

It is this guide’s goal to provide a relatively straightforward road map that will help water utilities manage the analytical process and reasonably minimize the probability of making incorrect compliance decisions by decreasing measurement uncertainty.

47


References

Georgia Tech (2004) The Determination of Radium-226 and Radium-228 in Drinking Water by Gamma-ray Spectrometry Using HPGE or Ge(Li) Detectors, Revision 1.2. Georgia Institute of Technology, Atlanta, GA. Standard Methods (2012) Method 7110 B - Evaporation Method for Gross Alpha-Beta Standard Methods for the Examination of Water and Wastewater, 22nd edition, 2012. American Public Health Association, Washington, D.C. Standard Methods (2012) Method 7110 C - Coprecipitation Method for Gross Alpha Radioactivity in Drinking Water Standard Methods for the Examination of Water and Wastewater, 22nd edition, 2012. American Public Health Association, Washington, D.C. Standard Methods (2012) Method 7500-Ra B - Precipitation Method Standard Methods for the Examination of Water and Wastewater, 22nd edition, 2012. American Public Health Association, Washington, D.C. Standard Methods (2012) Method 7500-Ra D - Sequential Precipitation Method Standard Methods for the Examination of Water and Wastewater, 22nd edition, 2012. American Public Health Association, Washington, D.C. USEPA (1984) Method 00-02 – Radiochemical Determination of Gross Alpha Activity in Drinking Water by Coprecipitation in: Radiochemistry Procedures Manual December 1984 EPA 520/5-84-006 Washington, DC USEPA (1980). Method 900.0 - Gross Alpha and Gross Beta Radioactivity in Drinking Water in: Prescribed Procedures for Measurement of Radioactivity in Drinking Water, EPA 600/4- 80-032, Cincinnati, OH USEPA (1980) Method 903.0 - Alpha-Emitting Radium Isotopes in Drinking Water in: Prescribed Procedures for Measurement of Radioactivity in Drinking Water, EPA 600/4-80-032 Cincinnati, OH USEPA (1980) Method 903.1 - Radium in Drinking Water, Radon Emanation Technique in: Prescribed Procedures for Measurement of Radioactivity in Drinking Water, EPA 600/4-80-032 Cincinnati, OH USEPA (1980) Method 904.0 - Radium-228 in Drinking Water in: Prescribed Procedures for Measurement of Radioactivity in Drinking Water, EPA 600/4-80-032 Cincinnati, OH USEPA (2005). Manual for the Certification of Laboratories Analyzing Drinking Water Criteria and Procedures Quality Assurance (5th Edition) EPA 815-R-05-004 Cincinnati, OH USEPA (2006) EPA-QA/G4 - Guidance on Systematic Planning Using the Data Quality Objectives Process, EPA/240/B-06/001 February 2006, Washington, DC USDHS (1990) Method Ra-05 - Radium-226 in Tap Water, Urine, and Feces Reference: EML Procedures Manual, HASL-300, 27th Edition, Volume 1, 1990 New York, NY


Government Affairs Office

1300 Eye St. NW, Suite 701W

Washington, DC 20005

T: 202.628.8303

F: 202.628.2846

Documents

Radionuclide Rule Compliance · Radionuclide Rule Compliance: ... approved analytical methods for radionuclides such as gross alpha ... set requirements for bid documents to ensure