Electronic Theses and Dissertations

Date

2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Civil Engineering

Committee Chair

Brian Waldron

Committee Member

Farhad FJ Jazaei

Committee Member

Daniel DL Larsen

Committee Member

Stephanie SI Ivey

Committee Member

Deborah DL Leslie

Abstract

Maintaining groundwater quality and availability is crucial, particularly in urban areas with multiple contamination sources and abandoned facilities. This study addresses the challenge of identifying breach locations in multi-layered aquifer systems where inter-aquifer exchange occurs through leaky aquitards. Aquitards act as natural barriers, but breaches can facilitate contamination migration, impacting water quality. Considering gradient changes and breach locations is vital in addressing groundwater leakage. Traditional methods of identifying breaches through particle tracking have limitations in accurately determining breach locations due to the neglect of groundwater flow velocity and the complex path taken by water. This study explores three approaches to model the flow of modern water into a confined aquifer, considering mean age and age ranges. The direct, constant, and pulse methods, based on contaminant transport concepts, provide accurate matches to calculated mean ages at production wells. The pulse and constant methods offer flexibility in simulating complex conditions, with similar mean ages and age range brackets. While mean age is not significantly dependent on dispersivity, age ranges strongly depend on this transport parameter. Additionally, two conceptual models, one with a known breach location and one with an unknown location, are utilized. The constant contaminant transport method is employed to calculate modern water characteristics at production wells. Genetic algorithms minimize discrepancies and optimize breach location and characteristics in the second model. Results show that assuming one breach yields a close approximation, with smaller breaches situated closer to the sampling point. Differentiating between contamination sources and breach locations necessitates modifications to flow simulations. Future research should consider diverse field data, additional observation locations, and multiple objective functions to enhance breach location identification accuracy.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest

Notes

Embargoed until 6/6/2024

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