Remediation of Acid Rock Drainage in a Changing Climate: Assessment of Bulkhead Closures and Long-term Water Quality Trends in the Colorado Mineral Belt

Petach, Tanya

Graduate Thesis Or Dissertation

Remediation of Acid Rock Drainage in a Changing Climate: Assessment of Bulkhead Closures and Long-term Water Quality Trends in the Colorado Mineral Belt Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/5d86p1522

Abstract

Acid rock drainage (ARD) produces low pH, high metal concentration waters into receiving waters down-gradient from oxidizing sulfide minerals. ARD can degrade habitat, poison aquatic organisms, and lead to the transport of heavy metals long distances down streams. This dissertation investigates ARD responses to three different perturbations: decadal-scale response to targeted AMD remediation strategies including source material removal and bulkhead installation, decadal-scale response to climate change, and month-scale response to bulkhead implementation in draining mine adits. The goal of these investigations is to advance the understanding of ARD responses to anthropogenic and natural changes to help optimize remediation actions and future management of ARD affected waters. First, monitoring water quality data were paired with USGS flow gage data and an estimator was used to estimate higher temporal frequency records of in-stream water quality in three ARD affected alpine watersheds. These data were then analyzed for trends in water quality corresponding with timing of treatment implementation. Two streams record decreased zinc concentrations following treatment implementation; one stream records a substantial increase in zinc concentration following a shift from active treatment to passive, bulkhead-oriented treatment strategies. A second study investigated trends in background ARD in response to local climate change at 24 headwater stream sites across the Colorado Mineral Belt. Zinc concentration increased at 75% of sites over the period of record (10-40 years) by 2-6 fold and sulfate concentration increased at 96% of streams. The final study presented in this dissertation investigates the short-term impacts of a bullhead closure on water quality in receiving waters. Results indicate that sulfate and heavy metal concentrations decreased during the test closure buy 65-68%. However, the short duration of the test closure and the relatively small volume of water impounded during the test closure (<1% of the estimated storage volume) leave uncertainty over longer-term impacts of the bulkhead test. Collectively, the studies presented in this dissertation expand the knowledge of ARD responses to both remediation-based changes and natural climate driven changes on the catchment scale.

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