From: Rob Bamford < rbamford@ndep.nv.gov >

To: Chuck French/RTP/USEPA/US@EPA

Cc: Mike Elges < melges@ndep.nv.gov >

Date: 10/21/2010 11:29 AM

Subject: ore dryer

Hello Chuck,

Sorry about the confusion on the dry grind paper, you ar e correct I sent the wrong document. The correct document is attached. Also, in regards to a phone call with the test group, there is a section of the attached document which I think would be relevant to the testing discussion if the testing group could read it first. It provides a basis and data examples for our concern regarding Test Methods other than M29 and the poor correlation between M29 and other Methods. Let me know what you think about sharing with that doc with the test group before

the discu ssion and I’ll go chat with Mike and see what is schedule looks like.

Thanks,

- Rob

(See attached file: Review of the Goldstrke Orer Dryers.doc)

|

------------------- +

----------------------------- | | (Embedded image |Rob Bamford | | m oved to file: |Supervisor, Nevada Mercury | | pic00138.jpg) |Control Program | | Description: |Nevada Division of | |logo_new01_print_s |Environmental Protection | | |Bureau of Air Quality | | |Planning | | | | | |Phone: 775

- 687

- 9330 | | |Cell: 775

- 315

- 3655 | | |Fax: 775

- 687

- 6396 | | |E

- mail: rbamford@ndep.nv.gov | |

------------------- +

----------------------------- |NDEP

- NMCP Review Summary

– Barrick Goldstrike

1 Recently, Barrick Goldstrike has submitted a note in response to NDEP’s questions associate d with ore dryer mercury source test results performed in August 2007. The review was conducted to obtain the following primary objectives: 1) to assess representative source test for 2007 annual emission reporting,

2 ) to investigate the possibility of con tamination during source testing

, 3) to analyze the loading of

mercury to mills over time , and 4 ) to estimate the effectiveness and appropriateness of the sorbent trap

method as a reference method proposed by Barrick Goldstrike.

1. Uncertainty Analysis of Source Test Results

The coefficient of variation (COV) is used to measure the consistency of the data across source test results. The coefficient of variation (COV) of each test result set is calculated as standard deviation divided by mean. It is kno wn that distributions with COV < 1 are considered low

- variance, while those with COV > 1 are considered high

- variance. In other words, a high COV value reflects inconsistency among the spiked samples within each test run. The statistical analysis is carrie d out with source test data set available. Average, standard deviation, and coefficient of variation (COV) are calculated for each test

data set and the results are presented in Table 1

. Figure 1 shows the v ariations of the minimum, average,

and maximum m ercury mass observed during each source test . In fact, the number of samples for each data set is insufficient to draw a clear conclusion from statistical analysis. Nevertheless, it seems that the October 07 source test data set would provide a relatively better consistency compared to other test data set with COV < 1 for Sys 15 and Sys 16, respectively.

Table 1 . Comparison of the C onsistency of V arious Source Test Results (Note: This result is obtained using source test data sets provided by Barrick Gol dstrike)

Date System Total Hg Mass ( **μ** m) Average Hg
Mass ( **μ** m) Std Deviation Coeff. of

Variance

(COV)

March 2007 Sys 15 Run #1 5.93

4.57 1.21 

### 0.27 Sys 15 Run #2 4.18
Sys 15 Run #3 3.60
Sys 16 Run #1 158.60

67.75 80.50 1.19 Sys 16 Run #2 39.35
Sys 16 Run #3 5.30

August 2007 Sys 15 Run #1 2292.92

868.00 1234.97 1.42 Sys 15 Run #2 204.24
Sys 15 Run #3 106.85
Sys 16 Run #1 57.49

50.66 10.22 

### 0.20 Sys 16 Run #2 38.91
Sys 16 Run #3 55.59 

## A Review o f

the Re sponse of Barrick GoldstrikeNDEP

- NMCP Review Summary

– Barrick Goldstrike

2 Date System Total Hg
Mass ( **μ** m) Average Hg
Mass ( **μ** m) Std Deviation Coeff. of

Variance

(COV)

October 2007 Sys 15 Run #1 11.78

7.62 5.26 

### 0.69 Sys 15 Run #2 9.37
Sys 15 Run #3 1.71
Sys 16 Run #1 6.03

4.86 1.86 

### 0.38 Sys 16 Run #2 5.84
Sy s 16 Run #3 2.72

April 2008 Sys 15 Run #1 2.29

17.45 26.35 1.51 Sys 15 Run #2 47.88
Sys 15 Run #3 2.19
Sys 16 Run #1 2.98
3.59 0.89 

### 0.25 Sys 16 Run #2 4.61
Sys 16 Run #3 3.19

Figure 1 . Variations of the M inimum

, A verage and M aximum Hg M ass O bserved during E ach S ource
T est (Note: This graph is created using source test data sets provided by Barrick Goldstrike)

1 10 100 1000 10000

1 2 3 4 5 6 7 8

Source Test EventsHg mass (um) in Logarithmic Scale Minimum
Average

Maximum

Sys 15

March 07 Sys 16

March 07 Sys 15
August 07

Sys 16
August 07

Sys 15

Oct. 07 Sys 16

Oct. 07 Sys 15
April 08

Sys 16
April 08NDEP

- NMCP Review Summary

– Barrick Goldstrike

3 2. Investigating the Po ssibility of C ontamination during S ource T esting

Ba rrick Goldstrike ’s pre

- heater system s (System 15 and System 16) w ere designed to operate identically so mercury emission rates should not show a considerable difference between the two systems

. However, source test results demonstrate a wide distribution r anging from 2.0 ( ug/dscm ) to 34.2 ( ug/dscm ) or 0.0008 (lb/hr) to 0.015 (lb/hr) in average total mercury concentration excluding the

erroneous August 07 test results (see Table 2 )

. In March 2007, Barrick Goldstrike conducted an

u nofficial source test of me rcury emitted from pre

- heaters for internal use. The test results seem to be

consistent except Sys 16

- Run 1 and Sys 16

- Run 2 of Table 3

. For this reason, NMCP proposes several possible scenarios for a sudden change in mercury emissions during stack source testing

.

Table 2 . Summary of Stack Source Test Results

System March 07 ug/dscm (lb/hr) August 07 ug/dscm (lb/hr) October 07 ug/dscm (lb/hr) April 08 ug/dscm (lb/hr)

Sys 15 1.9 (0.001) 341.2 (0.154) 3.5 (0.0017) 10 .0 ( 0.0037 )

Sys 16 34.2 (0.015) 25.2 (0.01) 2.5 (0.001) 2 .0 ( 0.0008 )

Table 3

. Unofficial March 07 Source Test Results

System & Run# Hg Emission (ug/dscm)

Sys 15

- Run1 2.44

Sys 15

– Run2 1.73

Sys 15

– Run3 1.54

Sys 16

- Run1 

### 82.43

Sys 16

– Run2 

### 17.58

Sys 16

– Run3 2.68

2. 1 Bag house o p eration & m aintenance

The baghouse operational data was investigated to estimate the impact of a substantial increase of particle bound mercury levels during source testing. Pressure drop across the baghouse gives an

indication of the resistance t o gas flow (drag) and the effectiveness of the filtration system. In general, when the baghouse is operating properly the removal efficiency is usually in excess of 99.9% 1

. However,

a bnormal baghouse operation s such as sudden failure or deviations outside of manufacture’s recommended parameters could cause greatly increased particle

- bound mercury levels due to very fine particles smaller than approximately 10 **μ** m 2

.

According to the EPA Baghouse design manual, a baghouse is normally operated with a pressure drop across the unit of 4 to 10 in H 2 O and m any units operate at less than 6 in of H 2 O

. It is known that

p erformance variations such as pressure drop, gas flow rate, and bag failure in a baghouse system could make it difficult to provide predictable parti culate levels which directly affect total mercury concentration. The following is a summary of the pressure drop of Sys 15 and Sys 16 and is given in

Table 4

.NDEP

- NMCP Review Summary

– Barrick Goldstrike

4 Overall, the baghouse pressure drops appeared to be in the manufacture’s recommended range (1.5 to
11.0 in H 2 O ). There were no significant differences in the pressure drops among the four stack source test
results

, although there was a slight increase of pressure drop on the October 07 source test. The data demonstrates that the increase in pressure drop had no impact on mercury emissions

.

Table 4

. Comparison of the Baghouse Pressure Drops and Mercury Emissions

Test Date System BH Static Classifier Avg. **∆** P (in H 2 O) BH Dynamic Cla ssifier Avg. **∆** P (in H 2 O) Hg Emission (lb/hr)

March 2007 System 15 4.4 4 4.25 0.001
System 16 4.88 4.25 0.015
August 2007 System 15 4.33 5.05 0.154
System 16 5.29 5.19 0.01 0

October 2007 System 15 9.11 7.69 0.00 2
System 16 7.21 6.26 0.001
April 2008 System 15 4.03 4.16 0.00 4
System 16 4.05 4.06 0.00 1

2. 2 Dust p i ckup p oints

I t was hypothesized that a large number of dust pickup points located at each air slide may be a potential unpredictable and intermittent mercury sou rce. Barri ck Goldstrike recently responded to

NDEP ’s question regarding the role of dust picku p points saying that it was designed to maintain a negative pressure in the air slides and to control fugitive dust (see Figure 2 )

. Any particulate fugitives would be under negative pressure and would be routed to the pick

- up point baghouse and not emit

di rectly to atmosphere. Thus, dust pick up points do not seem affect a dramatic increase in mercury emission.

Figure 2 . Schematic Diagram of Dust Pickup Points

Dust pickup pointsNDEP

- NMCP Review Summary

– Barrick Goldstrike

5 2. 3 Contamination of s ample i mpinger s olutions

Figure 3 illustrates the EPA reference method 29 for total mercury analysis. Generally, the first two impingers containing hydrogen peroxide (H 2 O 2 /HNO 3 ) solution are used to capture only oxidized mercury (Hg 2+ ) and the acidified potassium permanganate (KMNO 4 /H 2 SO 4 ) impingers are used to capture elementary mercury (Hg o ) 3

.

Figure 3 . EPA Ref. Method 29

- Sampling TrainNDEP

- NMCP Review Summary

– Barrick Goldstrike

6 Complete mercury level analysis results by each impinger were provided to NDEP

- NMCP . Most of

the mercury source test results seem relatively consistent except for the August 07 source test results.

Oxidized m ercury (Hg 2+ ) concentration levels after the HNO 3 rinse show ed much lower concentration

levels than t he hydrogen peroxide impingers. It seems reasonable to assume that ther e is almost no mercury residue left on the surface of the impingers.

However, considerably high levels of elemental mercury (Hg 0 ) w ere found in an aqueous solution of

the KMNO 4 impingers and HCl rinse for March 07 Sys 16 and August 07 Sys 15 stack source tests. It

could be evidence of possible contaminat ion. According to Serne 4 , KMnO 4 /H 2 SO 4 absorbing agent used in the impingers should be prepared onsite so it is fresh each test day. To avoid contamination of the absorbing reagent during preparation onsite

, a clean sample train preparation and cleanup area must be

used.

In addition

, Laudal 5 from the Federal Energy Technology Center of DOE (Department of Energy) reported that “ I t has been found that the greatest source of error in the Ontario Hydro Method ( OHM) procedure is not in the sampling but in the preparation of the impinger solutions following sampling. The preparation steps include 1 ) tearing down the impinger train, 2) transferring solutions to flasks or bottles, and 3) digesting of the solutions ”

. OHM is a modification of EPA Method 301

, and is identical to Method 29 except for three additional impingers containing KCl. Hence, a m ercury ( mostly in elementa l

mercury fo r m ) leak to the surrounding area could likely be the cause of potential contamin ation while conducting sample recovery in the field

. As a result , elemental mercury levels may be abnormally high in

the KMNO 4 im pingers which capture elemental mercury

.

S ource test results of Sys 16 Run #1 and Run #2 illustrated in Table 3 could be a g ood example of contamination, showing unexpectedly high mercury levels compared to other results. Mercury emissions

from Sys 15 and Sys 16 would be expected to be in the range of 1 to 3 (ug/dscm) because source testing

was conducted under nearly the same o peration al conditions ( ore mercury content, throughput,

temperature, velocity, flow rate, baghouse pressure drop

, and so on )

. However, some observed values

showed extremely high level s of mercury during the continuous source testing event s

. Therefore, Sys 16

Run #1 and Run #2 shown in Table 2 impl y a strong evidence of contamination.

3 . Effect of the Mercury Loading:

The effect of the mercury loading on mercury emissions was investigated using the data set available. Figure 4 depicts the variation in t he daily feed level of mercury for Sys 15 from May ‘07 to May ‘08 . A polynomial curve fitting is used to best fit a series of data points to a line and is shown by a red line in Figure 4 below. The average feed levels of mercury on August 3 and October 2 w ere found to be approximately 25.2 (ppm) and 8.2 (ppm), respectively. The mercury feed level on August 3 was increased

about 2 8.6 % higher than the daily average mercury feed level of approximately 18 (ppm). On the contrary, the mercury feed level on Octobe r 22 was decreased by 5 4.4 % lower than the average mercury feed level. The October stack source test results showed a relatively lower emission of mercury with a given lower mercury content in ore (see Table 5 ).

In conclusion, it would be difficult to co nclude that the relatively high levels of mercury feed ( 7 ppm higher than daily average) on August 3 could make unexpectedly high contributions of mercury emissions when compared with the October test result s

.NDEP

- NMCP Review Summary

– Barrick Goldstrike

7 Figure 4

. Variation s in the D aily F eed L evel of M ercury for Sys 15 (May ’07

- May ‘08 )

0 10 20 30 40 50 60

1 51 101 151 201 251 301 351 401 451 501 551 601 651

Test EventHg Loading (ppm) Sys 15

Poly. (Sys 15)

Average Hg loading level = 18.1 (ppm) Polynomial curve fitting August 3, '07
(25.2 ppm)

Oct. 22, '07
(8.2 ppm) May 11 - July August - October Jan. - March Nov. - Dec. April - May

April 4, '08
(13.6 ppm) **Year 2007 Year 2008** 

Mercury Emissions Observed

Log Hg

Emissions
( **μ** g/dscm)

0.5

0 .0 1 .5

1.0 2 .5

2.0NDEP

- NMCP Review Summary

– Barrick Goldstrike

8 Table 5 . Comparison of the Average Feed Levels and Emissions of Mercury

Date Average Feed Level of Mercury (ppm) Mercury Emissions ug/dscm (lb/hr)

August 3, 2007 (Sys 1 5) 25.2 341.2 (0.154)
October 22, 2007 (Sys 15) 8.2 3.5 (0.0017)
April 4, 2008 (Sys 15) 13.6 10.0 (0.0037)

According to Barrick Goldstrike’s memo on September 18, 2008, total mercury contents in ore w ere measured by Barrick Goldstrike and third party analytical laboratory using 2 different analytical methods,

ICP (inductively coupled plasma) and CVAA (cold vapor atomic absorption) , for the same ore samples. The results showed remarkable differences between the ICP and CVAA methods. In general, the ICP method allows simultaneous or rapid sequential determination of mercury in a short period of time 6 . The CVAA method is extremely sensitive to interference from volatile organics, chlorine, and sulfur compounds 6 . Knight et. al 7 conducted a comparative study and found that the ICP

- MS measurements appeared to be 57% of the CVAA values for the real hair samples. The authors confirmed that there were significant losses of mercury that occur when using ICP

- MS. Clearly

, further investigations might be

necessary to assess th is issue , and p articular attention should be paid to quantitative analysis of mercury

content in ores.

4. Estimating the E ffectiveness and A ppropriateness of the S orbent T rap M ethod

Barrick Goldstrike stated that EPA Method 29 ( H 2 O 2 and KMnO 4 impingers) and OHM ( H 2 O 2 , KMnO 4 and KCl impingers) are very similar methods in theory and should produce very similar results if

total mercury is only considered. However, a ccording to the D

. O

. E

. EERC (Energy & Environmental Research Center) final report 5 , OHM appears to be much higher than EPA Method 29 in total mercury concentration. The main reason was primarily due to additional three impingers containing potassium

chloride solution s (KCl) which exhibited high mercury spikes compared to H 2 O 2 and KMnO 4 impinger

solutions as shown in Table 6

. The OHM test results from mining sites in Nevada also showed similar

trends like the D

. O

. E

. EERC test results. Therefore, it seems obvious that OHM is considerably higher

than EPA Method 29 in total mercury concentra tion

.

Originally, Ontario Hydro M ethod ( OHM ) and EPA Method 29 were the only acceptable reference

methods for mercury measurement

. In August 2007, EPA released a direct and final rule that allowed two

other reference methods such as EPA Method 30A (ins trumental reference method) and 30B (sorbent trap method)

. EPA Method 30B ( sorbent trap ) was developed to analyze vapor phase mercury levels ( e.g., Hg o and Hg2 + ) 8

. Method 30B does not consider quantifying partic le

- bound mercury. M ethod 30B is known to

be v ery sensitive to high temperature and pressure

. Furthermore , sampling using the Method 30 B procedures is strongly affected by the high particulate loading. T he sorbent trap tests conducted by Nunn showed that the high temperature of the off

- gas stream resu lted in desorption of the spiked mercury samples, and prevention of adsorption of the native mercury vapors in the gas stream 9

.

Table 6 . Direct Comparison of Performance of Three Mercury Absorbing Impingers 5

Sample ID KCl (g/m 3 ) H 2 O 2 (g/m 3 ) KMnO 4 (g/m 3 ) Total Hg (g/m 3 )

ZM

- D1

- OH

- 1 17.36 0.07 7.80 25.24

ZM

- D1

- OH

- 2 9.47 0.07 4.30 13.85

ZM

- D1

- OH

- 3 17.41 0.01 7.14 24.57NDEP

- NMCP Review Summary

– Barrick Goldstrike

9 ZM

- D1

- OH

- 4 4.92 0.04 4.47 9.44

ZM

- D2

- OH

- 1 4.21 0.06 2.17 6.45

ZM

- D2

- OH

- 2 10.12 0.45 5.96 16.54

ZM

- D2

- OH

- 3 5.45 0.36 3.37 9.19

ZM

- D2

- OH

- 4 11.27 0.56 5.78 17.62

On the other hand, Barr i ck Goldstrike compared the relationship among three source test methods (Method 29B, OHM, and Sorbent Trap) using August 07 source test results and proposed that the sorbent trap method would provide co nsistent results (see Table 7 ). In fact, the sorbent trap method does not require the complex sample recovery procedures which could cause a possible source of error. However,

i t would not be appropriate to conclude with only one data set. Hence, further t est results are required to support Barrick’s statement.

Table 7 . Comparison of Three Source Test Methods Used ( August 2007)

System M29 OHM Sorbent #1 Sorbent #2 Sorbent #3

Sys 15 (ug/dscm) 341 3953 0.68 1.05 0.91
Sys 16 (ug/dscm) 25 1598 0.61 1.13 0. 32

5

. Conclusions & Recommendations

Conclusions

The following conclusions are obtained based upon the analysis of source test results provided by

Barrick Goldstrike.

1. Statistical analysis is performed to compare the consistency among source test d ata sets. The October 07 source test data set shows a better consistency with low COV values for both Sys 15 and Sys 16.

2. Baghouse pressure drops and several dust pickup points do not seem to have the effect of a sudden increase in mercury concentration during source testing.

3

. U nexpectedly high levels of total mercury would seem to have happened by contamination while preparing impinger solution s and performing sample recovery including acid

- rinsing the impinger

surfaces

. Therefore, f urther investigat ion of future source test data are more likely required to
understand and clarify the impact of contamination

.

4. The effect of the mercury loading on mercury emissions was investigated and found that the relatively high levels of mercury feed on August 3 could not be a main reason for extremely high levels of mercury emissions.

5

. Each mercury emission test method has distinct advantages and disadvantages depending on the test objectives. Impinger methods require much attention to many factors includin g : acid rinse of the impinger surfaces (or sample recovery) , moisture content, particle size, flue gas temperature, flowrate, isokinetic sampling, etc. The sorbent trap method is relatively simple to prepare in the field and potentially lead to less contam ination while conducting source sampling 6 . However, it should beNDEP

- NMCP Review Summary

– Barrick Goldstrike

10 noted that the sorbent trap method is only designed to measure total vapor phase mercury levels under low particulate conditions. In addition, the high temperature of the off

- gas stream could result in desorption of the spiked mercury samples, and prevention of adsorption of the native mercury vapors in the gas stream. Thus, the sorbent trap method would seem not to be appropriate

.

6 . I t would be unfound to conclude that Sys 16 (south pre

- he ater) showed produce substantially more mercury emission s than Sys 15 (north pre

- heater) due to somewhat different operational conditions

such as ore mercury content, throughput, and baghouse performance

.

7

. In closing, t he March 07 test data submitted f rom Barrick Goldstrike was unofficial and t he August

07 test showed a strong evidence of contamination. Moreover, the April 08 test was outside of the reporting year

. Therefore, NDEP

- NVMC concludes that the October 07 test data is the most appropriate for the 2007 annual emission reporting of ore mill dryers (Sys 15 & 16)

.

Recommendations

1. F ield blanks are recommended a s part of the QA/QC activities associated with stack sample

collection . If the field blanks show contamination above background or surro unding levels, steps must be taken to reduce the contamination to below background levels 5

. For this reason, field blank sample

results would be very important in int erpreting and understanding source test results

. Therefore, it would be helpful if Barrick Goldstrike could provide the results for blank samples to ensure that there is no possible contamination around the sampling location

.

2. It would be recommended that M ethod 29 stack source testing should be made by at least two or three trained operator s for effective stack sampling and source recovery

. Ideally, the operator should

be a licensed or certified technician t o minimize contamination errors. It is questionable if one operator, alone, could conduct a proper Method 29 test.

References

1. U.S . Environmental Pollution Agency, “Operation and maintenance manual for fabric filters”, 1984.

2. Sigma

- Aldrich

, Whatman quantitative filter papers, Ashless and Grad 40.

3

. U.S. Environmental Pollution Agency , “Method 29

– Determination of metal emission s from stationary
sources”, http://www.epa.gov/ttn/emc/promgate/m

- 29.pdf

.

4 . J. Serne, “An overview and comparison of available mercury emission test methods for boilers”, SES (Source Evaluatio n Society) Conference, 2006

.

5 . D. Laudal, “Field validation of the Ontario Hydro mercury speciation sampling method at site E

- 29”,

U

. S

. DOE Federal Energy Technology Center, July 1999.

6. U.S. Environmental Pollution Agency, “Test methods for evaluati ng solid waste, physical/chemical methods”, http://www.epa.gov/waste/hazard/testmethods/sw846/pdfs/chap3.pdf , 2007.

7

. R

. Knight

, S.J. Haswell, S.W. Stephen, and J. Batty, “ Determination of mercury in hair by coupled

CVAA

- ICP

- MS ”, J. of Analytical Atomic Spectrometry

, Vol. 14, pp.127

- 129, 1999.NDEP

- NMCP Review Summary

– Barrick Goldstrike

11 8

. U.S. Environmental Pollution Agency , “Method 30B

– Determination of total vapor phase mercury

emission from coal

- fired combustio n sources using carbon sorbent traps”, August 2007.

9 . A

. Nunn, “Mercury methods evaluation test program results”, The Air Compliance Group, August

2007.