BHP Billiton

Southwestern Copper

Florence Project

Well Field Reclamation Test

And

Well Field Metallurgical Balances

By: John Kline

September 12, 2001

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Introduction

The purpose of this report is to discuss the results of the Florence Project Copper In Situ

Field Reclamation Test and the metallurgical balances associated with that test. The data

presented here is for the period October 31, 1997 through June 30, 2001. The test was

still in progress at the time this report was written.

Background of the Test

In 1997, twenty test wells were drilled at the Florence Project Copper In Situ test site.

Figure 1 in the attached Brown and Caldwell report 1 shows the layout of the wells. In

general, the injection and production wells were spaced on 70-foot centers. Wells CH1

and CH2 were fitted with discrete interval samplers and used to measure geochemical

changes in the in situ leach solutions. Well OWB2 was drilled and screened as an

observation well in the Upper Basin Fill (UBFU) unit and was sited about 70 feet directly

down-gradient of the test system. OWB2 was monitored routinely and indicated no

migration of leach solution into the UBFU.

Many of the wells were fitted with conductivity probes spaced every 3 meters along the

casing. Test work conducted by Steamtech Inc. of California showed that the solutions

migrated up into the lower basis fill (LBFU) unit about 22 feet. The hydrologic model

(Modflow) indicated the solution would move upward about 25 feet but not enter the

upper basin fill unit. A fine-grained unit called the Middle fine grain unit (MFGU)

separates the two units. The MFGU was hydrological tested in numerous location and

found to be an aquitard.

Furthermore, as part of the permit requirements, annular conductivity probes were built

into the well and attached to the well casing at the junction of the LBFU and MFGU.

Routine measurements since October 1997 has shown that no solutions have migrated

upward along the casing to these probes, nor is there any indication that conductivity of

the pore water in the casing cement increased. The cement thickness was less than 2

inches between the casing and hole walls.

San Manuel raffinate (SMOR) was trucked into the test site and placed in one of three

storage tanks at the Pilot Plant Tank Farm. The SMOR was diluted with groundwater

taken from Well WW4 (a.k.a. PW4) which was located about 1000 feet southeast of the

evaporation pond. This solution was blended to simulate mature raffinate from the actual

proposed Florence SX/EW Plant operation. The blend was designed by the Project

Geochemist. Sulfuric acid (98%) was trucked in from the San Manuel Acid Plant and

placed in the Tank Farm acid storage tank. The acid was added as needed to bring the pH

of the synthetic injectate to the wells to about pH 1.7.

The acid and raffinate trucks were weighed on the certified scales at San Manuel and the

tare weights used to calculate received weights. The solutions were analyzed at the San

1 “Post-Pilot Test Water Screening Report, BHP Billiton Florence Operations,” Brown and Caldwell,

September 5, 2001

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Manuel Metallurgical Laboratory and the analyses recorded for the metallurgical

balances discussed later in this report. The truck weights are listed in Appendix I.

Solutions were injected into Injector Wells BHP6, BHP7, BHP8, and BHP9 at the design

tenor from November 1, 1997 until February 8, 1998 when the acid addition was ceased

as a result of a decision to terminate the copper recovery test and begin the reclamation

test. The SMOR inventory was drawn down and the SMOR tanks emptied.

Water injection into BHP Injectors 6,7,8, and 9 was initiated on April 13, 1998 and

continued until May 12, 1998. On May 13, 1998, fluids from the evaporation pond were

routed to the PLS tank and added through Well BHP1. Injectors BHP 6,7,8, and 9 were

converted to production wells on that same date and a bromine injection and recovery test

began. The results of this bromine tracer test are discussed elsewhere in the draft Field

Test Report. Evaporation Pond water was injected into BHP1 through July 20, 1998.

On July 21, 1998 water from Well WW4 was routed through the PLS tank and into BHP1

in order to begin wash out of the in situ system. Water injection continued until

December 17, 1998. All wells were variously used as production wells from that time

forward. No injection occurred after December 17, 1998. Appendix II gives the specific

cycle and use of each of the test wells during the test and reclamation period. Appendix

III contains the individual well flow history.

Sampling of the wells and flows was done regularly and is further discussed in detail later

in this report.

Restoration Requirements

The two major permits that are application to this test are the Underground Injection

Control Permit (UIC) AZ396000001, which is regulated by the U.S Environmental

Protection Agency and the Aquifer Protection Permit (APP) #101704, which is regulated

by the Arizona Department of Environmental Quality. The permits are similar in their

requirements for restoration with minor differences. These are summarized below:

UIC Permit

UIC is less stringent than the APP and requires that the mine block be restored to either

the primary maximum contaminant levels (MCL’s) or pre-mining background.

APP Permit

APP requires that the restoration continue until the Level II parameters specified in Part

IV Table III.C. of the permit are met. These levels are referred to as the Arizona Water

Quality Standards (AWQS).

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Results Thus far

Brown and Caldwell sampled the test wells on September 20 and 21, 2000 and again on

June 4 and 5, 2001. The data and discussion by Brown and Caldwell is discussed fully in

the aforementioned report2. All samples were taken by Brown and Caldwell and the

samples were subsequently submitted to a certified laboratory for analyses by EPA

authorized methods and under a chain of custody procedure.

In summary, the results so far are:

Thirteen of the 19 wells sampled meet the secondary drinking water standard for pH.

The others fall between pH 3.83 and pH 5.81.

No process related organic was found and all of the results are below the AWQS.

Nickel was exceeded only in chemical monitor well CH2 by a small amount.

All other wells meet the AWQS for the inorganic.

Nitrate in the UBFU ranges in the area from 7-40 PPM; however, nitrates were

measured at near non-detect levels in the in situ test zone. This fact is a strong

indication that no downward migration of solution from the upper basin fill to the

oxide zone during the test occurred.

Seven of the 19 wells sampled exceeded the AWQS for Gross Alpha

Sulfate has decreased in the test system to near background levels in all of the test

wells except the original injectors BHP 6,7,8, and 9.

Sulfate in BHP 6,7,8, and 9 was measured at concentration ranging from 280-420

PPM in June 2001 and had decreased from the original inject 10,000 PPM. Sulfate

continues to decline as a result of slow elution of gypsum near the injector well bores.

Sulfate balances around the pond and well field indicate recovery of sulfate at >88

percent.

No loss of leach solution from the test system was measured based upon:

well field analyses of the observation and barrier wells

conductivity measurements from the down-hole devices installed by Steamtech

Inc.

routine measurement of the annular conductivity probes

sulfate and chloride balances.

Chemical Reactivity of the System

Acid injection occurred over a 105-day period and resulted in an acid consumption of 1.1

pounds of acid per ton of ore. Laboratory test work indicated peak copper tenors would

be expected when consumption reached the 3-6 pound per ton range with ultimate

expected acid consumption of 17 pounds acid per ton ore at the planned copper recovery.

The preemptive termination of the test greatly contributed to low copper results and

impacted both the recovery of copper and the ionic availability to the produced leach

solutions. The impact on these ions is discussed below:

2 ibid

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Calcium

Calcium exists in several of the minerals in the system and its primary reactive mineral is

calcite. Calcite decomposes to gypsum in the presence of an acid sulfate solution.

Calcite concentration of 0.05-0.20 percent are found in the ore zone, while calcite can

reach values of 3.1 percent in the lower basin fill. The test results have definitively

shown solutions moving through both the ore and LBFU zones. Gypsum solubility is

about 2.5 gram per liter, so loss of sulfate to gypsum formation occurred as the ore and

lower basin fill reacted with the acidic solutions and gypsum saturation was reached.

Gypsum does resolubilize and most sulfate (>88 %) has eluted back out over the

reclamation test period as will be shown later in this report.

Table 1.

Carbon Dioxide Content of the Ore and LBFU

Sample identity Location Carbon dioxide, %

BHP1 344'-357' LBFU 3.1

BHP1 364.3'-750.7' Ore zone 0.15

BHP6 340'-360' LBFU 2.9

BHP6 360'775' Ore Zone 0.21

BHP8 340'-370' LBFU 1.55

BHP8 370'-770' Ore Zone 0.20

CH2G 420'-520' Upper Ore Zone 0.20

CH2B 560'-660' Middle Ore Zone 0.15

CH2R 770'-775' Lower Ore Zone 0.15

The high calcite content in the LBFU attenuated any significant movement of the metal

ions in the injectate solution especially due to the short term of the injection period in this

test.

pH

Hydrogen ion was introduced in the SMOR and sulfuric acid. Only wells BHP 6,7,8,and

9 has pH values in the 3.8-4 range. The other wells are neutral at pH 6.5-8.

Solution from BHP 6 taken in June 2001 and was mixed with well water taken from

BHP10. One part BHP6 at pH 4 was mixed with 3 parts BHP10 and the resultant pH

became 6.9. The low ionic strength of the in situ test zone tends to remove any

significant buffering, so neutralization occurs quickly with ambient groundwater.

The low pH in the four injectors may be due to several causes. These are:

Hydrogen ion release may be occurring as gypsum dissolution opens blocked

pathways and release small packets of leach solution.

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Hydrogen ion may be released as a result of cation exchange with the clay sites that

were altered during leaching.

There may be release as the bisulfate gives up its one hydrogen ion as the bisulfate

shifts chemically to sulfate.

In any case the total dissolved solids in the well field is approaching background

condition prior to the test. The cleaner the water becomes, the more influence any

released hydrogen ion will have on the pH.

Magnesium

Magnesium is generally considered to be a conservative ion in leach solution, when those

the pH stays in the1.5-2.5 pH range. In this test, magnesium suffered some lose in part

as the leach solutions were neutralized to pH > 8 in the ore zone and lower basin fill

areas. Precipitation of magnesium as Epsomite is believed to have occurred.

A second loss of magnesium occurred as the Pregnant Leach Solution (PLS) was pumped

into the evaporation pond. These solutions were neutralized by the additions of a 50

percent sodium hydroxide solution. The pH was difficult to control automatically due to

the design of the caustic injection system, so the pH normally averaged in the 8-10 range

during the times when caustic was added. The pond was maintained at pH 6- 7 by

turning the caustic pump on and off. The magnesium was measured in the PLS over the

life of the test and 77,943 pounds were placed in the pond via the PLS. The most recent

magnesium analysis of the pond sampled on June 5, 2001 indicates a concentration of

330 PPM (42,293 pounds Mg) so some magnesium (35,650 pounds) is unaccounted for

in the pond and has precipitated probably as Epsomite. Epsomite is insoluble.

Iron, Copper, Aluminum

These ions are soluble at lower pH levels, but not at pH 7. The PLS was measured and

over the life of the test. The following mass of these ions was sent to the pond

Table 2.

Mass to the Evaporation Pond for Iron, Copper and Aluminum

Ion Quantity to Pond, LBS

Iron 101

Copper 42,917

Aluminum 19,348

The strengths of these ions measured in the pond in June 2001 and all tenors were

measured at than 0.1 PPM, so it is presumed that the these ions precipitated as sulfates.

Chloride

Chloride is un-reactive in this system and was introduced from the synthetic raffinate

made on-site (160 PPM), infiltration water (140 PPM), or from water Well WW4 (88

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PPM). Chloride was measured periodically in the leach system and in the evaporation

pond. The most recent measurement of the pond taken in June 2001 was 690 PPM.

Chloride, because of its conservative nature, will be used as a reconciliation ion in the

material balance section of this report.

Sulfate

Sulfate was introduced through several sources during the leaching phase and

reclamation phase of the test. These sources are shown below in Table 3.

Table 3.

Source of Sulfate Ions

Source Concentration of

Sulfate , PPM

How introduced Quantity, LBS

Infiltration groundwater 61 As a result of over

pumping in the leach

field (79,966,160

gallons)

40,706

Sulfuric acid 98.2 percent Truck shipments (7)

from San Manuel and

injected via metering

pump

351,257

Raffinate 80,500 Truck shipments (237)

from San Manuel and

injected via metering

pump

869,400

Groundwater 88 Sourced from Well

WW4 and added three

ways:

Directly to the pond

to hold down the

liner during

construction

(15,790,530

gallons)

Injected directly

into BHP1

(4,682,840 gallons)

Blended with

SMOR and acid and

added as injectate

(28,8343,779)

11,596-initial fill to

hold liner

3,439-directly into

BHP1

21,175-as injectate

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Calibration and Measurement of Flow and Quantities

Any reconciliation must include the volumetric component for an injection recovery

system. Each individual well was fitted with an Endress-Hauser Mag Flow Meter sized

to be able to read at an accuracy rate at 0.1 percent mid-scale. The meters were sized

prior to installation to attain this accuracy based upon the design flows. The meters were

field checked and calibrated by an instrumentation technician from Sturgeon Electric

Company. Mag flow meters were also installed on the PLS and Injectate flow lines.

Sturgeon also calibrated these upon installation and weekly by the pilot plant operators.

The operators would do draw down tests in the pilot plant storage tanks to confirm the

PLS and Injectate flow meter readings. Occasionally, the well head flows meters would

fail and the operator would check the flow via bucket and stopwatch. Similarly, a mag

flow meter was attached to the Well WW4 line and calibrated both electronically and by

rising levels in the fresh water storage tanks. Flows were gathered electronically through

the SCADA system and checked manually for correct input. Some adjustments were

made if errors were found, however, overall the flows are felt to be within a few percent

of accurate.

As noted earlier, truck weights for SMOR and sulfuric acid were determined via the San

Manuel calibrated truck scale. Trucks were tare weighed prior to filling at San Manuel

and weighed after filling. Some slight error is possible due to differences in truck fuel,

but for this exercise, weights are assumed to be accurate.

The evaporation pond was surveyed by Marvin Davis and Associates, a contracted

surveyor, who subsequently issued a certified as-built on the pond. He also calculated the

volume of the pond incrementally by elevation in reference to mean sea level. The

survey was checked by Physical Resource Enterprise Inc of Tucson.

The San Manuel Metallurgical Laboratory initially conducted assays on the SMOR and

in-situ leach solutions. Laboratory quality checks were conducted at Skyline (now

known as ACTLABS) Laboratory, Nel Laboratories, and others. It was decided to use

ACTLABS as the third party laboratory and re-run the San Manuel Metallurgical

Laboratory results. Some of the analyses used in this report are from historical San

Manuel Oxide records and consequently were source from the San Manuel Laboratory.

The samples taken by Brown and Caldwell were all sent to Nel Laboratories and as such

were run using EPA approved methods. The analyses are certified by the laboratory.

These analyses are acceptable for submission to EPA as they underwent third party

sampling, chain-of-custody and analysis by an EPA certified laboratory. When

duplicates for some ions were sent to both ACTLABS and NEL, they results matched

within normal limits.

Effect of Rain Fall and Evaporation Pond System Losses

Rainfall was recorded for the life of the test. Rainfalls in the subject period were 2.52,

9.71, 7.49, 6.08, and 5.79 inches for calendar years 1997,1998,1999, 2000, and 2001

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respectively. The surface area of the pond was known at the time of the rainfall, so total

rainfall to the pond was estimated at 6,990,310 gallons. This report assumes that the

rainfall contributed no sulfate or chloride.

The evaporation pond was fitted with four spray lines fitted with high volume

evaporation Senniger Evaporation Spray heads. Some windbourne losses may have

occurred; however, they are felt to present minor impacts on this material balance

analysis.

Caustic Additions

A 50 percent sodium hydroxide solution was purchased from Great Western Chemical

Company. Eight truckloads were off-loaded into the pilot plant storage tank and of this

amount 363,566 pounds (source weigh tickets) were added to the evaporation pond as

neutralizing agent for the PLS. Great Western issued certified analysis for chloride on

these loads and the average was 0.925 percent. Sulfate was determined to be negligible.

Metallurgical Balances

Sulfate is still being recovered, so this report will cover the time period October 31, 1997

through June 30, 2001. The evaporation pond is a dual lined pond with a leak collection

system that is checked weekly. No leakage to the inner liner sump has occurred to date.

Three system balance checks will be discussed here. These are described below:

Chloride Balance for Volume to Pond

Since chloride is non-reactive and was measured throughout the test albeit sporadically,

one check can be done for flow into the evaporation pond. The PLS averaged 156 PPM

for the period up through day 163 of the test. Chloride added via caustic was 3,359

pounds. A single analysis was run on the pond in June and the solution was found to 690

PPM. There were 17,910,900 gallons in the pond at the time. The chloride quantities and

balance is shown in Appendix IV. The chloride mass sent to the pond is shown in Table

4 below:

Table 4.

Evaporation Pond Chloride Balance

Chloride source Comments Chloride, LBS Subtotal PLS to Pond From Excel flow sheet 118,337

Initial WW4 Water to

pond to hold down liner

Calibrated pond

measurement

11,596

Caustic addition From truck weight and

certified analyses

3,359

Rainfall Estimated 0 133,292

As analyzed June 5,

2001

690 PPM Cl in

17,910,900 gallons

103,132 103,132

Accountability, % 77.4

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Many of the chloride quantities were estimated based upon periodic analyses. Although

the 77 percent accountability is poor, it maybe due to assay error on the final pond assay

as the volume is probably the most correct estimate.

Sulfate Balance around the Well Field

Sulfuric acid from San Manuel Acid Plant was mixed with the San Manuel Raffinate,

water from Well WW4, and intermingled with groundwater infiltration from the well

field. Appendix V contains the sulfate concentrations, which were applied against the

flows as shown in Appendix III. Sulfate was taken from the pond during the time pond

solution was injected into BHP1 during the bromine recovery test. The net balance

around the well indicates a total positive sulfate balance to the pond of 1,134,805 ponds.

The material balance is shown in the following table:

Table 5

Sulfate Balance

Source Quantity, pounds San Manuel Raffinate 869,400

Sulfuric Acid 351,257

Groundwater from the infiltration 40,706

WW4 injected directly into BHP1 during the

bromine test

3,439

WW4 added to acid and San Manuel raffinate as

injectate make up water

21,175

Total to the system 1,286,077

Appendix III net to evaporation pond 1,134,077

Accountability, % 88.2

Presently, the sulfate at all of the in situ wells is at near background except BHP 6,7,8,

and 9, which were the original injector wells. Well BHP1 is in the center of the system

and is also at background. Calcium is also higher than background in these four injector

whereas the calcium is at background in the surrounding well and near background in

BHP 1. The 88.2 percent accountability is in part due to the fact that gypsum is still

dissolving slowly from the system in the zone around each of the injectors. The balance

may never all come out of the system as sulfate may have precipitated in part as Epsomite

where the leach solutions were either neutralized to about pH 8. This most likely

occurred in the LBFU primarily and to some extent in the oxide leach zone.

A second balance may be calculated from the June 5, 2001 analysis in the pond and some

assumptions around precipitation. The evaporation pond peaked in storage volume on

January 13, 1999 with 34, 703, 405 gallons with calcium and sulfate concentrations of

575 PPM and 2,850 PPM respectively. Evaporation from the pond caused the volume to

decrease to its June 5, 2001 volume of 17,900,109 gallons. Since the solutions were

saturated in gypsum at peak and current levels, it is assumed for this exercise that the

gypsum precipitated out as the volume decreased and concentrations increased.

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Likewise as noted earlier in this report, quantities of iron, aluminum, copper, and

magnesium were sent to the pond and are not now in solution due to pH adjustments or

precipitation or magnesium precipitation as Epsomite. The following table shows the

material balance around the pond solutions.

Table 6

Sulfate balance around the Evaporation Pond

Balance ion Description Equivalent ponds sulfate Sulfate in solution (June 30,

2001)

Pond analysis indicated sulfate in

solution at 4.1 g/l and a pond

volume of 17,900,109 gallons

612,443

Sulfate precipitated as gypsum as

a result of pond volume

reduction

Pond volume decreased from

34,703,405 gallons on Jan. 13,

1999 to 17,900,109 gallons on

June 30, 2001 (assumes 1.8 g/l

sulfate)

252,402

Sulfate precipitated due to iron

precipitation

101 pound of iron sent to pond

with June 30, assay <0.1 PPM.

All iron assumed to have

precipitated as ferrous sulfate

174

Sulfate precipitated due to

aluminum precipitation

19,348 pounds of Aluminum sent

to pond with June 30, assay <0.1

PPM. All aluminum assumed to

have precipitated as aluminum

sulfate

103,266

Sulfate precipitated due to copper

precipitation

42,917 pounds of copper sent to

pond with June 30, assay <1

PPM. All copper assumed to have

precipitated as copper sulfate

64,842

Sulfate precipitated due to

magnesium precipitation

77,943 pounds magnesium were

sent to the pond and on June 30,

the pond assay were recorded at

330 PPM. This means 35,650

pounds is unaccounted for and is

presumed to have precipitated as

Epsomite

194,338

Estimated total in pond 1,162,623

Sulfate to pond From Appendix V 1,134,805

Sulfate in water to hold down the

pond liner

15,790,531 gallons of WW-4 well

water added to pond to hold down

the liner.

11,596

Net to the pond Hold down water plus sulfate to

pond

1,146,401

Accountability, % 98.6

The two balance methods for sulfate agree reasonably well, so one can conclude that at

least 88 percent of the sulfate injected has been recovered. The balance of the sulfate as

noted earlier is still eluting or will never report to the pond as it was lost to the ore zone

or lower basin fill as insoluble aluminum, iron, magnesium, or copper sulfate salts.

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Impact of the Test Configuration on Time and Cost

Impact of the Test Design

The test zone was designed as a five spot surrounded by barrier wells. In actual full-scale

production operations, each five spot would be bounded by other five spots, so the

dispersion that occurred to some extent in this test would not occur in a larger system.

Consequently, the wash out of leach solutions would occur more efficiently. The wash

out of sulfate as gypsum would still be dependent on the solubility of gypsum. The

present economic model assumes a two-year reclamation period, and certainly from the

analysis of this test, all of the leach solution metal ions could be removed to an

acceptable level in that time.

Impact of pH on Reclamation

The long term pH issues and sulfate wash-out need to be addressed as separate but

important issues. The pH will, as it did in this test, tend to buffer itself to around 4. The

acceptable water quality standard is 6-8. Laboratory test results show that mixing with

bicarbonate bearing groundwater will cause the pH to increase to acceptable levels. In

addition, the permits allow injection of neutralizing agents such as sodium bicarbonate,

which in laboratory tests have resulted in acceptable levels of ionic strength and pH.

Laboratory tests have shown that once the pH in the ore zone reaches 4, a solution of 2

g/l of sodium bicarbonate will bring the pH up to 7 with excess bicarbonate in the system.

A typical ore block of 75" x 75" x 400' at 12 cubic feet per ton and 6 percent porosity will

require 0.09 pounds of sodium carbonate per ton of ore.

The lower basin fill has 2-4 percent of carbonate and likely has sufficient neutralization

capacity even after long term leaching to create the proper level of neutralization in the

LBFU. The estimated ultimate recovery of copper at the 62 percent of total copper

recovery will occur at 17-20 pound per ton of ore gangue acid consumption. The fact

that the ore consumes up to 30 pounds gangue per ton at extinction says that long term, it

is likely that some acid consumers will be left after economic levels of leaching have

occurred.

Impact of Gypsum Solubility on Reclamation

Although sulfate is not presently a regulated primary maximum contaminant, it may be in

the future. The work done by Brown and Caldwell that showed that once the sulfate was

lowered in the leach system to 750 PPM, most of the regulated ions were at acceptable

levels. Their work however, showed that the pH was higher than experienced in the

actual reclamation test. In addition, even though wash out to acceptable sulfate levels

could occur initially, gypsum solubility would cause the fluid to increase to around 2.5 g/l

as calcium sulfate. Closure of a well set can occur according to the permit condition,

when the sulfate level decrease to 750 PPM and metal ions meets the appropriate

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standards. The well is then shut in for 90 days and retested. If the metal ions still meet

federal and state standards, the wells can be closed. This indicates the need to continue to

elute the sulfate out at flows regulated to maintain the sulfate at gypsum saturated levels.

As sulfate falls below that level, flows could be reduced, but the economic impact is that

pumping and treating will continue to be required as sulfate washes out of the system.

Residual consequence and risk should be considered. The re-dissolution of gypsum also

causes packets of entrapped leach solutions to be released, so neutralization would also

have to occur concurrent to sulfate removal. The goal is to meet federal MCl’s and

AWQS.

Impact of Volumetric Treatment

The economic model3 includes a membrane filtration system

4 capable of reducing

volume to the evaporation system by 80 percent. The volume reduction also results in

higher ionic strength in the filtration concentrate liquor would results in more efficient

neutralization and more compacted solids for disposal in the evaporation ponds. A

system to treat up to 4,000 gallons per minute has been included in the economic package

along with the neutralization costs. The eluate will contain about 200 PPM of sulfate,

which when neutralized can be recycled to the leach system to wash out the ore zone.

The amount of necessary washing will impact the size of the water treatment plant. The

results of this test could be used to make estimates of the ultimate volume that would

need to be treated and the storage volume required in the ponds.

Impact of the Early Termination of the Field Test

The termination of the field test leaching has allowed the reclamation test to occur, but

unfortunately not at the mature levels of leaching in the ore zone, that would have been

experienced under normal operation. The data does allow forecasting of the end results

to some extent. Technically the ore zone can be reclaimed to acceptable AWQS and

Primary Maximum Contaminant levels. A key will be an understanding of the

geochemistry that allows hydrogen ion to elute long term, and the amount of gypsum that

may be formed and that will ultimately dissolve. Some pre-treatment laboratory tests

were done with aluminum sulfate as an ion exchanger with calcium that showed promise

of reduction of system calcium ion as a pre-treatment. More work needs to be done in

this area as a pretreatment to the system. This work was not done in this test.

3 “BHP Copper, Florence Project, Final Pre-Feasibility Report, Volume V, Mine facility Design and

Financial Analysis, Part 5”

4 BHP Copper, Florence Project, Final Pre-Feasibility Report, Volume V, Mine facility Design and

Financial Analysis, section 1.6.2, p26 ”

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