Abstract

Dams have served a vital role in American industry, providing flood control, irrigation, navigation, and hydropower. However, many of these dams no longer serve their initial purpose or are potentially hazardous to downstream communities because of aging infrastructure. Dam removals are becoming increasingly popular methods of reducing the risk of dam failure, restoring river ecological function, and eliminating long-term costs associated with maintenance and repairs. Dams do more than just store water; as water approaches the impoundment area, its velocity is reduced, which allows suspended sediment to settle and accumulate in the impoundment area. Removing a dam allows some fraction of this sediment and any associated contaminants such as heavy metals, organochlorines, and polynuclear aromatic hydrocarbons to mobilize downstream. To protect aquatic life and river health, an analysis of the quantity and quality of impounded sediment is required before dam removal. My research characterized the grain size, organic matter fraction, and mercury content of sediment impounded at Mill Pond and Sawyer Mill. Understanding the relationships between these variables and their spatial distribution throughout an impoundment could reduce the number of samples required to characterize an impoundment before dam removal, as potential hot-spot areas can be identified and targeted for sampling efforts. Though my results displayed no statistically significant relationships between variables, discovering mercury content levels of close to 4,000 parts per billion in fine-grained sediments at Mill Pond displays the need for such research.

Publication Date

Spring 4-7-2020

Journal Title

Inquiry Journal

Mentor

Anne Lightbody

Publisher

Durham, NH: Hamel Center for Undergraduate Research, University of New Hampshire

Document Type

Article

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