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<br />l\) All data collection has been completed, and a report will be <br />~. published in 1993. <br />.,J <br />C.H Animas Valley Methane study <br /> <br />This study will map the distribution of and determine the sources <br />and migration pathways of methane in shallow ground water of the <br />AnimasRi ver Valley between Durango, Colorado, and Aztec, New <br />Mexico.' Between August 1990 and May 1991, methane concentrations <br />were meil,sured in 205 ground-water samples, 192 soil columns at <br />ground-water sites, and 352 soil columns by gas-well casings, In <br />addition, gas samples were collected from 16 water samples, 3 open- <br />field soil seeps, 11 soil columns adjacent to gas-well casings, and <br />30 gas wells for analysis of molecular and isotopic composition. <br />The latter samples were collected to provide information about <br />possible sources of methane. <br /> <br />Two reports have been prepared covering this study. A Water- <br />Resources Inve-stigations Report (WRI) describing how data were <br />colI ected and I isting the data is in the review process, An <br />interpretative WRI has undergone colleague review and is being <br />prepared for cooperator review. <br /> <br />Irrigation Drainage Detailed study of the Lower Gunnison and Grand <br />Valley areas <br /> <br />The Gunnison and Uncompahgre Rivers and Sweitzer Lake in wes,t- <br />central Colorado were selected for a reconnaissance investigation <br />in 1987 to evaluate potential water-quality problems relat~d to <br />Reclamation's Uncompahgre Project, Existing data indicated that <br />the Uncompahgre Pro ject area may contribute large amounts of <br />selenium and possibly other toxic contaminants to streams and~ther <br />water bodi,es. The investigation team for the study performed in <br />1987-88' was made up of representatives from the USGS, Fish and <br />Wildlife Service, and Reclamation. The report describin~ the <br />results of the investigation was released in 1991, <br /> <br />The results of the reconnaissance investigation indicated that the <br />Uncompal).gre Project was a significant source of selenium. A <br />detaileq study was initiated in 1991 to determine source areas of <br />selenium, geochemical processes affecting selenium concentrations <br />in water, and to document effects to biota. Grand Vall ey is a <br />significant source of salt to the Colorado River, and the geologic <br />formation that is the source of the salt also is a likely SOUrce of <br />selenium. Therefore, Grand Valley was included in the detailed <br />study of the Uncompahgre Project. <br /> <br />Data collection for the detailed study was initiated in March 1991 <br />and was concluded in August 1992, Sampling included collection of <br /> <br />I <br />,;t "' <br /> <br />, . <br /> <br />':"1. <br /> <br />ill <br />i\ 'i.>..;~~:.c-",,~, o.L_",.i-"" . <br />