Screen shot from the National Pipeline Mapping System (NPMS) Public Map Viewer shows the Silvertip pipeline crossing the Yellowstone River on its way to Billings. Click to enlarge.

The AP reported that EMPC and government officials speculated that high waters in recent weeks may have scoured the river bottom and exposed the pipeline—which is buried—to debris that could have damaged the pipe. Eastern Montana received record rainfall in the last month and also has a huge snowpack in the mountains that is melting, resulting in widespread flooding.

Pipeline pumps were shut down within seven minutes of a pressure loss and action to isolate the pipeline was immediately initiated. Air quality monitoring throughout the impacted area is ongoing and has confirmed no danger to public health, according to EMPC. Municipal water systems are being notified to monitor water quality but no reports of impacts have been received to date.

The pipeline burst about 10 miles west of Billings near Laurel, where it crosses underneath the Yellowstone River, according to the company. EMPC said oil has been found as far as five miles down the river from the pipeline location and additional reports of oil sightings are being investigated. The US Environmental Protection Agency (EPA) said its staff had spotted oil at least 40 miles downstream, and other reports said oil was as far as 100 miles away.

More than 120 people were involved in the response and cleanup effort including ExxonMobil’s North America Regional Response Team, the Clean Harbors oil spill response organization, and additional contractors. An additional 80 people are expected on site Monday.

For the purposes of the response, the area downriver of the spill has been organized into four zones. Cleanup activities are focused in the first two zones, Laurel to Duck Creek Bridge, a distance of seven miles from the spill location; and Duck Creek Bridge to Johnson Lane (12 miles). Reconnaissance and evaluation activities are under way in the second two zones, Johnson Lane to Miles City (144 miles) and Miles City to Glendive (78 miles).

Cleanup crews are using absorbent pads to soak up oil, boom to isolate oil that has pooled adjacent to the river and vacuum trucks and tankers to pick up and dispose of the oil.

Air quality monitoring is ongoing and has confirmed no danger to public health, according to EMPC. Municipal water systems are being notified to monitor water quality but no reports of impacts have been received to date.

Daily aerial flights over the river are being undertaken to locate additional oil locations and monitor and direct cleanup activity. Montana Governor Brian Schweitzer, among others, is calling for use of boats on the river for closer inspection.

More than 70 calls to the community claims line have been received. A claims hotline number (1-888-382-0043) was established to assist individuals who might have been impacted by this event.

Workers from the International Bird Rescue are expected to arrive on Monday. The Montana Audubon Conservation Education Center and Yellowstone Valley Audubon have offered to provide wildlife recovery services and facilities. One report of impacted wildlife has been received.

Contacts with senior government officials were made throughout the day. ExxonMobil is coordinating the response with the Environmental Protection Agency; the Montana Department of Environmental Quality; US Department of Transportation Pipeline and Hazardous Materials Safety Administration; Montana Fish, Wildlife and Parks; Yellowstone County Disaster and Emergency Services; and Yellowstone County commissioners.

An investigation team has been established to determine the cause of the release.

A number of residents in nearby Laurel were temporarily evacuated from their homes early Saturday as a precaution but were able to return later that morning.