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Last modified
7/14/2009 5:02:34 PM
Creation date
5/22/2009 4:35:55 PM
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UCREFRP
UCREFRP Catalog Number
9317
Author
Spahr, N. E., L. E. Apodaca, J. R. Deacon, J. B. Bails, N. C. Bauch, C. M. Smith and N. E. Driver.
Title
Water Quality in the Upper Colorado River Basin, Colorado, 1996-98.
USFW Year
2000.
USFW - Doc Type
Denver.
Copyright Material
NO
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<br />o <br /> <br />CONCENTRATION, IN MICROGRAMS PER LITER <br />50 100 150 200 <br /> <br />. 1 <br />. . <br />~ 1 I <br />. I I <br />'. I I Concentration <br /> ._9.1-- _"t. MCL or HA <br />9. 1 L Frequency of detection <br /> <br />METHYL TERT-BUTYL ETHER <br /> <br />TETRACHLOROETHENE <br /> <br />CHLOROFORM <br /> <br />1,1,1-TRICHLOROETHANE <br /> <br />1,2,4- TRIMETHYLBENZENE <br /> <br />DICHLOROMETHANE <br /> <br />o <br /> <br />5 10 15 20 <br />FREQUENCY OF VOC DETECTION, IN PERCENT <br /> <br />Figure 10. Volatile organic compounds were detected at low frequencies in <br />monitoring and drinking-water wells sampled in the Southern Rocky Mountains. <br />With a few exceptions (2 samples), concentrations of VOCs were substantially <br />less than water-quality standards. All concentrations shown are greater than <br />o l-lg/L. (MCL, maximum contaminant level; HA, health advisory.) <br /> <br />MTBE was detected in water from <br />one municipal well. MTBE con- <br />centrations greater than the drink- <br />ing-water lifetime health advisory <br />of 20-40 )lg/L (U.S. Environmen- <br />tal Protection Agency, 1997) were <br />not detected. However, once <br />MTBE enters the ground water, it <br />is less vulnerable to decomposition <br />and travels farther than other <br /> <br /> <br />Urban land use in the Southern Rocky Mountains, <br />near Fraser, Colorado. (Photograph by Jeffrey B. <br />Bails, U.S. Geological Survey.) <br /> <br />gasoline compounds (Squillace and <br />others, 1996). <br /> <br />Tetrachloroethene is present in <br />solvents for adhesives and is also a <br />by-product of dry cleaning. Chlo- <br />roform can occur naturally or result <br />from the chlorination of drinking <br />water. I, I , I-Trichloroethane is <br />present in solvents and cleaning <br />agents. 1,2,4- Trimethylbenzene is <br />present in petroleum by-products. <br /> <br />250 <br /> <br />Dichloromethane is predominantly <br />used as a solvent in paint strippers <br />and removers. Concentrations of <br />dichloromethane and tetrachloro- <br />ethene were greater than the <br />USEPA drinking-water standard of <br />5 )lg/L at one site in Silverthorne. <br /> <br />Total coliform bacteria were <br />detected in 21 percent of the <br />ground-water samples collected <br />in urban areas. Total coliform <br />bacteria were detected only in sam- <br />ples collected from the shallow <br />monitoring wells and in none of the <br />water samples from drinking-water <br />wells. Bacteria in ground water <br />may occur naturally in soils or may <br />be related to human or animal <br />waste and, therefore, may be an <br />indication of the sanitary quality of <br />the water (Myers and Sylvester, <br />1997). However, the presence of <br />total coliform bacteria does not <br />necessarily indicate the presence of <br />potentially pathogenic bacteria <br />such as Escherichia coli (E. coli), <br />which was not detected in any of <br />the samples. <br /> <br />25 <br /> <br />Chlorofluorocarbons (CFCs) were used to determine the age <br />of ground water <br />Shallow ground water, which is used for drinking water in part of the <br />Southern Rocky Mountains, is generally young (less than 10 years old) <br />and is more susceptible to contamination as a result of land-use practices. <br />The age of the ground water refers to the time from when the water <br />recharged, or entered, the aquifer to the time it was withdrawn from the <br />aquifer. The presence of contaminants, if any, in ground water can reflect <br />land-use conditions at the time of recharge. The age of the ground water <br />was determined in five urban areas where water-quality samples were <br />collected from shallow alluvial aquifers. The age of ground water at most <br />of the sites sampled ranged from 0 to 10 years old. Ground-water ages of <br />greater than 10 years were found in 7 of 25 wells. <br />In the samples where CFC dates were obtained, four of the five nitrate <br />concentrations greater than 2.0 mg/L were from recently recharged <br />ground water (10 years or younger). This is an indication that current land <br />use may be affecting water quality. Increasing urban development may <br />add nitrate to the ground water from different sources, such as septic sys- <br />tems, application of fertilizers, and domestic animal wastes. Effects of <br />increased urban development on ground-water resources are not extensive <br />· in the study area at present. <br /> <br />10 Water Quality in the Upper Colorado River Basin <br />
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