North Dakota oil spill recovery efforts are underway near Tioga in Williams County and it will likely be weeks before we know the full story.

The spill affected a little more than 7 acres and did not penetrate groundwater sources or impact wildlife.

Many have criticized the state for taking 11 days to notify the public. One reason for the delay was officials thought the spill was less than 1,000 bbls.

Tesoro now estimates more than 20,000 bbls of oil were spilled from the pipeline. Some are questioning those estimates, but again it's early and very difficult to estimate the true impact.

"As unfortunate as it is, it is actually very beneficial with a clay layer and not hitting water," one Tesoro official stated.

Tesoro and locals are actually lucky as there is thick clay layer approximately 10-12 feet deep that helped contain the oil. The seal has allowed Tesoro to recover more than 3,000 bbls already. Trenches have been dug to allow the oil to flow out of the soil. Those trenches will likely be used like french drains throughout the winter, while remediation efforts continue.

The section of pipe that was leaking has been sent to an independent lab to be studied and a replacement pipe circumventing the spill site is already being installed.

Watch for an official announcement from Tesoro as the cause and impact of the spill can be more confidently determined.