### Queenstake Resources Jerritt Canyon Mine February 23, 2010

Ore Roaster Circuit Ge neral Description: There are two identical Roaster Circuits (Eas t and West) with independent off gas handling systems located at the Jerritt Ca nyon Mine. The Roasters operate as two-stage, countercurrent, fluid bed type units which fluidize and oxidize re fractory ore in a pure oxygen environment. The Roaster system is designed to oxidize sulfide bearing materials and organic carbon found in the refractory ore. To begin the roasting process, ore is fed unifo rmly into each Roaster through a fluidized feed distributor that maintains a barometric seal. The ore that is fed into the Roaster has already been mixed with pulverized coal to increase the fuel va lue. A coal star feed system and Roaster bucket elevator feed airslide are respons ible for supplying a consistent or e/coal blend to the Roaster. In the first stage, which lasts approximately 24 minutes, the ore forms an aerated bed where it becomes almost completely oxidized. The bed will be at approximately 110 inches water gauge (WG) while the temperatur e is typically around 1,030 o F. Once the first-stage retention time is reached the ore is discharged to the second st age at the bottom of the bed through the lower interstage transfer box. This method of transfer is utilized to prevent oversized feed material and accumulation of refractory brick spallings. Control of the process retention times of the ore in the first and second stage is important as the times are directly proportional to the fluid bed level. These levels are measured indirectly by the pressure drop in inches of water column from the bottom to the top across the fluidized bed. The pressure taps measure the drop in inches of wa ter column and are located at the bottom of the stage beds and the freeboard. In the second stage, the roasting process last s approximately 12 minutes with operation at a temperature of approximately 700 o F and 65 inches WG. Once processing is completed in the second stage of the Roaster, the final product exits from the bed underflow. This discharge, like the first stage, is controlled by one of two radial action discharge cone valves. The amount of oxidized material or calcine exiting the second stage secondary cyclones cannot be controlled. From the bottom of the second stage, the fina l product is piped through a second stage windbox, through one of two Roaster discharge quench heads, and discharged into the quench launder.Particulate Control: Control of particulates in the Roaster off gas is very important and starts with the two stage cyclones located on the first and second stages of the Roaster. The exhaust gas from the first stage roasting process contains entrained dust par ticles containing enriched gold that is partially roasted because of the relativelyshort retention time. The material must be returned to the Roaster for more complete combustion to av oid gold loss and overloading downstream gas cleaning equipment. The first stage collected dust is returned via a stai nless steel primary and secondary cyclone system before entering the gas handling circ uit. The first stage primary cyclone returns collected dust back into the firs t stage of the Roaster reactor. The first stage secondary cyclone returns collected dust to th e upper interstage transfer box, where the first stage underflow exits, for en trance into the second stage Roaster reactor. The refractory lined primary and dual, unlined stainless steel second stage secondary cyclone removes approximately 95 percent of the entrained dust from the exhaust gas before discharge to the interstage box. The exhaust gas from the second stage of the roasting process will contain a large amount of dust that tends to be sticky. Th is dust must be removed from the second stage exhaust gas to prevent the interstage windbox from plugging and scale build-up on the gas dispersion nozzles called the tuyeres. The second stage primary cyclone returns collected dust back into the second stage of the Roaster. The primary and secondary cyclones are designed to have control efficien cies between 90 and 95 percent. The efficiency is highly dependent upon three variables. Fi rst, the system pressure drop, which is dependent upon the volume of gas flowi ng through the cyclones. Next, the size of the dust particles exiting the Roaster, which is depe ndent upon the adequacy of the grinding circuit. The final variable is the dust lo ading in the gas stream, which is dependent upon the gas velocity in the Roaster and the particle size of the feed. Pure oxygen is fed into the bottom of the second stage of the Roaster through the second stage windbox. Non-sifting tuyeres, which are gas dispersion nozzles, in the second stage are used to distribute gas into the bed. The windbox then dist ributes the oxygen across a distributor plate to provide uniform flow of gas across the second stage bed. The 95 percent oxygen is used to fluidize the second stage and complete combusti on of the residual organic carbon from the first stage burn. The oxygen travels upwa rds through the second stage bed, into the freeboard, and exits through the second stage primary and sec ondary cyclones where dust is partially captured before entrance into the interstage windbox. The second stage exhaust gases, which contai n approximately 70 percent oxygen, are used to fluidize the first stage bed and in itiate the combustion of the coal and refractory components in the feed ore. Sifting tuyeres within the refractory dome distribute gas into the first stage bed. The exhaust from the first stage will contain appr oximately 20 percent oxygen and discharges to the gas handling circuit. The Gas Qu ench Tower and Entoleter, which follow the cyclones, provide additional particulate removal before treatment in the remainder of the gas handling circuit. In addition to oxygen, the exhaust gas contains SO 2 , CO, NOx, and Hg vapor as a result of combustion processes and ore composition. The NOx and CO levels are kept in line through control of the first stage bed and freeboard temperatures. The SO 2 , and Hg vapors are dischargedinto the gas handling circuit for removal before discharge to the atmosphere through the stack.

Particulate Control Work Practices Work practices to maintain proper operation of the East and West Roaste r's First and Secondary Cyclones include the following parameters: Maintain temperature in the discharge lines of each cyclone to avoid plugging in the cyclone discharge or bridging in th e cone valves above 800 o F. Maintain the content of Hg in the ore between zero to 30 parts per million (ppm), and determine sulfur content in the ore through ore characterization.

Particulate Control Maintenance The Roasters are inspected three times a shift on a daily basis. Inspections include ore sampler operating, feed bin levels, visible leaks in the Roas ters and cyclones, operation of the coal feed system, baghouse operations, Roaster feed valve ope ration, etc. Weekly and monthly inspections and maintenance are conducted by the mechanical and electrical depa rtments as part of preventative maintenance measures. The SOPs for Roasters, including appropriate rou tine maintenance of the Roasters and training requirements of personnel.

Particulate Control Set Points The main set points for the Roaster's primary and s econdary cyclones that ar e integral to the to the proper functioning of the gas hand ling system include the following: The temperature settings on the cyclones ore discharge must remain above 800 o F. The Roaster first stage freeboard is set at -2.0 inches of WC; The Roaster ore throughput is set at 90 tph. This set point is a system cap that controls the instantaneous f eed rate; and The Hg content of the ore must be maintained between zero to 30 ppm, and the sulfur content will be determined through ore characterization.

Particulate Control Alarms and Interlocks

There are several alarms associated with the Ro aster and cyclone operation to warn of problems. The alarms that pertain specifica lly to proper functioning of the ga s handling are set as follows: The Roaster first stage freeboard high alarm is set at 17.5 inches of WC; The Roaster first stage freeboard low al arm is set at -27.5 inches of WC;The Roaster first stage freeboard deviati on alarm is set at 10.0 inches of WC; The cyclone ore discharge temperature is set to alarm if the temperature falls below 800 o F. The alarm is set to notify the operator of a temperatur e deviation. The temperat ure drop is usually an indication of plugging in the circuit lin e, which will need to be cleared. An interlock on the Roaster first stage fr eeboard is set at 17.5 inches of WC. Particulate Control Recordkeeping The following data is recorded: The cyclone ore discharge temperature is l ogged every hour on the Roaster Area Daily Production Log; The Hg and sulfur content of the ore is logged once per shift in the Mi ll Production Report. The sample that is used to measure these values is from a composite sample that is collected every 15 minutes; Total ore processed for each hour of operation and the hours of operation of each Roaster circuit on an hourly basis; and The origin of the ore, coal, or other material, and the amount of each type of material processed in the Roaster circuit on a monthly basis.Quench Tower Hot dust-laden off gas from the Roaster first stage secondary cyclone is pulled to the inlet of the gas quench tower, where it is sprayed with fresh or seepage water. The hot gas is cooled from approximately 1,200 to 165 o F. The cooling step reduces th e total gas volume by about 40 percent. The volume of gas decreases in direct proportion to the absolute temperature and indirect proportion to the pressure. This is de monstrated by the ideal gas law, where pressure multiplied by the volume of the gas is equal to the number of moles times the universal gas constant times the absolute temperature (PV=nR T). Most of the heavier PM, larger than two microns in diameter is captured in the water an d leaves the quench tower as a dilute slurry. The cooled gas stream then enters the Entoleter wet dust scrubber. The resulting slurry from both the Entoleter and the gas quench towe r discharge to the seal tank. The seal tank serves as a barometric seal for the gas quench tower and the Entoleter, both of which operate below atmospheric pressure. The gas quench tower and the Entole ter are located within the Roaster structure above the top of the Roaster. Seal tanks are located one floor below the gas quench tower and the Entoleter within the Roaster building. Hot (1,100 to 1,200 o F) gas from the Roaster first stage secondary cyclone is routed through a 30 inch stainle ss steel duct to the inlet at the top of the gas quench tower . An Inconel 625 gas inlet nozzle projects two inches through the lid to maintain a sharp temperature transition into the tower, which minimizes corro sion and solids buildup on the inlet nozzle. As the hot gas passes through the in let nozzle, four water spray no zzles quench the gas stream. These nozzle assemblies are located at 90" angles just below the inlet. Each six-inch nozzle projects a 12 gpm flat spray perpendicular to th e direction of the gas st ream. Consequently, the gas stream is completely surrounded by a wall of wa ter, which penetrates the gas stream to its core. There are four additional spray noz zles in the upper section of th e Gas Quench Tower that spray water onto the vessel walls to minimize corrosio n and solids deposition. The hot gas evaporates approximately eight gpm of water an d are cooled to approximately 165 o F in the process. As the gas passes through the water sprays, the Gas Qu ench Tower vessel diameter increases to 48 inches. Both the cooling and increased diameter serve to slow down the gas from the inlet 55 to 60 feet per second (fps) to approximately ten to 11 fps.

Another water nozzle located near the bottom of the Gas Quench Tower projects a water spray upwards against the gas flow. Approximately 60 gpm of water is sprayed upwards from this nozzle-This fifth nozzle accomplishes the majority of the gas cooling. The spray travels upward to the inlet and then falls to the bottom such th at heat transfer occurs in both directions. Approximately four gpm of water is condensed inthe lower section of the Gas Quench Tower so that the net amount of water evaporated in this un it is greater than four gpm. The gas leaving the Gas Quench Tower is saturated with water at 130 to 140 o F and contains some water mist. Slurry discharging from the Gas Quench Tower passes through a six-inch drainpipe to the Seal Tank located directly below the Entoleter. The Gas Quench Tower operates at a draft of about -22 inches of water column differential pressure a nd requires a barometric (vacuum) seal, provided by the Seal Tank. Water flow to the upper quench nozzles in the Gas Quench Tower is manually controlled bymeans of a local flow meter and valve located at each inlet. Water flow to the lower spray nozzle is controlled by a flow controller, which receives a flow rate input from an orifice plate in the three inch water line feeding the nozzle. A temp erature controller (TI-48 001) located in the gas stream leaving the Gas Quench Tower may override the water flow set point. The water flow rate to the lower nozzle may be read from the DC S (FI-48001), but the upper nozzle flow rates may only be read at the local flow meters. If the water flow rate to the lower nozzles fails, a flow switch on the DCS will activate the interlock to the ID Fan which cascades to shut down the Roaster. High Pressure Water Systems Two high pressure water systems service the Roaster Gas Quench Tower and the Entoleter circuits. One system involves fresh water pumps located in the fresh water pump-house. This system is utilized approximately two percent of the time. The other system involves the seepage water booster pump located on the bottom floor of the Roaster buildi ng, and is utilized approximately 98 percent of the time. The seep age water booster pump provides water flow to the Gas Quench Tower and the Entoleter. Fresh Water Pump System A separate high pressure water pump and pipe feed each Roaster gas handling circuit so that failure of one pump will only shut down one Roas ter. The three high-p ressure booster pumps (two primary, one spare) are located on the north west corner of the fresh water pump house. The east pump is dedicated to the East Roaster, the we st pump is dedicated to the West Roaster, and the center pump is a common sp are. Although there is a crossove r between the tw o lines at the pumps, this crossover is normally shut and should only be opened at the operation foreman's instruction.

The total water flow for each line can be read from the flow mete rs directly above the pumps and should be 200 gpm. Individual flows may also be monitored on the DCS through FIC-48001 for the Gas Quench Tower and FIC-48010 for the Ento leter. Significant deviations (50 gpm) from this 200 gpm total indicate a problem in the fres h water supply that must be investigated and corrected. Seepage Water Booster Pump The seepage water booster pump is located on the bottom floor of the Roaster building and is used to boost the seepage water pr essure to a level high enough to provide 200 gpm flow to each of the Gas Quench Towers and 80 gpm to each Entoleter. Individual water flows may be monitored on the DCS through FIC-48001 for the Gas Quench Tower and FIC-48010 for the Entoleter. Significant deviations (50 gpm) from this 200 gpm total indicate a problem in the seepage water supply that must be investigated and corrected. Quench Tower Work Practices Work practices to maintain proper operation of the quench tower include the following parameter:Maintain total inlet wa ter flow at 200 gpm. Quench Tower Maintenance Once per month, or more often, eac h Roaster is taken offline to inspect the Gas Quench Tower, Entoleter, and Gas Scrubbers. The inspection of the Gas Quench Tower includes checking the crossover between the Gas Quench Tower and the Entoleter and clean if needed. The sprays are checked for proper operation and flow. The piping and drain pipes are inspected and cleaned as needed. Any deficiencies are noted and an approp riate work order is written. All problems noted are corrected before the unit is placed back into operation. A visual inspection is conducted while service is being done for loose or missing nuts/bolts, cracks, breaks, defects, leaks, and condition an d security of oil hydraulic-lines and wiring. The items will be cleaned, inspected, tested, adjusted, tightened, or replaced as re quired. For the pumps, a weekly check of the condition of the sh aft seal, a check for excessive heat, couplings are checked, and the nozzles are inspected to make sure they are clean and working. Quench Tower Set Points The set points and normal operating conditions for the Gas Quench Tower, that are integral to the proper functioning of the gas handling system are as follows: Total inlet water flow at 200 gpm. Quench Tower Alarms and Interlocks Alarms associated with the Gas Quen ch Tower operation are as follows:

The inlet water flow will have a low alarm at 50 gpm and a low- low alarm set at ten gpm. Upon warning, the valve and pump operation is checked. The water flow deviation alarm is set at 25 gpm.

The inlet water flow interlock data low flow ra te of ten gpm and will shut down the ID Fan. Quench Tower Monitoring Monitoring for the Gas Quench Tower includes the following: Inlet water flow will be monitored to keep at 200 gpm. Once per day the totalizer readings will be taken off the fresh and seepage water flow meter feeding the Quench Towers and Entoleters. Quench Tower Recordkeeping The following parameters will be monitored and recorded:The inlet water flow rate will be logged every four hours and da ta entered on the Roaster Daily Production Log. The totalizer readings will be taken off the fr esh and seepage water flow meters feeding the Quench Towers and Entoleters and will be record ed on the Water Management Log Sheet.Dust Scrubber - Entoleter The Dust Scrubber, or Entoleter, is a high efficien cy liquid/gas confractor that utilizes a patented Centripetal Vortex Contractor to clean contaminated gases of pa rticulate matter before gases are discharged to the scrubbing system. The Entoleter is located next to the Gas Quench Tower and is connected to it with a short section of rectangular duct. Saturated gases from the Ga s Quench Tower, laden with mist, dust, SO, and Hg vapor enters the Scrubber ta ngentially near the bottom. Maximum feed to the Entoleter is 5,200 standard cubic feet per minute (scfm) at 185"F. The inner wall of the lower section is protected from abrasion with a ceramic shield. Ga s is forced through the stationary vane cage in the lower section, where it comes in contact w ith water from the high-pressure seepage/fresh water line. The water spray is broken into tiny droplets by the action of the swirling gas as it passes through the vanes of the cag e. The water droplets capture dus t particles as the gas passes up through the Scrubber. The resulting slurry is dr ained from the bottom of the Entoleter to the Seal Tank. The gas and mist pass up into the disengaging secti on of the Entoleter where the water droplets are collected on th e vessel walls. The clean gas passe s out of the Entoleter through the top flange and then travels down through the fiberg lass reinforced plastic (FRP) duct to the SO, Scrubber. Efficient scrubbing by the Entoleter increases w ith increasing pressure drop. The pressure drop across the scrubber is controlled by the vane cage he ight and, to a lesser extent, by the water flow rate. The vane cage height is automatically set by the DCS based on the di fferential pressure set point used in the DCS; however, the vane cage height can be adjusted manually from the control room. The primary water flow to the Entolete r is through the upper spray nozzle. This water flow, at 40 to 60 gpm, is directed to spray onto the vane cage and is controlled automatically by a valve in the control room. The s econdary spray nozzles are used to keep the scrubbing unit clean and flushed. This water flow, at 1 5 to 20 gpm, is controlled by manual control valves located at the scrubbing unit. The pressure differential across the Entoleter should be maintained at 25 inches of water column (WC). Pressure differential indi cator PDI-4801 measures the total pressure drop across both the Gas Quench and Entoleter. Allowing eight inch es of WC differential pressure for the Gas Quench Tower, the total drop for both units should be kept at33 inches of WC.

The Entoleter has a total of thre e drains to the seal tank. Two dr ains are provided in the lower section, while the third is fitted into the upper sec tion. All three of the drains must be kept open at all times when water is flowing to the Entolete r. Blockage of any of these drains will result in slurry backup into the Entoleter. The center dr ain is the main drain for the bottom section and will normally carry most of the slurry flow. The outboard bottom drain is a standby overflow for the lower chamber and will not normally carry any fl ow. If slurry is flowing from this outboard drain it indicates that the center drain is plugg ed and needs to be cleaned. The drain from the upper chamber carries slurry collec ted on the wall of the upper chamber. Slurry flow rate through this upper drain is very low compared to that through the main drain.In comparison, the Entoleter out performs the conventional scrubber and is more efficient for the designed facility. A Venturi Scr ubber was first proposed to be m ounted ahead of the low energy unit and to be operated at 34 inches of WC di fferential pressure. A Entoleter was placed in service on a trial basis. Subsequent tests proved that the Entoleter operations at I 8 to 1 9 inches of WC differential pressure could replace both the proposed Venturi Scrubber and the original low energy unit while achieving e fficiencies as high as 99.9 perc ent, meeting the new stricter codes. The better efficiency of the Entoleter provi des considerable savings in energy and water. High Pressure Water System Two high pressure water systems service the Ro aster Entoleter and Gas Quench Tower. One system involves fresh water pumps located in the fresh water pump-house. This system is utilized approximately two per cent of the time. The other syst em involves the seepage water booster pump located on the bottom floor of the Ro aster building, and is u tilized upwards to 98 percent of the time for providing water flow to the Entoleter and Gas Quench Tower. Fresh Water Pump System A separate high pressure water pump and pipe feed each Roaster gas handling circuit so that failure of one pump will only shut down one Roaster. The three high pressure booster pumps (two primary, one spare) are lo cated on the northwest corner of the fresh water pump-house. The east pump is dedicated to the East Roaster, the we st pump is dedicated to the West Roaster, and the center pump is a common sp are. Although there is a crossove r between the tw o lines at the pumps, this crossover is normally shut and should only be opened at the operation foreman's instruction.

The total water flow for each line can be read from the flow mete rs directly above the pumps and should be 200 gpm. Individual flows may also be monitored on the DCS th rough flow controller (FIC-48001) for the Gas Quench Tower and flowcontroller (FIC-48010) for the Entoleter. Significant deviations from this 200 gpm total indicate a problem in the fresh water supply that must be investigated and corrected. Seepaqe Water Booster Pump The Seepage Water Booster Pump is located on the bottom floor of the Roaster building and is used to boost the seepage water pr essure to a level high enough to provide 200 gpm flow to each of the Gas Quench Towers and 80 gpm to each Entoleter. Individual water flows may be monitored on the DCS through FIC-48010 for the Entoleter.

Entoleter Work Practices Work practices implemented for the Entoleter in clude the following to maintain proper operating ranges and to ensure proper functioning: Maintain the pressure differential drop at 25 in ches of WC to maintain proper and efficient particulate cleaning. This is accomplished by th e DCS automatically adjusting the vane cageheight.

Entoleter Maintenance Once per month, or more often as needed, each Roas ter is taken offline to inspect the Entoleter, Quench Tower and Gas Scrubbers. The inspection of the Entoleter includes checking the crossover between the Quench Tower and the Entole ter and cleaned as needed. The vane cage is inspected and cleaned as needed. The sprays ar e to be checked for proper operation and flow. The fiberglass reinforced piping on the discharge of the unit is inspected and cleaned as needed. The drain pipes are inspected and cleaned as need ed. Any deficiencies are noted and appropriate work orders are written. All problems noted are corrected before the unit is placed back into operations Entoleter Set Points The following are the set points for the Entoleter that are integral to the proper functioning of the gas handling system: The pressure differential drop is maintained at 25 inches of WC.

Entoleter Alarms and Interlocks The system controls are set up to alarm before ga s emission control parameters are outside of the required set points to ensure emission standards are maintained as follows: The alarms for pressure drop across the Entoleter low alarm is set at 15 inches of WC and the high alarm is set at 60 inches of WC; The deviation alarms for pressure drop across the Entoleter are set at five inches of WC; and The differential pressure will interlock at the lo w of 15 inches of WC, shutting down the ore feed and oxygen flow. Entoleter Monitoring The following are monitoring practices for the Entoleter: Differential pressure will be monito red continuously and logged hourly. Control data for the system will be monitored and displayed on the DCS monitors. These data will be tracked and logged. Further readings will be taken in the field and the data logged on the appropriate forms. Entoleter Recordkeeping The following parameters will be monitored and recorded:Differential pressure will be l ogged every four hours and the data entered into the Title V log. Water flow will be logged every four hours and the data entered on the Roaster Area Daily Production Log. Daily data from the DCS are also logged into the current datahistorian unit.Sulfur Dioxide Scrubber

The SO 2 packed bed scrubber measures five feet in diameter, 32 feet tall, and is constructed of 0.5 inch thick FRP. Within the Scrubber is a l4 -foot bed packed with two inch polypropylene Intalox saddles and a 600 gallon sump.

The SO 2 Scrubber is designed to use a dilute (ten percent) soda ash solution to scrub SO 2 from the quenched waste gas leaving the Entoleter; however, the scrubber does remove some elemental Hg, which is collected from the Scr ubber reservoir. A lower soda ash content is necessary to avoid scaling and pr ecipitation. The sulfur di oxide in the waste ga s is absorbed into the recirculating soda ash solution. The solution is pumped from the integral sump at a nominal rate of 300 gpm to the spray nozzles located above the packed bed. Upon entering the SO 2 Scrubber, waste gases travel thr ough a duct opening located below the packing section which is sloped to allow for liquid drainage in to the Scrubber sump. The waste gas passes up through the 14-foot pa cked bed where it is countercurre nt with the dilute soda ash solution. The soda ash solution is pumped from the nozzle near the bottom of the sump and is discharged into the recirculation pumps through a manifold. The amount of sulfur is to be 0.I percent by weight of th e gas stream with a range from zer o to 1.7 percent with approximately 0.25 percent of the total sulfur being present as SO 2 . The amount of sulfur that is converted to SO 2 is determined by utilizing the Mill Blending repor t, that provides the ore feed number for the sulfur/ sulfide content of 0.75 perc ent, and the monthly reagent report, that has data for soda ash consumption, at approximately 4.94 pounds pe r ton. The calculation is as follows: . 4.941bs/ton of soda ash x 64 (molecular weight of SO 2 ) / 106 pounds of SO2: 2.98 lbs of SO 2 ; and

. 2.98 lbs of SO 2 X 32 (atomic weight of sulfur) / 64 (molecular weight of SO 2 ) : l.49 lbs of sulfur/sulfide. Based upon the above calculation, approximately 1.5 lbs of sulfur per ton is converted to SO 2 . Taking into account that 0.75 percent of the ore feed is su lfur/ sulfide, the following is derived:

. 0.75 (of I ton) x 2000 lbs per ton / 100 : 15 lbs/ ton of the sulfur/ sulfide in the ore; and

. Since only 1.5 lbs of sulfur per ton of SO 2 is produced, 1.5 x 100 / 15 lbs/ton: 10 percent. Therefore 10 percent of the sulfur is converted to SO 2 . No other sulfur species have been identified. At the discharge manifold the four inch line is co nverted to a two inch pipe that provides a bleed stream discharge to maintain the sump level, th is is controlled by the DCS sump level controller with a control valve. The main line of the pump returns to th e Scrubber spray nozzle through the magnetic flow meter. The pH of the soda ash solution needs to be be low 8.0 to avoid scale formation in the packedbeds and Scrubber piping. Soda ash that is fed to the SO 2 Scrubber is converted to sodium bicarbonate. The soda ash solution provides a great deal of buffering there by aiding pH control. As the pH drops, more soda ash solution is need ed. Soda ash make-up may be sent to the sump or into the recirculation line. The pH controller, controls the soda ash feed rate through a control valve. A bypass line allows for manual soda ash fl ow control while maintenance is performed on the control valve. The soda ash make-up flow ra te is measured through the magnetic flow meter DCS readout as well as the sump level and pH level. The magnetic flow meter provides a side stream for the pH probe to allo w control of the soda ash make- up rates (1.2 gpm of ten percent soda ash at 100 o F ). Differential pressure is measured to detect bu ildup in the packed bed and is measured by taps located in the inlet and outlet ducts. There is significant potential for Na 2 CO 3 , scale to form on the packing in the SO 2 Scrubber, as well as Hg and the Tails Gas Scrubbers. This scale can lead to excessive differential pressure in any of the Scrubbers, which may result in an interlock shut down of the Gas Handling circuit. The scrubbed gases pass through an eight inch Chevron-type mist eliminator screen located at the top of th e column before moving to the ID Fan. The mist eliminator is designed for 99 pe rcent removal of all droplets great er than 28 microns. Located at the top of the Scrubber is the water spray that keeps the mist eliminator from becoming clogged and helps trap mist. The water flow rate, target ed at 10 gpm, is controlled by a ball valve and local flow meter and is checked each shift.

There are no threshold values for the SO 2 Scrubber to meet. The Hg Scrubber can deal with SO 2 being present, in fact in other installations the Hg sc rubbing occurs before the SO 2 removal. Design parameters have been determined for optimal operation of the SO 2 Scrubber. The recirculating soda ash solution is cooled by a tubular heat exchanger using cold water from the seepage or fresh water. The purpose of cooling th e solution is to keep the temperature of the recirculating solution entering th e Scrubber at approximately 85 o F. The optimization of pH was considered as a result of an evaluation and report completed by Focus Environmental, Inc. in December 2007. As discussed previously, effective SO 2 removal is achieved by addition of soda ash to control pH. Th is is critical for efficient oxidation of Hg because SO 2 will act as a reducing agent inhibiting e ffective oxidation in the Hg Scrubber. The chemical reactions occurring in the Scrubber is detailed as follows:

SO 2 + Na 2 CO 3 → Na 2 SO 3 + CO 2 and;

SO 2 + Na 2 CO 3 + 1/2 O 2 → Na 2 SO 4 + CO 2 These reactions occur best at neut ral to slightly alkaline conditions . As a result, an initial target pH of 8.0 has been chosen as the set-poi nt pending further optimization of the SO 2 Scrubber. The pH will be monitored and controlled to ensure efficient removal of SO 2 . SO 2 Scrubber Maintenance

Maintenance for the SO 2 Scrubber includes monthly scheduled inspections, cl eaning, testing,adjusting, tightening, and replacing of parts as needed. Defects reco rded in the visual inspections will be addressed during scheduled maintenance. Weekly inspections and calibrations are conducted on the pH probes. SO 2 Scrubber Set Points The following are the set points for the SO, Scrubbe r, that are integral to the proper functioning of the gas handling system:

Operating pH set at 8.0 based upon Focus Enviro nmental, Inc. Reports from2007 and 2008; and Scrubber solution temperature set at 85 o F as a result of the addition of the heat exchanger.

SO 2 Scrubber Alarms and Interlocks The alarms for the SO 2 Scrubber to notify of necessary para meters out of range are as follows:

A high pH alarm will trigger at pH of 8.5 a nd a low alarm will trigger at a pH of 7.5; pH deviation alarm is set at 0.2 pH; high alarm will warn of the heat exchange temperature out of range at 95 o F and an additional high-high alarm will trigger at 104 o F; A heat exchanger deviation alarm is set at 3 o F; and A high alarm to warn of a high pr essure drop is set at 20 inches of WC. This was increased from the original high alarm of eight inches of WC to match the increase of the operation set point. A new low alarm is set at five inches of WC. The pressure drop deviation is set at five inches WC.

The SO 2 has interlocks for the following:

The scrubber will interlock at a low pH of 7.0, shutting down the plant ore feed and oxygen flow; and The heat exchanger will interl ock at a high temperature of 104 o F, shutting down the ore feed and oxygen flow. SO2 Scrubber Monitoring The following are monitoring practices for the SO 2 Scrubber:

SO 2 Scrubber differential pressure will be mon itored continuously with the DCS and loggedhourly; SO 2 , Scrubber solution pH control room readout will be monitored continuously with the DCS and logged hourly; SO 2 Scrubber solution pH field measurem ent will be monitored and logged three times per shift, coinci dent with the hourly logging of pH in the control room; Soda ash injection rate for the entire gas handling system is m onitored continuously at the entry to the Roaster gas handling circuit;

Soda ash concentration will be monitored onc e per shift by titrati on method Precipitates (turbidity) in the scrubber solution will be monitored one per shift; and

SO 2 Scrubber solution temperature will be monito red continuously with the DCS and logged three times per shift.

SO 2 Scrubber Recordkeeping The following parameters will be monitored and reported:

SO 2 Scrubber differential pressure will be logged hour ly and the data entered on the Title V Log;

SO 2 Scrubber solution pH control room readout will be logged hourly and the data entered on the Title V Log;

SO 2 Scrubber solution pH field measurement will be logged three times per shift and the data entered on the Gas Handling Sample Log. This samp le will be taken from the recirculation pump discharge; Soda ash injection rate will be record ed on the Gas Handling Sample Log;

Soda ash concentration will be determined thr ough a titration conducted each shift and logged on the Gas Handling Sample Log; Turbidity measurements will be logged on the Gas Handling Sample Log; and

SO 2 Scrubber solution temperature will be logged three times per shift and the data entered on the Gas Handling Sample Log.Induced Draft Fan The ID Fan is a Robinson single-stage surge-le ss blower that boosts the Roaster gases through the off gas cleaning system by increasing the pr essure. The ID Fan receives and boosts the gas from the SO, Scrubber and discharges approxima tely 5,000 scfm of gas downstream to the Hg Scrubber (Appendix T, page l6). The ID Fan cons ists of a 300 hp blower that boosts the waste gas pressure byapproximately3.T pounds per square inch (psi), increasing the temperature by 11"F. The pressure boost of 3.7 psi at 10,700 cfm was determined by the Differential Static Pressure versus Volume Chart in the Figure 3.2 belo w. This is an appropriate pressure increase for the efficiency necessary for the Gas Handling System.

There are three water nozzles wi thin the ID Fan unit. Two nozzles are fitted in the ID Fan housing and one nozzle is fitted into the ID Fa n suction. The SO, Scrubber may discharge gas containing sulfuric acid mist. The water spra y nozzles function to minimize possible corrosion and prevent excessive pressure increases by k eeping the gas saturated and cooled. The water sprays also reduce solids buildup on the fan bl ades, which could resu lt in significant shaft vibrations. Plant air is fed to the nozzles, atom izing the water spray for more efficient cooling. Excess water and gas are blown down a drain in the bottom of the ID Fan housing and transferred to a gas/water separato r; where the gas is recycled to the blower suction and the water is transferred to the Roaster Quench Sump. The ID Fan suction damper maintains a negative pressure environment, which is regulated by th e Roaster pressure controller. The Gas Handling train and Roaster will shut down in re sponse to a failure of the ID Fan. The increased gas pressure, in itiated by the ID Fan, has two effects on the removal of Hg. Increased pressure would correspon d with an increased flow rate as well as an elevated quantity of Hg vapor at the liquid/vapor interface. Howeve r, the increased pressure would also correspond with reduced residence time of the gas in the Hg Scrubber. In controlling the pressure, the system maintains a desired level of efficiency. The ID Fan will shut down in response to: temperatures in excess of 200'F; flow in the Gas Quench Tower than ten gpm; head greater than 60 inches at the blower discharge; and vibra tions in the blower bearing in excess of four mils. Normal operating conditions consist of an average gas flow rate of approximately 5,000 scfm at 9.6 actual pounds per square inch (psia) and temp erature range at the ID Fan suction damper between 130 and 140"F. The temperature of the gas discharge ranges between 140 and 150"F and approximately 12.5 psia. Fresh water flow to a spray nozzle is one gpm. Turbine bearing temperatures must be below 200'F.

Induced Draft Fan Work Practices Work practices implemented at the ID Fan include maintaining the proper function of the fan to ensure proper flow rate, vibrations, temperatur e, unusual noises, draft, washing of the fan, resetting the multilin, mister syst em, interlocks and gas flows. Inspections will be completed on a weekly basis, as well as every six months. Weekly inspection includes checking oil levels, as well as the temper ature and vibration of the shaft bearings. Also included in the weekly inspections is the gear reducer's oil level. The semi-annual inspection includes a steam clean of the fan and the lubr ication of the fan couplers. Work practice procedures include visual inspections while se rvice is being done for loose or missing nuts andbolts, cracks, breaks, defects, leaks, and condi tion and security of oil hydraulic-air lines and wiring. Defects will be r ecorded and addressed.

Induced Draft Fan Maintenance

Maintenance for the ID Fan includes schedule d inspections, cleaning, testing, adjusting, tightening, and replacing of parts as needed. Def ects recorded in the visual inspections will be addressed during scheduled maintenance. Mainte nance is closely related to the monitoring procedures. Induced Draft Fan Set Points There are not direct set points for the ID Fan. The ID Fan operation is controlled by the first stage freeboard. However, there are operating range s that are monitored for the load on the fan, turbine bearing temperature, and turbine vibration levels, which are listed in Appendix U in the ID Fan section.

Induced Draft Fan Alarms and Interlocks

The alarms and interlocks for the ID Fan ar e identified in Appendix U. The alarms and interlocks, which are not recorded, include a hi gh and high-high blower discharge pressure, a high and high-high blower bearing vibrat ion, and a high and hi gh-high amperage. Induced Draft Fan Monitoring The following parameters will be monitored on the DC S, but not recorded as they do not directly pertain to the functioning of the gas handling system: The ID Fan amperage.

Turbine vibration of the inboa rd and outboard bearings The temperature of the turbine bearings.Hg Scrubber Elemental Hg in the waste gas from the ID Fan is further scrubbed out in the Hg Scrubber and the cleaned gas is sent on to the Tails Gas Sc rubber. Waste gas from the Roaster contains Hg vapor derived from mercuric compounds in the ore that oxidize within the Roaster. Most of the Hg vapors are condensed in the SO, Scrubber and the Hg Scrubber captures the remainder. This waste gas is contacted countercu rrent with a dilute, ten percen t soda ash solution in the 20- footpacked bed. The gas contact time in the be d is approximately 5.7 se conds. The pH of the Scrubber solution is controlled by addition of sodaash. A bleed stream from the Hg Scrubber is combined with the bleed from th e SO, Scrubber and sent to the e ffluent tank and on to the tails. The Hg Scrubber and Tails Gas Scrubber are 38 feet tall packed tower, five feet in diameter, and have 5/8 inch thick FRP walls. Each tower has a 600 gallon sump, an eight inch Chevron-type four-pass mist eliminator with a water spray, and two spray heads for solution recycle (one operating, one spare). The towers are rated at si x pounds per square inch gauge (psig) pressure and 100 inches of WC vacuum. The Hg Scrubbe r has a 2}-foot bed packed with two inch titanium Intalox saddles while the Tails Gas Scrubbe r has a ten foot bed pack ed with two inch hiflow polypropylene packing. The Tails Gas Scrubber has upper and lower nozzles for sump recycle to allow for future conversion to a 2O-f oot packed bed should the need arise. In every other aspect, the construction of the Hg Scrubbe r and the Tails Gas Scrubber is identical. The Hg Scrubber solution recycle stream is taken from the four inch nozzle on the sump and sent to a header that feeds three recycle pumps. The inside pump is the primary recycle pump for the Hg Scrubber. The outside pump is the primary recycle pump for the Tails Gas Scrubber. The middle pump is a spare, which can serve either the Hg Scrubber or the Tails Gas Scrubber. Each pump operates at not less than 150 gpm. The four inch line from the pump discharge recycles solution to one of the spray heads at the top of th e tower. The sump level controller operates the bleed stream control valve on the one inch line from the pump discharge to maintain the sump level. The pH probes are located in the four inch recirculation line. Soda ash is fed to the Hg Scrubber sump from the ten percent soda ash makeup tank. The soda ash makeup rate is controlled by the pH controller set at 8.0 pH . Raw water is controlled by a ball valve and is monitored locally. Raw water is also piped to the Tails Gas Scrubber sump with its flow rate monitored locally. Soda ash is fe d to the Tails Gas Scrubber sump under the control of the pH controller. A high pH alarm is incl uded in this controller to warn of high pH conditions, which can result in plugging of the packed bed due to sodi um bicarbonate scale formation on the packing. The pressure drop acro ss the Hg Scrubber column is measured on the DCS. Hg Scrubber Work Practices Work practices implemented at the Hg Scrubbe r include maintaining proper operating ranges of the following parameters: Maintain the differential pressure from the Hg Scrubber gas inlet to Tails Gas Scrubber discharge is set at eight inches of WC;Maintain the pH setting of 6.9; and

Maintain the ORP set at 825 mV. Hg Scrubber Maintenance Maintenance for the Hg Scrubber includes mont hly scheduled inspecti ons, cleaning, testing, adjusting, tightening, and replacing of parts as n eeded. Defects recorded in the visual inspections will be addressed during scheduled maintenan ce. Weekly inspections and calibrations are conducted on the pH probes. Examples of the main tenance logs with detailed inspection can be found in Appendix X. Hg Scrubber Set Points The following are the set points for the Hg Scrubber that are integral to the proper functioning of the gas handling system and ar e detailed in Appendix U: The pH is set at 6.9.

The ORP set at 825 mV. Hg Scrubber Alarms and Interlocks Several alarms exist for the Hg Scrubber to warn of deviations in set points as follows: The low pH alarm is established at pH of 6.5 and the high alarm at pH of 7.5; The pH deviation alarm is set at 0.2pH; The ORP will high alarm at 850 mV and low alarm at750 mV; The ORP deviation alarm is set at 25 mV; The low pressure measured in the Hg Scrubber w ill alarm at five inches WC and will high alarm at 20 inches WC. The alarms were set to meetthe proper operating range of the Scrubber; and The pressure drop deviation is set at five inches WC.

The interlocks for the He Scrubber are as follo ws: The Hg Scrubber deviation of pH at 6.5 will interlock the system and shut dow n the ore feed and oxygen flow. The Hg Scrubber ORP deviation at 750 mV w ill interlock and shut down the ore feed and oxygen flow. Hg Scrubber Monitoring The following are monitoring practices for the Hg Scrubber: Differential pressure wi ll be logged daily;Solution pH control room readout will be mon itored continuously with the DCS and logged hourly;

Solution pH field measurements will be logged thr ee times per shift, coincident with the hourly logging of pH in the control room. This sample will be taken from th e recirculation pump discharge; Hg solution ORP control room readout will be monitored continuously with the DCS and logged hourly; and Hg solution NaOCI concentration will be m onitored and logged thr ee times per shift. Hg Scrubber Recordkeeping The following parameters will be monitored and recorded: Hg Scrubber differential pressure will be logged daily and the da ta entered on the Title V Log. Hg Scrubber solution pH control room readout will be logged hour ly and the data entered on the Title V Log. Hg Scrubber solution pH field measurements will be logged three times per shift and the data entered on the Gas Handling Sample Log. This samp le will be taken from the recirculation pump discharge. Hg solution ORP control room readout will be lo gged hourly and the data entered on the Roaster Area Daily Production Log. Hg solution NaOCI concentration wi ll be logged three times per sh ift and the data entered on the Gas Handling Sample Log. Daily data from the DCS is also logged into the current data historian unit.Tails Gas Scrubber

The Tails Gas Scrubber is a l0-foot packed bed. As stated in the Hg Scrubber section, elementary Hg in the waste gas from the ID Fan is furthe r scrubbed out in the Hg Scrubber and the cleaned gas is sent on to the Tails Gas Scrubber. Waste gas from the Roaster contains Hg vapor derived from mercuric compounds in the ore that oxidize within the Roaster. Mostof the Hg vapors are condensed in the SO, Scrubber and the Hg Scrubbe r captures the remainder. This waste gas is contacted countercurrent with a di lute soda ash solution in the 20- foot packed bed. The pH of the Scrubber solution is controlled by addition of soda ash. A bl eed stream from the Tails Gas Scrubber is combined with the bleed from the SO , and sent to the effluent tank and on to the tails. The Hg Scrubber and Tails Gas Scrubber are 38-foot tall packed towers, fi ve feet in diameter,and have 5/8 inch thick FRP walls. Each tower has a 600 gallon sump, an eight inch Chevrontype four-pass mist eliminator with a water sp ray, and two spray heads for solution recycle (one operating, one spare). The towers are rated at si x psig pressure and 100 inches of WC vacuum. The Hg Scrubber has a 20-foot bed packed with two inchtitanium Intalox sa ddles while the Tails Gas Scrubber has a 10-foot bed packed with two inch high-flow polypropylene packing. The Tails Gas Scrubber has upper and lower nozzles for sump recycle to allow for future conversion to a 20-foot packed bed should th e need arise. In every other as pect, the construction of the Hg Scrubber and the Tails Gas Scrubber is identical. The Tails Gas Scrubber solution recycle stream is taken from the four inch nozzle on the sump and sent to a header that feeds 3 recycle pumps. The inside pump is the primary recycle pump for the Hg Scrubber. The outside pump is the primary recycle pump for the Tails Gas Scrubber. The middle pump is a spare, which canserve either the Hg Scrubber or the Tails Gas Scrubber. Each pump operates at not less than 150 glm. The four inch line from the pump discharge recycles solution to one of the spray heads at the top of the tower. The sump level controller operates the bleed stream control valve on the one inch line from the pump discharge to maintain the sump level. The pH probes are located in the four inch recirculation line. Soda ash is fed to the Tails Gas Scrubber sump from the ten percent soda ash makeup tank. The soda ash makeup rate is controlled by the pH cont roller set at 8.0 pH. Raw water is also piped to the Tails Gas Scrubber sump with its flow rate monitored locally. Soda ash is fed to the Tails Gas Scrubber sump under the control of the pH c ontroller. A high pH alar m is included in this controller to warn of high pH conditions, which can result in pl ugging of the pack ed bed due to sodium bicarbonate scale formation on the pack ing. The pressure drop across the Hg Scrubber column is measured on the DCS.

Tail Gas Scrubber Work Practices Work practices implemented at the Tails Gas Scrubber include maintaining proper operating ranges of the following parameters: Maintain the pH of the solution at7.5;No visible precipitate in scrubber solution; and Maintain the pressure drop across the Hg Scrubbe r inlet to the Tails Ga s Scrubber discharge at eight inches WC.

Tail Gas Scrubber Maintenance

Maintenance for the Tails Gas Scrubber include s monthly scheduled in spections, cleaning, testing, adjusting, tightening, and replacing of parts as needed. De fects recorded in the visual inspections will be addresse d during scheduled maintenan ce. Weekly inspections and calibrations are conducted on the pH probes. Examples of th e maintenance logs with detailed inspection can be found in. Tail Gas Scrubber Set Points Following are the set points for the Tails Gas Scrubbe r that are integral to the proper functioning of the gas handling system: Solution pH of 8.0. The pH of 8.0 is based upon th e Focus Environmental, Inc. analysis results for the optimal pH of the SO, and Hg Scrubber.

Tail Gas Scrubber Alarms and Interlocks The alarms for the Tails Gas Scrubber necessary to ensure proper functioning for air pollution control includes the following: Low pH alarm has been set at pH of 7.5 and a high alarm at pH of 8.5; The pH deviation alarm is set at 0.2; The pressure differential across the Tails Gas Scr ubber will low alarm at five inches WC and high alarm at 20 inches of WC; and The pressure differential deviation alarm is set at five inches of WC . The Tails Gas Scrubber interlocks include an interloc k for a pH of 7.0, shutting down the plant feed and oxygen flow. Tail Gas Scrubber Monitoring The following are monitoring practices for the Tail Gas Scrubber: Tail Gas Scrubber differential pressure will be monitored continuously with the DCS and logger hourly: Tails Gas Scrubber solution pH control room r eadout will be monitore d continuously with the DCS and logged hourly; Precipitates (turbidity) in the scrubber so lution will be monitored one per shift; andTails Gas Scrubber solution pH field measuremen ts will be logged three times per shift, coincident with the hourly logging of pH in the control room. This sample will be taken from the recirculation pump discharge. Tail Gas Scrubber Recordkeeping The following parameters will be monitored and recorded: Tails Gas Scrubber differential pressure will be logged daily and the data entered on the Title V Log; Turbidity measurements will be logged on the Gas Handling Sample Log; and Tails Gas Scrubber solution pH field measurements will be logged three times per shift and the data entered on the Gas Handling Log.