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General Overview

From 1942 through 1946, the Vanadium Corporation of America operated a vanadium and uranium mill in Monticello, Utah. In 1948, the U.S. Atomic Energy Commission (AEC) purchased the mill site and milled uranium from 1949 until the mill was permanently closed in January 1960. During operation of the mill, associated contaminants were released into the surrounding environment through atmospheric releases, effluent discharges into Montezuma Creek which flows through the middle of the mill site, and runoff and soil infiltration from associated tailing piles. In 1961, the AEC stabilized the tailing piles by covering them with soil, and by 1975 the mill structure had been demolished and buried. These actions however, did not eliminate surface water or ground water contamination. In 1989, the mill site was placed on the Comprehensive Environmental Response, Compensation, and Liability Acts National Priorities List. Remediation of portions of the properties was initiated in approximately 1992 and completion was anticipated in the late 1990's.

Elevated concentrations of several contaminants have been found in the surface water of Montezuma Creek and in ground water on and near the mill site. Arsenic, iron, manganese, molybdenum, selenium, uranium, vanadium, and zinc are at least periodically elevated downstream of the mill site, and activities of gross alpha, gross beta, and radium-226+228 are above background. Additionally, high concentrations of total dissolved solids, sulfate, phosphate, and nitrate+nitrite typically occur, specific conductance and alkalinity are elevated, and pH has exceeded 9.0 on a few occasions.

The primary objectives of this study were to provide the data needed to (1) assess the ecological risk of biota in Montezuma Creek to contaminants associated with the mill site, and (2) evaluate and document the current ecological condition of Montezuma Creek so that the effectiveness of future remedial actions can be evaluated.

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Last Modified: April 17, 2001