The sampling area of interest in the Uncompahgre Valley includes the land to the east of the river and to the west of the Black Canyon uplift, which is underlain with Mancos shale. This sampling has taken place during the course of the soil survey staff's primary activity, which is mapping the soils of the valley. Last field season, the soils staff obtained samples from over forty sites. After sending these samples to the Bureau of Reclamation in Denver to be prepared for selenium analysis, they were sent to the US Geological Survey lab. Here, the samples are analyzed for total and soluble Se.
Soluble selenium is the part of the total selenium that is available to be released into solution.
It is during this infiltration process that the Se which is soluble may travel with the groundwater until it eventually reaches the river. This is the fraction of selenium with which the STF is most concerned, since water sampling has shown that the Uncompahgre River does not presently meet EPA standards for Se levels. The data for these samples were received in the Montrose Soil Survey Office in March. Generally speaking, the highest levels of Se exist in the Mancos shale areas that have not been irrigated. Therefore, the brunt of the problem does not lie in established cropland, but in creating additional irrigated areas in and around the adobe hills.