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CARBON 14 <br />Carbon 14 is a carbon atom with two additional neutrons (14C). It also has a <br />cosmogenic origin. It was first proposed for radiometric use in water in 1957 <br />(Munnich). Carbon 14 has a decay half-life of 5,730 years for an age range of <br />about 30,000 years or five to six half-lifes. <br />Carbon 14 analysis was a second test of the age of Yampa River water. The <br />Williams Fork Formation sample was analyzed primarily for completeness since <br />the method is unreliable in coal formations. The coal seams were deposited at <br />least 65,000,000 years ago (Cretaceous Age). The carbon 14 in the coals has <br />long ago decayed away. The large available quantity of carbon 12 or "dead <br />carbon" could skew any analysis of coal formation waters and raise doubt as <br />to the validity of any measured value. Coal outcrop drainage in the Yampa <br />River watershed may also be subject to the "dead carbon" issue. The carbon 14 <br />ages measured for this project are shown on Figure 4. <br />FIGURE 4- CARBON 14 AGES, SAGE CREEK MINE <br />I YAMPA RIVER, 2009 NOV 4=1,434 years +1-150 <br />MONTOR WELL COV23, 2 MW 40^ Ys&*- <br />NOT APPUCAKE {4 COALS <br />0 5,000 10,000 15,000 20,000 25,000 30,000 <br />Carbon 14 Minimum Apparent Age, years <br />The Yampa River minimum apparent age was measured as 1,434 years which <br />classifies as recent water (Oldaker 2005). Drainage over coal outcrops in the <br />watershed has probably skewed the results from modern to recent <br />classification. A similar carbon 14 result of 500 years was found for the <br />Apishapa River in the Raton Basin (Oldaker 2004). Another possible source of <br />carbon 12 contamination may be dry deposition from the Hayden Station coal <br />fired power plant. Future surface water sampling should be moved further <br />upstream in the watershed to try and minimize these sources. The tritium <br />modern age classification of less than 65 years was more reliable since it was <br />unaffected by the coal outcrop drainage or dry deposition by the power plant. <br />The Monitor Well COV23 carbon 14 minimum apparent age was approaching <br />30,000 years. Either the "dead carbon" in the coal was skewing the apparent <br />age or the water sample was older than the range of 30,000 years. In either <br />case the dead carbon issue makes the monitor well result unreliable. <br />6