Date of Award

Fall 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering

Committee Chair

Raja Nagisetty

First Advisor

Jeanne Larson

Second Advisor

Glenn Shaw

Third Advisor

Pat Cuneen

Abstract

Historical mining activities in Butte, Montana contributed to the deposition of heavy metal contaminated mine waste/tailings along the tributary streams of the Clark Fork River. These tributary streams, Silver Bow Creek (SBC), Blacktail Creek (BTC), and Grove Gulch make up the headwaters of the Clark Fork River, which flows through western Montana. SBC is currently impaired for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), mercury (Hg), zinc (Zn), and sedimentation (MTDEQ, 2016). BTC is the headwaters of SBC, while Grove Gulch discharges into BTC. Grove Gulch is an intermittent stream south of Butte, that is approximately 6 miles in length. The Grove Gulch watershed is the location of the historic Timber Butte Zinc Mill, which throughout its thirty-five-year life produced an estimated one million cubic yards of tailings that were impounded along the path of Grove Gulch. These “in-place” tailings have since been buried, capped (with a geotextile membrane), and developed into the Copper Mountain Recreational Complex (CMRC), but mine tailings are still present in the watershed and creek.

The aim of this study is to characterize Grove Gulch Creek and its watershed, identify heavy metal sources, and conduct a feasibility study. Grove Gulch Creek spatial sample analysis data suggest that the concentrations are significantly elevated immediately downstream of the wooden culvert discharge and decrease as the creek flows towards BTC. Of the ninety-five water samples analyzed, 42% exceeded aquatic life standards and 18% exceeded human health standards for at least one heavy metal. Soil sampling results identified small patches of mine waste around the perimeter of the CMRC. In general, As, Cu, Pb, Zn were elevated in these mine waste patches, however, two of the twenty-seven samples exceeded recreational human health standard for arsenic. Heavy metal concentrations in the streambed and banks varied spatially along Grove Gulch with higher concentrations near the wooden culvert and trailer park areas.

A feasibility study was conducted to evaluate the Best Management Practices (BMPs) based on technical feasibility, cost-benefit analysis, environmental benefits, and human health and safety. Given the complex nature of sources (groundwater, soil, and runoff), the study recommends a combination of three remedial options. A retention basin could be constructed on Grove Gulch before the confluence with BTC to capture runoff and precipitate sediments and associated adsorbed heavy metals. A sulfate reducing bio-reactor could be used to capture and treat the metal-laden groundwater discharge from the wooden culvert. Stabilization of exposed mine tailing and revegetation along the CMRC perimeter would minimize weathering and reduce risk to recreational users in the area. Together these three remedial options could reduce the human health risk along the lower section of Grove Gulch and also reduce the heavy metal loading into BTC.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Masters of Science in Environmental Engineering

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