Invited Luncheon Speaker - September 7, 2010 - Dr. Mindy Erickson - USGS

Crude Oil at the Bemidji Site: 27 Years of Research, Modeling and Understanding

Abstract

On August 20, 1979, a crude-oil pipeline burst, spilling and spraying about 10,700 barrels of crude oil onto a glacial outwash deposit approximately 10 miles northwest of Bemidji, Minnesota.  After cleanup efforts were completed, about 2,500 barrels of crude oil remained in the unsaturated zone or on the water table.
 
In 1983, a long-term and ongoing interdisciplinary research project sponsored by the U.S. Geological Survey (USGS) Toxic Substances Hydrology (Toxics) Program began at this spill site, also known as the National Crude Oil Spill Fate and Natural Attenuation Research Site (site). Studies at the site were among the first to document the importance of anaerobic biodegradation processes for hydrocarbon removal and remediation by natural attenuation.  In 2009, USGS joined into a collaborative agreement with Enbridge Energy, Limited Partnership, the Minnesota Pollution Control Agency, and Beltrami County.  The collaborative agreement was created to foster and partially fund new and continuing research at the site.
 
Site research by scientists from the USGS, academia, and industry is directed toward understanding the physical, chemical, and biological processes controlling the subsurface fate of hydrocarbon contaminants. The goal is to provide information and methods for evaluating the performance of bioremediation of petroleum hydrocarbon contamination across the nation.
 
Important results include:

• The hydrocarbon plume degrades mainly under anaerobic conditions, and the anaerobic zone expands a few meters each year.
• In the source zone, oil saturations are 10-70%, oil migration is negligible, and degradation is more rapid in an area of focused recharge.
• Soil gas above the source zone was initially high in volatile petroleum hydrocarbons, but now contains mainly methane and CO2 from biodegradation of the oil.
• Simulation of hydrocarbon fate and transport affirmed concepts developed from field observations, and provided estimates of field-scale reaction rates and hydrocarbon mass balance.
 

Bio

Dr. Mindy Erickson is the groundwater specialist in the Minnesota Water Science Center of the U. S. Geological Survey (USGS), and a faculty member of the University of Minnesota. Her primary research interests are the geochemistry, fate, and transport of organic chemicals and metals in groundwater.