Area of the spill in Mayflower. Source: City of Mayflower. Click to enlarge.

On Saturday, the Mayflower Incident Unified Command Joint Information Center said that emergency response personnel were on the ground within 30 minutes after the leak was detected. Approximately 100 ExxonMobil employees are responding to the incident in addition to federal, state, and local resources. Emergency response efforts are focused on ensuring the safety of the community members and the response workers, addressing community concerns and the clean-up process. Efforts are being made to keep oil away from Lake Conway.

The City of Mayflower recommended that 22 homes be evacuated; all residents evacuated following notifications by the Mayflower Police Department.

CTEH (Center for Toxicology and Environmental Health) is conducting continuous air quality monitoring. The air quality does not likely present a human health risk, with the exception of the high pooling areas, where clean-up crews are working with safety equipment.

Clean-up crews have deployed 2,000 feet of boom and have mobilized 15 vacuum trucks to the site to clean up the oil. Approximately 4,500 barrels of oil and water (189,000 gallons US) have been recovered.

The Pegasus pipeline is a 20-inch (51 cm), 858-mile (1,381-kilometer) link from the Patoka Oil Terminal Hub in Illinois to Nederland, Texas. It carries 90,000 barrels of oil per day, almost exclusively Western Canadian crude oil.

(According to a company spokesperson, the pipeline was carrying Canadian Wabasca Heavy crude at the time of the spill. Wabasca Heavy is a heavy oil from the Athabasca region obtained by polymer injection and water flooding and typically has a 19-20 API gravity and 4.15 wt% sulfur content (i.e., “sour”), according to Crude Quality Inc. in Canada. Principal producers of Wabasca include Cenovus Energy and Canadian Natural Resources. Wabasca Heavy is initially delivered to Edmonton via the Pembina Pipeline and Rainbow Pipelines in a heavy crude/diluent mix.)

The Pegasus pipeline originally transported crude from the Gulf coast to Patoka. In 2006, its reversal was completed, and in 2009, ExxonMobil completed a project that increased its capacity by 50% (about 30,000 barrels per day).

The expansion project included the reactivation and enhancement of several pump stations along the pipeline. The additional capacity enabled the transportation of additional Canadian crude from the Midwest to Gulf Coast refineries.

Operational enhancements, such as new leak detection technology, were also incorporated.

Earlier last week, the US Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) initiated an administrative enforcement action with a proposed fine of $1.7 million to ExxonMobil Pipeline Company as a result of the operator’s July 2011 crude oil pipeline failure in the Yellowstone River near Laurel, Mont. (Earlier post.)

The Silvertip Pipeline is a 12-inch (30 cm) pipeline approximately 69 miles in length and transports crude oil from the Silvertip station in Elk Basin, Wyoming, to an ExxonMobil Refinery in Billings, Montana. A failure involving the operator’s Silvertip Pipeline resulted in the release of 1,509 barrels (97,000 gallons) of crude oil during excessive flooding and adverse weather conditions on 1 July 2011.

In addition to the proposed fine, PHMSA issued a proposed compliance order, directing the operator to implement ongoing training for supervisory and control room personnel on emergency response procedures, including reacting to abnormal conditions involving the natural environment surrounding their pipelines and the proper operation of remote control valves.

Immediately following the Silvertip Pipeline failure, PHMSA issued ExxonMobil a Corrective Action Order directing the company to take a number of measures to ensure its safe restart and continued operation. Among other things, the order required ExxonMobil to replace and re-bury the pipeline underneath the Yellowstone River, evaluate the pipeline for any existing or potential damage in all areas where it intersects with waterways, and revise its operation and emergency response procedures. All of the required actions of PHMSA’s order were completed by August 2012.