• Site Characterization
• Natural Attenuation Evaluation

Cass Lake, Minnesota

• Enbridge Energy Company
• Leech Lake Band of Ojibwe

• Hydrocarbons, Crude Oil
• BTEX

Knowledge and expertise obtained from research at the Toxic Substances Hydrology Program Bemidji Crude-Oil Spill Research Site, Minnesota, are being applied at a crude-oil spill site near Cass Lake, Minnesota. Leaks at a crude-oil pipeline pumping station created a pool of oil on top of the water table in the subsurface, and a corresponding plume of dissolved constituents in ground water. Objectives of the study are to:

1. Characterize the three-dimensional extent of the ground-water contaminant plume;
2. Characterize the redox zones and microbial populations with in the plume and estimate plume scale biodegradation rates;
3. Estimate ground-water recharge and evaluate the possible effects of focused recharge on enhanced biodegradation of petroleum hydrocarbons; and
4. Evaluate the site's natural attenuation capacity.

Results of the study will extend and supplement results from previous data collection studies conducted by Enbridge Energy Company and its consultants. Improved knowledge of the biodegradation rates at the site will provide the Leech Lake Band of the Ojibwe with information needed to assess the rate of migration of petroleum hydrocarbons and the potential for off-site transport of contaminants, and to determine how best to proceed with remediation and management of the Cass Lake crude-oil spill site.

• Cleanup Information for the Enbridge South Cass Lake Pumping Station Site, Leech Lake Band of Ojibwe

• Geoffrey N. Delin, USGS, Mounds View, MN,

Toxics Program Hydrocarbon Remediation Projects

• Crude Oil Contamination in the Shallow Subsurface -- Bemidji , Minnesota
• Processes Affecting the Natural Attenuation of Fuel Oxygenates in Ground Water -- Laurel Bay, South Carolina
• Processes Affecting the Natural Attenuation of Gasoline in Ground Water - Galloway Township , New Jersey
• Osage-Skiatook Petroleum Environmental Research Project, Oklahoma