Limestone-Graveyard Creeks Watershed Plan and Environmental Assessment

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p5��> aquatic life standard. The increase in dissolved selenium is similar I to the total selenium concentration trend. The maximum selenium concentration detected in fish from the stream sites was 18.5 micrograms /gram in a sample of common acarp from the , Arkansas River near Lamar, Colorado guaging station. 2/ Five species ' of fish in the Arkansas River had selenium concentrations ranging from 2.1 to 18.5 micrograms /gram. Three species in the tributaries had selenium concentrations ranging from 3.6 to 16.9 micrograms /gram. All but 3 of the 59 total fish samples exceeded the 85th percentile ' national baseline for selenium in fish (2.45 micrograms /gram dry weicht), and 21 of the samples had concentrations exceeding the range asscciated with reproductive failure in bluegill. About one -half of the samples had selenium concentrations that exceeded the dietary concentration known to increase the rate of mortalities and deformities , in mallard embryos. Selenium levels in aquatic plants exceeded acceptable dietary limits of avion species. Selenium concentrations in surface water was 1 microgram /liter in Puelo Reservoir upstream from the project area. Data from EPA, STORET database, indicates that the stretch of the Arkansas River from below ' John Martin Reservoir to Lamar, Colorado, has significant higher levels of selenium. 117 Samples taken indicated average total selenium concentration increases from 7.2 micrograms /liter to 19.7 micrograms /liter between the two gage stations. The mean value of 19.7 ' micrograms /liter total selenium was determined using 96 values from 1968 to 1994. Additional USGS outflow data from John Martin Reservoir indicates a trend in increased selenium concentrations. Data from 1980 and 1981 that was used with comparison data from 1988 through 1993 indicates that dissolved selenium is increasing by .2 micrograms /liter annually. The trend indicates that selenium standards for agriculture use, 20 micrograms /liter, will be exceeded in the near future. ' Altough the project was not formulated to reduce other toxic trace elements or heavy metals, project action will help reduce those problems and improve water quality. Dissolved uranium levels of the Arkansas River are also increasing. Uranium ingested by humans and wildlife goes to both the kidneys and bone. It is a chemical poison to the kidneys. Kidney inflammation and failure can occur. Sampling of the Arkansas River from Manzanola to Lamar found that dissolved uranium increases at a much higher rate than in the upper , reaches. An abrupt increase in dissolved uranium is observed along the section of river where flow is greatly reduced because of extensive diversions for irrigation and the remaining flow is largely composed of irrigation return water. Water samples in this section of river are more enriched in dissolved uranium compared to the average concentration found in water outside the irrigated areas. _ The mean concentration of uranium in ground water was 19.4 micro grams /liter for uranium in the Lamar Quadrangle of Southeastern Colorado (825 samples) . Wells of less than 100 feet depth were 15