Master of Science (MS)
Emmanuel J. Gabet
Chemostratigraphy, Fluvial Geomorphology, Gold Rush, Hydraulic Mining, Mercury Contamination, Yuba River
Geomorphology; Physical education
Since the onset of hydraulic mining in the Sierra Nevada in 1852, the environmental damage caused by displacement and storage of hydraulic mining sediment (HMS) has been a significant problem in downstream environments. Large volumes of mercury-laden HMS from the Yuba River watershed were deposited within the river corridor between the present site of Englebright Dam and the city of Marysville, CA, creating the anthropogenic Yuba Fan. However, there are outstanding uncertainties about how much HMS is still contained within this fan. To quantify the deep storage of HMS, I collected sediment from borings and outcrops along the lower Yuba Fan and analyzed mercury concentrations at multiple depths. The mercury concentrations served as chemostratigraphic markers, which I used to find the stratigraphic contact depths between the HMS and underlying pre-mining deposits. I found in these hydraulic mining sediments mercury concentrations of order 10-1 ppm orders of magnitude, which are ten-fold higher than the pre-mining deposits. My analysis of the lower Yuba Fan’s volume suggests that over the span of 147 years approximately 8.99 × 107 m3 of HMS have been deposited within the study area between 1852 and 1999. Moreover, I estimate that 4.24 × 103 kg of mercury are presently stored along the floodplains of the Yuba River where the mercury may continue to enter the food web and have detrimental effects on the local ecosystems.
Nakamura, Tyler Kou, "Remains of the 19th Century: Deep Storage of Hydraulic Mining Sediment Along the Lower Yuba River, California" (2017). Master's Theses. 4815.