1997-04-24_REVISION - M1977493 (17)

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Mr. Bryce Romig • 2 • September 9, 1996 • Analysis of total recoverable iron and total recoverable manganese may be analyzed on an intermittent basis only, depending on total suspended solids (TSS) and dissolved iron and manganese concentrations in the reservoir water. Dissolved iron and dissolved manganese will continue to be monitored. Sampling Events and Analyses Each sampling event included collecting one composite soil sample from the reservoir bottom material and obtaining surface water samples from the reservoir. The surface water samples were collected prior to complete removal of the tailings to determine what analytes are present and to assess water quality under worst-case conditions. Soil samples were collected in areas where tailings had been removed to obtain baseline metal concentrations of the remaining bottom material in the reservoir. Sampling procedures followed are outlined in the SAP. To provide Quality Assurance/ Quality Control (QA/QC), one split surface water sample was analyzed per sampling event. Field pH, conductivity, temperature, and dissolved oxygen measurements were also taken in the field for the water samples. Laboratory analyses were conducted on the surface water samples for parameters regulated by the Colorado Department of Health (CDH), Water Quality Control Commission(see Tables 1 and 2). Water quality standards • for each sample were calculated based on water hardness as outlined by the CDH and are also included in Tables 1 and 2. The standards were calculated using the most conservative hardness value per sampling event. For the May event, a hardness value of 658 mg\L as CaCO3 (sample SW-2) was used, and for the July event, a hardness value of 491 mg\L as CaCO3 (sample SW-I) was used. Total metal concentrations in soils were determined by laboratory analyses (see Table 3). During the May sampling, approximately one-third of the original tailings remained in the Eagle Park Reservoir. Excavation had been delayed due to high water levels in the reservoir which formed two large ponds to the east and west of the access road. Water was being pumped from the east pond, causing some flow over the road from the west pond. Three water samples were taken from the west pond (two near the dam and one near the road), and one sample was taken from the east pond. The split sample was taken from a sample on the west side, near the north side of the dam. A composite of three soil samples was collected from locations on the south side of the west pond. The water level during the July sampling was significantly lower than during the May sampling. The remaining tailings near the dam were being excavated. Water in the reservoir existed in four shallow (4 to 6 feet) disconnected ponds. Samples were taken from two ponds near the dam face and from a pond on the east side of the access road. The split sample was taken from a sample near the north side of the dam face. Because of the low water to tailings ratio (especially near the dam face), these water samples are ---- �— C:\PROJECTS\6102-001\T1696102.00I[9-Sep-96] Environmental