Date of Award

Spring 2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering

Committee Chair

Raja Nagisetty

First Advisor

Kumar Ganesan

Second Advisor

William Drury

Third Advisor

Alysia Cox

Fourth Advisor

Gary Wyss

Abstract

Silver Bow Creek (SBC) – the headwaters for the Clark Fork River – is impaired for total nitrogen (TN) and total phosphorus (TP), as well as several heavy metals, including arsenic, cadmium, copper, lead, and mercury. Blacktail Creek (BTC) is the main tributary of SBC, with Grove Gulch entering BTC before it discharges into SBC. Grove Gulch flows approximately six miles before entering BTC approximately 75 feet upstream of Lexington Avenue, and the stream drains primarily open, rolling range, a historic metal milling site (Timber Butte zinc mill) and a reclaimed mine waste repository that is now Copper Mountain Recreation Complex (CMRC).

Surface water samples were collected during six different sampling events at different flow stages and locations spanning the entire reach of Grove Gulch, and analyzed for heavy metals and nutrients. The results indicated that there are consistently high levels of TP, which could be due to the predominant geologic formations in the Grove Gulch drainage. The TN and TP concentrations increased linearly from upstream to downstream locations, especially during storm runoff events. Private land that is used for grazing appears to be a potential non-point source of TN and TP, as well as the wetland areas that contribute high algal growth near the mouth of Grove Gulch. The longitudinal sampling also indicated that Grove Gulch is contributing significant levels of heavy metals into BTC, primarily zinc, copper, lead, and iron, with elevated concentrations downstream of the CMRC for both base flow and storm water runoff samples. This substantial increase in heavy metals downstream of the CMRC suggests that the groundwater is flowing through the mine tailings before entering Grove Gulch, with additional contamination possibly coming from surface runoff near the reclaimed mine waste repository.

To reduce the nutrient loading and heavy metals in Grove Gulch, two primary bestmanagement practices (BMPs) are suggested for implementation. Vegetated stream buffers at selected sites along Grove Gulch could reduce the TN and TP loading in the creek. Additionally, a passive subsurface bioreactor system that could be located near the wetlands or near the creek’s discharge point with BTC could precipitate out the heavy metals of concern, as well as convert the nitrates to nitrogen gas before they enter BTC. The treatment of pollutants in headwater streams such as Grove Gulch is more feasible and efficient than treatment in higher-order streams such as Silver Bow Creek.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of

Master of Science in Environmental Engineering

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