Date of Award
As beaver dam analogue (BDA) structures become an increasingly popular restoration technique, the need to better understand the capabilities of natural beaver dam complexes has become evident. While several components of the natural systems have been extensively studied, very little investigation has focused on the physical makeup and chemical capacity of sediments retained in these complexes. Since the physical and chemical properties of sediments have the potential to positively affect water quality by attenuating contaminants, the aim of this study is to uncover what types of geologic materials are retained in natural beaver dam complexes and if they are participating in sorption. To that aim, sediment cores were drilled on an abandoned, dry pond surface near the outlet of Muddy Gulch catchment located within a Wildlife Management Area in Deer Lodge County, Montana. The sediment cores were analyzed to determine type and texture, pH values, nutrient content, and contaminant concentrations. Sediment type and texture was determined with standard mud-logging techniques and the commonly accepted Udden-Wentworth grain-size scale. Testing for pH and nitrate (NO3-) was conducted with simple water leachates to replicate water naturally flowing through the system and realistically represent values that plant root systems may encounter at various depths. Contaminant levels of Arsenic (As), Cadmium (Cd), Copper (Cu), Lead (Pb), and Zinc (Zn) were collected with a handheld X-ray Fluorescence analyzer (XRF), utilized in a manner consistent with industry standard practices. Data was evaluated based on ‘Reclamation Criteria’ set forth by the EPA as part of the Anaconda Regional Water, Waste, & Soils Baseline Ecological Risk Assessment which outlined minimum physiochemical specification for soils in this area impacted by historic mining and smelting activities. Contaminant and pH criteria exceedances were found in pre-restoration fine sediments (particularly clays) indicating that metals appear to be sorbed to clay-rich sediments. This suggests that clays play an important part in the natural system’s capacity to attenuate contaminants and should be incorporated into BDA designs in order to increase their effectiveness for improving water quality.
Peach, Carly, "BEAVER PONDS AS CATCHMENT-WIDE RETENTION BASINS FOR HEAVY METALS SEQUESTRATION" (2021). Graduate Theses & Non-Theses. 261.