1 Memorandum

Review of Analytical Methods Used for Industry Se lf-Monitoring Data Considered for FGD

Wastewater Effluent Limits

December 8, 2014 U.S. EPA, Office of Water, Office of Scie nce and Technology, Engineering and Analysis

Division

1 Introduction

In addition to the data EPA used at proposal to calculate effluent limitations for flue gas desulfurization (FGD) wastewater, EPA evalua ted industry self-monito ring data that were submitted along with comments on the proposed rule in 2013, and self-monitoring data that were submitted in response to data request letters se nt by EPA in 2013 and 2014. In order to assess the quality of the industry self-monitoring data received and to determine whether or not to

include the effluent data in its calculations, EPA gathered all available information about the analytical method used and re levant FGD system and treatm ent system process operations

associated with the data.

This memorandum discusses whether, based on an in itial review of the an alytical methods used and information about how the analyses were performed, the industry self-monitoring effluent data are considered generally acceptable for use in calculating effluent limits. This initial review

evaluated whether the methods used were appropriate, were sufficiently sensitive 1 to measure pollutant concentrations, and th at the reported results reflect proper sampling and analytical practices and that the effluent data appear to be valid for use in calculating effluent limits.

This evaluation was limited to a review of self-m onitoring data appropriate for EPA to consider using to calculate effluent limits based on the ope ration of either (1) chemical precipitation/iron coprecipitation treatment technol ogy; or (2) chemical precipita tion/iron coprecip itation followed by anoxic/anaerobic biological treatment technology. 2 As such, discussion is limited to effluent data for the following pollutants under these t echnology bases: arsenic, mercury, selenium and nitrate-nitrite. EPA evaluated self-monitoring data from four plants that operate chemical precipitation/iron coprec ipitation treatment technology: Ha tfield’s Ferry Power Station, Keystone Generating Station, Miami Fort Station, and Pleasant Prairie Power Plant. Also, EPA evaluated self-monitoring data from two plants that operate chemical precipitation/iron coprecipitation followed by anoxic/anaerobic bi ological treatment technology: Belews Creek

Steam Station and Allen Steam Station.

1 For data used to calculate effluent limits for the steam electric effluent guidelines, a sufficiently sensitive reporting limit (or a sufficiently sensitive analyti cal method) means that the analytical me thod is capable of and was used in a manner that most analytical results were above the level of quantitation. In instances where most analytical results were below the level of quantitation, sufficiently sens itive means that EPA is not aware of any other method approved in 40 CFR Part 136 that can produce substantially lower reporting limits for analyses of FGD wastewater.

2 EPA did not receive self-monitoring data for vapor-co mpression evaporation treatment of FGD or gasification wastewater subsequent to publishing proposed revisions to the effluent guidelines.2 In addition to the initial data assessment described in this memorandum, consistent with the methodology used at proposal, EPA thoroughly evalua ted the available data for each plant to identify any data that should not be used when deriving effluent limits due to: (1) the samples being collected during the initial commissioni ng period for the treatment system prior to reaching steady state (or quasi-steady state) operatio n; (2) the analytical results being identified as questionable due to quality control issues, abnormal conditions or treatment upsets, or analytical anomalies; or (3) othe r relevant factor s. The results of this additional evaluation are

described in the memorandum Effluent Limitations for FGD Wastewater, Gasification Wastewater, and Combustion Residual Leachate fo r the Final Effluent Limitations Guidelines and Standards for the Steam Electric Rulemaking , (hereafter referred to as the “Effluent Limitations Memorandum”).

2 Analytical Methods Associated with the Industry Self-Monitoring Data

2.1 Arsenic and Selenium by EPA Method 200.8

EPA used EPA Method 200.8, in conjunction with a co llision cell, to anal yze samples collected during EPA’s sampling episodes, as well as the sa mples collected by industry as directed by EPA under authority of section 308 of the Clean Wate r Act. EPA has approved Method 200.8 for the

measurement of arsenic and selenium in wastew aters subject to compliance monitoring under the National Pollutant Discharge Elimination Syst em (NPDES) in 40 CFR Part 136. These data were used to develop effluent limits for propos ed revisions to the e ffluent guidelines.

EPA Method 200.8 utilizes inductively coupled pl asma (ICP) and mass spectrometry (MS) to determine metals in acid digestates from aque ous samples. The method includes a strong-acid digestion procedure that is used to prep are the sample for instrumental analysis.

Using the MS detector with the ICP provides greater sensitivity for many metals, including arsenic, in comparison to the ICP-AES system used in EPA Method 200.7. Method 200.8 also employs internal standards (non-target metals a dded to the samples) to improve the quantitative accuracy. The use of the MS detector avoids the spectral interferences common to the ICP-AES methods, but there are other interf erences specific to this detect or. The most prominent potential

interferences are isobaric elemen tal interferences, which are caused by isotopes of different elements forming atomic ions with the same nominal mass-to-charge ratio (m/z), and isobaric molecular and doubly-charged ion interferences, which are caused by ions consisting of more than one atom or charge, respectively.

Most of these interferences have been well studied and reported in the literature. For arsenic in particular, the argon gas (as 40 Ar) used to create the plasma in the ICP can combine with chloride (as 35 Cl) in the sample to form ArCl + . ArCl + has a nominal m/z of 75, the same m/z as the most prominent arsenic isotope, 75 As. As with EPA Method 200.7, correction factors can be developed for the instrument data system to compensate for the exp ected interferences.

The potential physical interferences in EPA Me thod 200.8 arise when high levels of dissolved solids in the digested sample affect the nebuliz ing system in the instrument. The most common3 approach to overcoming the physical effects of dissolved solids is to dilute the sample digestate prior to analysis, thereby raising the reporting limits. However, these interferences can be reduced by using a nebulizer on the instrument th at is designed to handl e high dissolved solids

loads.

Concerns about the various poten tial interferences in FGD wast ewaters led EPA to develop a laboratory standard operating procedure (SOP) wh ich uses a collision cell in conjunction with the ICP-MS procedure. This approach (or a si milar approach using a dynamic reaction cell, or “DRC”) is highly effective at resolving the poten tial interference effects. The collision cell and DRC act by affecting the ions exiting the ICP por tion of the instrument on the way to the MS detector. A gas is introduced into the ion stream that either collides with (collision cell) or reacts with (in DRC) the molecular ions formed fr om two non-target elements, so that those

interferences do not enter the MS detector with the same m/z as the target analyte.

Analyses of arsenic and selenium conducted wi thout the use of a collision cell (or a dynamic reaction cell) may result in high-bias ed data for these analytes as a result of those interferences. For this reason, results generated using EPA Method 200.8 without the collision cell or dynamic reaction cell are generally unaccep table for calculating effluent limits for the steam electric effluent guidelines. Data collected using Met hod 200.8 with a collision cell or dynamic reaction cell are generally acceptable for these purposes, provided that the laboratories achieved a sufficiently sensitive reporting limit and further ev aluation of the data as described in section 3.1 does not identify other reasons for excluding the da ta, such as treatment system upsets or other

factors.

2.2 Arsenic by EPA Method 200.7

EPA Method 200.7 utilizes inductively coupled plas ma (ICP) equipped with an atomic emission spectroscopy (AES) detect or to determine metals in aqueous samples. EPA has approved Method 200.7 for the measurement of arsenic and selenium in wastewaters subject to compliance monitoring under the National Pollutant Discharge Elimination System (NPDES) in 40 CFR Part

136. The method advises users that there can be physical, chemical, and spectral interferences present in some samples that will affect the ab ility of the method to produce accurate data for

some metals.

The physical interferences noted in the method in clude changes in viscos ity and surface tension that can cause significant inaccuracies, especially in samples containing high dissolved solids. These interferences can be reduced by using a ne bulizer on the instrument that is designed to handle high dissolved solids loads, by diluting the sample, or by usi ng an internal standard. High dissolved solids may also cause sa lt buildup at the tip of the nebuliz er, which affects aerosol flow rate and causes instrumental drift. This pr oblem can be controlled by a high-solids nebulizer, wetting the argon prior to nebu lization, using a tip washer , or diluting the sample.

While not normally significant, the method notes that chemical interfer ences include molecularcompound formation, ionization effects, and solu te-vaporization effect s. These potential chemical interferences are highly dependent on matrix type and th e specific analyte element, and4 if present, may be minimized by techniques su ch as “matrix matching” of the samples and

standards and the use of the method of standard additions.

Spectral interferences are those that affect the atomic emissions of the ta rget analytes after they are excited by the energy of the plasma. Th ey may be caused by instrument background, stray light, and overlap of the wavelengths of light emitted by the target analytes. The method specifically addresses these spec tral interferences th rough the analysis of standards containing the known interferences from co-occurring metals in the digested sample. The instrument data system can be used to develop “inter-element correction factors” that compensate for these interferences. The presence of aluminum, cobalt, iron, nickel, or vanadium may produce

emissions at the 193.759 nm atomic emission line for arsenic, and thus bias the results for arsenic by this method.

The most common solution to the potential physical interferences from dissolved solids is to dilute the original sample or its digestate fo r analysis. However, this dilution reduces the sensitivity of Method 200.7 and is reflect ed in increased re porting limits.

Data collected using Method 200.7 are generall y acceptable for calculating effluent limits, provided that the laboratories ac hieved a sufficiently sensitive reporting limit, there are no indications of analytical interferences, and further evaluation of the data (described in section 3.1) does not identify other reasons for excluding the data, such as treatment system upsets or
other factors.

2.3 Arsenic by EPA Methods 6020 or 6020A (SW 846)

Method 6020A was issued by the Office of Re source Conservation and Recovery (ORCR) in 2007 as part of the SW-846 methods manual. Method 6020A utilizes inductively coupled plasma (ICP) and mass spectrometry (MS) to determ ine metals in acid digestates from samples of various matrices, including aqueous and solid samples. Method 6020A covers only the determinative (instrumental analysis ) portions of the analytical proce ss. It must be coupled with digestion of the sample matrix using strong ac ids as described in one of the SW-846 sample preparation methods in the 3000-Series, e .g., Method 3005A, 3010A, or 3015A, which differ in the equipment used to heat the sample during the digestion process. When coupled with one of these sample preparation met hods, Method 6020A is similar to Method 200.8 from the Office of

Water. The differences are la rgely a function of the fact th at the SW-846 methods manual is issued as guidance for monitoring compliance wi th ORCR solid waste regulations, and thus does not contain quality control requir ements of the rigor that are typical of an Office of Water compliance monitoring method.

Method 6020 is an earlie r version of the SW-846 ICP/MS pr ocedure, issued in 1994. Although it uses the same ICP/MS instrumentation, it was a s impler version of the pr ocedure than the later revision, Method 6020A. It lacked a multi-point in strument calibration and detailed calibration instructions, contained fewer ta rget metals, and provided less detailed discussions of quality control. EPA no longer provides copies of Method 6020 on its website since it has been superseded by Method 6020A. EPA has not approved Methods 6020 and 6020A for NPDES compliance monitoring in 40 CFR Part 136.5 As with Method 200.8, using the MS detector wi th the ICP in Method 6020A provides greater sensitivity for many metals, including arsenic, in comparison to the ICP-AES system used in Method 200.7. The method also employs internal standards (non-target metals added to the samples) to improve the quantitative accuracy. Th e use of the MS detector avoids the spectral

interferences common to the ICP-AE S methods, but there are other in terferences specific to this detector. The most prominent potential interf erences are isobaric elemental interferences,

described above in section 2.1.

The potential physical interferences in Method 6020A are similar to th ose in Methods 200.7 and 200.8, arising when high levels of dissolved solids in the digested sample affect the nebulizing system in the instrument. As with Method 200.8, the most common approach to overcoming the physical effects of dissolved solids is to dilute the sample digestate fo r analysis, raising the reporting limits.

The “guidance” aspect of SW-846 methods a ffords the opportunity to utilize additional instrumental components as part of the ICP-MS system. Two related components are a dynamic reaction cell (DRC) or a collis ion cell accessory that can be used to overcome some of the

interferences. Both of these accessories act by affecting the i ons exiting the ICP portion of the instrument on the way to the MS detector. A ga s is introduced into the ion stream that either reacts with (in DRC) or collides with (collis ion cell) the molecular ions formed from two nontarget elements, such that those interferences do not enter the MS detector with the same m/z as the target analyte.

Arsenic concentration data submitted by indus try collected using Method 6020A will not generally be considered acceptabl e for calculating effluent limits unless the laboratories achieved a sufficiently sensitive reporting limit and the method was approved for compliance monitoring by the permitting authority. Additionally, as is the case with data collected using Method 200.8, results generated using Method 6020A without the collision ce ll or DRC are generally not acceptable for calculating effluent limits fo r the steam electric effluent guidelines.

As noted above, Method 6020 does not include many of the quality control re quirements that are part of Method 6020A. Because of the limited qual ity control associated with this method and that the method is not approved for NPDES co mpliance monitoring under 40 CFR Part 136, data collected using Method 6020 are generally not acce ptable for use in calculating effluent limits.

2.4 Mercury by EPA Method 1631E

EPA Method 1631E utilizes a cold vapor atomic fluorescence instrument to determine mercury in aqueous samples. The method involves adding bromine monochloride (BrC l) to the sample to oxidize all mercury in the sample to the Hg +2 ion. After oxidation, hydroxylamine hydrochloride (NH 2 OH•HCl) is added to the sample to destroy any free halogens remaining from the BrCl treatment. Stannous chloride (SnCl 2 ) is added to convert the Hg +2 ions to volatile elemental mercury (Hg 0 ). The Hg 0 is separated from solution by either purging with nitrogen, helium, or argon, or by vapor/liquid separation, and is collected on a series of two gold traps. The mercury6 is then thermally desorbed from the gold trap into an inert gas stream that carries it into the cell of a cold-vapor atomic fluorescence spectrometer (CVAFS) for detection.

The method contains extensive quality control pr ocedures designed to ensure efficacy of the sample preparation, purging, and detection systems. The nominal quantitation limit for Method 1631E is 0.5 ng/L, three orders of magnitude lo wer than the detection limit for Method 245.1. EPA has approved Method 1631E for the measurem ent of mercury in wastewaters for NPDES compliance monitoring in 40 CFR Part 136.

EPA used EPA Method 1631E to analyze samples collected during EPA’s sampling episodes, as well as the samples collected by industry as di rected by EPA under authority of section 308 of

the Clean Water Act. These data were used to develop effluent limits fo r proposed revisions to the effluent guidelines. I ndustry self-monitoring data collected using Method 1631E are generally acceptable for calculati ng effluent limits for the final ELG rulemaking, provided that the laboratories achieved a sufficiently sensit ive reporting limit, there are no indications of analytical interferences, and further evaluation of the data (d escribed in section 3.1) does not identify other reasons for excluding the data, such as treatment system upsets or other factors.

2.5 Mercury by EPA Method 245.7

Like EPA Method 1631E, Method 245.7 utilizes an atomic fluorescence detector to achieve much greater sensitivity than the atomic abso rption detector used in EPA Method 245.1 and SM 3112B. However, Method 245.7 uses liquid-gas sepa ration and a dryer tube to separate the mercury from the sample matrix, while Met hod 1631 purges the mercury and collects it on a gold trap. Method 245.7 also contains the same ex tensive suite of quality control operations as Method 1631E that are designed to ensure that the method is capable of measuring mercury at very low levels without background contaminati on from mercury in other sources, including the laboratory itself. EPA has a pproved Method 245.7 for the me asurement of mercury in wastewaters subject to compliance monito ring under the National Pollutant Discharge Elimination System (NPDES) in 40 CFR Part 136.

The nominal quantitation limit for Method 245.7 is 5 ng/L. Therefore, while not quite as sensitive as Method 1631E, Method 245.7 can produce va lid results in the same general range of mercury concentrations. EPA’s review of th e industry data generate d using Method 245.7 found only a few non-detects among the observations, which minimizes concerns about how to incorporate the Method 245.7 resu lts with those from Method 1631E.

Industry self-monitoring data collected us ing Method 245.7 are generally acceptable for calculating effluent limits, provided that the laboratories achieved a sufficiently sensitive reporting limit, there are no indications of analytic al interferences, and fu rther evaluation of the data (described in section 3.1) does not identify othe r reasons for excluding the data, such as treatment system upsets or other factors.

2.6 Mercury by EPA Method 245.17 EPA Method 245.1 uses a cold vapor atomic absorp tion (CVAA) procedure to analyze samples. It involves purging an aqueous sample with air to sweep mercury from the sample into a quartz absorption cell. A light source set to 253.7 nm, the characteristic absorption wavelength for elemental mercury, passes light through the ab sorption cell and onto an atomic absorption detector system. The absorption of light as it passes through the cell is proportional to the concentration of the absorbing species (mercury) and is used to determine the concentration in the sample. EPA has approved the method for the measurement of mercury for NPDES compliance monitoring in 40 CFR Part 136.

EPA collected its mercury data for the rulema king using EPA Method 1631E, which utilizes an atomic fluorescence detector to achieve much gr eater sensitivity than the atomic absorption

detector used in Method 245.1. Method 245.1 wa s approved by EPA in 1974 and typically can achieve measurements of mercury down to 200 ng/L. EPA approved Method 1631E in 2002. This newer method has a nominal quantitation level of 0.5 ng/L, making it 400 times more

sensitive than Method 245.1.

In a memorandum issued by EPA’s Office of Wa stewater Management, EPA advised permitting

authorities to ensure that su fficiently-sensitive anal ytical methods are used when deciding whether to set a permit limitation for mercury a nd for sampling and analysis of mercury pursuant to the monitoring requirements within a NPDES permit 3 . In the memorandum, EPA noted that Method 245.1 is “not likely to be sensitive enough to detect or quantify the concentration of mercury in the discharge” at levels that match the effluent limitations th at may be established by a permit. That assessment is consistent with data EPA has collected during this rulemaking, showing that Method 245.1 typically is not sens itive enough to quantify mercury concentrations

in the effluent from FGD wastew ater treatment systems. Because of this, data collected using Method 245.1 are generally unaccep table for calculating effluent limits for FGD wastewater.

2.7 Mercury by Standard Method 3112B

Standard Method 3112B (SM 3112B) is a method published jointly by the American Public Health Association, American Water Works Association, and Water Environment Federation as part of Standard Methods for the Exami nation of Water and Wastewater. EPA has approved

Method 3112B for the measurem ent of mercury for NPDES co mpliance monitoring in 40 CFR

Part 136.

The method does not provide example detection or reporting limits. However, functionally, SM 3112B is very similar to EPA Method 245.1, and the nominal detection limit for Method 245.1 is approximately 200 ng/L, which suggests that SM 3112B is capable of pro ducing mercury results at similar levels. SM 3122B also employs quali ty control operations similar to those in EPA

Method 245.1.

EPA collected its mercury data using EPA Met hod 1631E, which utilizes an atomic fluorescence detector to achieve much greater sensitivity than the atomic absorption detector used in SM 3112B. The nominal quantitation limit for Method 1631E is 0.5 ng/L. Method 1631E also

3 James A. Hanlon, Director, Office of Wastewater Management. “Analytical Methods for Mercury in National Pollutant Discharge Elimination System (NPDES) Permits,” August 23, 2007.8 incorporates a larger suite of quality control operations than SM 3112B or Method 245.1 that are designed to ensure that the method is capable of measuring mercury at very low levels without background contamination from mercury in othe r sources, including the laboratory itself.

SM 3112B is typically not sensitive enough to quan tify the concentration of mercury present in FGD wastewater treatment system effluent. As a result, data collected using SM 3112B are generally unacceptable for calculating effluent limits for FGD wastewater.

2.8 Nitrate-Nitrite by EPA Method 353.2

Nitrate (NO 3 - ) and nitrite (NO 2 - ) are two ionic forms of oxidized ni trogen that frequently occur in wastewaters. These two pollutants can be importa nt nutrients for aquatic plants, and therefore, EPA regulates them to reduce eutrophication of ri vers, streams, and lakes receiving wastewater discharges. Under routine conditions in wast ewaters and receiving wa ters, oxidation-reduction reactions can rapidly lead to conversion of nitrite to nitrate. Therefore, a nd as is the case for the steam electric effluent guidelines, EPA tends to regulate these nitrogen forms as the combined parameter called “nitrate-nitrite (as N).” 4

EPA Method 353.2 is a colorimetric procedure fo r determining nitrate-nitrite in aqueous samples. The method uses cadmium as a reducing agent to convert all of the nitrate in the sample to nitrite. The nitrite that was originally present in the sample, plus any reduced nitrate, reacts with two reagents to form a colored azo (nitrogen containi ng) dye. The intensity of the color is proportional to the nitr ate-nitrite concentration in the sample and is measured with a colorimeter. EPA Method 353.2 is approved for NPDES compliance monitoring in 40 CFR Part 136 and was used to analyze the EPA-collected samples and CWA 308 samples used to calculate effluent limits for the proposed rule.

Data collected using Method 353.2 are generall y acceptable for calculating effluent limits, provided that the laboratories ac hieved a sufficiently sensitive reporting limit, there are no indications of analytical interferences, and further evaluation of the data (described in section 3.1) does not identify other reasons for excluding the data, such as treatment system upsets or
other factors.

3 Plant-Specific Review of Self-Monitoring Data

3.1 Data Evaluations

4 Industry submitted also submitted effluent data for nitrat e that had been analyzed using either EPA Method 300.0

or Hach test kits. The Method 300.0 and Hach test kit da ta measure the concentration of nitrate alone, and not the combined parameter nitrate-nitrite, an d therefore these data would underes timate the value for the combined parameter nitrate-nitrite. Since the parameter that would be regulated is the combined ni trate-nitrite, and not nitrate alone, the Method 300.0 and Hach test kit data do not pr ovide sufficient information about the regulated parameter and are not acceptable for calculating effluent li mits for nitrate-nitrite in FGD wastewater.9 Plant-specific considerations arise when engine ering, laboratory, or other factors influence the sensitivity of the method used or the quality of the data obtained. This section discusses the sources of industry self-monitori ng data, which analytical methods were used, and whether the data are acceptable for calculating effluent limits . Section 2 discussed whether or not a method is acceptable in general , however this section evaluates specific factors related to the data for each plant to determine whether they are appropriate for calculating effluent limits based on the

considerations discussed in section 2.

In sections 3.2 through 3.5, EPA di scusses the self-monitoring data from four plants that operate chemical precipitation/iron coprec ipitation treatment technology: Hatfield’s Ferry Power Station, Keystone Generating Station, Miami Fort Station, a nd Pleasant Prairie Power Plant. Sections 3.6 and 3.7 discuss the self-monitoring data from two plants that operate ch emical precipitation/iron coprecipitation followed by anoxic/anaerobic bi ological treatment technology: Belews Creek

Steam Station and Allen Steam Station.

The conclusions in this document about data acceptability only appl y to the assessments

described herein. In addition to assessing whether the industry se lf-monitoring data described in this memorandum are generally acceptable for us e (as discussed in section 2 and sections 3.2 through 3.7), EPA thoroughly evaluated the available da ta for each plant to identify any data that

should not be used when derivi ng effluent limits due to: (1) th e samples being collected during the initial commissioning period for the treatment system; (2) the analytical results being identified as questionable due to quality control issues, abnormal conditions or treatment upsets, or analytical anomalies; or (3) other relevant factors. Therefor e, while this document may deem data to be acceptable, additional evaluation may have led EPA to determine otherwise. The final

determination as to whether EPA determined th e data are acceptable for calculating effluent limits for the final rule is presented in the Effluent Limitations Memorandum, along with the

results of this additional eval uation and plots of the data.

3.2 Hatfield’s Ferry Power Station

FirstEnergy’s Hatfield’s Ferry Po wer Station operates a chemical precipitation system to treat the FGD wastewater. This facility is one of the BA T plants used by EPA to calculate limits for both the proposed and final rule. EPA collected data from Hatfield’s Ferry during an EPA sampling episode and from samples collected by industry as directed by EPA (i.e., “CWA 308 samples”).

In their comments on the proposed rule, UWAG submitted plant self-monitoring data for arsenic (EPA Method 200.7) and mercury (EPA Method 245.7) for the effluent from the chemical precipitation treatment system.

FirstEnergy also submitted self-monitoring da ta for arsenic (EPA Methods 200.7 and 200.8) and mercury (EPA Methods 245.7 and 245.1) for the e ffluent from the chemical precipitation treatment system. These data were submitted in response to a letter fr om EPA requesting the company to provide existi ng analytical data for the treatment system.

Hatfield’s Ferry Power Station was decommissione d in late 2013. FirstEnergy advised EPA that data associated with samples collected afte r October 6, 2013, the last day Hatfield’s Ferry10 generated electricity, are not representative of ty pical FGD wastewater treat ment system effluent (DCN SE04679).

3.2.1 Arsenic

Arsenic by EPA Method 200.7

Both UWAG and FirstEnergy provided arsenic data using Method 200.7. The data submitted by UWAG spans the period 7/7/2009 through 10/25/2011 a nd is a subset of the data provided by FirstEnergy. The Method 200.7 data provided by FirstEnergy includes anal ysis results from two company laboratories: Allegheny lab spanni ng 6/30/2009 through 11/29/ 2011, and FirstEnergy’s Beta lab spanning 12/6/ 2011 through 12/10/2013.

Data collected after 10/6/2013 are associated with the decommissioning period for Hatfield’s Ferry and are not representative of typical FGD wastewater treatment system effluent. Therefore, the arsenic data for 10/8/2013 (the first sampling date during the decommissioning period) through 12/10/2013 are not acceptable fo r use in calculating effluent limits.

As discussed in section 2.2, data collected using Method 200.7 ar e generally acceptable for use in developing effluent limits, provided the labor atories achieved a sufficiently sensitive reporting limit, there are no indications of analytical inte rferences, and evaluation of the data does not identify other reasons for excluding the data, such as treatment system upsets or other factors.

The data from the Allegheny lab do not appear to be adversely affected by the types of interferences generally observed with Method 20 0.7 for FGD wastewater, as indicated by (1) the ability of the laboratory to achieve low repor ting limits (i.e., MDL of 2 ug/L and quantified values as low as 3 ug/L reported to the permitting authority for compliance monitoring); (2) the consistency between values reported by the Allegheny lab and the values reported by a

commercial lab under contract to EPA that anal yzed samples from the EPA sampling episode and the CWA 308 samples, as well as the spl it samples collected a nd analyzed by UWAG on behalf of FirstEnergy during the EPA sampli ng episodes and CWA 308 sampling; and (3) the values reported by the Allegheny lab being cons istent with the observed performance of chemical precipitation/iron coprec ipitation for FGD wastewater generally, especially by power plants operating treatment systems that represent the BAT level of performa nce (for example, see the treatment system effluent concentrations fo r Miami Fort, Pleasant Prairie, and Keystone, and the chemical precipitation effluent for Belews Creek and Allen). For th ese reasons, the arsenic data from the Allegheny lab (for 6/30/2009 thro ugh 11/29/2011) are acceptable for calculating effluent limits, subject to the additional data evaluations described in section 3.1.

Conversely, the data from the Beta lab bear stark contrast to the data from the Allegheny lab (and thus, data for Hatfield’s Ferry from other labs ). The Allegheny lab provides approximately 2.5 years of arsenic data for Hatfield’s Ferry, with 60 percent of observations below 10 ug/L. In fact, only one observation for effluent arsenic (out of 127 observati ons) from the Allegheny lab is above 20 ug/L. The Beta lab data, however, exhi bit a strikingly different pattern which began with its first sample result (Beta’s first ar senic result of 159 ug/L on 12/6/2011, as compared to Allegheny’s last arsenic result of 8 ug/L on 11/29/2011). The data from Beta lab were routinely11 in the upper double-digit parts-per-billion or even triple-digit parts-per billion. Only two

observations for effluent arsenic (out of 106 observations) were be low 10 ug/L, and 37 percent of observations were reported at or higher than 100 ug/L (a number of thes e were substantially higher than 100 ug/L, with the highe st at 424 ug/L). All of the reas ons explained above as to why the Allegheny lab results are accepta ble help to explain why the Beta lab results are questionable.

The Beta lab results are inconsistent with the effluent concentrations observed for chemical precipitation treatment systems and are particularly suspect given that th is radically different pattern of data coincided with FirstEnergy shifting analyses to the Beta lab. FirstEnergy was unable to explain the unusual re sults from the Beta lab and noted there were no known processrelated reasons (e.g., changing coal type, modifi cations to FGD scrubber or treatment system operation) that would expl ain a change in effluent quality. Thes e factors suggest that the Beta lab data very likely reflect quality c ontrol issues related to analytical interferences that would impart a high bias to the arsenic results, such as thos e noted above in section 2. For these reasons, the

arsenic data from the Beta la b (for 12/6/2011 through 10/1/2013) 5 are not acceptable for use. 6

Arsenic by EPA Method 200.8

FirstEnergy provided arsenic data analyzed by the Beta lab usi ng Method 200.8 for three days in

late 2012. The concentrations associated with thes e data are at unusually hi gh levels for effluent from a chemical precipitation tr eatment system. As noted above in section 2.1, Method 200.8 is an ICP-MS method that is subject to isobaric el emental interferences, including interferences that can result in high-bias ed results for arsenic. Concerns about potential interferences such as these led EPA to develop a laboratory standard operating procedure (SOP ) which uses a collision cell in conjunction with the ICP-MS procedure. Use of the collision cell (or a dynamic reaction cell) is highly effective at resolving such interference effects. FirstE nergy confirmed that the Method 200.8 analyses from the Beta lab did not include the use of either a collision cell or dynamic reaction cell, supporting EPA’s conclusion that th e results provided by FirstEnergy very likely reflect quality control issues related to analytic al interferences such as those noted above in section 2 (DCN SE04316A6). Because of this, Fi rstEnergy’s Method 200.8 data for arsenic for these three days are not acceptabl e for calculating effluent limits.

3.2.2 Mercury

Mercury by EPA Method 245.7

Both UWAG and FirstEnergy provided mercury data using Method 245.7. The data submitted by UWAG with their comments on the proposed rule spans the pe riod 7/7/2009 through 10/25/2011 and is a subset of the data provided by FirstEnergy. The data from FirstEnergy was provided in response to an EPA request for data and spans the period 6/30/2009 through

12/10/2013.

5 10/1/2013 is the last date that samples were collected fo r arsenic prior to the start of the decommissioning period.

6 In addition, as noted earlier in this section, arsenic data from the Beta lab for the period 10/8/2013 through 12/10/2013 are associated with the decommissioning period for Hatfield’s Ferry Power Station and, since the data are not representative of typical FGD operation, are not acceptable for use in cal culating effluent limits.12 Data collected after 10/6/2013 are associated with the decommissioning period for Hatfield’s Ferry and are not representative of typical FGD wastewater treatment system effluent. Therefore, the mercury data for 10/8/2013 through 12/10/2013 are not acceptable for use in calculating effluent limits.

As discussed in section 2.5, industry self-mon itoring data collected using Method 245.7 are generally acceptable for effluent limits provide d that the laboratories achieved a sufficiently sensitive reporting limit. The re porting limits associated with Hatfield’s Ferry’s 245.7 data are sufficient for the purposes of the steam electri c ELG rulemaking because the laboratory results for most samples were reported at levels above the level of quant itation. Therefore, the Method 245.7 mercury data from Hatfield’s Ferry (for 6/30/2009 through 10/1/2013) 7 are acceptable for calculating effluent limits, subjec t to the additional data evaluations described in section 3.1.

Mercury by EPA Method 245.1

FirstEnergy provided mercury data analyzed by Method 245.1 for three days in late 2012, including a nondetect observati on on 11/29/2012 (reporting limit of 200 ng/L). As discussed in section 2.6, Method 245.1 often is not sensitive enough to meas ure the mercury present in treatment system effluent and therefore data using this method are generally unacceptable for calculating effluent limitations for FGD wastewat er. Most of the observations in the weeks preceding the 11/29/2012 observation were below 200 ng/L, as was the observation immediately following that date, demonstrati ng that Method 245.1 is not sensit ive enough to reliably measure the concentration of mercury in the treatment system effluent. 8 Therefore, FirstEnergy’s Method 245.1 mercury data for these three days are no t acceptable for calculating effluent limits.

3.3 Keystone Generating Station

NRG Energy’s Keystone Generating Station operat es a chemical precipitation system to treat the FGD wastewater. This facility is one of the BA T plants used by EPA to calculate limits for the proposed and final rules. EPA collected data from Keystone during an EPA sampling episode and samples collected by industry as dire cted by EPA (i.e., “CWA 308 samples”).

NRG Energy also submitted self-monitoring data for arsenic (EPA Methods 200.7, 200.8, and 6020) and mercury (SM 3112B) for effluent from the chemical precipita tion treatment system. These data were submitted in response to a lett er from EPA requesting the company to provide existing analytical data for the treatment system.

3.3.1 Arsenic

Arsenic by EPA Method 200.7

NRG Energy provided effluent data for ar senic using Method 200.7, spanning the period 1/3/2012 through 1/6/2014. As discussed in se ction 2.2, data collected using Method 200.7 are

7 10/1/2013 is the last date that samples were collected for mercury prior to the start of the decommissioning period.

8 These quantified results below 200 ng/L were measured using EPA Method 245.7, a much more sensitive analytical method.13 generally acceptable for use in developing effl uent limits or estimating pollutant reductions, provided the laboratories achieved a sufficiently sensitive reporting limit, there are no indications of analytical interfer ences, and evaluation of the data does not identify ot her reasons for excluding the data, such as treatment system upsets or other factors.

Keystone’s NPDES permit does not include effluent limits fo r arsenic; instead, the permit requires the plant to “monitor and report” the ar senic concentrations in the treatment system effluent. Because of this, NRG Energy stated that the plant was not concerned with attempting to achieve a low reporting limit and their laboratory determined that 20 ug/L was the level they

could achieve on a routine ba sis (DCN SE04318). Analyses conducted on EPA-collected samples and the CWA 308 samples showed effluent arsenic concentrations of approximately 4 ug/L. Method 200.8 self-monitoring data prov ided by NRG Energy show similar effluent concentrations, in the range of 1-5 ug/L (see fu rther discussion in the section below). The reporting limit for the Method 200.7 data is an or der of magnitude higher than these Method 200.8 effluent concentrations and, as a result, most of the Method 200.7 data are reported as

nondetects. 9 Because the Method 200.7 data for Ke ystone do not have a low enough reporting limit to reliably measure the arsenic concentrations in the treatment system effluent, these data (from 1/3/2012 through 1/6/2014) are not accep table for calculating effluent limits.

Arsenic by EPA Method 200.8

NRG Energy provided effluent data for ar senic using Method 200.8, spanning the period 1/13/2014 through 4/28/2014. NRG Energy began usi ng this method in January 2014 to analyze for arsenic in the treatment system effluent. The ICP-MS instrumentation used for the 200.8 analysis was operated in collision mode (i.e., usin g a collision cell). As discussed in section 2.1, data collected using Method 200.8 with a collisio n cell or dynamic reaction cell are generally acceptable for use in calculating effluent limits , provided the laboratorie s achieved a sufficiently sensitive reporting limit, there are no indications of analytical interference s, and evaluation of the data does not identify othe r reasons for excluding the data, such as treatment system upsets or other factors. The data provided typically ha d a reporting limit of 1 ug/ L, with the highest sample-specific reporting limit at 5 ug/L (due to sample dilution). This reporting limit is sufficient for the purposes of the ELG rulema king and Keystone’s Method 200.8 arsenic data (from 1/13/2014 through 4/28/2014) are acceptable for calculating effl uent limits, subject to the

additional data evaluations described in section 3.1. 10

Arsenic by EPA Method 6020 (SW-846)

9 Keystone reported only two quantified results using Method 200.7, out of more than 100 observations. In a phone conversation, company represen tatives acknowledged that these two quantif ied results appear to be outliers. (DCN SE04318)

10 NRG Energy reported that the laboratory’s quantitation limit for arsenic using Method 200.8 is 1 ug/L (DCN SE04318). Even after accounting for elev ated reporting limits due to sample dilution, much of the effluent data for arsenic using this method are reported as nondetect at 4 ug/L. This reporting limit is comparable to the concentrations achieved by laboratories during the EPA sampling and 308 sampling episodes, and EPA is not aware of any other Part 136-approved methods reliably achieving substantially lower reporting limits for arsenic in FGD

wastewater.14 NRG Energy provided a single resu lt (nondetect at 5 ug/L) for effluent arsenic using Method 6020. NRG Energy stated that this sample was co llected as part of a sampling event conducted by EPA Region 3 related to a hydraulic fracturin g study. NRG Energy collected a split sample with EPA Region 3 and used Method 6020 in an effo rt to be consistent with the analyses being performed by Region 3. 11 NRG Energy analyzed only one sample using this method and the company representatives stated that they are not familiar with the method or how the sample was analyzed. 12 (DCN SE04318)

Method 6020 is issued by EPA’s Office of Res ource Conservation and Recovery (ORCR) as part

of the SW-846 methods manual. It is an ICP- MS method used to determine metals in acid digestates from samples of various matrices, in cluding aqueous and solid samples. Although Method 6020 is similar in some respects to EPA Method 200.8, the SW-846 methods manual is issued as guidance for monitoring compliance wi th ORCR solid waste regulations and does not contain the degree of quality c ontrol requirements that are typi cally included in analytical methods issued for NPDES compliance monito ring. EPA has not approved Method 6020 for compliance monitoring under the Na tional Pollutant Discharge Elim ination System (NPDES) in 40 CFR Part 136. Additionally, EPA no longer provi des copies of Method 6020 on its website because the method has been superseded in the SW-846 methods manual by Method 6020A. 13
Because of this (and because NRG Energy is not familiar with how the sample was analyzed), the Method 6020 data for a single day at Keystone are not acceptable for calculating effluent

limits.

3.3.2 Mercury

Mercury by Standard Method 3112B

NRG Energy provided mercury data using Stan dard Method 3112B (SM3112B). These data were provided in response to a data request from EPA, and span the period 1/3/2012 through 4/28/2014. This analytical method does not in clude example detection or reporting limits; however, SM 3112B is very similar to EPA Me thod 245.1 which has a nominal quantitation limit of 200 ng/L. Given its similarity to Method 245. 1, SM 3112B is generally expected to have comparable reporting limits -- three orders of ma gnitude higher than Method 1631E (quantitation limit of 0.5 ng/L). Because of this, SM 3112B is often not se nsitive enough to measure the mercury present in treatment system effluent and therefore is generally unacceptable for calculating pollutant loadings and effluent limita tions for FGD wastewater. This is the case for the Keystone effluent mercury data, where 99 percent of the nearly 250 observations were reported as nondetect at concentrat ions of 200 ng/L or higher. As discussed in section 2, a more sensitive analytical method, such as Method 1631E, likely would ha ve been able to quantify the amount of mercury present in the effluent, as de monstrated by the results of the EPA-collected

11 EPA Region 3 actually used EPA Method 6020A to analyze their sample, not Method 6020.

12 Based on the summary-level data report NRG Energy provided from their contract laboratory in Pennsylvania, EPA confirmed that the laboratory’s accreditation thr ough the Pennsylvania Depa rtment of Environmental Protection is for the older version, Method 6020, and that they do not hold an accreditation for Method 6020A. Neither NRG Energy nor their contract laboratory provided any supporting quality control data for the analysis of arsenic, reinforcing EPA’s decision that the data ar e not acceptable for use in calculating effluent limits.

13 See section 2 for a comparison of the quality control requirements in Methods 6020 and 6020A.15 samples and CWA 308 sampling (these observations were all quantified at concentrations below 200 ng/L). For this reason, the NRG Energy’s SM 3112B data (for 1/3/2012 through 4/28/2014) are not acceptable for cal culating effluent limits.

3.4 Miami Fort Station

Duke Energy’s Miami Fort Station operates a ch emical precipitation system to treat the FGD wastewater. This facility is one of the BAT plants used by EPA to calculate limits for both the proposed and final rules. EPA collected data from Miami Fort during an EPA sampling episode and samples collected by industry as dire cted by EPA (i.e., “CWA 308 samples”).

In their comments on the proposed rule, UWAG submitted plant self-monitoring data for mercury (EPA Method 1631E) in the effluent from the chemical precipitation treatment system. Duke Energy submitted effluent self-monitori ng data for arsenic (EPA Method 200.8) and mercury (EPA Method 1631E) with their comments on the proposed rule.

Duke Energy also provided additional effluent data for arsenic (EPA Method 200.8) and mercury (EPA Method 1631E) in response to a letter fr om EPA requesting the company to provide existing analytical data for the treatment system.

3.4.1 Arsenic

Arsenic by EPA Method 200.8

Duke Energy provided arsenic data using Me thod 200.8 as part of their comments on the proposed rule and in response to a request from EPA. As discussed in section 2.1, data collected using Method 200.8 with a collision cell or dyna mic reaction cell are generally acceptable for rulemaking purposes, provided that the laborator ies achieved a sufficiently sensitive reporting limit and additional evaluation of the data does not identify other reasons for excluding the data. The data submitted with Duke Energy’s comm ents spans the period 7/13/2009 through 5/8/2013. These arsenic data were included again in Duke Energy’s response to EPA’s data request, along with additional data, resulti ng in the arsenic data spa nning the period 7/13/2009 through 12/3/2013. Multiple laboratories were involved in analyzing the Miami Fo rt arsenic data, and important characteristics of thes e analytical results warrant eval uating their acceptability as four different sets of data: (1) split samples from the EPA sampling episode and CWA 308 sampling, analyzed by three non-Duke Energy labs (Applied Sp eciation, Southern Research Institute, and Ohio State University); (2) plant self-monito ring data analyzed by Duke Energy’s company laboratory; (3) a single analyt ical result from a commercial laboratory; and (4) round robin analyses by four laboratories for samples coll ected on one day (5/8/2013; Pace Analytical, Heritage, TestAmerica, and Duke Energy’s McGuir e lab). These four sets of arsenic data are

discussed below.

Split Samples from EPA Sampling Episode and CWA 308 Sampling16 For the EPA sampling episode and CWA 308 sampling events, Duke Energy collected split samples and had them separately analyzed by three different labs. The results from these three labs are similar in magnitude to each other, as well as to the results from the laboratory that analyzed samples under contra ct to EPA. These results provided by Duke Energy for the three labs are all quantified valu es at approximately 5 ug/L or lower, and therefore the labs achieved a sufficiently se nsitive reporting limit (i.e., the quantitation limits for these analyses were low enough to me asure the concentrati on of arsenic present in the samples). This set of arsenic data for Miami Fort Station is acceptable for calculating effluent limits, subject to the addi tional data evaluations described in section

3.1.

Samples Analyzed by Duke Energy’s Company Lab

The samples analyzed by Duke Energy’s co mpany lab span the period 7/13/2009 through

12/3/2013. All observations in this set of data were reported as nondetect, with reporting limits for most observations at 20 ug/L. No samp le within this set of data had a reporting limit below 10 ug/L. In contrast, multiple independent laboratories analyzing the samples from the EPA sampling episode and CWA 308 sampling, which occurred within the time period represented by this set of observations, were able to attain much lower reporting limits and, as a result, better qua ntify the concentration of arse nic present in the treatment system effluent (all EPA-contracted and indus try-contracted lab results for the EPA and CWA 308 sampling episodes were quantifie d at concentrations below 10 ug/L). 14 This demonstrates that Duke Energy’s company lab did not achieve sufficiently sensitive reporting limits and therefore this set of da ta from Duke Energy’s company lab for Miami Fort are not acceptable for use.

Single Sample Analyzed by a Commercial Laboratory Duke Energy provided the analytical result for arsenic for a sample collected on 6/28/2011. The sample was analyzed by a comm ercial laboratory and, according to the lab report, the reported valu e of 4.34 ug/L is above the re porting limit of 2 ug/L.

There are no indications of an alytical interferences and ev aluation of the data does not identify other reasons for excluding the data, such as treatment system upsets or other factors. The lab report stated that the reporting limit for the sample was 2 ug/L. This reporting limit is sufficient for the purposes of the ELG rulemaking and Miami Fort’s Method 200.8 arsenic data for this day (6/28/ 2011) are acceptable for calculating effluent limits, subject to the additional data evaluations described in section 3.1.

Round Robin Laboratory Analyses

14 EPA contracted with a commercial laboratory to an alyze samples from the EPA sampling episode and the CWA 308 sampling. In addition, Duke Energy collected sp lit samples during those sampli ng events, which were then analyzed by three labs not affiliated with Duke Energy: Applied Speciation, Southern Research Institute, and Ohio State University.17 Duke Energy provided results for round robin an alyses conducted by four laboratories for samples collected on 5/8/2013. 15 The results provided for th ese four labs were nondetect at 5 ug/L (Pace Analytical), nondetect at 5 ug /L (Duke Energy’s McGuire lab), detect at 46 ug/L (Heritage), and nondete ct at 500 ug/L (TestAmerica) . The TestAmerica result demonstrates an extremely high reporting limit, particularly in comparison to all other arsenic data provided by Duke Energy and Method 200.8 arsenic data for other plants. The result reported by the Heritage lab is unusually high for effluent from a FGD wastewater chemical precipita tion treatment system and the results from Pace Analytical and Duke Energy’s McGuire lab strongly suggest the Heritage result may be in error.

Since EPA is unable to confir m the validity of any of the round robin results, the Miami Fort arsenic data for 5/8/2013 are not acceptable for use.

3.4.2 Mercury

Mercury by EPA Method 1631E

Both UWAG and Duke Energy provided mercury data using Method 1631E. The data submitted by UWAG with their comments on the proposed ru le spans the period 7/1/2009 through 5/4/2011 and is a subset of the data provided by Duke Energy. Duke Energy provided mercury data with their comments on the proposed rule for th e period 7/1/2009 through 5/8/2013. These mercury data were included again in Duke Energy’s response to EPA’s da ta request, along with additional data, resulting in the mercury data spanni ng the period 7/1/2009 through 12/3/2013. Multiple laboratories were involved in analyzing th e Miami Fort mercury data, and important characteristics of these analytical results warran t evaluating their acceptab ility as two different sets of data: (1) recurring plant self-monitori ng data and split samples from the EPA sampling episode and CWA 308 sampling episodes; and (2) round robin analyses by four laboratories for samples collected on one day (5/8/2013; Pace An alytical, Heritage, TestAmerica, and Duke Energy’s McGuire lab). These two sets of mercury data are discussed below.

Recurring Self-Monitoring and Split Sam ples from EPA & CWA 308 Sampling

These mercury effluent data span th e period 7/1/2009 through 12/3/2013 (excluding round robin data for 5/8/2013). As discussed in section 2.4, data collected using Method 1631E are generally acceptable for use pr ovided that the laboratories achieved a sufficiently sensitive reporting limit and addi tional evaluation of the data does not identify other reasons for excluding the da ta. The reporting limit for these data is sufficiently sensitive for the purposes of the ELG rulemaking (i.e., a ll analytical results for mercury were reported as quantified va lues) and these Method 1631E mercury data (for 7/1/2009 through 12/3/2013) are acceptable fo r calculating effluent limits, subject to

the additional data evaluations described in section 3.1.

15 According to Duke Energy’s comments on the proposed rule, samples collected from the treatment system effluent were sent to the Duke Energy Environmental Lab, where they were split into four individual samples. Three of the samples were sent to commercial labs for analysis, while the fourth sample was analyzed internally at Duke Energy’s Environmental Lab. The spreadsheet of data subm itted by Duke Energy refers to the internal company lab as Duke Energy’s McGuire lab.18 Round Robin Laboratory Analyses Duke Energy provided results for round robin an alyses conducted by four laboratories for samples collected on 5/8/2013. 16 As discussed in section 2.4, data collected using Method 1631E are generally acceptable for use provided that the laboratories achieved a sufficiently sensitive reporting limit and addi tional evaluation of the data does not identify other reasons for excluding the da ta. The reporting limit for these data is sufficiently sensitive for the purposes of the ELG rulemaking (i.e., all round robin analytical results for mercury were repor ted as quantified valu es) and these Method 1631E mercury data from the round robin la boratory analyses (for 5/8/2013) are acceptable for calculating effluent limits, subject to the additional data evaluations

described in section 3.1.

3.5 Pleasant Prairie Power Plant

We Energies’ Pleasant Prairie Power Plant operates a chemical precipitation system to treat the FGD wastewater. This facility was not used by EPA to calculate effluent limits for the proposed rule; however, based on public comments and other information in the record EPA may include Pleasant Prairie as one of the BAT plants that will be used by EPA to calculate limits for the final effluent guidelines. EPA collected data from Pleasant Prairie during an EPA sampling episode and samples collected by industry as directed by EPA (i.e., “CWA 308 samples”).

In their comments on the proposed rule, UWAG submitted plant self-monitoring data for mercury (EPA Method 245.7) in the effluent from the chemical precipitation treatment system. We Energies submitted self-monitoring data for arsenic (EPA Method 6020A) and mercury (EPA Methods 245.7 and 1631E) for chemical precipi tation effluent with their comments on the proposed rule.

We Energies also provided additional efflue nt data for arsenic (Method 6020A) and mercury (Method 245.7) in response to a letter from EPA requesting the compa ny to provide existing analytical data for the treatment system.

3.5.1 Arsenic

Arsenic by EPA Method 6020A

We Energies provided effluent da ta for arsenic in its comments to the proposed rule and in response to an EPA data reque st letter. The submitted data spans the period from 11/13/2007 through 4/17/2013. These data were analyzed using EPA Method 6020A in conjunction with a dynamic reaction cell.

16 According to Duke Energy’s comments on the proposed rule, samples collected from the treatment system effluent were sent to the Duke Energy Environmental Lab, where they were split into four individual samples. Three of the samples were sent to commercial labs for analysis, while the fourth sample was analyzed internally at Duke Energy’s Environmental Lab. The spreadsheet of data subm itted by Duke Energy refers to the internal company lab as Duke Energy’s McGuire lab.19 Method 6020A was issued by EPA’s Office of Res ource Conservation and Recovery as part of

the SW-846 methods manual. It is an ICP-MS me thod that generally is similar to EPA Method 200.8; however, EPA has not approved Method 6 020A for NPDES compliance monitoring in 40 CFR Part 136. As discussed in section 2, arse nic concentration data collected using Method 6020A generally are not considered acceptabl e for calculating effluent limits unless the laboratories achieved a sufficiently sensitive reporting limit and the method was approved for compliance monitoring by the permitting authorit y. Additionally, as is the case with data collected using Method 200.8, resu lts generated using Method 6020A without the collision cell or dynamic reaction cell are generally not acceptable for calculating effluent limits for the steam electric effluent guidelines.

In the case of Pleasant Prairie, We Energies ’ use of Method 6020A, which included use of the dynamic reaction cell, was authorized under Wisconsin Administrative Code as part of a blanket approval of SW-846 methods that use the same instrumentation as the wastewater methods approved at 40 CFR Part 136, and that cont ain rigorous quality control requirements. 17 As noted in section 2, Method 6020A does contain more qua lity control informa tion than the earlier version, Method 6020, especially with regard to in strument calibration. Mo reover, We Energies provided additional information about the quality control operations that were implemented as part of the analyses for these data, along with th e summary level quality control data associated with the analysis results (DCN SE04328A3). These quality control operations are comparable to the quality control requirements included in Method 200.8 and the quality control acceptance criteria employed by the laboratory are at least as stringent as those in Method 200.8. Because of this, consistent with the Me thod 6020A discussion in sectio n 2, the Method 6020A data for Pleasant Prairie (for 11/13/2007 through 4/17/2013) are acceptable for calculating effluent limits, subject to the additional data ev aluations described in section 3.1.

3.5.2 Mercury

Mercury by EPA Method 245.7

Both UWAG and We Energies provided plan t self-monitoring data for mercury using EPA Method 245.7. The data submitted by UWAG span the period 1/5/2009 through 5/10/2011 and are a subset of the data provided by We Energi es. Mercury data submitted by We Energies span the period 10/4/2007 through 12/18/2013. As discu ssed in section 2.5, i ndustry self-monitoring data collected using Method 245.7 are generally acceptable for calculating effluent limits provided that the laboratories ac hieved a sufficiently sensitiv e reporting limit. The reporting limits associated with Pleasant Prairie’s mercury data are sufficient for the purposes of the steam electric ELG rulemaking (i.e., nearly all result s were reported as quant ified values above the reporting limit). Therefore, the Method 245.7 me rcury data (for 10/4/ 2007 through 12/18/2013) are acceptable for calculating effluent limits, subject to the additional data evaluations described

in section 3.1.

Mercury by EPA Method 1631E

17 Dinsmore and Weber, Wisconsin Department of Natural Resources, letter to USEPA Region 5, October 14, 1997. (DCN SE04328A3)20 We Energies provided mercury data for the effl uent from the secondary clarifier using Method 1631E. The Method 1631E data were submitted with We Energies’ comments on the proposed rule and represent a single day (12/15/2010).

As discussed in section 2.4, data collected usi ng Method 1631E are generally acceptable for use provided that the laboratories achieved a suffi ciently sensitive reporting limit and additional

evaluation of the data does not identify other reasons for excl uding the data. The reporting limit for these data is sufficient for the purposes of the ELG rulemaking (i.e., the result was reported as a quantified value above the reporting limit) and We Energies’ Me thod 1631E mercury data (for 12/15/2010) are acceptable fo r calculating effluent limits, s ubject to the additional data

evaluations described in section 3.1.

3.6 Allen Steam Station

Duke Energy’s Allen Steam Station operates a F GD wastewater treatment system that includes chemical precipitation/iron coprecipitation fo llowed by anoxic/anaerobic biological treatment. This facility is one of the BAT plants used by EPA to calculate limits for both the proposed and

final rules. EPA collected data from Alle n during an EPA sampling episode and samples collected by industry as directed by EPA (i.e., “CWA 308 samples”). 18

In their comments on the proposed rule, UWAG submitted plant self-monitoring data for selenium (EPA Method 200.8) in the e ffluent from the treatment system.

Duke Energy provided effluent da ta for selenium (EPA Method 200.8) and nitrate-nitrite (EPA Method 353.2) in response to a letter from EPA requesting th e company to provide existing analytical data for the treatment system.

Selenium by EPA Method 200.8

Both Duke Energy and UWAG provided seleni um data analyzed using Method 200.8 in conjunction with a collision cell. The data s ubmitted by UWAG with their comments span the period 7/15/2009 through 5/23/2011 a nd are a subset of the plan t self-monitoring data EPA obtained from Duke Energy prio r to proposal (spanning 3/3/2 009 through 5/23/2011). The data submitted by Duke Energy partially overlaps th e data submitted by UW AG, with the Duke Energy submittal spanning the period 5/10/2010 through 10/22/2013.

As discussed in section 2.1, selenium data coll ected using Method 200.8 with a collision cell or dynamic reaction cell are generally acceptable for rulemaking purposes, provided that the laboratories achieved a sufficiently sensitive repor ting limit and additional evaluation of the data does not identify other reasons for excluding the data. The reporting limits for these data are sufficient for the purposes of the ELG rulemaki ng. Many results were reported as quantified

18 Prior to proposing revised effluent guidelines, EPA al so obtained self-monitoring data for Allen from Duke Energy. These data include effluent concentrations for selenium spanning the period 3/3/2009 – 5/23/2011 and were considered when deriving the proposed effluent limits.21 values above the reporting limit. All of the nond etected results were at 10 ug/L or lower, comparable to the reporting limits achieved by laboratories during the EPA sampling and 308 sampling episodes, and EPA is not aware of a ny other Part 136-appr oved methods reliably achieving substantially lower reporting limits fo r selenium in FGD wastewater. For these reasons, the Allen selenium data (for 3/3/2009 through 10/22/2013) are acceptable for calculating effluent limits, subjec t to the additional data evaluations described in section 3.1. 19

Nitrate-Nitrite by EPA Method 353.2

Duke Energy provided nitrate-nitr ite data analyzed using EPA Method 353.2. These data were provided in response to a data request from EPA, and sp an the period 9/29/2011 through

10/22/2013. As discussed in sec tion 2.8, industry self-monitoring data collected using Method 353.2 are generally acceptable for effluent limits provided that the la boratories achieved a sufficiently sensitive reporting limit. The reporting limits associated with Allen’s nitrate-nitrite data are sufficient for the purposes of the st eam electric ELG rulemaking because the reporting limits for nondetect observations were below 1 mg /L. Therefore, the Method 353.2 nitrate-nitrite data from Allen (for 9/29/2011 through 10/22/ 2013) are acceptable for calculating effluent limits, subject to the additional data evaluations described in section 3.1.

3.7 Belews Creek Steam Station

Duke Energy’s Belews Creek Stea m Station operates a FGD wastewater treatment system that includes chemical precipitati on/iron coprecipitation followe d by anoxic/anaerobic biological treatment. This facility is one of the BAT pl ants used by EPA to calculate limits for both the proposed and final rules. EPA collected data from Belews Creek during an EPA sampling episode and samples collected by industry as directed by EPA (i.e., “CWA 308 samples”). 20

In their comments on the proposed rule, UWAG submitted plant self-monitoring data for selenium (EPA Method 200.8) in the e ffluent from the treatment system.

Duke Energy provided effluent da ta for selenium (EPA Method 200.8) and nitrate-nitrite (EPA Method 353.2) in response to a letter from EPA requesting th e company to provide existing analytical data for the treatment system.

Selenium by EPA Method 200.8

Both Duke Energy and UWAG provided seleni um data analyzed using Method 200.8 in conjunction with a collision cell. The data s ubmitted by UWAG with their comments span the period 2/6/2008 through 5/25/2011 a nd are identical to the plan t self-monitoring data EPA

19 Note that the data for 3/3/2009 – 8/26/2009 were collected during the commissioning period for the wastewater treatment system and were excluded when calculating effluent limits for the proposed and final rules, as a result of

data evaluations described in section 3.1. See the Effluent Limitations Memorandum for more information.

20 Prior to proposing revised effluent guidelines, EPA also obtained self-monitoring data for Belews Creek from Duke Energy. These data include effluent concentrations for selenium spanning the period 2/6/2008 – 5/25/2011 and were considered when deriving the proposed effluent limits.22 obtained from Duke Energy prio r to proposal (also spanning 2/6/2008 through 5/25/2011). The data submitted by Duke Energy partially overlaps the data submitted by UWAG, with the Duke Energy submittal spanning the period 6/9/2010 through 11/28/2013.

As discussed in section 2.1, selenium data coll ected using Method 200.8 with a collision cell or dynamic reaction cell are generally acceptable for rulemaking purposes, provided that the laboratories achieved a sufficiently sensitive repor ting limit and additional evaluation of the data does not identify other reasons for excluding the data. The reporting limits for these data are sufficient for the purposes of the ELG rulemaki ng. Many results were reported as quantified values above the reporting limit. All but one of the nondetected results were at 10 ug/L or lower, comparable to the reporting limits achieved by laboratories during the EPA sampling and 308 sampling episodes, and EPA is not aware of a ny other Part 136-appr oved methods reliably achieving substantially lower reporting limits fo r selenium in FGD wastewater. For these reasons, the Belews Creek selenium data (f or 2/6/2008 through 11/28/2013) are acceptable for calculating effluent limits, subjec t to the additional data evaluations described in section 3.1. 21

Nitrate-Nitrite by EPA Method 353.2

Duke Energy provided nitrate-nitr ite data analyzed using EPA Method 353.2. These data were provided in response to a data request from EPA, and sp an the period 5/15/2013 through

11/28/2013. As discussed in sec tion 2.8, industry self-monitoring data collected using Method 353.2 are generally acceptable for effluent limits provided that the la boratories achieved a sufficiently sensitive reporting limit. The reporting limits associated with Belews Creek’s nitratenitrite data are sufficient for the purposes of the steam electric ELG rulemaking because the reporting limits for nondetect observations were below 1 mg/L. Therefore, the Method 353.2

nitrate-nitrite data from Bele ws Creek (for 5/15/2013 through 11/ 28/2013) are acceptable for calculating effluent limits, subjec t to the additional data evaluations described in section 3.1.

21 Note that the data for 2/6/2008 – 7/28/2008 were collected during the commissioning period for the wastewater treatment system and were excluded when calculating effluent limits for the proposed and final rules, as a result of

data evaluations described in section 3.1. See the Effluent Limitations Memorandum for more information.23 Table 1. Summary of initial determinations regarding acceptability of effluent self

‐ monitoring data,
prior to additional data evaluations described in section 3.1.

Analyte Description Method Date Acceptable/

Exclude

HATFIELD’S FERRY POWER STATION

Arsenic Plant Self

‐ Monitoring (Allegheny lab) 200.7 06/30/09

– 11/29/11 Acceptable

Plant Self

‐ Monitoring (Beta lab) 200.7 12/6/11

– 10/1/13
10/8/13

– 12/10/13 (decommissioning period) Exclude

Plant Self

‐ Monitoring (Beta lab) 200.8 11/29/12, 12/19/12, 12/21/12 Exclude

Mercury Plant Self

‐ Monitoring 245.7 6/30/09

– 10/1/13 Acceptable

Plant Self

‐ Monitoring
Decommissioning period 245.7 10/8/13

– 12/10/13 Exclude

Plant Self

‐ Monitoring 245.1 11/29/12, 12/19/12, 12/21/12 Exclude

KEYSTONE GENERATING STATION

Arsenic Plant Self

‐ Monitoring 200.7 1/3/12

– 1/6/14 Exclude

Plant Self

‐ Monitoring 200.8 1/13/14

– 4/28/14 Acceptable

Frac study split sample 6020 2/21/13 Exclude

Mercury Plant Self

‐ Monitoring SM 3112B 1/3/12

– 4/28/14 Exclude

MIAMI FORT STATION

Arsenic Split samples from EPA &

CWA 308 sampling episodes 200.8 7/13/10

‐ 7/16/10, 9/28/10, 11/2/10,
12/7/10, 1/14/11 Acceptable

Plant Self

‐ Monitoring (Duke Energy company lab) 200.8 7/13/09

– 12/3/13 Exclude

Commercial lab 200.8 6/28/11 Acceptable

Round robin lab analyses 200.8 5/8/13 Exclude

Mercury Plant Self

‐ Monitoring and
split samples from EPA &

CWA 308 sampling episodes 1631E 7/1/09

– 12/3/13 Acceptable

Round robin lab analyses 1631E 5/8/13 Acceptable

PLEASANT PRAIRIE POWER PLANT

Arsenic Plant Self

‐ Monitoring 6020A 11/13/07

‐ 4/17/13 Acceptable

Mercury Plant Self

‐ Monitoring 245.7 10/4/07

– 12/18/13 Acceptable

Plant Self

‐ Monitoring 1631E 12/15/10 Acceptable

ALLEN STEAM STATION

Nitrate

‐ Nitrite Plant Self

‐ Monitoring 353.2 9/29/2011

– 10/22/2013 Acceptable

Selenium Plant Self

‐ Monitoring 200.8 3/3/09

– 10/22/13 Acceptable

BELEWS CREEK STEAM STATION

Nitrate

‐ Nitrite Plant Self

‐ Monitoring 353.2 5/15/2013

– 11/28/2013 Acceptable

Selenium Plant Self

‐ Monitoring 200.8 2/6/08

– 11/28/13 Acceptable