# Estimated Emissions of HCN from Gold Mine Facilities in the U.S.

Metals and Minerals Group Sector Policies and Programs Division Office of Air Quality Planning and Standards U.S. Environmental Protection Agency Research Triangle Park, NC

Final Draft December 2010

### Methods and Approach:

In year 2009 extensive emissions testing of hydrogen cyanide (HCN) was conducted at the three large st gold mine facilities in Nevada to gather data to be used to estimate emissions of hydrogen cyanide f rom these facilities. The main approach and method used was the application of the flux box chamber. The specific methods are described in the document titled “Quality Assurance Project Plan (QAPP), Comprehensive Air Emissions Testing for Hydrogen Cyanid e at Three Nevada Gold Mine Sites Using the USEPA Surface Isolation Flux Chamber Technology”
, by Mr. Tom Card and Dr. C. E. Schmidt, O ctober 7, 2009, which is available in the docket (Document number: EPA

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- 0239

- 0101.pdf). The comprehensive resu lts of the testing completed for these 3 facilities are described in detail in the “ Evaluation of Air E missions of H ydrogen C yanide from F ugitive S ources at N evada G old M ines U sing the USEPA S urface I solation F lux C hamber T echnology : Cortez, Gold Quarr y & Round Mountain Mines ”, by Dr. C.E. Schmidt and Mr. Tom Card . This document is also available in the docket ( Document number: EPA

- HQ

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- 01 63 .pdf).


### Estimating HCN Emissions for the Three Largest Facilities :

As described in the two documents cited above, fugitive emissions of HCN were estimated at the three largest facilities b ased on the test data gathered and appl ication of various mathematical and scientific equations. Emissions estimates were also obtained for other facilities in the U.S
., as discussed below. However, no testing of the fugitive emissions of HCN

w ere conducted at those other facilities. The estimates of fugitive emissions for those other facilities were mainly based on application of emissions factors and various calcula tions

. Therefore, the results for those other facilities are less reliable , and are presented separately below

.
The specific calculations and emissions estimates for Cortez, Gold Quarry, and Round Mountain are presented on pages 16

- 18 (and on other pag es) of the document mentioned above ( EPA

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- 01 63 .pdf )

. 

### Correction Factors for Surface Area and Windspeed:

With regard to the mathematical and scientific equations (described in th e two documents cited above), which were applied to estim ate the emissions for the three largest facilities (Cortez, Gold Quarry, and Round Mountain), those equations a n d calculations include the use of correction factors for wind speed and large surface areas. The documents cited above explain the rationale fo r applying these factors and what they adjust for.

However, there has been some debate among scientists as to whether and how the correction factors for surface area and wind should be applied, and for which surface areas they should be applied. If the se correction factors are not used, then the estimated emissions for these types of sources are somewhat higher (e.g., about 40

– 6 0% higher ) than the estimates derived when applying the correction factors. Since there has been some scientific debate abou t the appropriateness of using these correction factors, we decided to calculate a range for these emissions for the three largest sources , to ensure that we included high

- end conservativeestimate s . Therefore, we recalculated the emissions estimates for those 3 facilities using the same equations, but without applying the correction factors . This resulted in conservative high

end estimates of the emissions from the three facilities. The estimates of fugitive emissions for the 3 facilities are shown in t able 1 below. The calculations to adjust for the correction factors

are shown in Attachment # 1

.
Stack emissions testing for HCN w as also completed in 2009 for these 3 facilities. Estimates of the emissions based on those results are shown in Table 2

. The data used to derive these estimates are available in the docket.



### Table 1. Estimates of the Fugitive Emissions of HCN f o r the Three Large Gold Mines Facilities for year 2009 at which flux chamber testing was conducted Facility Initial estimate of emissions, with use of Correction Factors (in pounds per year) Conservative High

- end estimate of emissions (in pounds per year), with no correction factors applied for surface area or wind applied) Cortez 8983 14996 Gold Quarry 8739 15109 Round Mounta in 7380 12246



### Table 2. Estimated Emissions of HCN from the Stacks (point sources)

Mine Facility total (lb/hr) Facility total ( pounds /yr) Facility total (ton/yr)

Cortez 0.0009 7. 9 0.0039

Round Mountain 0.008 69.4 0.03 5
Gold Quarry 0.10 885.6 0.44



### T able 3. Estimates of the Total Potential Emissions for HCN from Three Large Gold Mines Facilities : stack emissions plus fugitive emissions for 2009 (in pounds per year) Facility Initial estimate Conservative High

- end estimate Cortez 8991 15004 Gold Qu arry 9625 15995 Round Mountain 7380 12246

### Conclusions from the R esults of Testing at the 3 Largest F acilities , and Estimates of the Potential to Emit for these Sources:

As shown above, the Initial estimates for the three largest facilities, resulted i n an estimate of 9
, 625 pounds per year (or about 5 tons per year) of HCN emissions for the largest source (i.e., Gold Quarry). Then, based the second set of calculations (i.e., without applying the correction factors ), we derive a conservative high

- end es timate of emissions for this same facility ( Gold Quarry ) of 15,995 pounds per year (about 8 tons). Based on these results, we estimate the largest emitting facility emits between 5 to 8 tons per year of cyanide. With regard to estimating potential emissi ons, based on our analyses and research of the industry, it is our understanding that these facilities operate continuous all year (24 hours per day, 365 days per year), or very close to continuous all year, and operate at full current capacity, or very cl ose to full current capacity. Moreover, the calculations used to derive these estimates were derived based on such continuous operations at full current capacity. Therefore, the emissions estimates shown in Table 3 are estimates of potential emissions. Nevertheless, to ensure we include a conservative upper

- end of the potential emissions from these facilities, we assume that they could possibly operate at about 10% higher production. Therefore, to calculate such a high

- end estimate, we assume that poten tial emissions from the largest facility could possibly be about 10% higher
, which results in an estimate of potential emissions of about 9 tons per year of HCN emissions

. Thus, we estimate that the potential emissions of HCN from the largest facility is between 5 to 9
tons. Moreover, we estimate that the other 2 large facilities mentioned above (Cortez and Round Mountain) have potential emissions less than 9 tons per year.


### Emissions of HCN from other gold mining operation facilities:

Emissions es timates were obtained for several other facilities in the U.S. However, no testing of the fugitive emissions was conducted at those other facilities. The estimates for those other facilities were based on application of emissions factors and various calc ulations

. Therefore, the results for those other facilities are less reliable. Nevertheless, we present emissions estimates for two other large facilities (Newmont Twin Creeks and Barrick Goldstrike) in this document , which we believe are the 2 next larg est sources after the 3 facilities described above. The emissions estimates for Twin Creeks and Goldstrike are available as separate documents in the docket. We also assessed information on e stimated emissions for other facilities in the U.S., from vario us data sources including the Toxics Release Inventory (TRI). All those other emissions estimates are considerably less than 9 tons. We believe that the five facilities described in this document are the largest gold mine ore processing and production fa cilities in the U.S. Below we present the estimates of HCN emissions for Twin Creeks and Goldstrike.

### Table 4

. Estimates of the Emissions (in pounds per year) of HCN from Twin Creeks and Goldstrike for 2009 Facility Estimate of Fugitive Emis sions of HCN (in pounds per year) Estimate of Emissions of HCN from Stacks (point sources) Estimate of Total Emissions of HCN (in pounds per year) Twin Creeks 10270 2899 13169 Goldstrike 5925 38 5963



### Estimate of Potential Emissions for Twin Creeks a nd Goldstrike :

With regard to estimating the potential emissions, similar to the facilities described above, it is our understanding that these facilities operate continuous all year (24 hours per day, 365 days per year), or very close to continuous all y ear, and operate at full current capacity, or very close to full current capacity. Moreover, the calculations used to derive these estimates were derived based on such continuous operations at full current capacity. Therefore, we believe the estimates sh own in Table 4 are estimates of potential emissions. The data used to estimate the stack emissions for these facilities are also available in the docket.



### Overall Conclusion of all the Analyses A bove:

We estimate that the potential emissions of HCN fo r the largest gold mine facility are between 5 to 9 tons per year, and we estimate that all other facilities emit less than this level.ATTACHMENT #1

Estimated Emissions (in pounds per year) for Three Large Gold Mine Facilities without using Correction Factors for Surface Area and Wind Speed (Draft - March 2010)

Round Mountain HCN Emissions Estimate w/ Fa Fw Inverse of the Fa & Fw Round Mountain HCN Emissions Estimate w/out Fa Fw Gold Quarry HCN Emissions Estimate w/ Fa Fw Inverse of the Fa & Fw Gold Quarry HCN Emissions Estimate w/out Fa Fw Cortez HCN Emissions Estimate w/ Fa Fw Inverse of the Fa & Fw Cortez HCN Emissions Estimate w/out Fa Fw 11.90 1.92 22.88 898.10 2.13 1910.85 1427.90 2.13 3038.09 799.80 1.92 1538.08 170.80 2.13 363.40 71.50 2.13 152.13 1.10 1.92 2.11 307.20 1.00 307.20 281.40 1.00 281.40 0.10 1.00 0.10 220.80 1.00 220.80 2.90 2.13 6.17 569.50 1.00 569.50 138.50 2.13 294.68 2.70 2.13 5.74 0.00 1.00 0.00 19.80 2.13 42.13 1.50 2.13 3.19 1.00 0.00 146.10 2.13 310.85 1182.40 2.13 2518.51 1.00 0.00 1029.60 2.13 2190.64 313.80 2.13 668.39 127.70 2.04 260.61 197.80 2.13 420.85 966.50 1.00 966.50 1326.20 2.04 2706.53 349.80 1.00 349.80 2309.70 2.27 5249.32 0.30 2.04 0.61 257.10 1.00 257.10 444.90 2.27 0.10 1 0.10 174.00 2.13 370.21 634.50 1.00 634.50 0.10 2.04 0.20 169.20 2.13 360.00 1.90 2.27 4.31 0.10 1 0.10 0.30 1.49 0.45 0.70 2.27 1.59 2.00 1.00 2.00 3.90 1.49 5.82 0.10 2.27 0.23 130.60 2.04 266.53 393.30 1.64 644.75 5.20 1.39 7.22 1356.20 2.04 2767.76 31.60 1.43 45.14 2.10 1.32 2.76

118.10 1.85 218.70 19.90 1.39 27.64 5.90 0.76 4.48 460.90 1.85 853.52 1.80 1.61 2.90 29.00 1.45 42.03

36.00 1.00 36.00 0.80 1.54 1.23 21.80 1.43 31.14 36.70 1.85 67.96 0.60 1.52 0.91 21.80 1.43 31.14 12.00 1.10 13.19 428.50 1.64 702.46 21.80 1.43 31.14 1.00 0.00 13.30 1.33 17.73 21.80 1.43 31.14 124.60 1.18 146.59 1.10 1.59 1.75 26.90 1.43 38.47 124.60 1.18 146.59 0.50 1.52 0.76 26.90 1.43 38.47 124.60 1.18 146.59 0.40 1.49 0.60 26.90 1.43 38.47 124.60 1.18 146.59 7.90 1.79 14.11 26.90 1.43 38.47 124.60 1.18 146.59 12.20 1.79 21.79 22.90 1.45 33.19 124.60 1.18 146.59 328.50 2.44 801.22 22.90 1.45 33.21 124.60 1.18 146.59 1393.40 2.44 3398.54 6.20 1.23 7.65 124.60 1.18 146.59 907.00 1.00 907.00 6.20 1.23 7.63 124.60 1.18 146.59 548.00 1.00 548.00 6.20 1.23 7.63 0.20 1.27 0.25 374.70 1.00 374.70 6.20 1.23 7.63 1.80 1.27 2.29 191.40 1.00 191.40 6.20 1.23 7.63 7.50 1.27 9.53 1.50 1.00 1.50 820.90 1.00 820.90 32.50 1.86 60.58 0.00 179.40 1.00 179.40 142.70 1.86 265.42 0.00 26.20 1.00 26.20 207.20 1.86 385.39 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 789.00 1.00 789.00 0.00 0.00

87.90 1.00 87.90 0.00 0.00 TOTAL 7379.60 12246.14 8739.40 15108.91 8982.70 14996.06