Date of Award

Spring 2015

Degree Type

Publishable Paper

Department

Environmental Engineering

Committee Chair

Raja Nagisetty

First Advisor

Alan English

Second Advisor

Kumar Ganesan

Third Advisor

Beverly Karplus Hartline

Fourth Advisor

Glenn Shaw

Abstract

This study was conducted to develop a hydrogeologic framework, and address water quality concerns in the South Hebgen Basin, near the town of West Yellowstone, Montana. The main goals of this research were to: (1) Develop a conceptual model of groundwater flow within the confined aquifer. (2) Use naturally occurring chemical tracers to investigate the confined aquifer’s extent and the connectivity. (3) Identify the influence of geothermal features on water chemistry. (4) Identify water quality issues related to arsenic (As) and fluoride (F-). Long-term static water elevation plots and surface water flow, combined with water ion chemistry were used to investigate the hydraulic gradients and the transport of chemical tracers. Statistical spatial analysis was used to generate water chemistry and temperature gradients within the confined aquifer. An observed qualitative trend between geothermal influenced areas and certain elevated chemical constituents was corroborated using multiple water chemistry analysis techniques. Water quality concerns were identified by comparing As and F- concentration gradient models to Environmental Protection Agency human health limits. Analysis of hydrogeological data suggests a link between surface water runoff events and groundwater head levels. Generated tracer concentration gradient models provide evidence of a large, interconnected confined aquifer, with multiple recharge sources. Groundwater chemistry and temperature analysis indicate the subsurface geothermals significantly impact water chemistry, and quality within the confined aquifer. Arsenic and F- concentrations were found to exceed the human health limits at numerous locations within the project site, and should be considered a human health concern in the area.

Comments

A non-thesis publishable paper submitted in partial fulfillment of the requirements for the degree of M.S. Environmental Engineering.

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