Department or Program

Earth and Climate Sciences

Abstract

This study investigates chloride loading mechanisms and contamination of Hart Brook, a Class B impaired tributary of the Androscoggin River in Lewiston, Maine. By examining the hydrologic and geochemical response to a precipitation event following one of Maine's most severe recorded droughts, I assessed whether specific conductivity serves as a reliable proxy for field-measured chloride concentrations and evaluated how Hart Brook responds to storm disturbances. Water samples collected from three sites (HB3, HB4, HB5) before, during, and after a 1.9-inch rainfall event on September 25–26, 2025, were analyzed using Mohr titration to quantify chloride concentrations and to validate its relationship as a proxy to measured specific conductivity data. Stream discharge at site HB3 was quantified using USGS standard gauging methods before and after the precipitation event. My results demonstrate a strong linear correlation between specific conductivity and chloride concentration. Sustained chloride in Hart Brook is suspected to stem from three main factors. These include legacy salt storage in permeable glacial-till and marine-regressive sand aquifers above the confining Presumpscot formation, increased impervious surface coverage from 22% in 1998 to 33.5% in 2025, and continued urban development that accelerates chloride release during precipitation and thaw events.

Level of Access

Open Access

First Advisor

Beverly Johnson

Date of Graduation

12-2025

Degree Name

Bachelor of Arts

Number of Pages

55

Components of Thesis

Introduction

Methods

Results

Discussion

Conclusions & Future Works

References

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