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000724 . USGS Accomplishments samples, The highest selenium concentration (88 ugfL) was a sample from Navajo Wash near Towaoc, which drains some of the area of long-term irrigation south of Cortez. All data collection for the reconnaissance study has been completed, and the final report is scheduled to be published in early FY 1995. Some additional data were collected in 1994 in parts of the Dolores Project and in the Mancos Project for a followup study and field screening. Selenium was detected in most water samples from the new irrigated area served by the Dolores Project between Yellow Jacket Canyon and Dove Creek. Most of the selenium discharge from the Mancos Project seems to be from the Mud Creek Basin, Irrigation Drainage Reconnaissance of the Pine River Area, Southern Ute Indian Reservation Large concentrations of selenium in ground water have been reported on parts of the Southern Ute Indian Re5frvation, A documented case of human selenium poisoning caused by drinking well water occurred in 1962, Livestock poisoning is reported occasionally on the reservation, These areas also receive irrigation water from the Federal Pine River Project. . This study evaluated the Pine River Project to determine if irrigation drainage is contributing selenium, other trace elements, and pesticides to water, bottom sediments, and biota. Ground water in the Ignacio-Oxford area and near Arboles were sampled for selenium, All data collection has been completed, and a report is published, Irrigation Drainage Detailed Study of the Lower Gunnison and Grand Valley areas The Gunnison and Uncompahgre Rivers and Sweitzer Lake in west-central Colorado were selected for a reconnaissance investigation in 1987 to evaluate potential water-quality problems related to Reclamation's Uncompahgre Project, Existing data indicated that the Uncompahgre Project area may contribute large amounts of selenium and possibly other toxic contaminants to streams and other water bodies. The investigation team for the study performed in 1987-88 was made up of representatives from the U,S, Geological Survey, Fish and Wildlife Service and Reclamation, The report describing the results of the investigation was released in 1991. The resultS of the reconnaissance investigation indicated that the Uncompahgre Project was a significant source of selenium, A detailed study was initiated in 1991 to determine source areas of selenium, geochemical processes affecting selenium concentrations in water, and to document effects to biota, Grand Valley is a significant source of salt to the Colorado River, and the geologic formation that is the source of the salt also is a likely source of selenium, Therefore, Grand Valley was included in the detailed study of the Uncompahgre Project. Data collection for the detailed study was initiated in March 1991 and was concluded in August 1992. Sampling included collection of surface-water, ground-water, soil, bottom- sediment, and various types of biological samples, Mineralogic analyses were done on drill . 14