Water Resources Professional Project Reports

Bryan Lawlis

Document Type

Technical Report

Publication Date

12-13-2013

Abstract

The Shiprock Disposal Site is located in Shiprock, NM and was the site of the former Navajo Mill, a uranium and vanadium ore processing facility. The site occupies approximately 230 acres on a terrace overlooking the San Juan River and its adjacent flood plain. Uranium and Vanadium were extracted from ores mined from various locations from 1954 through 1968. The contaminants of this leaching process percolated into the groundwater on the terrace and the floodplain. The remediation of the Navajo mill site was recommended by the EPA in 1974. The Department of Energy (DOE) completed the Shiprock Uranium Mill Tailings Remedial Action (UMTRA) in 1986, which consisted of consolidating all tailings and other materials from two tailings piles and waste from raffinate ponds that were combined and placed in one on-site disposal cell. Many Devils Wash (MDW) is one of two prominent arroyos near the former mill site that has continuous groundwater seeps. Surface water and groundwater in MDW contain the same constituents as the groundwater located under the processing site. Tailings from the mill were not discarded near MDW. The groundwater constituents at MDW are hypothesized to have two potential sources. Due to similar chemical constituents between MDW and the mill, one of these sources could be the former mill site. The other source suggests that the constituents are naturally occurring from minerals present in the weathered Mancos Shale. This study examined whether groundwater from beneath the mill site is migrating to or away from MDW. This study depended on various sources including multiple age dating techniques, the directional flow of groundwater, and the relationship of stable isotopes O and H. Since the mill site operated from 1954 to 1968, elevated levels of age-dating tracers were used in investigating the age of groundwater that recharged from the milling process. The goal of this research was to identify the location of the water recharged during the milling process as well as age of the groundwater in MDW. The results of this research demonstrate that groundwater from several wells to the west of the mill contain age dating tracers that suggest the majority of groundwater was derived from the mill operation era. The complementary results are not evident elsewhere, thus the constituents in MDW may not be related to past milling operations.

Language (ISO)

English

Keywords

Radioactive pollution of water--New Mexico--Shiprock., Radioactive waste disposal in the ground--Environmental aspects--New Mexico--Shiprock., Radioisotopes--Migration--New Mexico--Shiprock., Groundwater--Pollution--New Mexico--Shiprock.

Comments

A Professional Project submitted in partial fulfillment of the requirements for the degree of Master of Water Resources, Water Resources Program, University of New Mexico.

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