1997-11-13_REVISION - M1977493 (50)

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iSamples were collected on a monthly basis during March, April and May, on a weekly basis during June and July, during water delivery operations, and will be collected biweekly during August and September when the reservoir is no longer filling and conditions are stable. The surface water investigation consists of obtaining grab samples with a reach sampler from the Eagle Park Reservoir at three different locations. Samples are collected near the North Interceptor, the Chalk Mountain Interceptor and on the north shore of the reservoir. One field replicate is collected for each sampling event. Measured field parameters include pH, conductivity, temperature, and dissolved oxygen. Photographs of the reservoir are taken at each sampling event. Analytical Results Surface water samples were analyzed for total recoverable metals, dissolved metals, inorganics and physical and biological constituents. The specific set of analytes for each sampling event has varied throughout the sampling investigation and has been revised periodically based on the results of previous sampling events. In general, when results have indicated that a parameter is not present on a consistent basis (3 or 4 sampling events), that parameter has been eliminated for analysis for the remaining sampling events. Concentrations of analytes have decreased significantly throughout the sampling investigation. • Analytes that were initially found to be higher than stream water quality standards were iron, manganese, nitrogen, sulfate and pH. As expected, results from the first two sampling events (March 28 and April 8, 1997) indicated the highest concentrations of analytes. During the months of March and April, the reservoir was not completely filled, therefore, analytes were present at their highest concentration. In addition, any suspension from bottom material that may occur, would occur in the first months of reservoir filling. To date, however, all analytes meet stream water quality standards. Results from the most recent three sampling events indicate that all analyte concentrations are below stream and secondary water quality standards in the Eagle Park Reservoir. A summary of the trends for all analytes is provided below. Iron Iron(total recoverable) [tr]) was higher than the chronic water quality standard of 1.0 mg/L in the first seven sampling events. Concentrations continued to decrease for each subsequent sampling event and by Sampling Event 5 (June 12, 1997) the chronic water quality standard of 1.0 was achieved in several samples. Sampling Event 6 (June 19, 1997) showed increased concentrations of iron (tr) compared to the June 12, 1997 results and concentrations were greater than the chronic water quality standard. Sampling Event 7 which took place on June 26, 1997 showed decreased concentrations of iron (tr) (1.20 - 4.82 mg/L) and the most recent three sampling events (July 2, July 10, and July 25, 1997) indicate that iron (tr) meets the chronic water quality standard. DAPROJ ECTS\6102-001\SWSUM3.DOC[8-Sep-97]