2006-07-03_REPORT - M1977403HR - Laserfiche WebLink

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Bill Lyle, /darndo Mining Company November 23, 2005 Page 4 the point of excavation, prior to transport to the repository. The remaining six samples consisted of individual samples of material that was known to have lead values exceeding 400 ppm. These six samples were taken from test pits in the Liberty Bell Area with the material later being excavated and placed in the repository. All soil samples were submitted to SVL Analytical, Inc. for ABA analysis. The ABA analysis was performed in accordance with the Modified Sobek Method using EPA Method 600. The sulfur forms (non-extractable sulfur, pyritic sulfur, sulfate-sulfur, and total sulfur) were analyzed using a Leco SC-132 Automatic Sulfur Determinator. The AGP is calculated based on only the rota] pyritic sulfur content. ABA Test Results The ABA test results for the 24 samples collected from the material removed from the Pandora Area are provided in Table 1. The ABA test results for the 18 samples collected from the material removed from the Liberty Bell Area are provided in Table 2. The NNP is determined by subtracting the AGP from the ANP. A negative NNP value (or an ANP/AGP ratio less than 1) indicates that a potential exists for the soil to form acid. On the other hand, samples with a positive NNP value are considered alkaline in nature and predicted to have a reduced potential to produce acid. Geochemically, it is believed NNP values greater than 20 (or ANP/AGP ratios greater than 3) are considered unlikely to generate acid. As shown in Table 1, the sample materials excavated from the Pandora Area demonstrate relatively low acid generation potential (AGP range of 0.9 to 20.0, a mean concentration of 5.9, and a median concentration of 5.3 tons CaCO3/1000 tons) and considerable neutralization potential (ANP range of 9.9 to 71.3, a mean concentration of 30.5, and a median concentration of 29.5 tons CaCO,/1000 tons). All samples had a positive NNP value except for one sample. The NNP sample values range from -S.1 to 65.1 tons CaCO3/1000 tons. The average NNP value for all 24 samples is 24.6 tons CaCO3/1000 tons (median NNP value of 21.6 tons CaCO3/1000 tons). The ANP/AGP ratios range from 0.6 to 22.4 with an average ANP/AGP ratio of 7.2 (median ANP/AGP ratio of 5.9). Based on the results of the ABA tests, the vast majority of the repository materials from the Pandora Area demonstrate a positive NNP which is unlikely to generate acidic conditions and of the few samples (4) with an ANP/AGP ratio less than 3, only one sample demonstrated anANP/AGP ratio of less than 1. It is believed the materials from the Pandora Area placed in the repository will be geochemically stable as placed.