Date of Award


Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Environmental Engineering (MS)

Administrative Home Department

Department of Civil and Environmental Engineering

Advisor 1

Noel Urban

Advisor 2

Judith Perlinger

Committee Member 1

Carol MacLennan

Committee Member 2

Martin Auer


Torch Lake was subject to approximately 100 years of industrial pollution due to the dumping of waste associated with copper mining in the Keweenaw Peninsula, which lasted from approximately the 1860s through the 1960s. It is well-known that this waste included copper-containing mine tailings. What was less understood are the impacts of polychlorinated biphenyls (PCBs) and heavy metals besides copper on the lake system.

The objectives of this thesis are to summarize the status of contamination and remediation activities in Torch Lake and to estimate the magnitude of potential sources of PCBs to Torch Lake. First, a brief overview of the history and problems at Torch Lake is provided. Next, the activities that generated the metals contamination and the impact of the dumping of mine tailings into the lake are described. Then, the history of remediation activities at Torch Lake is summarized. These two historical summaries provide context for the analysis of heavy metals and PCBs in Torch Lake. Following that is an analysis of the spatial and temporal distribution of heavy metal observations and occurrence of criteria concentration exceedances. Finally, an analysis of the contamination of Torch Lake by polychlorinated biphenyl compounds (PCBs) is performed, in which evidence for possible local and ongoing sources of PCBs to Torch Lake is presented.

Analysis of metals in Torch Lake revealed two major findings: 1) that the western shoreline is not safe for development, and 2) that a more effective remediation method for the shoreline soils and lake sediment should be considered. The western shoreline is not safe for residential development because arsenic, and lead are present in the soil at concentrations that are considered harmful to humans. Many of the concentrations of the metals in sediment are above the Threshold Effect Concentrations, which implies that the vegetated soil caps along the shoreline are failing to achieve one of the goals of their creation. . The possible failure of vegetated soil caps and natural sedimentation suggest that a more effective remediation method is necessary.

Evidence points to the existence of a local and possibly ongoing source of PCBs in Torch Lake. This is inferred from several facts. Concentrations of PCBs in water and fish from Torch Lake are higher than concentrations found in water and fish from other area lakes. The location of concentrations of PCBs above detection limits in sediment, soil and groundwater, compared to the locations of historical industrial buildings, indicate that a source of PCBs to Torch Lake besides atmospheric (re)deposition does exist. A possible ongoing source of PCBs to Torch Lake was inferred from comparison of mass balance modeled concentrations to SPMD-estimated concentrations of dissolved PCBs. The mass-balance-modeled concentrations of PCBs in Torch Lake were lower than the SPMD-estimated concentrations, which implies that an input of PCBs to the lake exists which has not yet been identified. In addition, over time, the concentrations of PCBs in fish caught in Torch Lake remain higher than fish caught in Huron Bay (a waterbody assumed to be subject only to PCB contamination from atmospheric (re)deposition).

This thesis demonstrates the advantage gained from examining the transport and transformations of chemicals in an environmental system when determining remedial action on that system. It is demonstrated that it is important to understand how a chemical can be transported before choosing a method of remediation for that chemical. It is shown that one cannot simply infer that because concentrations of a chemical in one medium are low, that it cannot cause high concentrations of that same chemical in another medium. This thesis also demonstrates how examining the historical activities of a site can be used to help predict the type, location and extent of contamination, especially when combined with examining the behavior of the chemicals involved. This thesis is a case study of how remediation policy should be re-examined to become more effective. (1744249 kB)