Forgrave, Rebecca
(2022)
Timing, Transport, and Impacts of Sewer Subsidies to Pittsburgh’s Nine Mile Run.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
This dissertation examines the surface and subsurface connections between sewer pipes and buried streams in a small watershed in Pittsburgh, PA. Rainfall-runoff responses from high-frequency precipitation and discharge records reveal that extensive channel burial led to storm flows that were substantially faster than other urban watersheds of comparable size and imperviousness. Further, several events with anomalously high runoff ratios suggest the contributions of other water subsidies such as sewer overflows, hydrant flushing, and water line breaks to the event flows. These rapid storm responses led to dilution of nitrate and other chemical parameters in the stream water, but an increase in nitrate concentration after the event, suggesting contributions from combined and sanitary sewers filled beyond capacity and subsequent transport to the stream. Triple nitrate isotopes reveal that sewage is the dominant contributor to total nitrate loads in all storms. In low flow conditions between storm events, daily fluctuations in chemical concentrations are affected by the seasonal variation in groundwater elevation, which determines the extent of hydrologic connection between leaking sewer pipes and adjacent buried or surface stream channels. Higher groundwater in spring led to mixing of different end-member chemistries and lack of distinct diurnal patterns, while lower groundwater in fall limited subsurface connectivity. The findings from this dissertation highlight the limitations of end of pipe solutions such as stream restoration to the challenges created by buried streams and sewer infrastructure failures. The rapid event responses from stream burial and solute fluxes from sewer overflows could get worse as climate change predictions suggest an increase in high intensity storms.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
3 April 2022 |
| Date Type: |
Publication |
| Defense Date: |
29 March 2022 |
| Approval Date: |
24 October 2024 |
| Submission Date: |
7 April 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
152 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Environmental Science |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Urban streams, hydrology, biogoechemistry, sewer leaks, sewer overflows, Nine Mile Run |
| Related URLs: |
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| Date Deposited: |
24 Oct 2024 15:37 |
| Last Modified: |
24 Oct 2024 15:41 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/42548 |
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