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affected by deep percolation of irrigation waters and were :markedly <br />higher than the mean. The current proposed EPA drinking water <br />regulation for uranium is 20 micro grams /liter. This 19.4 micro <br />grams /liter concentration is 2 -4 times as high as other quadrangles <br />tested in western U.S. Future levels are anticipated to ccntinue to be <br />high if irrigation practices remain the same. <br />Uranium concentrations in the drains and creeks flowing into the <br />Arkansas River from the watershed area have readings at times from 20- <br />50 micro grams /liter. The extensive irrigation in this reach of the <br />Arkansas River significantly elevates the dissolved concentrations of <br />uranium. This combination of natural and man made effects could <br />compromise the water quality for domestic use (farms, communities,) and <br />agricultural use (irrigation, livestock) that derive water from the <br />alluvial aquifer as well as the high concentrations in the river <br />itself. Excessive levels may also be dangerous to wildlife including <br />endangered species. Downstream water quality is also decreased to <br />irrigators who reuse the Arkansas River water. <br />There are a number of shallow wells in the area that are also high in <br />nitrates. EPA Storet Data indicates there are six wells in the <br />watershed found to exceed the EPA standards (10 mg /lppm) NO3 -N. The <br />Arkansas Rivers' water approaches the nitrate level standard at times. <br />The sources of the nitrates are a combination of naturally occurring <br />and applied. The top two feet of soil were generally found to have <br />very high concentrations of nitrates. The higher nitrate well <br />' concentrations generally occur in the lower portions of the watershed. <br />There are about 26 wells that were found to have nitrate levels <br />approaching or exceeding standards in the watershed area. <br />Salinity is another serious water quality problem in the Arkansas <br />Valley. There are 3 important factors in the salinity problem: salt <br />pick up, concentration, and the management of water, soils, and crops. <br />Although it is desirable to control salt .loading, high salt levels will <br />remain as long as the water is used. Therefore, the greatest potential . <br />for reducing salinity is through more effectively using water <br />throughout the valley. Irrigation water diverted into the Fort Lyon <br />Canal, upstream 53 channel miles from the project, has a mean TDS of <br />807 milligrams /liter (obtained from USGS records). The mean TDS in the <br />Arkansas River at Las Animas which is just above the project area is <br />1041 milligrams /liter. Just downstream from the project at the Lamar <br />gaging station the mean total dissolved solids (TDS) is 1694 <br />milligrams /liter for the Arkansas River. The TDS levels are therefore <br />increasing downstream due to concentrations of salt in the remaining <br />water. No TDS standards have been set for Colorado, however, TDS <br />levels of 500 is deemed desirable and below 1000 is acceptable for <br />agricultural pur-poses. It is anticipated that total TDS will be <br />lowered through project action. <br />Eight organcchlcrine pesticides were detected in some samples of bird <br />livers and eggs and in fish from the reservoirs. All concentrations <br />were well within the ranges of reported background concentrations <br />and were less than levels of biological concern. <br />16 <br />