From the Guardian:
Clean-up crews have yet to reach the site of the pipeline break nearly a week after the rupture, which leaked 42,000 US gallons (159,000 litres) of oil into the Yellowstone, one of the last undammed rivers left in America.
State officials in Montana criticised oil company executives for offering conflicting accounts of the pipeline breach and its safety record.
There is also evidence that ExxonMobil was aware the pipeline was in a geologically vulnerable location and that the company was aware of potential serious vulnerabilities to rupture and to a serious spill into the Yellowstone River. There are now questions about whether any pipeline should be buried at such shallow depth below a shifting riverbed vulnerable to erosion.