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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 />shallow ground-water system have <br />been affected by urban land use, <br />but these effects were not found in <br />the deeper ground water used for <br />drinking water. <br />Generally, low levels of pesti- <br />cides and volatile organic com- <br />pounds were detected in ground <br />water from shallow alluvial aqui- <br />fers in urban areas. Most agricu]- <br />ture (and pesticide use) in the basin <br />occurs in the Colorado Plateau <br />where ground-water studies were <br />not conducted. The pesticides that <br /> <br />were detected in the ground water <br />sampled in the Southern Rocky <br />Mountains were primarily herbi- <br />cides used for controlling grasses <br />and weeds in nonagricultural areas. <br />Concentrations were very low (less <br />than 0.] /lg/L) for most of the pes- <br />ticides detected. Two herbicides, <br />bromaci] and prometon, were <br />detected in urban areas at concen- <br />trations less than the USEPA drink- <br />ing-water guidelines (U.S. <br />Environmenta] Protection Agency, <br />]996). <br /> <br />Volatile organic compounds <br />(VOCs) were detected in ground- <br />water samples at generally low <br />concentrations. The six most fre- <br />quent]y detected VOCs were <br />methyl tert-buty] ether (MTBE), <br />tetrach]oroethene, chloroform, <br />],], I-trichloroethane, 1,2,4-tri- <br />methylbenzene, and dich]oro- <br />methane (fig. 10). MTBE, a <br />gasoline additive, was detected in <br />at least one well in four of the five <br />urban areas where shallow ground <br />water was sampled. In addition, <br /> <br />RADON CONCENTRATIONS IN UCOL GROUND WATER WERE <br />GENERALLY HIGHER THAN OTHER AREAS OF THE NATION <br /> <br />Radon concentrations in alluvia] aquifers of the UCOL are among the highest of all NAWQA ground-water <br />samples nationwide (S.J. Ryker, USGS, written commun., 1999). Radon is a naturally occurring, colorless, odor- <br />less, radioactive gas derived from the decay of uranium. Radon has been identified as a human carcinogen and <br />can enter a building from seepage of air through dirt floors, cracks in concrete floors or walls, floor drains, or <br />through the use of water supplied from wells. A greater risk of exposure to radon exists in urban areas due to the <br />prevalence of enclosed structures, such as basements, which can trap radon gas. <br />Though the USEPA does not currently (2000) regulate radon in drinking water, there is a proposed maximum <br />contaminant ]evel (MCL) of 300 picocuries per liter (pC ilL) for radon in drinking water (U.S. Environmenta] <br />Protection Agency, 1999). Radon concentrations were greater than the proposed MCL for all wells sampled in <br />the Southern Rocky Mountains. Higher radon concentrations were measured in the Winter Park/Fraser and <br />Silverthorne areas. Igneous and metamorphic rocks, which can contain uranium-bearing minerals, are common <br />rock types in these areas. <br /> <br /> <br />Ranking of ground-water radon concentrations <br />relative to all NAWQA ground-water studies <br />(data from multiple wells in indicated areas) <br /> <br />. Greater than the 95th percentile <br /> <br />. Between the 90th and 95th percentile <br />o Between the 75th and 90th percentile <br /> <br />. 1,000 in at least 25 percent of samples <br />m 600 in at least 25 percent of samples <br />a 300 in at least 25 percent of samples <br />o 300 in fewer than 25 percent of samples <br /> <br />Major Findings 9 <br />
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