New science from an old oil spill
A research hydrologist at the U.S. Geological Survey says an oil spill northwest of Bemidji in 1979 has taught them about the environmental effects of oil contamination. In fact, it's the same pipeline that ruptured and ignited this week near Clearbrook in northern Minnesota.
In August of 1979, a crude oil pipeline going from Alberta, Canada to Chicago, Ill. broke open and spilled 1.7 million liters of crude oil. The pipeline was owned by Lakehead Pipe Line Partners. Today, that company is Enbridge Energy.
Geoff Delin, a research hydrologist at the USGS has been studying the consequences of that spill for 24 years. He says that accident was far worse environmentally than the fire and explosion that took place this week.
Delin says the geology of a region can determine how much damage an oil spill will cause. The spill near Bemidji in 1979, happened in sandy, gravely soil. But the soil at the Clearbrook spill is clay down to 50 feet.
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"Clay is a very low permeability or relatively low permeable material compared to the sand and gravel that's over at the Bemidji site," Deline says. "Any oil that did spill and wasn't contained is much less likely to go down to the water table."
Delin says damage to an adjacent wetland near the spill this week may be limited as well.
"That's an indication that the water table is fairly shallow, but if they cleaned it off of the wetland, that should do it," Deline says.
Just knowing the differences in the hydrogeology would provide some answers about the consequences for groundwater contamination.
"So the results that we obtained at Bemidji can be used as a reference point and the migration of contaminants at Clearbrook -- if it were the exact same size spill and what have you -- would be much less just because it's clay material."
At the time of the spill in 1979, the pipeline company recovered about 60 percent of the crude oil, but that still left about 400,000 liters in the ground. According to Delin, the Minnesota Pollution Control Agency said leaving 40 percent was acceptable.
The pipeline company continued to do remediation at the site. They pumped oil from the water table and planted trees after removing contaminated soil. They also installed a lot of wells.
In 1983, scientists at the USGS and colleagues at a number of universities began studying the Bemidji spill area. They found that the natural microbial population that feeds on the oil prospered. The organisms immediately started consuming the oil and regenerated, causing a bloom, what scientists call natural attenuation. As a result, the contamination didn't travel very far and for the past ten years, it's been moving at an even slower pace.
In 1988, the MPCA required all pipeline companies in Minnesota to take a look at the contamination in old pipeline spill sites and they required Enbridge Energy to use current technology to get as much of that remaining oil out of the ground. The company kept pumping out remaining oil through 2004. That's when they stopped because there was only so much remaining oil they were able to retrieve from the ground. Any extra efforts would have been costly to Enbridge.
Today the USGS is working with Enbridge, the local county, and the Minnesota Pollution Control Agency on a collaborative agreement to continue monitoring the site. Geoff Delin says they hope to use it as a model to study the environmental effects of oil spills.
