1988-06-21_HYDROLOGY - M1977378 - Laserfiche WebLink

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Alkalinity was not measured on the samples. An average pH of 7.2 was measured. It is uncertain how this relatively neutral condition could result without more information on the concentration of base constituents in the sediment and reactivity of the sulfur present in the material . In summary, the data indicates the Terry Tunnel sediment sampled to be acidic and potentially toxic. Metal Concentrations Analysis of selected metals were performed on the samples of sediment deposited in the ditch. Two considerations were made in evaluating these data: (1 ) a comparison to "unsuitablility criteria" as published by the State of Montana; and, (2) a comparison to metal concentrations in sediments at other locations at the Sunnyside Mine in order to characterize the type of sediment sampled at the Terry Tunnel . The following data as presented in Table 1 were used in making these comparisons. The data in Table I indicate cadmium, copper, lead, zinc and manganese are found at levels significantly above the unsuitability criteria. These concentrations would limit the use of this material as a plant growth media. If this sediment were to enter surface waters directly in runoff, or leachate derived from the material were to enter ground water, relatively high concentrations of these metals would result in limiting beneficial uses of the water. In the correspondence received from Sunnyside Gold Corporation on January 4, 1988 the statement is made that: . . .copper, lead, manganese and zinc concentrations are relatively high, but generally consistent with Lake Emma sediments in the Sunnyside Basin." I would agree that the concentrations are high, but disagree with the interpretation that they are similar to Lake Emma sediments. The concentrations are more consistent with both the Pond 2 gray slime and the Pond 3 reddish sludge from the American Tunnel ponds. In particular, iron, zinc and cadmium concentrations are more consistent, whereas the levels of these constituents in Lake Emma sediments do not support the conclusion that the sediment sampled at the Terry Tunnel are derived from Lake Emma sediments. Textural Analysis Textural analysis is also used to support the interpretation that the pond muds are derived from Lake Emma sediments and not sludges derived from the chemical treatment of mine drainage waters. The statement is made that by comparison to data in Table D-4, the Terry Tunnel pond muds sampled show an increased silt/sand ratio over lake sediments, and that this is due to selective transport through the mine. While it may be correct that deposition of larger particle sizes does occur when lake sediment travels through the mine, the data on textural analysis in the permit show all sediments to have a 40-60 percent sand fraction, as shown in Table 2.