_REVISION - M1980244 ‎(31)‎

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Name: Adequacy Response
• From: Cripple Creek & Victor Gold
• To: DMG
• Type & Sequence: AM8
• Media Type: D
• Archive: No

l8
characteristics" would indicate a neutral pH, even though only about t/3 of the
samples have a pN greater than 5.
Respottsc: We believe that you are referring to the discussion at the top of page 23, the last 2 paragraphs of
Section„4.1, [itled "ExistinE Overburden Storage Areas" in Appendix 1. The initial part of this
discussion seeks to establish that a NNP of zero is a reasonable cutoff between samples with and
without;ARD risk (not the aforementioned Q 8% total sulfur discussed earlier). Then in the middle of
the last;paragaph of the section, it is stated:
"Based on these average chazacteristics, along with the Carlton Mill tailing material at
an NNP of +38 T CaCO~/1CI', the AGOSA can be expected to generate circum-neutral
'leachates:'
Tlu: interpretation of static and humidity cell data did not contend that overburden placed in AGOSA
would not become locally acidic. [t was inferred only that any interstitial solutions that may migrate out
of the AGOSA (whether acidic or not) would intact with the undazlying Carlton MiU tailing material
that has an average NNP of +38 d1,000t. The resulting leachates, after contacting the acid-neutralizing
mill tailing, will have a cucum-neutral pH. Statements in this section of the report recapitulate the
geochetitical assessment of the AGOSA that was approved as part of Amendment No. 7.
+(b) The discussion ors page 23 apparently projects the NNPfor all of the waste rock, but
r .:. the j-figure does not disNn~+uish behveen AGOSA waste rock and SGOSA waste rack.
Evidently. data in FiPUre 4-2a were meant ro be repeated in 46. bat aboat 15 of the
~~ ~ ~ sample results appear to be missing from 4-2b.
s
Response: The.basis for the estimated average NNP of all overburden to be mined in Amendment No. 8 was
described in Section 4.1 of Appendix 1 in Volume A where the correlation between the total sulfur and
carbon measured by LECO furnace on blasthole pulps and measured NNP values using standard
methods was desctllteti The correlation equation was based on 33 samples shown In Fgure 4.1. Then
based an the fact tha[ the estimated NNP from blasthole data and measured NNP were correlated, the
blasthde NNP values were used to construct the estimate of the NNP for the deposit as a whole. In that
cdnteXCit.was stated:
~.
`"~Y aPPlying This tnetbod of NNP calculation w the blasthale data oa total carbon and
o = : ;total sulfur rnntents in overburden, an average NNP value of +B.S T CaCO3/Kf is
'- c. nobtained for the AGOSA and SGOSA."
In revlewing this section, SMI has determined that if the slope (0.78) and Intercept (0.44) of the
predict)ve equation are taken into account, in fact the average NNP is +10.3, not +8.5 as staled above.
Consequently, the average NNP for the existing overburden storage areas is not based on humidity cell
tents but on the blasthole LECO data as is suggested by the OMLR. (LECO C value of 0.2296 *83.38 -
LEGO S of 0.4896 * 67'ili pyritic S * 31.25 = 9.3 d1,000t blasthole NNP. (Blasthole NNP - 0.44)/0.78 =
measuted NNP of 10.1 t/1,000tj
(a) Please clar(~y how it was concluded that the overburden "can be expected ro
generate circum-neutral leachates. " (f clarlfcations or corrections offigures
4-2a and/or 4-Zb are necessary to explain the conclusion. please include those.
Response: We believe that you aze referring to the discussion at the top of page 23, the last 2 paragraphs of
Sectior4:1, titled "Existing Overburden Storage Areas" in Appendix 1. The initial part of this
~., ~ ~