Page 1 of 3 “MONITORING OPTIONS AND/OR CONSIDERATIONS FOR MERCURY FROM GOLD MINES”

NDEP RESPONSE February 26, 2010

A. CEMS to Roasters

NDEP re-asserts that CEMS for roasters would not be feasible at this time, gi ven the current state of the CEMS technology and the inab ility to certify a CEM for the mercury concentration levels typical of an ore roaster. Also pertinent is the concern that the data generated by the CEMS could

not be restricted to use as a tool for evaluati ng “operations and maintena nce.” Any data monitored and recorded using CEMS could be deemed “cred ible evidence” and would be ripe for compliancerelated litigation.

Of further concern is that the CE M standard would be based on “man ufacturer’s specifications.” To our knowledge, CEMS technology varies by manuf acturer and, as a result, the associated maintenance, calibration and operatio ns also varies. This variabil ity would make it difficult to evaluate the performance of contro ls between the roasters. NDEP’s preference would be to suspend consideration of mercury CEMS on roasters until a monitor st andard and a certification/calibration standard have been promulgated. Due to the rapi d promulgation of the FMACT, it is unlikely that the proposed CEM requirement (for only 4 ore roas ter stacks) could drive the technology to meet implementation timelines.

NDEP does find merit in the approach of annua lly reviewing and re-e stablishing operational parameters during a stack perfor mance test. This approach could help verify operational parameters, especially if ore resources or processes vary.

The NDEP recognizes EPA’s concerns that emission units with the potential to be very large mercury emitters may deviate or “spike” between annual stack tests. This concern is alleviated with

additional test data to increase statistical confidence, comprehe nsive parametric monitoring, and

alarms and interlocks.

B. Carbon adsorbers

1. NDEP reiterates its previous stance that por table mercury analyzers are currently not an appropriate regulatory monitoring or compliance t ool. Their usefulness is limited for a number of reasons. There is no promulgated standard for the analyz ers or the calibration of the analyzers. Typically, portable analyzers are intended for am bient air measurements and not an exhaust gas stream. Acquiring a time-weighted average from th e analyzer’s measuremen ts and the application of the data is questionable and re-visits legal concerns regarding “credible evidence.” Proper training, operation, maintenance of the portable anal yzer and prevention of contamination will also be crucial, as the mining facilities, and not prof essional test companies, would perform the portable analyzer measurements.Page 2 of 3 2. NDEP recognizes EPA’s concern that carbon beds may experience “break through” and “spikes” between annual stack test events. Of note, it is not clear if all carbon beds would be required to have the proposed sorbent trap. Would a threshold PTE establish applicability? It may have limited value to manage/regulate traps on units with low PTE that already have multiple parametric monitoring requirements. NDE P would recommend that the so rbent trap option not be implemented alone, but co-implemented with option #3 of this Section.

3. This is NDEP’s preferred option and is most si milar to the NMCP approach. This approach has been vetted by the NDEP and the industr y and is currently being implemented.

4. The NDEP does not feel that this should be a stand-alone option. If implemented, it should be co-implemented with item B.3, above. The “trigg er” to re-examine the fixed replacement time based upon a “change in process” is a bit clumsy and perhaps ma kes this option unnecessary, given the relative simplicity of directly measuring th e carbon as established in B.3, above (and in conjunction with annual stack testing).

C. Carbon adsorber temperature

The NDEP does not take issue with the proposal to measure carbon bed temperature. However, it

needs to be clarified if the c ontinuous monitoring requires conti nuous record keeping and what, if any, averaging periods might apply. The NDEP also notes that it is more difficult (and costly) to retrofit existing units with continuous monitori ng. Continuous monitoring also requires more Agency resources to review the records--it is not clear to NDEP that this is a meaningful ROI.

Other options for consideration are alarms and in terlocks to replace continuous monitoring. Alarms and interlocks are more readily retro-fitted onto existing equipment and can alert, or automatically shutdown process that vary from pre-defined opera tional parameters. Alarms and interlocks are useful to ensure continuous performance.

D. Venturi Scrubber

Water flow rate and pressure drop are meaningf ul parameters. EPA may also consider some language regarding the quantity an d/or maintenance of packing ma terials/trays. As noted in Sections above, interlocks and alarms may be effective to perform “continuous monitoring.”

E. Monitoring for roasters (scrubbers)

In the EPA-provided draft notes, unique roaster regulations were proposed for each roaster by facility. The NDEP recommends that regulations not be specifically tailored for each facility, but rather to write standards that could apply to a ll roasters, including potential new roasters. The NDEP proposes that roaster regulati ons be generated for two groups of roasters: roasters that use

titration and roasters that use real time monitoring of ORP and pH.

The Newmont and Barrick roasters both use titrati on to manage their mercury scrubbers. Barrick measures chloride ion content by titration 1x pe r day and Newmont does it 4x per day. Newmont likely does it 4x per day due to the requirements of the acid plant.Page 3 of 3 Of note, the draft document provided by EPA states that Barrick also monitors additional scrubber parameters such as spray header pressure and temp erature and states that nothing beyond titration is performed for Newmont. A review of Title 5 and Phase-2 permits for Newmont and Barrick reveals

that both roasters monitor addi tional operational parameters and se veral of those parameters are

common to both roasters.

It makes sense that any facility which recovers Hg 0 from calomel via electrowinning have a scheduled bleed event. This would apply at Newmont and Jerritt. Al though Barrick does not electrowin their calomel, their bleed events are still critical for scrubber performance. Of note,

Newmont’s and Jerritt’s electrow inning of chlorinated calomel has not been specifically identified in a permit or been stack-tested to assess the po tential mercury emissions from this process.

In contrast to the Barrick and Newmont scr ubbers, Jerritt performs continuous ORP and pH monitoring with multiple monitors to follow the chem ical reaction of their mercury scrubber. While the continuous ORP and pH are surrogates for titration, the bene fit is that the continuous measurements will follow any potential material or process deviations closer to “real time” than daily or shift titration measurements and allow qu icker correction. The ORP and pH monitors are

attached to alarms and interlocks. The real-t ime ORP and pH monitoring at Jerritt is required pursuant to the current Consent Decree. It would be undesirable to put Jerri tt in a situation where their real-time monitoring would c onflict with the FMACT requirement to perform lab titration.

For NvMACT, NDEP will also focus on quench/condens ers/heat exchangers prior to scrubber trains which are critical to conditioning the gas stream. In addition, particulate contro ls such as entoleters (Jerritt) and wet ESPs (Newmont and Barrick) also play a critical role in conditioning the gas streams prior to the mercury scrubbers.

Roasters and their relate d control technology trains could also be nefit from alarms and interlocks on crucial components.