In 2012, Enbridge was performing an abandonment project for small diameter pipelines associated with crude oil production lease sites in oil fields throughout Enbridge’s North Dakota gathering system. Enbridge’s gathering system extends across northwestern North Dakota into northeastern Montana. The small diameter pipelines (typically 2-inch) connected crude oil production wells and associated tank batteries to Enbridge’s pipeline gathering system. The practice of moving oil through the small diameter pipes into Enbridge’s gathering system terminated more than 10 years ago. Oil from production wells has since been transported off the sites via tanker trucks. The small diameter pipes were therefore no longer necessary and, Enbridge has been disconnecting, also known as abandoning, them from its gathering system pipelines.

Evidence of an historical crude oil release was discovered at the Grenora Dig #12 Site in the Dwyer Field during the abandonment work. The site is on Enbridge’s gathering system right-of-way [Barr, 2012]

1.1.2.1 Location

Site Address: Dwyer Road, Dagmar, Montana
Zip Code: 59219
County: Sheridan
Township: 32N Range: 59E Section: 19 (SE¼ of NW¼)
USGS 7.5-Minute Quadrangle Map: Brush Lake
Latitude: 48.51495 Longitude: -104.10210

The site is located approximately 1/2 mile from Cottonwood Creek; however, much of the area between the river appears to be an adjacent welant under the Clean Water Act. The release location is less than 50 feet from the wetland. It should also be noted that the site is approximately 5 miles upstream from the Medicine Lake National Wildlife Refuge.

1.1.2.2 Description of Threat

Given the unknown nature of the release and its proximity to the wetland, the OSC has initiated an assessment effort to evaluate the threat posed to the wetland.

1.1.3 Preliminary Removal Assessment/Removal Site Inspection Results

The OSC had determined that additional assessment was necessary after reviewing the initial reports of the abandonment work and discovery of the discharge. To that end, Enbridge had planned to do additional soil removal last summer. Significant rainfall and the discovery of a previously unknown and improperly abandoned line precluded the scheduled work. A small quantity of oil was discovered when the newly discovered line was uncovered. Limited assessment was done by hand boring, with results presented in an August 2013 memo from Barr. It is unknown at this time how much product remains in the newly discovered line.

Enbridge was unwilling to open up someone else's line and was, in any event due to the unexpected discovery, un-prepared to recover even a modest amount of oil if the line was anything other than empty.

At this time, EPA is assuming the lead for further assessment activities.