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~ ( ~ 1 Division of Mining and Geology Department of Natural Resources January 13, 1993 Page 3 greater than the total values. Core reported that the results were verified through re-analysis and independent total analysis. Core Laboratories suspects that those dissolved samples may have been contaminated. It should be noted, however, that the analytical technique for total metals analysis is different than dissolved metals analysis. while both the total and dissolved metals are analyzed using the inductively coupled plasma technique (ICP), the total metals sample undergoes a digestion process. while total values are not analyzed for ground water samples, dissolved cadmium concentrations were also detected at monitoring wells M-4, M-9, D87-24 and in the bailer rinse blank. Table 1 is a list of the monitoring points which exhibited dissolved cadmium concentrations and their respective values. We believe that the cadmium nitrate used to precipitate out potential sulfides in the process point samples is a possible source for cadmium contamination. In accordance with the protocols, all equipment used for sample collection is cleaned before sampling and between samples by non- phosphatic detergent and tap water wash, tap water rinse, followed by final rinse with de-ionized water. Potential contamination from the use of cadmium nitrate may explain the low dissolved cadmium values in surface water stations RS-1, RS-2 and RS-5, as they were the first samples collected during this sampling event. In addition, the M-9 sample was collected after using cadmium nitrate to treat the sample from the upper tailings impoundment. Potential contamination from the use of cadmium nitrate would not explain the dissolved cadmium values in M-4, M-24, 87-24 and BLRB. These samples were collected in the middle of this sampling event and do not follow the collection of a process point sample. Table 2 is a chronological listing of the samples collected during this sampling event. The discrepancy between the dissolved cadmium values for sample M-4 and M-24 (duplicate) should also be noted. This discrepancy, in addition to the dissolved cadmium values in the D87-24 and BLRB samples, and the differing analytical techniques for total versus dissolved metals, may suggest potential laboratory analysis error or alternate sources of contamination. Alternate sources of contamination may include the paper filter elements, contaminated tap water used to wash and rinse the barrel filters, and/or contaminated de-ionized water used as a final rinse agent.