As a result of these efforts, we had fewer spills in 2015 compared with 2014. Over the past five years, we have reduced the number of spills greater than 1 barrel by more than 30 percent.
If a spill does occur, we ensure a rapid, comprehensive response. The total volume of hydrocarbons spilled to soil and water was 10,800 barrels in 2015, and more than 55 percent was recovered at the spill sites. The majority of these spills did not affect third parties or the communities that surround our assets. In 2012, we started measuring significant spills to the environment (SSEs) across the corporation. SSEs are a subset of our overall spills, which we define as spills that have impacted or have the potential to impact surface water, groundwater, sensitive environments or communities.
We had 11 SSEs in 2015, which represented approximately three percent of the total number of spills. Our largest SSE occurred when 10 U.S.-Midcontinent production facility tank releases occurred during a flooding event related to a tropical storm. Other SSEs that occurred were related to valve and flow line failures during normal operations. The findings from our SSEs have prompted further preventive work on facility integrity and reliability upgrades, as well as addressing human factor causal elements. We are increasing focus on learning from these spills to prevent their recurrence.
ExxonMobil recognizes the potential risk for spills from marine vessels and we take a diligent approach to safe and environmentally responsible marine transportation. The worldwide marine business of ExxonMobil’s affiliates, which involves about 500 vessels in daily service, logged more than 21,500 voyages and 47,000 port calls in 2015, safely transporting approximately 1.5 billion barrels of crude oil and refined products. This year, ExxonMobil’s marine affiliate, SeaRiver Maritime Inc., placed the Eagle Bay, the second of its two new U.S. crude oil tankers, into service transporting crude oil from Alaska’s North Slope. This vessel incorporates the latest safety technologies and greatly reduces air emissions, which earned it the 2015 Green Ship Award from the Port of Long Beach. For additional information on our efforts to reduce air emissions in our operations, see our air emissions page.
In addition to marine transportation, ExxonMobil Pipeline Company transports approximately 2.6 million barrels of petroleum and chemical feedstocks and products through approximately 5,000 miles of active pipelines operated in the United States every day. We are committed to pipeline safety and carefully maintain and monitor our infrastructure to identify and prevent corrosion, third-party damage or illegal intrusions onto our rights of way. We patrol our pipeline routes and monitor pipeline operations using state-of-the-art systems, alarms and other monitoring technologies. For more information on how we are managing products transported by rail, see our safety and security page.
Offshore oil spill response
As part of ExxonMobil’s commitment to maintaining operational excellence everywhere we work, we have developed specialized offshore spill response capabilities and tactics. We have the industry’s only dedicated, in-house oil spill response research program, which includes a focus on cold water and remote locations, such as the Arctic.
ExxonMobil has participated in and provided technical leadership to several joint industry projects to enhance industry offshore spill response capability. These initiatives include the American Petroleum Institute (API) joint industry task force, the International Association of Oil and Gas Producers (IOGP) Arctic oil spill response technology joint industry program, an IOGP and IPIECA joint industry project and the API oil sands technical subcommittee. These initiatives allow us to share best practices and learn from our peers.
Additionally, for the past five years, ExxonMobil has been an active member of the Marine Well Containment Company (MWCC), an independent not-for-profit company that provides well containment equipment and technology in the deepwater U.S. Gulf of Mexico. In 2015, we re-entered a pre-existing exploratory well for development in the Gulf of Mexico’s Julia oil field after receiving a cap-and-flow permit from the Bureau of Safety and Environmental Enforcement. This permit was awarded based on the enhanced response capability of MWCC capture vessels. MWCC added two modular capture vessels to its inventory in 2015. These vessels, which ExxonMobil took the lead in constructing, are maintained and operated on behalf of the MWCC’s 10 member companies.
We continually identify and develop advanced technologies to manage risks and improve offshore oil spill response. For example, we commercialized the use of biodegradable surfactants that can be sprayed onto the water surface around the perimeter of an oil slick, causing the oil to retract and thicken so that it can be burned in a controlled fashion without using a fire-resistant boom.