Aerial view of surface oil contamination from the pipeline rupture at the Bemidji Crude Oil Spil Research Site, Minnesota (circa 1979). Much of the black area was caused by oil spraying from the rupture.

Map of surface oil areas resulting from the pipeline rupture at the Bemidji Crude Oil Spil Research Site, Minnesota. The map delineates areas where the oil pooled in the subsurface, where oil drained, where oil sprayed from the rupture, and where soil was removed.

Oblique areal view of the crude oil spray area at the pipeline rupture site. USGS scientists and others have been studying the long-term fate of the spilled crude oil.

Conceptual model of the subsurface contaminant plume's microbial geochemistry. The model show the right to left progression of what electron acceptors are being used by subsurface microbial communities to degraded dissolved oil constituents in groundwater.

Collecting vapor samples from contaminated areas in the unsaturated zone. The USGS scientist is using a syringe to extract air from a small sampling tube that extends into the subsurface.

USGS scientists cutting a frozen core for later biogeochemical analysis. Freezing the core keeps the natural pore fluids in place. The scientists have been studying the natural attenuation of plume of dissolved constituents in groundwater that resulted from a curde oil spill.

A scientist operating a gas chromatograph in an on site laboratory. The on site laboratory enables the scientists to make measurements quickly so sampling plans can be adjusted on the fly.

Installing a tensiometer in the unsaturated zone prior to a tracer test. Tensiometers are used to measure water pressure in the unsaturated zone.

USGS scientist measuring hydrogen gas in groundwater samples in the on site laboratory at the Bemidji Crude Oil Spil Research Site, Minnesota. Hydrogen is an important intermediate compound that is both produced and consumed during biodegradation. The hydrogen gas concentrations can help identify the types of microbial communities that are degrading contaminants.

USGS scientists conducting a subsurface tracer test at the Bemidji Crude Oil Spil Research Site, Minnesota. The scientists use tracer tests to study subsurface contaminant transport processes.

USGS scientist working on geochemical characterization of the contaminant plume at the site. A multidisciplinary team of scientists from the USGS and other organizations have been studying the natural attenuation of crude oil in the subsurface.

USGS scientist collecting an unsaturated-zone gas sample with a syringe from a vapor sampling well. The sample was used to study the natural attenuation of hydrocarbon vapors in the unsaturated zone.