Water Resources Professional Project Reports


Martha A. Hall

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Recent studies have shown that hexavalent chromium (Cr(VI)) is present in some drinking water systems across the United States. These studies are important because stricter standards on chromium are currently being researched by the United States Environmental Protection Agency (EPA) and implemented by California. With renewed attention to the occurrence and toxicology of chromium, a better understanding of its occurrence in the Albuquerque Bernalillo County Water Utility Authority (Water Authority) water supply is important. The Water Authority water system receives water from approximately 90 production wells and surface water from the Rio Grande. The San Juan Chama Surface Water Treatment Plant was completed in 2008 to reduce the dependence upon the aquifer. In 2011 a study was conducted to determine the presence of Cr(VI) in groundwater wells and measured general chemistry, metals, field parameters, and chromium speciation. The general chemistry and metals analyses were completed by the Water Authority Water Quality Laboratory (WQL) while the hexavalent speciation and total chromium analyses were performed by Montgomery Watson Harza (MWH) Laboratory in California. The purpose of this project was to develop a better understanding of the occurrence of total and hexavalent chromium in the Water Authority water supply. The project consisted of two fundamental objectives. Graphical and statistical methods were used to determine if a correlation of Cr(VI) exists with other analytes which could allow for easier identification of areas with suspicion of increased Cr(VI) levels. Secondly, using Geographic Information Systems (GIS) mapping determined the spatial distribution of total and hexavalent chromium in the Water Authority source waters. Results for total and hexavalent chromium in the Water Authority system approach a one to one relationship in both the production wells and distribution system. Statistical analyses determined that seven analytes correlated to chromium concentrations. These include calcium, barium, sodium, fluoride, nitrate, field pH, and temperature. Coefficients of determination were higher than found in previous national studies. The best correlation and point distributions were associated with calcium and sodium. The highest correlation analytes also displayed similar occurrence patterns as in the correlation analyses when displayed on GIS plots. When comparing the spatial distribution of total chromium to that reported by Bexfield (et al., 1999) study, a stronger presence on the west side of Albuquerque was noted with the occurrence pattern in the remainder of town exhibiting little change. New wells that were drilled and equipped in the area since 1999 show that total and hexavalent chromium concentration correlates to volcanic deposits located west of Albuquerque.

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hexavalent chromuim, water systems, Water Authority


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