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SRK_pH+SO4_Video_Readme_20100624.docx

MemoTo: Terry Linde, Curis Resources Date: June 24, 2010

cc: File From: Cori Hoag

Subject: pH and SO4 Water Quality Videos – BHP Field Test

Project #: 204400.03

SRK was asked to compile water quality data and other records related to the BHP Copper field test performed at the Florence Project in 1997 and 1998. The intent was to compile the existing data, review results, and prepare a list of findings that may have relevance to overall copper recovery and application to the future production test facility. The findings will pre presented in a separate memo.

Water quality analyses related to the field test and subsequent rinsing phase are available in a Microsoft Access database (FlorenceDB.mdb-revised 6/28/2010) for the period from November 1, 1997 through October 1999. Although the number of sampling points decreases after March 1998, sporadic sampling data are also available from 2000 through 2007.

The database contains records of water quality sampling, well construction and well history details, flow data, the results of mechanical integrity tests, and other information. Data entry forms, queries, and reports that generate graphical views of the concentrations of constituents for various sets of wells are also available in the database. The data were originally entered by BHP employees to record the results of drilling (well construction details, costs, integrity tests) and the results of solution analyses related to an in-situ leach, recovery, and rinsing field test. Water quality analyses were performed by the BHP Copper San Manuel Metallurgical Laboratory, ACTLABS-Skyline (now Skyline Assayers & Laboratories), and ACTLABS-Enzyme (formerly Enzyme Laboratories). Field data (electrical conductance and pH) were also recorded and entered by field technicians. The water quality database lacks standard laboratory quality assurance/quality control (QA/QC) information such as minimum detection limits, date of analysis, dilution factors, QA/QC codes/comments, etc. SRK has found some apparent data entry errors and outlier results in the Access database but has not cross-checked the database entries against the original laboratory sheets or field record sheets to estimate overall accuracy or completeness of the database. An effort was made through the sampling program to collect duplicate samples and to record the meter calibration results.

Graphical interpretation and presentations of the water quality data were prepared by BHP and have also been prepared by SRK in an attempt to understand the interactions and recoveries in each well and in groups of wells. The graphs quickly become too busy to interpret easily and the horizontal and vertical water quality changes occurring through time in the injection and recovery wells is not easy to understand using a standard Excel graph. To provide a more spatial and temporal interpretation of the solution chemistry and understand the reactions that occured, the data were exported from the Access database into 3-dimensional gridding/contouring software and an animation was created. This memo is intended to provide a brief explanation of what data were extracted and how they were prepared and manipulated into short videos that display concentration changes through time within the field test area.

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1 Preparation of Water Quality Visualization

Compilation of Water Quality Data

Raw water quality data extracted from the Access database and used in the water quality visualization videos consist of pH (su) and sulfate (SO4 mg/L) measurements recorded in the injection, recovery, and chemical observation wells operated during the field test. Copper data have been compiled but are not yet imported into a format for 3-D visualization. Flow data were used to indicate when the individual wells and total wellfield was active or inactive. Flow measurements were originally recorded as one average value per 12-hour shift resulting in two average values per 24-hr period. SRK compiled the two daily measurements to calculate a single average flow value per day. The data were reviewed to identify obvious outliers and errors, and were sorted by date, laboratory, and method (field versus lab). Laboratory data were preferred but there was a lack of consistency in the primary laboratory used during the field test. The San Manuel Lab was the primary lab for daily analyses from November 1 though the end of December 1997; thereafter Skyline was the primary lab but the analyses decreased to a weekly frequency. Field pH was used exclusively after January 1, 1998 as no pH values are available from Skyline.

The raw data for copper, pH, SO4, and flow were compiled by day for each well sampling point. Flow data are available for each day but there are gaps in water quality analyses. The gaps vary by well and by period of time ranging from daily to weekly analyses. Certain wells have more analyses than others as they ceased to be used for pumping/rinsing purposes. After the data were chronologically sorted, the dates that were missing water quality data were added and water quality results were interpolated to fill the gaps. This was done for the purpose of calculating the mass of copper and sulfate injected into the wells via the injectate and extracted from the pumping wells.

Export of Downhole Surveys for Wells

MineSight software was used to export downhole survey data for the BHP injection, recovery, and chemical wells. The survey data consists of easting (X), northing (Y), and elevation (Z) points in 5-ft increments below surface starting with “collar” coordinates located at the top of bedrock elevation. The X, Y, Z downhole survey points for each well were paired in a second Excel spreadsheet with the relevant water quality data in mg/L or su units for the specific well. This generated a spreadsheet containing X, Y, Z, and concentration data for each well for each 5-foot increment below the top of bedrock.

One simplification for the visualization was that the water quality analyses were applied to the entire length of the well below top of bedrock rather than to just the screened interval. The wells actually contain blank casing that extends from ground surface to 40-ft below top of bedrock. Another simplification is that the water quality concentrations for the three discrete sampling points located at 410’, 610’, and 710’ below ground surface in the two CH wells were applied to a drillhole length from the mid-points above and below the discrete sampling points.

The paired downhole survey and water quality data (in 5-ft increments) were then sorted by month, then by day; the rows were separated by month and copied into multiple Excel spreadsheets. The monthly spreadsheets contain worksheet tabs for each day of the month. Selected Excel worksheets (weekly from November 1, 1997 through May 14, 1998) were imported into the 3-D interpolation software called Voxler2 by Golden Software. The drillhole traces were plotted by the software to form a 3-D scatter plot. The scatter plot data (concentrations or pH) were scaled according to minimum and maximum concentrations. The data were gridded, contoured, and “volume rendered” to reflect the concentrations in and between the wells. The gridding was done using an Inverse Distance weighted to the second power (IDW2) interpolation method with an interpolation distance of 50 ft and isotropic anisotropy. The wells are located within 50-72 feet of each other. A spherical projection/interpolation radius of 50 ft was selected as the best projection radius after experimenting with interpolation methods, anisotropy ratios

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and distances, and isotropic interpolation distances. Distances greater than 50 ft caused unrealistic results and contours.

Images of the weekly contoured data in planar or vertical view were exported from Voxlar2 into .jpg format for animation in Adobe Flash Professional CS5. Using Voxlar2, rotating 3-D animations in perspective view were also created and exported as an .avi-format file to show the state of the entire wellfield at the end of the three stages of the field test including the:

End of raffinate injection on February 8, 1998,

End of pond water injection on March 26, 1998, and the

End of groundwater (WW4) injection on May 14, 1998.

These weekly .jpg-format images and .avi-format wellfield animations were consolidated into a single video using Adobe Flash Professional CS5. The video was saved as a Shockwave Flash Object (.swf) file format and exported as a .html file for internet browsing. The Shockwave Flash format will allows the user to control the video (pause, play, fast-forward, rewind) using the Swiff Player. The URL for downloading the free Swiff Player is found at http://www.globfx.com/products/swfplayer/.

2 Sulfate Visualization

The sulfate animation primarily shows a perspective view looking down from immediately above the field test area. The wellfield layout and well traces are shown in Figure 1. Sulfate concentrations were interpolated by day on a weekly basis, displayed with cutoff grade colors, and captured as jpg images for display. Examples are shown in Figure 2 at two dates—November 7, 1997 and February 1, 1998. The injectate, a mix of sulfuric acid and local groundwater, had a concentration of approximately 10,120 mg/L SO4 when it was injected via BHP6, BHP7, BHP8, and BHP-9 beginning October 31, 1997. The injectate concentration varied and was approximately 6,387 mg/L in early February. Note the early detection of elevated sulfate in perimeter recovery well BHP-5 one week into the test while other perimeter recovery wells are still below 1,000 mg/L (concentrations less than 1,000 mg/L are shown in white). Near the end of the test, elevated sulfate was uniformly measured throughout the field test with the exception of upgradient, perimeter recovery well BHP13 where continual inflow of fresh groundwater prevented concentration of the sulfuric acid. Upgradient well BHP2 showed markedly lower concentrations and mass of copper extracted than upgradient well BHP5 suggesting that some structure or other feature preferentially directed flow from BHP9 to BHP5.

Figure 3 shows the rinsing progress that was achieved during the following two months based on sulfate concentrations and pH. The intermediate pH, residual process water in the evaporation pond was injected back into the test area via the same four injection wells from mid-February to March 21, 1998. Groundwater from WW4 was injected into the test area until May 14, 1998. The upgradient portion of the field was rinsed to below 1,000 mg/L in less than two months.

Figure 1 Planar view showing field test layout and location of the wells in mine coordinates (ft). The injection wells are shown with yellow drillhole collars, recovery wells have green collars, and chemical monitor wells have white collars. The white drillhole traces are shown in perspective view using downhole surveys.

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Figure 2 Planar view showing SO4 (mg/L) concentration near the start of raffinate injection on November 7, 1997 (left) and end on February 1, 1998 (right). The interpolated extent of high-sulfate injectate away from BHP6, BHP7, BHP8, and BHP9 is shown in red.

Figure 3 Planar view showing SO4 (mg/L) concentration at the end of pond water injection on March 21, 1998 (left) and the end of groundwater injection on May 14, 1998.

3 pH Visualization

The pH visualization begins with a perspective view looking down from immediately above the field test area and transitions to an east-west profile looking north. Background groundwater quality ranges from pH7 to over pH8 as shown in the plan view in Figure 4. During the raffinate injection phase, pH values ranged from approximately 1.5 to 1.7 in the injectate. Although pH values have a lognormal relationship, the values were treated as integers in this simplified approach and were interpolated using IDW2 method with50’ projection distances. Images were created for weekly results using cutoff grade colors for values ranging from pH1 to pH9. Injectate is visible as red color in the visualization and in Figures 4 and 5.

In the animation, you will note the steady decrease in pH spreading outward from injection wells BHP6 and BHP8 first at the upper elevations, then middle, and lower one-third of the profile. Starting in the last week of January, the central recovery well has finally reached the pH3.5 to pH3 level where copper dissolution can begin. It took more than 3 months for the injectate to migrate across a 50-foot distance through rock of variable fracturing and hydraulic conductivity, partially consume the carbonate gangue minerals present on the fractures, and start to reach a state of acid equilibrium in the central test area that could overwhelm the inflow of fresh pH7-8 groundwater. This visualization, in conjunction with one on

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copper concentrations measured through the test, emphasizes the time component needed to move enough volume of injectate across the flow path between injection and recovery wells and through the volume of rock in order for the rock and pore solutions to start to become acid-equilibrated. Without acid-equilibration, copper cannot be effectively dissolved and recovered.

Figure 4 Planar view showing pH (su) on November 1, 1997 before injection begins (left). Note the background concentrations are between pH7 and pH8. On November 3, injection of pH1.5 injectate is visible in BHP6, BHP7, BHP8, and BHP9.

Figure 5 Vertical E-W profile from BHP12 though BHP10 looking north showing pH on November 7, 1997 (left) and at the end of the raffinate injection phase (February 8, 1998). The well traces are faintly visible and begin at the top of bedrock. The injection wells are clearly seen by trace of red color (pH1.5) on left with near-neutral water in the vicinity ofBHP1 and neutral, pH7 water inflowing into the perimeter recovery wells. At the end of the test, the injectate has reacted with materials in the top one-third of the rock profile and is decreasing to pH4 (yellow) in the bottom portions of CH1 and CH2. Near-neutral water is measured in perimeter well BHP12.

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During the rinsing phase, intermediate (4.8 to 6.05) pH pond water was reinjected back to the wellfield and the water quality recovered in the central and perimeter showed a similar range of pH values (Figure 6). On March 14, the visualization shows a sudden decrease in pH measured in BHP10; this occurred when acidic injectate was used to kill and remove organic growths on the well screen. Continued injection through May 14 with fresh groundwater had increased the pH from pH4.95 to over pH7 in the perimeter wells. Low pH concentrations ranging from 4.5 to 5.5 are noted in the animation in the CH wells at the end of the three-month rinsing phase.

Figure 6 Vertical E-W profile from BHP12 though BHP10 looking north showing pH on March 21, 1998 (left) at the end of pond water injection and at the end of the groundwater injection phase (May 14, 1998). The pond water injectate ranged from At the end of the March, the injectate has reacted with materials in the top one-third of the rock profile and is decreasing to pH4 (yellow) in the bottom portions of CH1 and CH2. Near-neutral water is measured in perimeter well BHP12.

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