GENERAL36621

• Permit No: M1980244
• IBM Index Class Name: General Documents
• Doc Date: 2/21/1995
• Doc Name: GEOCHEMISTRY OF LEAK COLLECTION WATER
• From: DMG
• To: BERHAN KEFFELEW
• Media Type: D
• Archive: No

- •

STATE • III IIIIIIIIIIIIIIII
9~
OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Depanmenl of Natural Resources

1313 Sherman 9., Room 215 ~
Denver, Colorado 80203 ~I~
Phone: [phone]
FA%: 13031 8328106
DEPARTMEN'T' OF
NATURAL
DATE: Febn,ary 21, 1995 RESOURCES
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TO: Berhan Keffelew ~
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~ Roy Romer
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FROM: Harry Posey
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/// Executive Director
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f Michael B. Lung

RE: Geochemistry of leak collection water Dwaian Director
I have attempted to determine what mixes of fluids may be responsible for the chemical composition
measured in the leak collection system at the Cresson Heap Leach Pad in the last couple of weeks.
You will recall from our discussion last week that we wondered whether meteoric water may be
entering the heap leach pad from some location other than direct application.
According to you, there leak collection fluid may contain parts of three fluids: Cresson process
solution, remnant process solution from the Iron Clad tailings, and meteoric water. Owing to this,
and because we do not know the the compositions of the fluids very well, the range of fluid mixes that
could lead to the measured values in the LCS is indeterminant. Also, a mixture of process solution
and lower pH fluids will likely break down cyanide- certainly in the long term; so the cyanide
measurements from the leachate collection may not reflect the actual load of cyanide from the process
solutions.
Below are the apparent measurements and known compositions of the three fluids and the leak
collection fluid.
Process Entrained Meteoric Leak
water water' water Collection
CN 200 ppm 0-100 0 10z
pH 9.5 6.0-8.0 5.83 7.S
Entrained water may be a mixture of process solutions left from earlier days of
mining and contained in the Iron Clad Tailings, meteoric water, and some derivative
of those that formed through interaction with the fluid. Process water pH values were
probably around pH 10; meteoric water would have been about 5.8 pH, and the derivative
water probably would have been lower in pH than a combination of the other two fluids
due to their interaction with sulfide minerals.
'Given that the cyanide analysis was conducted using a Hach meter, the measured
value of 7 is suspiciously precise. Therefore, I have assigned a value of 10 mg/L.
'This pH is assumed.