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 7-05 
i

CONTENTS 

Page 

1.0 SITES VISITED AND DATES....................................................................................... 6 

2.0 ATTENDEES.............................................................................................................. 6 

3.0 BACKGROUND AND OBJECTIVES.............................................................................. 6 

4.0 COPPER MINING AND BENEFICIATION...................................................................... 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 BAGDAD MINE AND CONCENTRATOR OPERATIONS ............................................... 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 MORENCI MINE OPERATIONS ................................................................................ 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 Electrowinning (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 SAFFORD MINE OPERATIONS ................................................................................. 50 

7.1 Mine Site................................................................................................... 50 
CONTENTS (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 REFERENCES .......................................................................................................... 58 

Appendix A: LIST OF SITE VISIT PARTICIPANTS 

Appendix B: BAGDAD GENERAL SITE MAP 

Appendix C: MORENCI GENERAL SITE MAP 

Appendix D: SAFFORD SITE MAP 
iii

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....................................................................................43 
iv

LIST OF FIGURES 

Page 

Figure 4-1. Overview of the Bagdad Mine Open Pit.......................................................................8 

Figure 4-2. Simplified Schematic of Common 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 Grinding 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 Stormwater Evaporation Pond ....................................................................30 

Figure 6-1. The Coronado Open Pit...............................................................................................32 

Figure 6-2. Stormwater Overflow from Leach Stockpile 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 Plated with Copper in EW Cell ...............................................38 

Figure 6-8. Steel Cathode Plated 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 Storm Water Ditch by Roadway..............................................................45 
LIST OF FIGURES (Continued) 

Page 

v

Figure 6-14. Lower Chase Creek Dam ..........................................................................................46 

Figure 6-15. Evaporation Basin Upgradient of Lower Chase Creek Dam ....................................46 

Figure 6-16. North Gold Gulch Dam.............................................................................................47 

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...........................................................................................50 

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 .......................................................................................57 
6 

1.0 SITES VISITED AND DATES

 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 wastewater and stormwater management techniques. EPA also 

visited FCX’s nonferrous metals manufacturing facility: the Miami Smelter on September 16, 

2009. Information from that site visit has not been included as this report focuses on ore mining 

and dressing operations (as defined at 40 CFR Part 440), not nonferrous metals manufacturing. 

2.0 ATTENDEES

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

3.0 BACKGROUND AND OBJECTIVES

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 water 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 guidelines 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 practices. 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 some type of permit coverage. 

 When required based on potential to discharge, FCX facilities have obtained and 

maintained permit coverage for these relatively small 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 subject to the effluent limitations at 40 CFR. Part 440, Subpart J, as 

well as the more stringent effluent limits pursuant to the state’s water quality standards. FCX’s 

Bagdad facility also maintains MSGP permit coverage for certain periphery areas at the site, 

which again requires compliance with the same state water quality standards. FCX’s Morenci 

and Safford facilities have obtained and maintained similar permit coverage, where required. 

 It is the general opinion of FCX that existing discharge permit requirements, 

including the existing effluent limitations guidelines in 40 C.F.R. Part 440, are more than 

sufficient to protect surface waters for potential discharges from the relatively small areas at each 

mine that have the potential to discharge as a result of storm events. 

4.0 COPPER MINING AND BENEFICIATION

 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 traditional 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 detonate one shot to blast a large volume 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 model 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 dominant feature across the walls 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 predominant technique used to extract 

copper ores in the US, extraction may also occur via underground 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 historic 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 used for pit backfilling. 

4.4 Ore Processing

 From extraction to copper sale, ore goes through many beneficiation and mineral 

processing operations to produce pure copper1

. 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 hydrometallurgical methods (used for oxide ores and 

some sulfide ores) or pyrometallurgical methods (used for sulfide ores only). The terms “sulfide” 

and “oxide” are used here to be consistent with industry terminology; these are not geological 

definitions. For the purposes of this report “sulfide” refers to a rock containing metal sulfide 

compounds (e.g., Cu2SO4), whereas “oxide” refers to a rock containing other metal compounds 

(e.g., CuO, CuCO3). Hydrometallurgical methods recover copper from the ore using aqueous 

chemistry that generally involves the following steps: leaching, solution extraction2

, and 

 

1

 For regulatory purposes, EPA distinguishes between the following three groups of activities: (1) Extraction:

Initial removal of ore from the earth, commonly 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 material (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 methods recover copper from the ore by thermally 

treating the ore to physically and chemically transform the materials in the following steps: 

grinding, flotation, smelting, and electrorefining processes. Figure 4-2 presents a general 

schematic summarizing the major processes in each of these methods. The following subsections 

describe these processes in greater detail. 

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

4.4.1 Hydrometallurgical Processing 

 Hydrometallurgical processing generally 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 Copper

Pyrometallurigical 

Method

Sulfide Ore

Grinding

Flotation

Smelting

Grade-A Copper to Sale

Concentrate

Tailings 

Impoundment

Gangue Slurry

Electrorefining

1 Process is optional (see Section 4.4.1.1).

Blister copper: 99 percent pure copper containing some impurities from the smelting process.

Gangue slurry: Non-economic minerals and host rock separated from copper-rich sediments.

PLS: Pregnant leach solution (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 extracted 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 leached uncrushed (referred 

to as run-of-mine). Crushing the mined material increases the surface area making more of the 

rock accessible to the sulfuric acid used in leaching. Ore is generally 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 unlined3. The leach solution is generally added to the stockpile using 

large sprinklers or drip irrigation equipment. After the leach solution runs through the mined 

material it is called pregnant leach solution (PLS) 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 acres and be several hundred feet high. 

Typical closure requirements for leach stockpiles 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 solvent 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 allow the organic phase (solvent solution) and aqueous phase 

(PLS) to separate. The organic phase containing the copper floats 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, the 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. After extraction, sulfuric acid is mixed into the 

solution in a mixing tank to form raffinate. The additional sulfuric acid is added to bring the acid 

strength to between 8-10 g/L prior to recycling 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 than 1). The copper moves from the organic phase 

back to the aqueous phase (the electrolyte), and the mixture moves on to another settling tank to 

separate. From the settling tank, the mixture flows to a stripper where the organic phase floats on 

top of the aqueous phase (copper-rich electrolyte). The aqueous 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 while the electrolyte now containing copper is further 

processed in the EW plant. 

Raffinate 

Pregnant Leach 

Solution 

Barren Organic 

Copper-Laden 

Organic 

Copper-Laden 

Electrolyte 

Barren Electrolyte 

Electrowinning 

Cell 

Mix Tank 

& Extractor 

Mix Tank 

& Stripper 

Heap 

Leach 
13 

 Due to potential air emissions of volatile 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 containing the copper from the SX plant is sent to the 

electrowinning (EW) plant and is placed in a large electrowinning cell with lead anodes and steel 

cathodes. A strong voltage is applied between the 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 removed from the electrolyte in rows and a machine flexes 

them back and forth to detach the copper sheets. 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 flotation processes is generally referred to as the 

concentrator or mill. The following subsections describe these processes. This report does not 

discuss smelting or electrorefining, because these processes 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 Processing: Grinding 

 The grinding process crushes ore into a size 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 mill4

. 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 concentrator 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 alkaline flotation solution to create a 

slurry. 

2. The slurry is fed into a primary flotation 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 float to the surface, while finely ground 

host rock and non-metallic minerals (referred to as “gangue”) settle to the 

bottom of the cell. 

3. Aerators at the bottom of the flotation cell create bubbles that 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 flotation 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 are 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. Descriptions of these techniques are included 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 separates 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 disposal sites include dewatering, capping with a low-permeability soil, 

and revegetation. 
16 

5.0 BAGDAD MINE AND CONCENTRATOR OPERATIONS

 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 facility, 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 operational areas at the site. 

5.1 Mine Site

 The Bagdad Mine began as an underground mine with a set of claims established 

by a father and son team in the 1880s. In response to World War II, the mine was modernized 

from 1943 to 1947 and converted to an open-pit 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 tailings from the concentrator operations to the western areas 

of the facility where the tailings impoundments are currently located. 

 Current operations at the Bagdad Mine include the 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 footprint of approximately 5 square miles (or 220,000 

acres). Approximately 533 acres are managed by the U.S. Bureau of Land Management (BLM); 

the rest are owned by FCX. The geology of the area can be described as a typical porphyry, halocopper deposit surrounded by granitic 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 material 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 relatively less acidic than the runoff from most copper mines. Most of 

the sulfide ores are processed at the mine’s concentrator. The remaining 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 located 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, represented 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 into the ore body using a portable drill rig. The 

cores that are removed during drilling are sent off 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 equipped with a blasting cap. Work 

crews prepare multiple boreholes in this manner and detonate one shot to blast a large volume 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 model 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 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 processes 
18 

all mineralized material for copper extraction. Therefore, 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 recover 90 percent of the copper from the mined 

ore. 

5.3 Copper Recovery from Ore: Concentrator Operations 

 The concentrator operations include the following major functions: crushing and 

grinding (grinding circuit) and flotation. 

5.3.1 Grinding Circuit 

 The grinding circuit crushes ore into a size suitable for flotation via a series of 

crushers and grinders, shown in Figure 5-1. The grinding circuit steps are: 

1. Primary crusher. A primary crusher breaks the 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 autogenous5 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 mill. Ore particles between 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 hydrocyclones separate the finer material 

from the rest of the feed; the coarser 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 Circuit at the Bagdad Concentrator 

Primary 

Crusher

Stockpile Autogenous 

Mill 

3⁄4” Screen 

3⁄8” Screen 

Secondary 

Crusher

Cyclone 

Passing Fraction SAG Mill 

Passing Fraction 

Passing Fraction 

Caught 

Fraction

Caught 

Fraction

Caught 

Fraction

To 

Flotation 

Circuit 
20 

Figure 5-2. Autogenous Mill and Feed Unit 
21 

Screen Deck 

Autogenous 

and Ball Mills 

Figure 5-3. Bagdad Grinding Circuit 

5.3.2 Flotation Circuit 

 The Bagdad froth flotation circuit, shown 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 alkaline flotation solution to create a 

slurry. 

2. The slurry is fed into a primary flotation 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 float to the surface, while finely ground 

host rock and noneconomic minerals (referred to as “gangue”) settle to the 

bottom of the cell. 

3. Aerators at the bottom of the flotation cell create bubbles that 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 flotation 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 efficiency is 90 percent copper recovery. The 

concentrator employs approximately 200-280 people including maintenance workers. Copper 

concentrate contains approximately 30 percent copper and is trucked from the Bagdad Mine to 

the Miami Smelter. The Bagdad Mine is currently trying to produce molybdenum with the same 

cathode process used for copper production. Further 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 stockpile 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 Miami 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 solution (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 solution dissolves approximately 20 to 30 percent of 

the copper from the ore. Each additional pass recovers less and less copper. 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, which has been operating for about 30 years. The plant operates at 
24 

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 copper – is supplemented with additional sulfuric acid to bring the 

acid strength up to between 8-10 g/L prior to applying 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 efficiencies, but the additional costs 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 increased copper recovery. The top three costs of 

running an SXEW plant in descending order are power, labor, and organic additions. 

5.6 Tailings Impoundments

 At the Bagdad Mine, FCX stores the majority of the tailings from mining 

operations in two impoundments: the Mammoth Tailings Impoundment and the Mullholland 

Tailings Impoundment. The Mammoth Tailings Impoundment – which is approximately 4,800 

acres – is contained by the longest centerpoint tailings dam in North America6

. Tailings slurry 

from the concentrator is conveyed to the impoundments 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 center line of the tailings dam. A cyclone 

separator is connected to the header where the slurry is discharged; this cyclone separates the fine-grained material 

(e.g., clay, silt) from the coarse material (e.g., gravel, sand). 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 support. 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 freeboard7 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 constraints, there is no run-on diversion on the south side of the 

Mammoth Tailings Impoundment, and the impoundment 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 generators 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 minimize groundwater use. The Bagdad Mine pumps 

approximately 6,500 gpm from the Wikiup Wellfield and approximately 1,500 gpm from Francis 

Creek, a deep, mildly thermal artesian aquifer. 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 water is recirculated from various areas 

around the mine site (e.g., tailings impoundments, open pit) back into mine processes. Of this, 

approximately 17,500 gpm is recirculated from 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 stormwater management to minimize pumping costs. 

Recirculated water from the tailings impoundment system is used at the concentrator and other 

facilities. Mine water pumped from the open pit is used for leach operations. 

5.8 Stormwater and Process Wastewater Management

 As part of their corporate policy, FCX minimizes all discharges from their mine 

sites and attempts zero discharge by recycling stormwater and process water. The Bagdad Mine 

holds both an individual NPDES permit and a stormwater 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 are covered by the individual NPDES permit. 

5.8.1 Sources of Discharge 

 The main source of the Bagdad Mine’s waters that could potentially be discharged 

via the Bagdad Mine’s individual NPDES outfalls is tailings reclaim water. The average annual 
27 

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 pumped out of the open pit for use in the facility’s 

leach operations. For a discussion of water recycling, 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 another discharge event sometime 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 water 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 precipitation), and site personnel 

discharged 1,500 gpm in 2005 for a sustained period of time (exact length unknown) from the 

Mammoth Tailings Impoundment. 

5.8.2 BMPs Used for Stormwater Control 

 The Bagdad Mine’s stormwater runoff covered 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 and 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 stormwater control in this area is to build berms at the edge of 

the plateau on which the mine shop is located. These berms cause precipitation on the plateau to 

flow back into the mining area. The stormwater around the mine shop is conveyed to groundlevel drains which flow back to a stormwater evaporation pond. Anything that falls outside of the 

plateau is controlled by check dams and other berms built up from overburden material8

 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 unsuccessful due to the high clay content of the native 

soils. According to Bagdad Mine personnel, these 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 evaporation ponds are used as stormwater controls. 

Figure 5-7 shows a roadside stormwater evaporation pond. Stormwater 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 this reason, all impacted groundwater 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 activities upon mine closure. Tailings impoundments 

currently have 2.8:1 slopes along their sides. Upon closure, Bagdad staff 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 reclaim the impoundment in sections. Because 

the tailings at Bagdad Mine have neutral to weak acid generating potential, Bagdad Mine staff do 

not anticipate significant problems with closure of the tailings areas. 
31 

6.0 MORENCI MINE OPERATIONS

 Staff from the Morenci Mine provided a tour of the facility’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 stormwater control areas, a Solution 

Extraction and Electrowinning (SXEW) plant, and their tailings areas. 

6.1 Mine Site

 At the time of the site visit, the Morenci Mine employed approximately 1,600 

employees and 100 contractors working on-site. The total surface disturbance 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 State of Arizona. Appendix C contains an overall 

site map for the Morenci Mine. 

6.2 Mining Operations

 The Morenci Mine handles approximately 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 Coronado pit is shown in Figure 6-1. In the open 

pits, mining personnel use 4,160-volt electric shovels to excavate material and place it into one 

of 64 haul trucks. Each truck has 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 Bagdad 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 Mine are Chalcopyrite and Chalcocite. 
32 

Figure 6-1. The Coronado Open Pit 

6.3 Concentrator Operations

 When operating, the Morenci Mine concentrator is capable of processing up toto 

75,000 tons of material per day. Because 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 operating. 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 now uses decommissioned tailings thickeners 

from the concentrator facility to bio-remediate petroleum contaminated soils (PCS). 

6.4 Leach Operations 

 After being blasted and extracted 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 stockpiles to boost bacterial activity and improve copper 

recovery. The Morenci Mine sponsors 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 smelting 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 solution flows to a PLS pond (Figure 6-2). Figure 6-3 

shows the stormwater overflow from the leach operation. 

 Leach stockpiles may cover several acres and be several hundred feet 

high. Typical closure requirements for leach stockpiles 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 potentially 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, monofilament 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 Stockpile 
35 

6.5 Solution Extraction Electrowinning (SXEW) Operations

 The Morenci Mine has four solution extraction (SX) and three 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 copper from the PLS. Because the copper has a higher 

affinity for the organic chelator than for the PLS, 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 Tank 
36 

 From the mix tank, the mixture of PLS and organic additions flows to a settling 

tank, where low-energy conditions allow the organic and aqueous phases to separate. The 

organic phase containing the copper is less dense than water and floats 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 organic 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 bring the acid strength to between 8-10 g/L prior to 

recycling it back to the leach stockpiles. After mixing with acid to bring up the strength of the 

BLS, it is referred to as “raffinate.” Around 92 percent of the copper in the PLS is recovered in 

the organic phase. 

Figure 6-5. SXEW Extractor 
37 

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 mixture moves on to another settling 

tank to separate. From the settling tank, the mixture flows to a stripper where the organic phase 

floats on top of the aqueous phase (copper-rich electrolyte). 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 electrolyte 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 cathodes. 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 environmental liabilities associated with lead 

flakes. The cathodes are then placed into the electrolyte in the EW cell, and a very strong voltage 
38 

is applied between the cathodes and the anodes. This voltage causes the copper 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 shows a cathode sheet plated 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 Cell 
39 

Figure 6-8. Steel Cathode Plated with Copper from EW 

 The cathodes are removed from the electrolyte 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 applications. The Morenci Mine crimps some copper 

sheets for buyers so that they melt more easily 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 treatment plant that treats water from Lower Eagle Creek (the only 

perennial stream in the area). To prevent the stream from drying up, the Morenci Mine augments 

the creek with groundwater pumped into the stream at a well field approximately 30 miles 

upstream from the Morenci Mine. This arrangement 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 treatment plant to run the facility’s processes. 

6.7 Tailings Areas 

 Tailings from the Morenci Mine are pumped to the tailings area through rubber 

lined steel header pipes. Tailings dams are built using the upstream deposition technique – this 
41 

means that the deposition site moves inward toward the impoundment center over time. A 

hydrocyclone at the end of the header drops coarse 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 illustrates 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 pumped 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 condition 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 discharge under its individual NPDES permit 

and the stormwater MSGP (administered by the State 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 covered 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 Morenci Mine does not routinely discharge process 

wastewater or stormwater from active mining areas. The Morenci Mine is permitted to discharge 

to two outfalls (001 and 002) under the individual NPDES permit. The only NPDES discharge 

that has occurred in the past twenty years was due to an upset condition caused by an electrolyte 

spill from incorrect piping. Table 6-1 lists the 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 structure, and conveys it via pipeline 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 fraction of water from Chase Creek flows into the 

Upper Chase Creek Dam and is allowed to trickle 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 for the portion of the site located outside 

of the main mine area. Runoff from historic stockpiles and tailings are conveyed to stormwater 

retention areas (either evaporation 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 roads. Figure 6-13 shows an example of a waddle, 

which is straw wrapped in wire nets to prevent 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 retention 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 Storm 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 the tailings dams). The dam was built in the mid 

1980s and cost approximately $1.5 million. This dam provides redundant control of stormwater 

from the mine area in case the 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 cleaned 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. According to FCX staff, FCX does not anticipate that future discharges 

from this outfall will ever occur. 
46 

Figure 6-14. Lower Chase Creek Dam 

Figure 6-15. Evaporation Basin Upgradient of Lower Chase Creek Dam 
47 

 In addition to the two dams on Chase Creek, the Morenci Mine has one dam and 

three lined evaporation ponds on the south side of the mine site and one dam on the north side of 

the mine site. These structures control stormwater from non-process areas only, including runoff 

from mine roads and historic stockpiles. 

 The dam on the south side of the mine site is the North Gold Gulch Dam and the 

dam on the north side of the mine site is the Rocky Gulch Dam. Figure 6-16 shows the North 

Gold Gulch Dam. This dam has a sump on the downgradient side which returns 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 evaporation ponds on the south side of the mine 

site collect stormwater from roads and historic stockpiles. Stormwater in these ponds may 
48 

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 beneath the liner back to the system. 

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

 In addition to the various structures discussed in this section, the Morenci Mine 

maintains a system of unlined evaporation ponds to control stormwater runoff from the tailings 

dams that surround the mine’s tailings areas. Precipitation that falls outside of the tailings 

impoundment areas is controlled in unlined evaporation 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 mining area, 30 stormwater control structures (mostly 

unlined evaporation ponds) retain stormwater runoff from the 12 canyons that drain the outside 

of the tailings areas. As required by the Aquifer Protection Permit from the state of Arizona, 

these ponds are capable of retaining stormwater from a 100-year, 24-hour storm. Stormwater 

facilities are systematically numbered and inspected, 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 activities that FCX is sponsoring in Clifton, 

the Morenci Mine is currently experimenting with various tailings reclamation scenarios at test 

plots on-site (see Figure 6-19). Moisture content in the plots is measured using piezometers. 

Morenci Mine personnel track evapotranspiration processes in test plot soils via moisture content 

to attempt to determine the effectiveness of soil thickness and plant species on re-vegetation. 
50 

Figure 6-19. Reclamation Experiment 

7.0 SAFFORD MINE OPERATIONS

 Staff from the Safford Mine provided a tour of the mining and leaching operations 

at the site on September 17, 2009. The tour began 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 producing 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 September 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 with BLM for the land around the Safford Mine. 
51 

FCX now owns all land at the Safford site. Appendix 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 later development of 

the underground mine began. Since then, the Dos Pobres 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 completing a 12-year permitting process that began with 

Phelps Dodge in the 1990s, FCX began construction of the Safford Mine facilities in June 2006 

to exploit a separate ore body near the Dos Pobres 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 exchange, 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, which considered a variety of 

mitigation options and identified a number of petroglyphs likely associated with Gila River 

Community. 
52 

7.3 Mining Operations

 The Safford Mine ore is an oxide ore (leachable) with approximately 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 currently mined goes through the hydrometallurgical 

process at the Safford Mine. Copper is leached from 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 Hematites. Figure 7-2 shows copper ore at the Morenci 

Mine containing chrysocolla. Chrysocolla is readily-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 Mine 
53 

 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 are all 1⁄2 inch or less in diameter. Baghouses 

controlling air emissions from the crushing equipment are regularly cleaned, and the dust is 

recycled back into the ore. Baghouses are not needed after agglomeration, where sulfuric acid is 

added during ore crushing, because the material has been wetted. 

Figure 7-3. Safford Crush/Convey Area 
54 

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 average 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 individual NPDES permit, but chose not to renew it 

when it expired a few years ago. No historical individual permit discharges have occurred at the 

Safford Mine. 

 The Safford Mine’s stormwater retention structures are capable of containing 

runoff for multiple 100-year storms. The Safford Mine has installed liner systems for leach pads 

as suggested by Arizona’s Best Available Demonstrated Control Technology (BADCT) mining 

document. The Safford Mine also uses process ponds 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 will 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 directly back to the pad. The normal emission rate of sulfuric acid 

(H2SO4) on the surface of the heap leach pad is approximately 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 solution (PLS). PLS from the heap leach pad enters 

into a main header for collection where it feeds into the PLS tank. Figure 7-5 shows the PLS 

tank. If necessary, PLS will go to the PLS overflow pond or even on to the stormwater pond, but 

the ponds are rarely used. Figure 7-6 shows the PLS overflow pond. There is 390 acre-feet of 

storage for PLS in the PLS pond. All piping is in secondary containment, to prevent spills in the 

event of a pipe break. 

Figure 7-5. Safford Heap Leach PLS Tank 
56 

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. Figure 7-7 and Figure 7-8 show the 

solution extractor and electrowinning cell at the SXEW plant. The organic addition at the Safford 

Mine contains 90 percent diluent and 10 percent reagent. The SXEW contains three extractors to 

separate copper-rich organic solution from the leach solution and one stripper to separate copperrich electrolyte from the organic solution. Before the barren leach solution (BLS) from the 

SXEW plant is recycled back to the heap leach pad, sulfuric acid is added to bring the acid 

strength up to 5 g/L. The reacidified BLS is now called raffinate. A stainless steel, pond-shaped 

tank at the bottom of the EW plant catches miscellaneous process wastewater and feeds it back to 

the raffinate mix tank. To control the concentration of unwanted byproducts (e.g., metals other 

than copper) in the SXEW circuits, barren electrolyte is periodically bled from the EW cells to 

the raffinate mix tank. This takes the byproducts out of the strong electrolyte circuit and puts 

them into the leach circuit where they will have a smaller effect on copper recovery. 
57 

Figure 7-7. Safford Organic Solvent Extractor 

Figure 7-8. Safford Electrowinning Cell 
58 

8.0 REFERENCES

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. AZ0022705. (Morenci Mine) April, 2005. 

3. FCX, 2009. Stormwater Pollution Prevention Plan for the Bagdad Mine. August, 

2009. 
Appendix A 

LIST OF SITE VISIT PARTICIPANTS
A-1 

Table A-1. List of Site Visit Participants 

Name Organization Title 

Bagdad Site 

Visit 

Mo

Tom Born U.S. EPA Office of Water Ore Mining Task Lead X Chris Krejci ERG (Contractor to EPA) Environmental Engineer X Tom Ripp U.S. EPA OECA OECA Staff Lead Dan Chadwick U.S. EPA OECA Geologist Emily Chow U.S. EPA OECA Chemical Engineer Jerry Roose FCX Corporate Office Environmental Services Director – Domestic Operations Bruce D. Taylor FCX Safford Chief Environmental Engineer John Korolsky FCX Safford Senior Environmental Engineer Jamie Davis FCX Safford General Manager Mike Windsor FCX Safford Environmental Engineer Brian Ford FCX Safford Senior Environmental Engineer Krishna Parameswaran Asarco, LLC Environmental Manager Tawny Bridgeford National Mining Association Legal Counsel Dennis Turner ADEQ Environmental Engineer (Wastewater and Stormwater 

Programs) 

 

Ned Hall FCX Corporate Office Manager Water Quality Programs X Marcus Middleton FCX Bagdad Environmental Services Manager X Nick Martin FCX Bagdad Environmental Engineer X Brad Dingee FCX Bagdad Chief Environmental Engineer X Mark Schumaker FCX Bagdad Senior Environmental Engineer X Brent Fletcher FCX Morenci Environmental Services Manager Jeff Campbell FCX Morenci Chief Environmental Engineer Wesley Word FCX Morenci Senior Environmental Engineer 

OECA – Office of Enforcement and Compliance Assurance. 
Appendix B 

BAGDAD GENERAL SITE MAP 










 



  







Interior Pit Basin

NPDES Basin

Non-D ischarging Basin

Basin

Mammoth

Mineshop

B

O

Copper Creek

Exterior Bagdad Basin

PLS Basin

S Mesa Basin tormwater

Basin West

Mulholland Tailings

E

x

i

s

t

i

n

g

C

rest Line

Mammoth Tailings Basin

_______

_____

____

Overburden

Mineshop

Overburden

Copper Creek

Basin

Existing

Crest Line

_______

Mill

SX/EW

PLS Pond

Mine Shop

Tucker Pond

Mammoth Wash

Tire Storage

Boulder Creek

Boulder Creek

New Alum Sump

Basalt Quarry

Mill Reagents

Mulholland Wash

Strong PLS Pond

Crusher Pit Stop

Mineral Creek Sump Native Borrow Area

Native Borrow Area

Native Borrow Area

Native Borrow Area

Native Borrow Area

Niagara Dump Leach

Plan IX Dump Leach

Concentrate loading

Mammoth Tailings Dam

Kimberly Leach Facility

Mulholland Tailings Dam

Mine Shop Lay-down Yard

Copper Creek Flood Basin

Mineral Creek Dump Leach

Butte Creek Lay-down Yard

Intermediate Ore Stockpile

Mammoth Seepage Return Pond

Copper Creek Leach Facility

Kimberley South Fuel St

Upper Niagara Pond (Garfield)

Love's Lake (Storm Water 1800)

Mulholland Seepage Return Pond

Small vehicle maintenance areaCrystal Mountain Leach Facility

001

003

006

Basin

Raffinate Pond

290000.000000 293000.000000 296000.000000 

3826000

.000000

3827000

.000000

3828000

.000000

3829000

.000000

3830000

.000000

3831000

.000000

3832000

.000000

3833000

.000000

 0 0.25 0.5 1Miles

SRK Job No. : 69538.01
Appendix C 

MORENCI GENERAL SITE MAP

Appendix D 

SAFFORD GENERAL SITE MAP