	Introduction

Oil is a dominant source of energy in the United States, accounting for approximately 37% of total energy consum ption in 2016. Vast quantities of oil continuously enter the country via vessel or pipeline. Vast quantities continually move throughout the country to various destinations. With such widespread use and nonstop movement, it is inevitable that some number of spills will occur. Over the past few decades, two major U.S. oil spills have had lasting repercussions that transcended local environmental and economic effects:
1. 2010 Deepwater Horizon oil spill: On April 20, 2010, an explosion occurred at the Deepwater Horizon drilling platform in the Gulf of Mexico, resulting in 11 fatalities. According to estimates, the well released more than 100 million gallons of oil before it was contained 86 days later. 2. The spill data include incidents from vessels, facilities, and pipelines. This historical decline is likely related, at least in part, to the Oil Pollution Act of 1990 (OPA), which was enacted after the 1989 Exxon Valdez oil spill. PHMSA Data

PHMSA collects oil spill data for pipelines and rail transportation—two modes of oil transportation that have received attention in recent years. Impacts of Oil Spills in Aquatic Environments

The impacts of an oil spill depend on the size of the spill, the rate of the spill, the type of oil spilled, and the location of the spill. Depending on timing and location, even a relatively minor spill can cause significant harm to individual organisms and entire populations. Oil spills can cause impacts over a range of time scales, from days to years, or even decades for certain spills. The governing framework for oil spills in the United States remains a combination of federal, state, and international authorities. Within this framework, several federal agencies have the authority to implement oil spill regulations. OPA Section 4201 amended Section 311(c) of the CWA to provide the President (delegated to the U.S. Coast Guard or EPA) with authority to perform cleanup immediately using federal resources, monitor the response efforts of the spiller, or direct the spiller's cleanup activities. The federal government—specifically the On-Scene Coordinator (OSC) for spills in the Coast Guard's jurisdiction—determines the level of cleanup required. OPA provided limited defenses from liability: act of God, act of war, and act or omission of certain third parties. The fund may be used for several purposes:
prompt payment of costs for responding to and removing oil spills; payment of the costs incurred by the federal and state trustees of natural resources for assessing the injuries to natural resources caused by an oil spill, and developing and implementing the plans to restore or replace the injured natural resources; payment of parties' claims for uncompensated removal costs, and for uncompensated damages (e.g., financial losses of fishermen, hotels, and beachfront businesses); payment for the net loss of government revenue, and for increased public services by a state or its political subdivisions; and payment of federal administrative and operational costs, including research and development, and $25 million per year for the Coast Guard's operating expenses. In complementary legislation, Congress imposed a 5-cent-per-barrel tax on the oil industry to support the fund. At the end of FY2017, the projected balance is $5.4 billion. Agency responsibilities can be divided into two categories: (1) oil spill response and cleanup and (2) oil spill prevention/preparedness. Oil spill response authority is determined by the location of the spill: the Coast Guard has response authority in the coastal zone, and the EPA covers the inland zone. Prevention and Preparedness

Regarding oil spill prevention and preparedness duties, jurisdiction is determined by the potential sources (e.g., vessels, facilities, pipelines) of oil spills. A series of executive orders (EOs), coupled with memoranda of understanding (MOU), have established the various agency responsibilities.
Oil is a primary source of energy in the United States. Domestic oil production has increased in recent years, and vast quantities of oil continually enter the country via vessel or pipeline, moving throughout the country to various destinations. With such widespread use and nonstop movement, it is inevitable that some number of spills will occur.
Oil spills have raised environmental concerns for decades. Several major U.S. oil spills have had lasting repercussions that transcended local environmental and economic effects: the1969 well blowout off the coast of Santa Barbara, California; the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska; and the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. More recent spills in various locations from other sources, including pipelines and rail transportation, have garnered attention from policymakers. The impacts of an oil spill depend on the size of the spill, the rate of the spill, the type of oil spilled, and the location of the spill. Depending on timing and location, even a relatively minor spill can cause significant harm to individual organisms and entire populations. Oil spills can cause impacts over a range of time scales, from days to years, or even decades for certain spills.
Over the past two decades, the annual number and volume of oil spills have shown declines—in some cases, dramatic declines. However, this trend was altered dramatically by the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. The incident led to a significant release of oil: According to estimates, the well released more than 100 million gallons of oil before it was contained on July 15, 2010 (86 days later). Scientists continue to study the fate and impact of the spill.
The governing framework for oil spills in the United States remains a combination of federal, state, and international authorities. Within this framework, several federal agencies have the authority to implement oil spill regulations. Agency responsibilities can be divided into two categories: (1) oil spill response and cleanup and (2) oil spill prevention/preparedness.
Oil spill response authority is determined by the location of the spill: the U.S. Coast Guard has response authority in the U.S. coastal zone, and the Environmental Protection Agency (EPA) covers the inland zone. The Clean Water Act, as amended by the Oil Pollution Act (OPA) in 1990, provides the federal authority to perform cleanup immediately using federal resources, monitor the response efforts of the spiller, or direct the spiller's cleanup activities. The lead federal responder (either from Coast Guard or EPA) determines the level of cleanup required. Federal responders have immediate access to funds in the Oil Spill Liability Trust Fund to support cleanup activities. The trust fund is primarily financed by a per-barrel tax on domestic crude oil and imported petroleum products. The fund's balance is estimated to reach $5.4 billion at the end of FY2017.
Parties responsible for an oil spill may be liable for cleanup costs, natural resource damages, and specific economic damages, including personal property damage and lost profits or earning capacity. OPA provided (1) limited defenses from liability—act of God, act of war, and act or omission of certain third parties—and (2) conditional liability limits (or caps) for cleanup costs and other damages.
Jurisdiction over oil spill prevention and preparedness duties is determined by the potential sources (e.g., vessels, facilities, pipelines) of oil spills. A series of executive orders, coupled with memoranda of understanding, have established the various agency responsibilities. For example, EPA oversees onshore facilities, the Coast Guard oversees vessels, the Department of Transportation oversees pipelines and rail transportation, and the Department of the Interior's Bureau of Ocean Energy Management oversees offshore facilities (e.g., oil platforms).