# Site Visit Report Arizona Copper Mines

Prepared for: 

## U.S. Environmental Protection Agency Engineering and Analysis Division Office of Water 1200 Pennsylvania Avenue, NW Washington, D.C. 20460

Prepared by: 

## Eastern Research Group, Inc. 14555 Avion Parkway Suite 200 Chantilly, VA 20151-1102

March 2010

EPA Contract No. 68-C-02-095 Work Assignment 7-05i CONTENTS
Page

1.0 S ITES V ISITED AND D ATES ....................................................................................... 6

2.0 A TTENDEES .............................................................................................................. 6

3.0 B ACKGROUND AND O BJECTIVES .............................................................................. 6

4.0 C OPPER M INING AND B ENEFICIATION ...................................................................... 7 4.1 Surface Mining Techniques ........................................................................ 8 4.2 Underground Mining Techniques............................................................... 8 4.3 Overburden and Waste Rock Management ................................................ 9 4.4 Ore Processing ............................................................................................ 9 4.4.1 Hydrometallurgical Processing..................................................... 10 4.4.2 Pyrometallurgical Processing........................................................ 13 4.5 Copper Mine Tailings Management ......................................................... 15

5.0 B AGDAD M INE AND C ONCENTRATOR O PERATIONS ............................................... 16 5.1 Mine Site................................................................................................... 16 5.2 Mining Operations .................................................................................... 17 5.3 Copper Recovery from Ore: Concentrator Operations ............................. 18 5.3.1 Grinding Circuit............................................................................ 18 5.3.2 Flotation Circuit............................................................................ 21 5.4 Leach Operations ...................................................................................... 23 5.5 Solution Extraction Electrowinning Operations ....................................... 23 5.6 Tailings Impoundments ............................................................................ 24 5.7 Freshwater Sources and Recycled Water.................................................. 26 5.8 Stormwater and Process Wastewater Management .................................. 26 5.8.1 Sources of Discharge .................................................................... 26 5.8.2 BMPs Used for Stormwater Control............................................. 28 5.9 Site Closure Plans ..................................................................................... 30

6.0 M ORENCI M INE O PERATIONS ................................................................................ 31 6.1 Mine Site................................................................................................... 31 6.2 Mining Operations .................................................................................... 31 6.3 Concentrator Operations ........................................................................... 32 6.4 Leach Operations ...................................................................................... 32 6.5 Solution Extraction Electrow inning (SXEW) Operations ........................ 35 6.6 Water Sources ........................................................................................... 40 6.7 Tailings Areas ........................................................................................... 40 6.8 Stormwater and Process Wastewater Management .................................. 42 6.8.1 Discharges under the Morenci Mine’s NPDES Permit................. 42 6.8.2 Stormwater Best Management Practices (BMPs)......................... 43 6.9 Mitigation/Remediation Operations.......................................................... 49

7.0 S AFFORD M INE O PERATIONS ................................................................................. 50 7.1 Mine Site................................................................................................... 50CONTENTS (Continued)
Page

ii 7.2 Mine History ............................................................................................. 51 7.3 Mining Operations .................................................................................... 52 7.4 Crush and Convey Operations .................................................................. 53 7.5 Water Supply and Discharge Operations.................................................. 54 7.6 Leach Operations ...................................................................................... 54 7.7 SXEW Operations..................................................................................... 56

8.0 R EFERENCES .......................................................................................................... 58
Appendix A: LIST OF SITE VISIT PARTICIPANTS
Appendix B: BAGDAD GENERAL SITE MAP
Appendix C: MORENCI GENERAL SITE MAP
Appendix D: SAFFORD SITE MAPiii LIST OF TABLES
Page
Table 5-1. Bagdad Mine NPDES Outfalls.....................................................................................27

Table 5-2. Stormwater Outfalls Permitted Under the MSGP ........................................................27

Table 6-1. Morenci Mine NPDES Outfalls....................................................................................43iv LIST OF FIGURES
Page
Figure 4-1. Overview of th e Bagdad Mine Open Pit.......................................................................8
Figure 4-2. Simplified Schematic of Comm on Processing Methods for Copper Ore ...................10
Figure 4-3. Simplified Schematic of the Solution Extraction Process...........................................12
Figure 5-1. Overview of the Grinding Circuit at the Bagdad Concentrator ..................................19
Figure 5-2. Autogenous Mill and Feed Unit..................................................................................20
Figure 5-3. Bagdad Gr inding Circuit............................................................................................ .21 Figure 5-4. Bagdad Flotation Circuit........................................................................................... ..22 Figure 5-5. Unlined Leach Stockpile Facility................................................................................23
Figure 5-6. Mammoth Tailings Dam .............................................................................................25
Figure 5-7. Roadside Stormw ater Evaporation Pond ....................................................................30
Figure 6-1. The Coronado Open Pit.............................................................................................. .32 Figure 6-2. Stormwater Overflow from Leach St ockpile on Left and Pregnant Leach Solution Pond on Right ........................................................................................................34
Figure 6-3. Stormwater Overflow from the Leach Stockpile ........................................................34
Figure 6-4. SXEW Pregnant Leach Solution Mix Tank................................................................35
Figure 6-5. SXEW Extractor..................................................................................................... .....36 Figure 6-6. SXEW Raffinate Mix Tank.........................................................................................37
Figure 6-7. Steel Cathodes Being Pl ated with Copper in EW Cell ...............................................38
Figure 6-8. Steel Cathode Plat ed with Copper from EW...............................................................39
Figure 6-9. Copper Cathode Sheets Ready for Sale ......................................................................40
Figure 6-10. Tailings Area..................................................................................................... ........41 Figure 6-11. Tailings Beach.................................................................................................... .......42 Figure 6-12. Upgradient Side of Upper Chase Creek Dam ...........................................................44
Figure 6-13. Waddle in Stor m Water Ditch by Roadway..............................................................45LIST OF FIGURES (Continued)
Page

v Figure 6-14. Lower Chase Creek Dam ..........................................................................................46
Figure 6-15. Evaporation Basin Upgrad ient of Lower Chase Creek Dam ....................................46
Figure 6-16. North Gold Gulch Dam.............................................................................................4 7 Figure 6-17. Lined Evaporation Pond with Historic Stockpile in the Background.......................48
Figure 6-18. Unlined Evaporation with a Tailings Dam in the Background.................................49
Figure 6-19. Reclamation Experiment...........................................................................................5 0 Figure 7-1. Safford Mine Open Pit .............................................................................................. ..51 Figure 7-2. Copper Ore at the Safford Mine..................................................................................52
Figure 7-3. Safford Crush/Convey Area........................................................................................53
Figure 7-4. Safford Heap Leach Pad............................................................................................. .55 Figure 7-5. Safford Heap Leach PLS Tank ...................................................................................55
Figure 7-6. Safford Heap Leach PLS Overflow Pond ...................................................................56
Figure 7-7. Safford Organic Solvent Extractor..............................................................................57
Figure 7-8. Safford Electrowinning Cell .......................................................................................5 76 1.0 S ITES V ISITED AND D ATES

From September 14 to 17, 2009, the U. S. Environmental Protection Agency (EPA) and its contractor, Eastern Research Group , Inc. (ERG), conducted site visits of copper mining facilities operated by Freeport McMoran Copper and Gold Inc. (FCX). FCX provided tours of the following facilities (dates visited in parenthesis):

 Bagdad Mine, Yavapai, AZ (September 14, 2009);

 Morenci Mine, Greenlee County, AZ (September 15, 2009); and

 Safford Mine, Graham County, AZ (September 17, 2009).

This report summarizes EPA’s site visits to each of these facilities, discussing mining and beneficiation operations and wa stewater and stormwater mana gement techniques. EPA also visited FCX’s nonferrous metals manufacturing facility: the Miami Sm elter on September 16,
2009. Information from that site visit has not be en included as this report focuses on ore mining and dressing operations (as defined at 40 CFR Part 440), not nonferrous metals manufacturing.

2.0 A TTENDEES

Appendix A contains a list of attendees for each of the site visits.

3.0 B ACKGROUND AND O BJECTIVES

EPA and ERG conducted site visits of FCX’s copper mining operations in Arizona on September 14 through 17, 2009. The purpose of the visits was to gather information about copper mine production practices and wate r management options. EPA organized these
site visits as part of the data collection efforts for EPA’s preliminary review of the Ore Mining and Dressing Point Source Category (Ore Mining Category). This review will determine if it would be appropriate to revise the effluent limitations guide lines and standards (effluent guidelines) for the Ore Mining Category (40 CFR Part 440). EPA is working with a range of stakeholders including industry representatives, Federal and State representatives, and water treatment experts to obtain information on the ore mining industry and its practices.7 During the site visits, FCX stated that it appropriately addresses and protects adjacent surface waters at all of its sites through containment, where practicable, and elsewhere through implementation of best management practic es. FCX also noted that it designs the vast majority of the disturbed acreage at each of its sites to be zero-discharging for federal Clean Water Act purposes, and that only relatively small areas at the FCX sites have the potential to discharge and therefore require so me type of permit coverage.

When required based on potential to di scharge, FCX facilities have obtained and maintained permit coverage for these relatively sm all areas based on the type of discharge (i.e., stormwater vs. process water or mine drainage). For example, FCX’s Bagdad facility maintains individual NPDES permit coverage for potential discharges of tailings reclaim water from the toe of the tailing facilities at the site that may occur in response to severe storm events. These infrequent discharges are subjec t to the effluent limitations at 40 CFR. Part 440, Subpart J, as well as the more stringent efflue nt limits pursuant to the state’s water quality standards. FCX’s Bagdad facility also maintains MSGP permit cove rage for certain periphe ry areas at the site, which again requires compliance with the same state water quality standards. FCX’s Morenci
and Safford facilities have obtained and mainta ined similar permit coverage, where required.

It is the general opinion of FCX that existing discharge permit requirements, including the existing effluent limitations guide lines in 40 C.F.R. Part 440, are more than sufficient to protect surface waters for potential di scharges from the relatively small areas at each mine that have the potential to disc harge as a result of storm events.

4.0 C OPPER M INING AND B ENEFICIATION

In the US, most domestic copper comes from surface mines located in western states. The following subsections describe the general copper mining and beneficiation methods
used at these mines.8 4.1 Surface Mining Techniques

Figure 4-1 shows an example of a surface mining operation (the Bagdad mining open pit). All three mines visited by EPA use tr aditional blasting and excavation techniques to remove overburden, waste rock, and ore from the open pit. Work crews drill boreholes into the ore body using a portable drill rig. The borehole is then filled with an explosive composed of ammonium nitrate and fuel oil and equipped with a blasting cap. Work crews prepare multiple
boreholes in this manner and detona te one shot to blast a large vol ume of ore at once. The ore is then excavated using electric shovels and hauled to the appropriate processing area (e.g., concentrator, leach stockpile) in Caterpillar m odel 793 Haulage trucks with 270-ton capacities. Blasting and excavation operations are designed to create 50-foot tall “benches” behind the mined areas; these benches become the dominan t feature across the wa lls of the open pit.

Figure 4-1. Overview of the Bagdad Mine Open Pit

4.2 Underground Mining Techniques

Although open-pit surface mining is the pr edominant technique used to extract copper ores in the US, extraction may al so occur via undergro und mining techniques.9 Underground mining was very common before mining companies began using fossil-fueled equipment for excavation activities. All of the mines that EPA visited in August 2009 were openpit mines located in areas with hi storic underground mining activities.

4.3 Overburden and Waste Rock Management

Overburden material, which is removed to access copper ore, may be used to
construct roads around the mine site or stored in stockpiles for future use. Mineralized material that is not currently economically feasible to process is placed in engineered, permitted stockpiles and is often us ed for pit backfilling.

4.4 Ore Processing

From extraction to copper sale, ore go es through many beneficiation and mineral processing operations to produce pure copper 1 . This section summarizes the beneficiation operations that EPA viewed during the August 2009 site visits. For more detailed descriptions of each process, see the chapters discussing individual facilities.

Mined ore typically contains less than one percent copper. To recover this small fraction of copper, ore may be processed by hydrom etallurgical methods (used for oxide ores and some sulfide ores) or pyrometallu rgical methods (used for sulfide ores only). The terms “sulfide”
and “oxide” are used here to be consistent wi th industry terminology; these are no t geological definitions. For the purposes of this report “sulfi de” refers to a rock containing metal sulfide compounds (e.g., Cu 2 SO 4 ), whereas “oxide” refers to a ro ck containing other metal compounds (e.g., CuO, CuCO 3 ). Hydrometallurgical methods recove r copper from the ore using aqueous chemistry that generally involves the fo llowing steps: leaching, solution extraction 2 , and

1 For regulatory purposes, EPA distinguishes betw een the following three groups of activities: (1) Extraction: Initial removal of ore from the earth, comm only known as mining (54 FR 36592); (2) Beneficiation: Initial attempt at liberating and concentrating the valuable mineral from the mined ore (54 FR 36592). The remaining material is often physically and chemically similar to the original materi al (ore or mineral) that entered the operation, except that the particle size is reduced and the material is concentrated; and (3) Mineral Processing: Processing operations generally following beneficiation, including techniques that change the chemical composition of the ore or mineral, such as smelting. Mineral processing generates waste streams that generally bear little or no resemblance to the materials that entered the operation.

2 Also commonly referred to as “solvent extraction” in the mining industry.10 electrowinning processes. Pyrometallurgical me thods recover copper from the ore by thermally treating the ore to physically a nd chemically transform the mate rials in the following steps: grinding, flotation, smelting, and electrorefini ng processes. Figure 4-2 presents a general schematic summarizing the major processes in e ach of these methods. The following subsections describe these processes in greater detail.

Figure 4-2. Simplified Schematic of Commo n Processing Methods for Copper Ore

4.4.1 Hydrometallurgical Processing

Hydrometallurgical processing ge nerally consists of the following steps:

1. Leaching; 2. Solution Extraction; and 3. Electrowinning. Raffinate Hydrometallurgical Method

Oxide Ore

Crushing 1

Leaching

Solution Extraction & Electrowinning

Grade

- A Copper to Sale PLS

Blister Coppe r Pyrometallurigical Method

Sulfide Ore

Grinding

Flotation

Smelting

Grade

- A Copper to Sale Concentrate Tailings Impoundment Gangue Slurry

Electrorefining

1 Process is optional ( see Sectio n 4

. 4 .1

. 1 ). Blister coppe r : 99 percent pure copper containing some impurities from the smelting process

. Gangue slurry: N on
- economic minerals and host rock separated from copper

- rich sediments

. PLS : Pregnant leach solutio n ( copper
- laden acidic leach solution ). Raffinate: Barren leach solution ( acidic leach solution stripped of copper ).11 The following subsections describe each of these processes.

4.4.1.1 Hydrometallurgical Processing: Leaching

After being blasted and ex tracted from the ore body, ore material is generally about six inches in diameter. The ore may then be crushed into pieces less than 1⁄2 inch in diameter for better leach recovery (referred to as mine-for-leach), or l eached uncrushed (referred to as run-of-mine). Crushing the mined material increases the surface ar ea making more of the
rock accessible to the sulfuric acid used in leaching. Ore is ge nerally only crushed when it has high copper content that can justify the additional costs of crushing.

After extraction and crushing (optional) , the ore is placed on a stockpile where leach solution (typically dilute sulfuric acid) is added. For the FCX mines, the sulfuric acid is produced from smelting gases at FCX’s Miami Smelter. The site of the stockpile may be fully lined, partially lined, or unlined 3 . The leach solution is generally added to the stockpile using large sprinklers or drip irri gation equipment. After the leach solution runs through the mined material it is called pregnant leach solution (P LS) and contains copper and other metals. This solution collects at the bottom of the stockpile and flows to a PLS storage area to wait for the next processing step: solution extraction.

Leach stockpiles may cover several ac res and be several hundred feet high. Typical closure requirements for leach stockpil es include capping with a low-permeability soil and stormwater run-on management.

4.4.1.2 Hydrometallurgical Processing: Solution Extraction

The PLS from the storage area flows to the Solution Extraction (SX) plant where the PLS is mixed in a tank with an organic solv ent chemically designed to only bind to copper. Because the copper has a higher affinity for the organic solvent than for the PLS, the copper moves out of the aqueous phase and into the organic phase.

3 According to FCX personnel, new leach stockpiles are generally required to be lined by the permitting authority.12 Figure 4-3. Simplified Schematic of the Solution Extraction Process

From the mix tank, the mixture of PLS and organic solution flows to a settling tank, where low-energy conditions a llow the organic phase (solvent solution) and aqueous phase (PLS) to separate. The organic phase containing the copper floa ts on top of the settling tank because it is less dense than the aqueous phase . From the settling tank, the two-phases flow slowly into the extractor. In the extractor, th e aqueous phase flows out from the bottom of the tank as the organic phase is pulled off the top. The aqueous phase is now called barren leach solution because it contains very little copper. Af ter extraction, sulfuric ac id is mixed into the solution in a mixing tank to form raffinate. The a dditional sulfuric acid is added to bring the acid strength to between 8-10 g/L prior to recy cling it back to the leach facilities.

The organic phase removed from the top of the settling tank is transferred to a second mix tank. In this tank, the organic phase mixes with an electrolyte solution (highly concentrated sulfuric acid with a pH of less th an 1). The copper moves from the organic phase back to the aqueous phase (the electrolyte), and the mixture move s on to another settling tank to separate. From the settling tank, th e mixture flows to a stripper wh ere the organic ph ase floats on top of the aqueous phase (copper- rich electrolyte). The aqueou s phase is removed from the bottom of the tank while the organic phase is removed from the top. The organic phase is recycled back to the head of the SX plant whil e the electrolyte now containing copper is further processed in the EW plant. Raffinate Pregnant Leach Solution

Barren Or g anic Copper-Laden Organic Copper-Laden Electrolyte

Barren Electrolyte Electrowinning Cell Mix Tank & Extractor Mix Tank & Stripper Heap Leach13 Due to potential air emissions of volat ile organic compounds (VOCs) associated with the solutions used in solution extraction, these operations use covered structures to limit VOCs emissions. FCX manages its SXEW facilities so that they do not discharge to surface

waters.

4.4.1.3 Hydrometallurgical Processing: Electrowinning

The acidic electrolyte cont aining the copper from the SX plant is sent to the electrowinning (EW) plant and is placed in a la rge electrowinning cell with lead anodes and steel cathodes. A strong voltage is applied between th e cathodes and the anodes, causing the copper in the electrolyte solution to plate (i.e., forming a thin sheet) on both sides of the steel cathode
sheets.

The cathodes are then remove d from the electrolyte in rows and a machine flexes them back and forth to detach the copper shee ts. Each copper sheet weighs approximately 230 pounds. At this point, the sheets are ready for sale and are sent to market by both truck and train.

4.4.2 Pyrometallurgical Processing

Pyrometallurgical processing generally consists of the following steps:

1. Grinding; 2. Flotation; 3. Smelting; and 4. Electrorefining.

The facility which performs the grinding and flot ation processes is generally referred to as the concentrator or mill. The following subsections describe these processes. This report does not discuss smelting or electrorefin ing, because these pro cesses do not generally impact surface water discharges from ore mining operations. They typically do not occur in the same location as the ore extraction, and they are controlled by a separate group of ELGs (40 CFR Part 421: Nonferrous Metals Manufacturing).14 4.4.2.1 Pyrometallurgical Pr ocessing: Grinding

The grinding process crushes ore into a si ze suitable for flotation via a series of
crushers. At the concentrator that EPA visited (Bagdad), this involved the following steps:

1. Primary crusher . Breaks the ore down into fragments smaller than 6.5 inches in diameter.

2. Autogenous grinding mill 4 . Breaks the ore down into fragments smaller than 3/8 of an inch in diameter.

3. Semiautogenous Mill (SAG) . Uses 3-inch steel balls to grind the ore into a fine consistency.

From the SAG mill, finely ground material moves on to the flotation circuit.

4.4.2.2 Pyrometallurgical Processing: Flotation

The flotation process separates metallic material (concentrate) from nonmetallic minerals and host rock (gangue). At the concentr ator that EPA visited (Bagdad), this involved the following steps:

1. From the SAG mill, the ground ore material is fed to the flotation circuit, where it is initially mixed with an al kaline flotation solution to create a slurry.

2. The slurry is fed into a primary flotat ion cell through a vertical pipe just below the fluid line in the center of the cell. The slurry billows over the sides of the pipe and into the cell. The agents in the flotation solution cause the copper-rich sediments to floa t to the surface, while finely ground host rock and non-metallic minerals (ref erred to as “gangue”) settle to the bottom of the cell.

3. Aerators at the bottom of the flotation cell create bubbles th at facilitate the flotation of copper-rich sediments. These sediments are pulled off the top of the cell and dewatered. They are then sent to smelting as concentrate.

4 The grinding mechanism in an autogenous mill is the ore itself; whereas semi-autogenous (SAG) mills supplement the grinding process with other agents (e.g., steel balls) to assist in the grinding of the ore.15 4. The gangue slurry is blown down from the bottom of the flotation cell and continues on to a secondary flotation cell to recover any additional copper.

5. Gangue from the secondary flota tion cell (approximately 50 percent moisture content) is gravity fed from the concentrator facility to the tailings impoundment system.

4.5 Copper Mine Tailings Management

Tailings from the flotation circuit ar e managed in a tailings impoundment. The impoundment is generally sited in a topographic low and bounded on the downgradient side with a dam composed of tailings or waste rock. The tailings dam is built up using one of the following
three methods:

 Upstream deposition;

 Centerpoint deposition; or

 Downstream deposition.

EPA visited tailings systems that use the upstream (Morenci) and centerpoint (Bagdad) deposition techniques. Descripti ons of these techniques are incl uded in the sections describing
these facilities.

At the mines that EPA visited, tailings impoundments were the main source of recycled water for the mine. Because the tailings are sent to the impoundment in slurry form, they contain considerable water. This water sepa rates from the tailings over time and forms pools from which the reclaim water can be pumped.

Tailings disposal sites may cover several hundred acres. Typical closure requirements for tailings dispos al sites include dewa tering, capping with a low-permeability soil, and revegetation.16 5.0 B AGDAD M INE AND C ONCENTRATOR O PERATIONS

Staff from the Bagdad Mine provided a tour of the mining and ore concentrating operations on September 14, 2009. The tour began with a safety briefing at the facility’s gate office and a facility overview conference at the environmental office. From the environmental office, FCX led EPA and ERG on a tour of their tailings impoundment system, various stormwater control areas, the ore concentrator faci lity, and the outer rim of the open pit. The tour of the ore concentrator facility included the grinding and flotation circuits and the facility control room. Appendix B contains a general site map for the Bagdad Mine including major geographical features and ope rational areas at the site.

5.1 Mine Site

The Bagdad Mine began as an underground mi ne with a set of claims established by a father and son team in the 1880s. In respons e to World War II, the mine was modernized from 1943 to 1947 and converted to an open-pi t operation. The open pit, which formerly contained the concentrator facility (for grinding and floating of sulfide ores) and multiple tailings deposits, has been continuously expanding during the past 60 years. In 1977, mine owners needed an increased workforce, and they funded significant expansions of the adjacent town. In 1978, mining staff began relocating ta ilings from the concentrator operations to the western areas of the facility where the tailings impoundments are currently located.

Current operations at th e Bagdad Mine include th e daily re-location of approximately 200,000 tons of material (e.g., ore, overburden). The concentrator facility processes approximately 85,000 tons per day. The entire Bagdad Mine site – including the support facilities and tailings areas – has a f ootprint of approximately 5 square miles (or 220,000 acres). Approximately 533 acres are managed by th e U.S. Bureau of Land Management (BLM); the rest are owned by FCX. The geology of the ar ea can be described as a typical porphyry, halocopper deposit surrounded by gran itic and basaltic material on all sides. Chrysocolla and chalcopyrite are the primary minerals found in the ore at the Bagdad Mine. An ephemeral drainage known as Boulder Creek runs along the north side of the property, and flows downgradient into Burro Creek.17 At the Bagdad Mine, FCX mines primarily sulfide ores that have a copper concentration of less than 0.5 percent by weight . The sulfide ores at the Bagdad Mine are generally less than one percent sulfide materi al and exhibit neutral or weak-acid generating potential relative to the sulfide ores at the Morenci Mine (see Section 6.0). The low
concentration of the sulfide material in the ores excavated from the Bagdad Mine produces
stormwater runoff that is relativ ely less acidic than the runoff from most copper mines. Most of the sulfide ores are processed at the mine’s concentrator. The re maining leachable sulfides from the sulfide ore as well as the small quantity of oxide ore produced at the Bagdad Mine are processed via leaching at a leach stockpile lo cated between the open pit and the tailings impoundment system. Mine staff estimated that cathode production resulting from the leaching operations, both now and in the past, represente d approximately 10 to 20 percent of the copper production at the Bagdad Mine. The remainder of the copper produced at the Bagdad Mine is copper concentrate from the concentrator which is transported to the FCX Miami Smelter for further processing.

5.2 Mining Operations

Ore is removed from the Bagdad Mine open pit by traditional blasting and
excavation methods. Work crews drill boreholes in to the ore body using a portable drill rig. The cores that are removed during drilling are sent o ff to the FCX Analytical Laboratory, located in Safford, AZ, to be assayed for copper and other minerals. The borehole is then filled with an explosive composed of ammonium nitrate and fuel oil and equi pped with a blasting cap. Work crews prepare multiple boreholes in this manner a nd detonate one shot to blast a large volume of ore at once. The ore is then excavated using electric shovels and haul ed to the appropriate processing area (e.g., concentrator, leach stockpile) in Caterpillar model 793 Haulage trucks with 270-ton capacities. Blasting and excavation opera tions are designed to create 50-foot tall “benches” behind the mined areas; these benches become the dominant feature across the walls of the mining open pit (see Figure 4-1).

Overburden material, which is removed to access copper ore, may be used to construct roads around the mine site or disposed in piles. According to FCX staff, FCX processes18 all mineralized material for copper extraction. Th erefore, FCX generates no mineralized waste rock during mining activities.

FCX uses both concentrator and leach operations to recover copper from ore. Using these two processes, FCX attempts to r ecover 90 percent of the copper from the mined

ore.

5.3 Copper Recovery from Ore: Concentrator Operations

The concentrator operations include th e following major functions: crushing and grinding (grinding circ uit) and flotation.

5.3.1 Grinding Circuit

The grinding circuit crushes ore into a si ze suitable for flotation via a series of crushers and grinders, shown in Figur e 5-1. The grinding circuit steps are:

1. Primary crusher . A primary crusher breaks th e ore down into fragments smaller than 6.5 inches in diameter . The fragments are then stockpiled immediately adjacent to the facility using a conveyor. From the stockpile, ore is conveyed into the mill circuit in the concentrator building using a belt conveyer and fed into the autogenous 5 grinding mills.

2. Autogenous grinding mills. FCX operates five autogenous grinding mills in parallel (see Figure 5-2). Ground ore is conveyed to the screen deck, where it is sorted by 3⁄4-inch and 3⁄8 -inch screens (see Figure 5-3). Ore particles larger than 3⁄4-inch screen are conveyed to a secondary crusher, and then back into the autogenous m ill. Ore particles be tween 3⁄4-inch and 3⁄8 -inch are screened and flow into a sump that feeds a hydrocyclone cluster. Ore particles smaller than 3⁄8 -inch flow into the semi-autogenous (SAG) 55 mill (ball mill).

3. Semiautogenous Mill (SAG). The SAG uses 3-inch steel balls to grind the ore into a finer consistency. The hydroc yclones separate the finer material from the rest of the feed; the coarse r material drops out of the bottom of the hydrocyclones and is fed back to the autogenous mill. The finer material moves on to the flotation circuit.

5 The grinding mechanism in an autogenous mill is the ore itself; whereas semi-autogenous (SAG) mills use steel balls to assist in the grinding of the ore.19 Figure 5-1. Overview of the Grinding Ci rcuit at the Bagdad Concentrator Primary Crushe r

Stock p ile Autogenous Mill

3⁄4” Screen

3⁄8 ” Screen Secondary Crushe r

Cyclone

SAG Mill Passing Fraction Passing Fraction Passing Fraction Caught Fr act i o n

Caught Fr act i o n Caught Fr act i o n

To Flotation

Circuit20 Figure 5-2. Autogenous Mill and Feed Unit21 Screen Deck Autogenous and Ball Mills

Figure 5-3. Bagdad Grinding Circuit

5.3.2 Flotation Circuit

The Bagdad froth flotation circuit, sh own in Figure 5-4, involves the following steps:

1. From the SAG mill, the ground ore material is fed to the flotation circuit, where it is initially mixed with an al kaline flotation solution to create a slurry.

2. The slurry is fed into a primary flotat ion cell through a vertical pipe just below the fluid line in the center of the cell. The slurry billows over the sides of the pipe and into the cell. The agents in the flotation solution cause the copper-rich sediments to floa t to the surface, while finely ground host rock and noneconomic minerals (referr ed to as “gangue”) settle to the bottom of the cell.

3. Aerators at the bottom of the flotation cell create bubbles th at facilitate the flotation of copper-rich sediments.22 4. The gangue slurry is blown down from the bottom of the flotation cell and continues on to a secondary flotation cell to recover any additional copper.

5. Gangue from the secondary flota tion cell (approximately 50 percent moisture content) is gravity fed from the concentrator facility to the tailings impoundment system.

Primary Flotation Cell Secondary Flotation Cell

Figure 5-4. Bagdad Flotation Circuit

The Bagdad concentrator’s target effici ency is 90 percent co pper recovery. The concentrator employs approxima tely 200-280 people including maintenance workers. Copper concentrate contains approximately 30 percent copper and is trucked fr om the Bagdad Mine to the Miami Smelter. The Bagdad Mine is curren tly trying to produce molybdenum with the same cathode process used for copper production. Furthe r details on this process are excluded from this report as FCX considers them to be confidential business information.23 5.4 Leach Operations

Figure 5-5 shows an unlined leach stoc kpile at the Bagdad Mine. Mine personnel stockpile uncrushed ore onto an unlined site where leach solution (containing concentrated sulfuric acid produced from off-gases at FCX’s Mi ami Smelter) is applied to the top of the ore stockpile. The leach solution percolates through the stockpile dissolving copper and other metals and flows from the base of the stockpile to a pregnant leach soluti on (PLS) pond. From this pond, PLS is pumped up to the Solution Extraction (SX) and Electrowinning (EW) plant. During the first pass through the stockpile the leach solu tion dissolves approximately 20 to 30 percent of the copper from the ore. Each additional pass re covers less and less coppe r. The leach operations use pit water and stormwater as make -up water to the raffinate stream.

PLS Pond Stormwater Overflow Pond Dump Leach

Figure 5-5. Unlined Leach Stockpile Facility

5.5 Solution Extraction Electrowinning Operations

The Bagdad Mine has the one of the oldest Solution Extraction (SX) and Electrowinning (EW) plants, whic h has been operating for about 30 years. The plant operates at24 a flow rate of approximately 7,500 gallons per minute (gpm) (7,500 gpm PLS going into the plant and 7,500 gpm raffinate coming out). After the SX process, the barren leach solution – which has been stripped of the coppe r – is supplemented with additi onal sulfuric acid to bring the acid strength up to between 8-10 g/L prior to ap plying it back to the leach stockpiles. For a detailed description of the SXEW process, see Section 6.5 discussing the Morenci SXEW.

The target efficiency of the SXEW system is roughly 89 to 92 percent copper recovery. The facility can achieve higher efficien cies, but the additional co sts incurred to achieve higher efficiencies do not justify the increased copper recovery. These costs include additional organic chelator in the SX to provide more copper carrying capacity in the organic phase, additional power consumption to increase the EW cell current, and additional processing steps to remove impurities (e.g., iron) associated with in creased copper recovery. The top three costs of running an SXEW plant in descending orde r are power, labor, a nd organic additions.

5.6 Tailings Impoundments

At the Bagdad Mine, FCX stores the majority of the tailings from mining operations in two impoundments: the Mamm oth Tailings Impoundment and the Mullholland Tailings Impoundment. The Mammoth Tailings Impoundment – which is approximately 4,800 acres – is contained by the longest cent erpoint tailings dam in North America 6 . Tailings slurry from the concentrator is conveyed to the impoundm ents by headers made of rubber-lined steel. Figure 5-6 illustrates the tailings dam, pump-back station, various road systems, and stormwater
culverts.

6 Centerpoint construction of tailings dams is performed by placing the header pipe – which conveys the tailings slurry from the concentrator facility to the impoundment – at the planned cente r line of the tailings dam. A cyclone separator is connected to the header where the slurry is di scharged; this cyclone separates the fine-grained material (e.g., clay, silt) from the coarse material (e.g., gravel, sa nd). The fine-grained material discharges to the upgradient (wet) side of the dam to act as a permeability barrier, and the coarse material discharges to the downgradient (dry) side of the dam to act as structural su pport. The coarse material also drains better, thereby reducing the dangerous buildup of pore water pressure – which could lead to dam failure – in the dam wall. As material continues to be deposited, the deposition site (where the cyclone is located ) is raised vertically, but the cyclone stays on the dam’s centerline.25 Header

Stormwater Culvert Pump-back Station

Figure 5-6. Mammoth Tailings Dam

The Bagdad Mine is required to maintain 4 feet of freeboard 7 on the Mullholland Tailings Impoundment and 10 feet of freeboard on the Mammoth Tailings Impoundment. At the time of the site visit, the freeboard at the Mammoth Tailings Impoundment was approximately 20 feet. Due to topographical cons traints, there is no run-on dive rsion on the south side of the Mammoth Tailings Impoundment, and the impoundme nt receives stormwater run-on from the
south side.

Two pump-back stations are located on the downgradient side of the Mammoth Tailings Dam. These stations pump seepage return water from the dam back into the impoundment. Both stations have backup generato rs to provide redundant power supply in the event of a power outage.

7 Freeboard is defined as the distance between water level and the top of an impoundment.26 5.7 Freshwater Sources and Recycled Water

Water used at the Bagdad Mine is a combination of groundwater pumped from the surrounding areas and process water recycled from on-site processes. Bagdad Mine personnel attempt to forecast the mine’s water needs approximately one month in advance to shut down unnecessary groundwater supply wells and minimi ze groundwater use. The Bagdad Mine pumps approximately 6,500 gpm from the Wikiup Wellfi eld and approximately 1,500 gpm from Francis Creek, a deep, mildly thermal artesian a quifer. In addition to pumped groundwater, approximately 150 to 200 gpm of treated effluent from the Bagdad town’s wastewater treatment plant is recycled into the mill process.

A total of approximately 26,000 gpm of wate r is recirculated from various areas around the mine site (e.g., tailings impoundments, open pit) back in to mine processes. Of this, approximately 17,500 gpm is recirculated fr om the Mammoth Tailings Impoundment and 400 gpm is recirculated from the Mullholland Tailings Impoundment. The Mullholland Tailings Impoundment – which is upgradient from the Mammoth Tailings Impoundment – is used as much as possible for water storage and stormw ater management to minimize pumping costs.
Recirculated water from the tail ings impoundment system is used at the concentrator and other facilities. Mine water pumped from th e open pit is used for leach operations.

5.8 Stormwater and Process Wastewater Management

As part of their corporate policy, FCX mi nimizes all discharges from their mine sites and attempts zero discharg e by recycling stormwater and pr ocess water. The Bagdad Mine holds both an individual NPDES permit and a st ormwater Multi-Sector General Permit (MSGP) (administered by the State of Arizona as of 2002) . Less than 10 percent of the Bagdad Mine area is covered under the MSGP; industrial wastewater and stormwater from the rest of the facility that could potentially be discharged ar e covered by the individual NPDES permit.

5.8.1 Sources of Discharge

The main source of the Bagdad Mine’s wate rs that could potentially be discharged via the Bagdad Mine’s individual NPDES outfalls is tailings reclaim water. The average annual27 precipitation in the area is 14.5 inches per year. Site personnel noted that the Bagdad Mine does not generate substantial quantities of run-off unless it receives more than an inch of precipitation during one storm event. In addition to stormwater , groundwater infiltrates into the open pit at a rate of approximately 600 gpm; this water is pump ed out of the open pit fo r use in the facility’s leach operations. For a discussion of water recy cling, see Section 5.7 Freshwater Sources and Recycled Water.

To minimize their discharges, Bagdad recycles stormwater and process water. Although the Bagdad Mine does not routinely discharge under its NPDES permits, the facility maintains its permits in case intermittent discharges are needed. Table 5-1 and Table 5-2 list the sources of Bagdad Mine discharges for each individual NPDES and MSGP permitted outfall. Appendix B shows the location of these outfalls relative to the rest of the mine site.

Table 5-1. Bagdad Mine Individual NPDES Outfalls

Outfall Number and Name Source Description Discharge Status Receiving Stream and Notes 001: Copper Creek North side of the mine site (vehicle maintenance and leach facilities areas) No discharges on record. Tributary to Boulder Creek.

003: Mulholland Wash Northwest side of the mine site (Mullholland tailings impoundment area) No discharges on record. Tributary to Boulder Creek.

006: Mammoth Wash West side of the mine site (Mammoth tailings impoundment area) Intermittent discharges during large storm events. Tributary to Burro Creek.

Source: AZPDES AZ0022268 Permit DEQ

Table 5-2. Stormwater Outfalls Permitted Under the MSGP

Outfall Industrial Activity Significant Materials Management Practices Activities Mammoth Storm Water Basin  Basalt Quarry  Unmineralized rock materials (overburden)

 Petroleum and Antifreeze in use in Access Vehicles  Vegetation

 Minimize vehicular traffic  Vehicular traffic on access roads; and

 Materials loading and unloading.28 Table 5-2. Stormwater Outfalls Permitted Under the MSGP

Outfall Industrial Activity Significant Materials Management Practices Activities Butte Creek Overburden Dump Basin  Storage of Overburden

 Storage of Equipment  Overburden

 Petroleum and Antifreeze in use in Access Vehicles

 Empty Dumpsters and haul truck beds

 Cable

 Equipment  Berms

 Vegetation

 Dimple Dumping

 Minimize vehicular traffic  Vehicular traffic on access roads;

 Storage area for equipment; and

 Materials loading and unloading.

Mine Shop Overburden Dump Basin  Storage of Overburden

 Storage of Equipment  Overburden,

 Petroleum and Antifreeze in use in Access Vehicles

 Empty Dumpsters and haul truck beds

 Equipment  Berms

 Vegetation

 Sediment Traps

 Riprap

 Minimize vehicular traffic  Vehicular traffic on access roads; and

 Materials loading and unloading; and

 Storage area for equipment

Inactive/ Unstaffed Hillside Loadout Facility  Inactive/Unstaffed Facility

 Former copper concentrate rail loadout facility

 Truck Wash (Inactive)  Sediment and Residual Copper Concentrate

 Petroleum and Antifreeze in use in Access Vehicles  Storm Water Impoundment

 Ditches

 Berms

 Cement Pads

 Minimize vehicular traffic  Vehicular traffic on access roads

Source: Bagdad Stormwater Pollution Prevention Plan, January 2001.

The Bagdad site has discharged twice under their NPDES permit since 2000. Mine staff also speculated that there was anot her discharge event some time in the 1990s. In October 2001, two successive 24-hour storm events (equivalent to a 120-year storm) caused the Bagdad Mine to discharge 400,000 gallons of wa ter from the Mammoth Tailings Impoundment (see Outfall 006 in Table 5-1). In late 2004 and early 2005, the Bagdad Mine received 31 inches of rainfall in 6 months (more than twice the average annual pr ecipitation), and site personnel discharged 1,500 gpm in 2005 for a sustained pe riod of time (exact length unknown) from the Mammoth Tailings Impoundment.

5.8.2 BMPs Used for Stormwater Control

The Bagdad Mine’s stormwater runoff c overed by the MSGP includes an area on the west side of the mine site (Mammoth Tailings Dam area) and a couple of areas on the Northeast side of the mine site (mine shop a nd overburden disposal areas). The stormwater outfalls for these areas are shown on the site map in Appendix B.29 The Bagdad Mine has chosen to control stormwater discharges on the north side of the mine site with best management practices (BMPs), consistent with the conditions of the MSGP. The general strategy for stor mwater control in this area is to build berms at the edge of the plateau on which the mine shop is located. Th ese berms cause precipitation on the plateau to flow back into the mining area. The stormw ater around the mine shop is conveyed to groundlevel drains which flow back to a stormwater ev aporation pond. Anything that falls outside of the plateau is controlled by check dams and other berms built up from overburden material 8 along the roads on the backside of the mine shop. The Bagdad Mine attempted to seed these areas for plant growth, but these attempts were unsuccessf ul due to the high clay content of the native soils. According to Bagdad Mine personnel, thes e BMPs have effectively managed and reduced stormwater discharges.

On the west side of the mine site (Mammoth Tailings Dam area) roadside culverts, basalt check dams, and unlined evapor ation ponds are used as stormwater controls. Figure 5-7 shows a roadside stor mwater evaporation pond. Stormwat er is conveyed in culverts along roads which are re-graded about every three months.

8 The Bagdad Mine uses only overburden material ( non-mineralized soil and rock) to construct roads and stormwater controls.30 Figure 5-7. Roadside Stormwater Evaporation Pond

5.9 Site Closure Plans

Bagdad Mine staff explained that the mine open pit has been excavated to a depth that causes it to act as a hydrologic sink. For th is reason, all impacted gr oundwater in the area flows to the pit lake. Staff are confident that they can dispose of water in the pit lake after closure via evaporation.

The tailings impoundment system is the area of the Bagdad Mine site that will require the most extensive reclamation activit ies upon mine closure. Tailings impoundments currently have 2.8:1 slopes along th eir sides. Upon closure, Bagdad st aff plan to deposit material in the impoundments to conduct drainage to one side. This will reduce the size of the impoundments and allow Bagdad Mine staff to r eclaim the impoundment in sections. Because the tailings at Bagdad Mine have neutral to w eak acid generating potentia l, Bagdad Mine staff do not anticipate significant problems w ith closure of the tailings areas.31 6.0 M ORENCI M INE O PERATIONS

Staff from the Morenci Mine provided a tour of the f acility’s mining and solution extraction operations on September 15, 2009. The tour began with a safety briefing and an overview conference at the facility’s gate office. From the gate office, Morenci Mine staff led
EPA and ERG on a tour of their mining operations, various stormw ater control areas, a Solution Extraction and Electrowinning (SXEW) plant, and their tailings areas.

6.1 Mine Site

At the time of the site visit, th e Morenci Mine employed approximately 1,600 employees and 100 contractors working on-site. Th e total surface disturba nce for the site is approximately 14,000 acres. While the majority of the disturbed land is owned by Morenci, some of the land is either managed by the BLM or St ate of Arizona. Appendix C contains an overall site map for the Morenci Mine.

6.2 Mining Operations

The Morenci Mine handles approximate ly 500,000 tons of material (e.g., ore, overburden) per day from its four open pits; the pits are referred to as the Coronado, Garfield, Shannon, and Lonestar Pits. A picture of the Co ronado pit is shown in Figure 6-1. In the open pits, mining personnel use 4,160-volt el ectric shovels to excavate ma terial and place it into one
of 64 haul trucks. Each truck ha s the capacity to hold 240 tons of material; these trucks operate continuously (both day and night ) removing material from the open pits and hauling it to processing areas. Unlike the Bagda d Mine, the ores at Morenci Mine are very heterogeneous. Mineral types and metal concentrations in the ore vary widely throughout the mine area. The primary minerals at the Morenci Mi ne are Chalcopyrite and Chalcocite.32 Figure 6-1. The Coronado Open Pit

6.3 Concentrator Operations

When operating, the Morenci Mine concentr ator is capable of processing up toto 75,000 tons of material per day. Beca use most of the ore currently extracted at the Morenci Mine is leachable ore, the concentrator operations process less than 20 percent of all ore mined at the facility.. At the time of the site visit, the concentrator was not ope rating. However, based on information provided by staff from FCX, FCX plans to restart operations at the Morenci mill in the second quarter of 2010. The Morenci Mine no w uses decommissioned tailings thickeners from the concentrator facility to bio-reme diate petroleum contaminated soils (PCS).

6.4 Leach Operations

After being blasted and ex tracted from the ore body, ore material is generally about six inches in diameter. Morenci Mine may then crush the ore for better leach recovery (referred to as mine-for-leach [MFL]), or leach it uncrushed (referred to as run-of-mine [ROM]). Approximately 60 percent of Morenci Mine’s leachable ore is MFL; the rest is ROM.33 The Morenci Mine crushes MFL into pieces that are 1⁄2 inch or less in diameter for better copper recovery during leaching. Crushing the mined material increases the surface area making more of the rock accessible to the sulfuric acid used in leaching. In some instances, the Morenci Mine may inject air into leach stockp iles to boost bacterial act ivity and improve copper recovery. The Morenci Mine s ponsors research and development activities to optimize copper recovery in leaching via air injection.

Morenci Mine personnel stockpile ore onto an unlined site and add leach solution (i.e. concentrated sulfuric acid produced from sm elting gases at FCX’s Miami Smelter). After the leach solution runs through the mined material it is called pregnant leach solution (PLS) and contains copper and other metals. This soluti on flows to a PLS pond (Figure 6-2). Figure 6-3
shows the stormwater overflow from the leach operation.

Leach stockpiles may cover severa l acres and be several hundred feet high. Typical closure requirements for leach st ockpiles include capping with a low-permeability soil and stormwater run-on management.

Because the Morenci Mine is located in a major flyway for birds, the PLS ponds and other open surface impoundments holding potent ially toxic materials must have equipment
on-site that deters birds. Around the PLS and overflow ponds, the Morenci Mine has propane cannons, dummy hawks triggered by radar, monof ilament lines above impoundments, and noise
makers to deter birds.34 Figure 6-2. Stormwater Overflow from Leach Stockpile on Left and Pregnant Leach Solution Pond on Right

Figure 6-3. Stormwater Overflow from the Leach Stockpile35 6.5 Solution Extraction Electrowinning (SXEW) Operations

The Morenci Mine has four solution ex traction (SX) and th ree electrowinning (EW) plants.

The SX plants receive the PLS from the leach stockpile and mix it in a tank with an organic solvent composed of a diluent and a chelator. The mix tank is shown in Figure 6-4.
The diluent is mixed with a chelator to lower its viscosity; the chelator is chemically designed to only bind to copper and is used to extract coppe r from the PLS. Because the copper has a higher affinity for the organic chelator than for the PL S, the copper moves out of the aqueous phase and into the organic phase to bond with the chelator.

Figure 6-4. SXEW Pregnant Leach Solution Mix Tank36 From the mix tank, the mixture of PLS a nd organic additions flows to a settling tank, where low-energy conditions allow the or ganic and aqueous phases to separate. The organic phase containing the coppe r is less dense than water and fl oats to the top of the settling tank. From the settling tank, the two- phases flow slowly into the extractor. In the extractor, the aqueous phase flows out from below as the organi c phase is pulled off the top of the mixture. The extractor is shown in Figure 6-5. The aqueous phase is now called barren leach solution (BLS) because it contains very little copper. After extraction, the BLS is supplemented with additional sulfuric acid in a mixing tank to bri ng the acid strength to be tween 8-10 g/L prior to recycling it back to the leach st ockpiles. After mixing with acid to bring up the strength of the BLS, it is referred to as “raffi nate.” Around 92 percent of the coppe r in the PLS is recovered in the organic phase.

Figure 6-5. SXEW Extractor37 Figure 6-6. SXEW Raffinate Mix Tank

The organic phase removed from the top of the settling tank is transferred to a second mix tank. In this tank, the organic phase mixes with an aqueous electrolyte solution (highly concentrated sulfuric acid with a pH of less than 1). The copper moves from the organic phase back to the aqueous phase (the electrolyte), and the mixtur e moves on to another settling tank to separate. From the settling tank, the mixt ure flows to a stripper where the organic phase floats on top of the aqueous phase (copper-rich el ectrolyte). The aqueous phase is removed from
the bottom of the tank while the organic phase is removed from the top. The organic additions are recycled back to the head of the SX plant while the elect rolyte now containing copper is further processed in the EW plant.

At the EW plant, the acidic electrolyte is placed in a large electrowinning cell where square lead sheets are used as anodes. Some EW plants also use lead sheets with 17-pound copper starter sheets on either side for cathod es. However, the Morenci Mine’s plants use
stainless steel sheets as cathode sites to reduce the high shipping costs for copper starter sheets (which must be produced at a smelter) and the en vironmental liabilities associated with lead flakes. The cathodes are then placed into the electrolyte in the EW cell, and a very strong voltage38 is applied between the cathodes and the anodes. This voltage causes the co pper in the electrolyte solution to plate on both sides of the steel cathode sheets. Figure 6-7 shows the tops of these cathode sheets in the EW cell, and Figure 6-8 s hows a cathode sheet plat ed with copper after it
has been removed from the EW cell. The time that it takes to coat a cathode depends primarily on the voltage used in the cell; at the Morenci Mine the EW plant is configured so that cathodes have a residence time of approximately seven days.

Figure 6-7. Steel Cathodes Being Plated with Copper in EW Cell39 Figure 6-8. Steel Cathode Plat ed with Copper from EW

The cathodes are removed from the electroly te in rows and a machine flexes them back and forth to detach the copper sheets. Each copper sheet weighs approximately 230 pounds. Copper sheets ready for sale are shown in Figure 6-9. Nearly all of the copper that the Morenci Mine’s SXEW plants produce is Grade A copper, meaning that it is greater than 99.99 percent purity and suitable for use in electrical applic ations. The Morenci Mine crimps some copper sheets for buyers so that they melt more eas ily in a furnace. The Morenci Mine sends the produced copper to market by both truck and train.40 Figure 6-9. Copper Cathode Sheets Ready for Sale

6.6 Water Sources

As with the other FCX facilities, the Morenci Mine recycles process water and stormwater from around the facility back into its processes. The Morenci Mine’s main source of
freshwater is an on-site treat ment plant that treats water fr om Lower Eagle Creek (the only perennial stream in the area). To prevent the st ream from drying up, the Morenci Mine augments the creek with groundwater pumped into the st ream at a well field approximately 30 miles upstream from the Morenci Mine. This arrangeme nt saves the Morenci Mine from having to install 30 miles of piping between the mine site and the well field. The Morenci Mine also uses
treated effluent from the town’s wastewater tr eatment plant to run the facility’s processes.

6.7 Tailings Areas

Tailings from the Morenci Mine are pu mped to the tailings area through rubber lined steel header pipes. Tailings dams are bu ilt using the upstream deposition technique – this41 means that the deposition site moves inward toward the impoundment center over time. A hydrocyclone at the end of the header drops coar se sands and sediments on the tailings dam. The lighter material that discharges from the top of the hydrocyclone goes to the inside of the tailings area. Figure 6-10 illustra tes the staggered effect created by upstream deposition of tailings. The outside the tailings dams are generally built up with Gila conglomerate.

Water from the tailings dams are pumpe d back into the processes in the mine area. The Morenci Mine periodically measures water levels (via piezometers), land movement, and seismic activity throughout the tailings areas. A geotechnical engineer specializing in dam
construction oversees the condi tion of the tailings area.

Figure 6-10. Tailings Area

At the face of the tailings dams, staff crimp hay into the tailings to consolidate them and prevent erosion. The dry area behind the dam is called the beach (shown in Figure 6-11). As a good management practice, Morenci personnel generally try to keep the beach between 500 and 2,000 feet in length.42 Figure 6-11. Tailings Beach

6.8 Stormwater and Process Wastewater Management

The Morenci Mine is permitted to disc harge under its individual NPDES permit and the stormwater MSGP (administered by the St ate of Arizona as of 2002). Areas outside of the active mining areas are covered under the MSGP ; industrial wastewater and stormwater from the rest of the facility that could potentially be discharged are covere d by the individual NPDES permit.

6.8.1 Discharges under the Morenci Mine’s NPDES Permit

Because average annual precipitation is 12.5 inches per year, the Morenci Mine operates on a water deficit. Therefore, the More nci Mine does not routin ely discharge process wastewater or stormwater from active mining ar eas. The Morenci Mine is permitted to discharge to two outfalls (001 and 002) under the indivi dual NPDES permit. The only NPDES discharge that has occurred in the past tw enty years was due to an upset condition caused by an electrolyte spill from incorrect piping. Table 6-1 lists th e outfalls covered by Morenci’s NPDES Permit.43 Table 6-1. Morenci Mine NPDES Outfalls

Outfall Number and Name Description of Sources Discharge status Receiving Waters 001 – Lower Chase Creek Spillway Mine process water, mine drainage, and stormwater One discharge in the past twenty years associated with an upset condition. Lower Chase Creek

002 – Gold Gulch Spillway Mine process water, mine drainage, and stormwater No discharges on record. Gold Gulch (ephemeral tributary to Eagle Creek) Source: AZPDES Permit AZ0022705 (ADEQ, 2005).

6.8.2 Stormwater Best Management Practices (BMPs)

Because the Morenci Mine is located in the Chase Creek stream bed, the Morenci Mine diverts water in Chase Creek away from the mine at the Upper Chase Creek Dam. This arrangement is permitted by the Army Corps of Engineers under a Clean Water Act Section 404 Permit. The current Upper Chase Creek Dam was built in 2005 of native borrow material. On the upgradient side of the dam, the Morenci Mine collects most of the water from Chase Creek (when flowing) at an intake st ructure, and conveys it via pipelin e to an area on the opposite side of the mine site downgradient of Lower Chase Creek Dam. The water in this pipeline flows entirely via gravity to bypass the mine site. A fr action of water from Chase Creek flows into the Upper Chase Creek Dam and is allowed to trickl e into the riparian area below it. Figure 6-12 shows the Upper Chase Creek Dam from the up-gradient side.44 Intake Structure

Figure 6-12. Upgradient Side of Upper Chase Creek Dam

The Morenci Mine has MSGP coverage fo r the portion of the si te located outside
of the main mine area. Runoff from historic stoc kpiles and tailings are conveyed to stormwater retention areas (either evaporat ion ponds or dams) that prevent the runoff from discharging to surface waters. In addition to these BMPs, Morenci uses stormwater culverts, waddles, and
check dams to control stormwater on access road s. Figure 6-13 shows an example of a waddle, which is straw wrapped in wire nets to preven t soil and other solids from running off the road during heavy rain. The culverts along these roads also convey water down to stormwater
retention structures. From the stormwater retent ion structures, water either evaporates or is pumped back to the active mining areas to be recycled back into various processes.45 Figure 6-13. Waddle in Stor m Water Ditch by Roadway

Figure 6-14 shows the Lower Chase Creek Dam. The Lower Chase Creek Dam is the largest dam at the Morenci Mine (excluding th e tailings dams). The dam was built in the mid 1980s and cost approximately $1.5 million. This da m provides redundant control of stormwater
from the mine area in case th e evaporation pond up-gradient of the dam (shown in Figure 6-15) malfunctions. The evaporation facility is lined with High-Density Polyethylene (HDPE) that is at least 60-mil thick in all areas and periodically cl eaned to remove settled solids. The Lower Chase Creek Dam does have a NPDES outfall (001) which can be used to discharge stormwater or wastewater, if necessary. Accordi ng to FCX staff, FCX does not anti cipate that future discharges
from this outfall will ever occur.46 Figure 6-14. Lower Chase Creek Dam

Figure 6-15. Evaporation Basin Upgr adient of Lower Chase Creek Dam47 In addition to the two dams on Chase Creek, the Morenci Mine has one dam and three lined evaporation ponds on th e south side of the mine site and one dam on the north side of
the mine site. These structures control stormw ater from non-process areas only, including runoff from mine roads and historic stockpiles.

The dam on the south side of the mine si te is the North Gold Gulch Dam and the
dam on the north side of the mine site is th e Rocky Gulch Dam. Figure 6-16 shows the North Gold Gulch Dam. This dam has a sump on the dow ngradient side which re turns stormwater that
has infiltrated under the dam back to the retention area. The dam facility includes an outfall which is registered under the Morenci Mine’s NPDES permit and capable of discharging
wastewater from the mine site and stormwater, if necessary. Rocky Gulch Dam is similar to the North Gold Gulch Dam; however, it does not have a NPDES outfall.

Figure 6-16. North Gold Gulch Dam

The Morenci Mine’s three lined evaporat ion ponds on the south side of the mine
site collect stormwater from roads and histor ic stockpiles. Stormwater in these ponds may48 evaporate or be recycled back into processes in the mining area. Figure 6-17 shows one of these ponds with a historic stockpile in the background. At these ponds, solar-powered pumps transfer
the leachate collected from beneat h the liner back to the system.

Figure 6-17. Lined Evaporation Pond with Historic Stockpile in the Background

In addition to the various structures di scussed in this section, the Morenci Mine maintains a system of unlined ev aporation ponds to control stormw ater runoff from the tailings dams that surround the mine’s tailings areas. Pr ecipitation that falls outside of the tailings impoundment areas is controlled in unlined ev aporation ponds built up from native material along local access roads. Figure 6-18 shows one of these evaporation ponds. Precipitation may evaporate from these ponds, infiltrate into the soil, or be recycled as process water. Outside of the tailings dams on the south side of the mini ng area, 30 stormwater control structures (mostly unlined evaporation ponds ) retain stormwater runoff from th e 12 canyons that drain the outside of the tailings areas. As required by the Aquife r Protection Permit from the state of Arizona, these ponds are capable of reta ining stormwater from a 100-ye ar, 24-hour storm. Stormwater facilities are systematically numbered and inspec ted, and inspections are tracked in a database.49 Figure 6-18. Unlined Evaporation with a Tailings Dam in the Background

6.9 Mitigation/Remediation Operations

In addition to ongoing remediation activiti es that FCX is sponsoring in Clifton, the Morenci Mine is currently ex perimenting with various tailings reclamation scenarios at test plots on-site (see Figure 6-19). Mo isture content in the plots is measured using piezometers. Morenci Mine personnel track evapot ranspiration processes in test pl ot soils via moisture content to attempt to determine the effectiveness of soil thickness and plant sp ecies on re-vegetation.50 Figure 6-19. Reclamation Experiment

7.0 S AFFORD M INE O PERATIONS

Staff from the Safford Mine provided a tour of the mining and leaching operations at the site on September 17, 2009. The tour be gan with a safety briefing and an overview conference at the facility’s main office. From the main office, Safford Mine staff led EPA and ERG on a tour of their mining operations, various stormwater control areas, an SXEW plant, and their leach pad facilities.

7.1 Mine Site

The Safford Mine, which began produci ng copper in 2007, is located in Southeast Arizona at the base of the Gila Mountains, approximately 20 miles from Morenci. Figure 7-1 shows the Safford Mine open pit. The mine employs approximately 500 people, many of whom worked at Morenci before Safford opened. Two major historic mining operations occurred in the area prior to the opening of the Safford Mine: the Dos Pobres Mine (near the site of the current Safford Mine) and the San Juan Mine (adjacent to the Safford Mine). Both mines are owned by FCX, but are not currently operating. As of Sept ember 2009, the Safford Mine is expected to last for 18 years. Part of the site is located on land previously managed by the BLM; however, FCX acquired and exchanged other parcels of land wi th BLM for the land around the Safford Mine.51 FCX now owns all land at the Safford site. A ppendix D contains an overall site map for the
Safford Mine.

Figure 7-1. Safford Mine Open Pit

7.2 Mine History

The Dos Pobres ore body was discovered in 1958. Ten years la ter development of the underground mine began. Since then, the Dos P obres Mine and nearby assets have changed ownership several times; copper production from the Dos Pobres Mine has been curtailed and restarted on numerous occasions. After completi ng a 12-year permitting process that began with Phelps Dodge in the 1990s, FCX began constructi on of the Safford Mine facilities in June 2006 to exploit a separate ore body near the Dos P obres Mine. By December 2007, all of the main facilities had been commissioned and were ready to operate. Copper was first produced for sale at the Safford Mine in late December, 2007.

The permitting process to open the Safford Mine took 12 years and included numerous obstacles, such as the BLM land exch ange, completion of an Environmental Impact Statement, and mitigation of archaeological issues identified by the mine’s archaeological team. FCX conducted a 100 percent Class III archaeological survey, whic h considered a variety of mitigation options and identified a number of pe troglyphs likely associated with Gila River Community.52 7.3 Mining Operations

The Safford Mine ore is an oxide ore (leachable) with appr oximately 0.4 percent copper. Another ore body contains sulfide ore of approximately 0.8 percent copper content; FCX has not yet determined whether they will extract the sulfide ore, which would require building a concentrator on-site to process it. All ore cu rrently mined goes through the hydrometallurgical process at the Safford Mine. Copper is leached fr om the ore at a heap leach pad and produced from the PLS at an SXEW Plant. The main copper mineral mined at the Safford Mine is chrysocolla, with some copper-bearing Hematite s. Figure 7-2 shows copper ore at the Morenci Mine containing chrysocolla. Chrysocolla is re adily-recoverable; however, some of the other minerals are less recoverable. Because the copper minerals at the Safford Mine are contained in andesite rocks that have high carbonate content, the Safford Mine is not expected to generate acid rock drainage.

Figure 7-2. Copper Ore at the Safford Mine53 The mine currently processes 180,000 tons of material (e.g., overburden, ore) per day. Maximum copper production is about 240 million pounds per year; current copper production is approximately 120 million pounds per year.

7.4 Crush and Convey Operations

Figure 7-3 shows the coarse ore stockpile on the left and a crushing facility on the right. Ore travels from the coarse ore stockpile to the screening plant and then on to fine crushing. At the primary crusher, ore is maintained at 2 to 3 percent moisture. To protect crushers, magnets are used to take out any scrap metal that may have mixed into the ore. At the end of the crushing process, the fragments ar e all 1⁄2 inch or less in diameter. Baghouses controlling air emissions from th e crushing equipment are regula rly cleaned, and the dust is recycled back into the ore. Baghouses are not need ed after agglomeration, where sulfuric acid is added during ore crushing, because the material has been wetted.

Figure 7-3. Safford Crush/Convey Area54 7.5 Water Supply and Discharge Operations

FCX pumps water from the Graben Aquifer – located on the west side of the Dos Pobres ore body – for the Safford Mine. The aver age annual precipitation at the Safford Mine is 9-10 inches per year.

Following FCX’s corporate policy, all facilities including the Safford Mine operate without routine discharges. The Safford Mine has MSGP coverage for a portion of the facility. The Safford Mine used to have an in dividual NPDES permit, but chose not to renew it when it expired a few years ago. No historical in dividual permit discharges have occurred at the
Safford Mine.

The Safford Mine’s stormwater retenti on structures are capable of containing runoff for multiple 100-year storms. The Safford Mi ne has installed liner systems for leach pads as suggested by Arizona’s Best Available De monstrated Control Technology (BADCT) mining document. The Safford Mine also uses process p onds and pipe corridors to protect groundwater
from contamination.

7.6 Leach Operations

Both run-of-mine (ROM) (uncrushed) and mine-for-leach (MFL) (crushed) ore is used in the leaching process. The Safford Mine’s decision to crush ore is dependent on copper concentration and recoverability. MFL ore is agglomerated with acid during crushing. Most of the acid used in the process (about 40 to 90 pounds acid per ton rock) is applied during agglomeration. The heap leach pad is lined with impermeable clay and a Low Linear Density Polyethylene liner. Figure 7-4 shows the Safford Mine’s heap leach pad. The liner is 60-mil in some areas, but mostly 80-mil. Some parts of the liner are textured to provide better friction and shear strength. In the future, the leach pad w ill expand to Phase II of the mine, at which time
another liner will be installed and attached to the existing liner via steel welds. Stormwater from the heap leach pad is routed dir ectly back to the pad. The normal emission rate of sulfuric acid (H 2 SO 4 ) on the surface of the heap leach pad is a pproximately 0.0015 grams per square foot per
second.55 Figure 7-4. Safford Heap Leach Pad

Sulfuric acid is added to the top of the heap leach pad. The sulfuric acid collected at the bottom is referred to as pregnant leach so lution (PLS). PLS from th e heap leach pad enters
into a main header for collection where it f eeds into the PLS tank. Fi gure 7-5 shows the PLS tank. If necessary, PLS will go to the PLS overf low pond or even on to the stormwater pond, but the ponds are rarely used. Figure 7-6 shows th e PLS overflow pond. There is 390 acre-feet of storage for PLS in the PLS pond. All piping is in s econdary containment, to prevent spills in the event of a pipe break.

Figure 7-5. Safford Heap Leach PLS Tank56 Figure 7-6. Safford Heap Leach PLS Overflow Pond

7.7 SXEW Operations

The SXEW at the Safford Mine works in the same way as the one at Morenci. See
Section 6 for more details on the steps of the SXEW process. Fi gure 7-7 and Figure 7-8 show the
solution extractor and electrowinni ng cell at the SXEW plant. The organic addition at the Safford Mine contains 90 percent diluent and 10 percent r eagent. The SXEW contains three extractors to separate copper-rich organic solution from the l each solution and one stripper to separate copperrich electrolyte from the organic solution. Befo re the barren leach solution (BLS) from the SXEW plant is recycled back to the heap leac h pad, sulfuric acid is added to bring the acid strength up to 5 g/L. The reacidified BLS is now called raffinate. A stainl ess steel, pond-shaped tank at the bottom of the EW plant catches misce llaneous process wastewater and feeds it back to
the raffinate mix tank. To control the concentr ation of unwanted byproducts (e.g., metals other than copper) in the SXEW circui ts, barren electrolyte is periodica lly bled from the EW cells to the raffinate mix tank. This takes the byproducts out of the strong electr olyte circuit and puts them into the leach circuit where they w ill have a smaller effect on copper recovery.57 Figure 7-7. Safford Organic Solvent Extractor

Figure 7-8. Safford Electrowinning Cell58 8.0 R EFERENCES

1. ADEQ, 2007. Authorization to Discharge under the Arizona Pollutant Discharge Elimination System, Permit No. AZ0022268. (Bagdad Mine) December, 2007.

2. ADEQ, 2005. Authorization to Discharge under the Arizona Pollutant Discharge Elimination System, Permit No. AZ 0022705. (Morenci Mine) April, 2005.

3. FCX, 2009. Stormwater Pollution Preventi on Plan for the Bagdad Mine. August, 2009.Appendix A

LIST OF SITE VISIT PARTICIPANTSA-1Table A-1. List of Site Visit ParticipantsNameOrganizationTitleBagdad SiteVisitMorenci SiteVisitSafford SiteVisitTom Born U.S. EPA Office of Water Ore Mining Task Lead X X XChris Krejci ERG (Contractor to EPA) Environmental Engineer X X XTom Ripp U.S. EPA OECA OECA Staff Lead XDan Chadwick U.S. EPA OECA Geologist XEmily Chow U.S. EPA OECA Chemical Engineer XJerry Roose FCX Corporate Office Environmental Services Director – Domestic Operations XBruce D. Taylor FCX Safford Chief Environmental Engineer XJohn Korolsky FCX Safford Senior Environmental Engineer XJamie Davis FCX Safford General Manager XMike Windsor FCX Safford Environmental Engineer XBrian Ford FCX Safford Senior Environmental Engineer XKrishna Parameswaran Asarco, LLC Environmental Manager XTawny Bridgeford National Mining Association Legal Counsel XDennis Turner ADEQ Environmental Engineer (Wastewater and StormwaterPrograms)XNed Hall FCX Corporate Office Manager Water Quality Programs X XMarcus Middleton FCX Bagdad Environmental Services Manager XNick Martin FCX Bagdad Environmental Engineer XBrad Dingee FCX Bagdad Chief Environmental Engineer XMark Schumaker FCX Bagdad Senior Environmental Engineer XBrent Fletcher FCX Morenci Environmental Services Manager XJeff Campbell FCX Morenci Chief Environmental Engineer XWesley Word FCX Morenci Senior Environmental Engineer XOECA – Office of Enforcement and Compliance Assurance.Appendix B

BAGDAD GENERAL SITE MAPS t o r m w a te r B a s i nInterior Pit Basin

N P D E S B a s i n N o n - D i s c h a r g i n g B a s i n B a s i n

Mammoth Coo

rs La

ke Ba

sinMineshopButte CreekOverburdenCopper CreekExterior Bagdad Basin P LS B asi n Me s a Ba s i n

S t orm w a ter Ba sin W e st

M ulhol land Tailin gs

E x i s t i n g C r e s t L i n e Mammoth Ta ilings Basin _ _ _ _ _ _ _ _ _ _ _ _

_ _ _ _ B asi

n

O

ver bu

r d

enMineshop

O ve r b

u r d

e n

C opper C

r eek

B a sin

E x i s t i n g C r e s t L i n e _ _ _ _ _ _ _MillSX/EWPLS PondMine ShopCoors LakeTucker PondMammoth WashTire StorageBoulder CreekBoulder CreekNew Alum SumpBasalt QuarryMill ReagentsMulholland WashStrong PLS PondCrusher Pit StopMineral Creek SumpNative Borrow AreaNative Borrow AreaNative Borrow AreaNative Borrow AreaNative Borrow AreaNiagara Dump LeachPlan IX Dump LeachConcentrate loadingMammoth Tailings DamSouth Waste Rock DumpKimberly Leach FacilityMulholland Tailings DamMine Shop Lay-down YardCopper Creek Flood BasinMineral Creek Dump LeachButte Creek Lay-down YardIntermediate Ore StockpileMammoth Seepage Return PondCopper Creek Leach FacilityKimberley South Fuel StationUpper Niagara Pond (Garfield)Love's Lake (Storm Water 1800)Mulholland Seepage Return PondSmall vehicle maintenance areaCrystal Mountain Leach Facility001003006

B a s inRaffinate PondShovel Assembly290000.000000293000.000000296000.000000299000.000000302000.000000

3826000 .000000 3826000 .000000

3827000 .000000 3827000 .000000

3828000 .000000 3828000 .000000

3829000 .000000 3829000 .000000

3830000 .000000 3830000 .000000

3831000 .000000 3831000 .000000

3832000 .000000 3832000 .000000

3833000 .000000 3833000 .00000000.510.25MilesLegendDischarge PointsNPDESStormwaterNPDES Sampling pointBMPsCulvertsOverland Stormwater FlowUnderground Stormwater FlowStreamsFacilitiesMine BoundaryNative borrow/fill areasBasinsNON-DISCHARGINGNPDESSTORMWATER BASINWasterock/ OverburdenMSGP 2008 -Site MapDate:Revision No:Figure:Approved:Bagdad Mine ArizonaSRK Job No. : 69538.0106/03/2009TB1BUpdated by: NMAppendix C

MORENCI GENERAL SITE MAPAppendix D

SAFFORD GENERAL SITE MAP