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<br />000727 <br /> <br />" '~ ''I;1IIi <br /> <br />. <br /> <br />USGS Accomplishments <br /> <br />Data interpretation and report preparation were emphasized during fiscal year 94, An <br />interpretive, peer-reviewed report entitled "Salinity increases in the Navajo aquifer in <br />southeastern Utah," was prepared and accepted by the journal Water Resources Bulletin. This <br />paper describes the bromide, iodide, and stable isotope mixing models that were developed and <br />indicate that oil-field brines are probably not the source of salinity to the freshwater Navajo <br />aquifer. A second report in the form of a USGS Fact Sheet entitled "Using geochemical data <br />to identify sources of salinity to the freshwater Navajo aquifer in southeastern Utah," was <br />prepared and is currently in technical review, This report describes how the geochemical <br />characteristics of the Upper Paleozoic aquifer are consistent with the proposed source of <br />salinity to the Navajo aquifer. Two abstracts describing the study results have been prepared. <br />A technical presentation on the study results received an award by the American Association of <br />Petroleum Geologists, Plans for fiscal year 1995 include completion of the summary final <br />report, publication of the journal article and Fact Sheet, and a technical presentation at the <br />1995 American Water Resources Association Spring Symposium, <br /> <br />Irrigation DrJinage and Selenium-Middle Green River Basin <br /> <br />. <br /> <br />Detailed study of wildlife areas in the middle Green River basin of Utah during 1986-90 has <br />shown that concentrations of selenium in water and biological tissues were harmful to wildlife <br />at the Stewart Lake Waterfowl Management Area, lower Ashley Creek, and the Ouray <br />National Wildlife Refuge, The sources of the Ashley Creek contamination were springs and <br />seeps that discharged water containing as much as 15,000 ,.g/L of selenium, Selenium <br />concentrations in irrigation drainage entering Stewart Lake ranged from 14 to 140 ,.g/L; liver <br />tissue from coots collected from the lake contained as much as 26 ,.gl g; and samples of carp <br />contained as much as 31 ,.g/g, The sources of selenium at Stewart Lake are irrigation <br />drainage and shallow ground water flowing through sedimentary deposits of marine and <br />nonmarine origin, <br /> <br />A significant linear relation (R2=0,65), exists between concentrations of dissolved selenium <br />discharging to Ashley Creek and concentrations of dissolved solids, but no relation <br />(R2= <0,01) exists between loads of selenium and loads of dissolved solids, This indicates <br />that salinity controls that are chosen only to treat large sources of salt loading may fail to <br />control loads of selenium, <br /> <br />The largest source of selenium contamination in the area is seepage originating from the <br />Vernal sewage lagoons, Water in the lagoons is free of selenium, but passes through fractured <br />Mancos shale and discharges to Ashley Creek carrying a selenium load in excess of 1 kilogram <br />per day, There is no direct involvement of a DOl project associated with the sewage lagoons, <br />so planning for remediation will address only selenium load contributed by the Jensen Unit of <br />the Central Utah Project, a DOl project. <br /> <br />In FY 1991, the Bureau of Reclamation, with input from USGS and Fish and Wildlife Service <br />(FWS), began planning remedial action at the contaminated sites, A series of public scoping <br />meetings were held in 1992-93 to solicit public comment on selenium contamination in the <br /> <br />. <br /> <br />17 <br />