What is a Tier 2 Spill

Tier 2 spill is one of the three levels of oil spills as categorized by the International Petroleum Industry Environmental Conservation Association (IPIECA).

Oil spill preparedness and response is one of the critical issues addressed by IPIECA guidelines and publications. IPIECA identifies spill preparations and containment and clean-up plans to be a fundamental priority which all companies in the oil and gas industry must include in their internal emergency management plans. As part of its recommended oil spill preparedness principles, IPIECA has developed a system of ranking spills by a scale consisting of three tiers.


A Tier 2 spill is the second of three levels of preparedness and response capability which make up the International Petroleum Industry Environmental Conservation Association's three-tier framework. The tiered structure provides the petroleum industry and governmental authorities with a system to prepare for, and mobilize the appropriate response to, three levels of environmental emergency. The goal of this framework is to mitigate the environmental consequences of any spill or accident to the greatest extent possible.

IPIECA has defined the three tiers according to various characteristics based more on the capabilities of the response than on the volume or size of the spill. They compiled a definition of 15 response capabilities, which work in conjunction with one another to provide immediate relief. Capabilities include in-situ controlled burning, shoreline clean-up, wildlife response, and waste management.

  1. Tier 1 events use locally held resources and are less severe spills allowing the containment and addressing by a company’s internal spill management team. These accidents tend to be operational in the cause and happen at or near the operator's facility. This team provides the initial response and include trained on-site staff and local contractors. 
  2. Tier 2 spills are accidents which may require national or regional response teams with specialized knowledge to intervene. These events extend outside the operational area of the oil or gas facility. A higher number of people are involved in a Tier 2 response. This team has access to additional training and equipment such as aircraft, communication, and the ability to institute mutual aid agreements between groups and government bodies.
  3. Tier 3 accidents are global in need for necessary, available, large-scale resource response. Tier 3 spills usually require resources from stockpiles of national or international cooperatives. In most cases, these co-ops will be subject to governmental control. The third tier will respond with industry-controlled, cooperatively-held equipment, stockpiles, and personnel. Examples of the type of common pool resources (CPR) and equipment available with a Tier 3 response include the high-volume aerial dispersant, at-sea and large-scale containment equipment, and specialized shoreline and inland clean-up capabilities. This team can respond to remote drilling sites which may not have access to extended local capabilities. Personnel on this level are equipped to train and direct large numbers of workers through wide-spread logistics. 

IPIECA publishes the Tiered preparedness and response: Good practice guidelines for using the tiered preparedness and response framework which summarizes current views on oil spill preparedness and response. The most recent publication is dated January 2015. IPIECA guidelines are internationally-recognized and help to guide the industry's response of personnel, equipment, and support to spill events.

Preparing for Future Tier 2 Spills

Not all spills are contributed to human error or equipment failures. Sometimes, Mother Nature plays a role in these events. An example can be seen after the 2017 Hurricane Harvey and the destruction left in its wake. As reported by Reuters, over 22,000 barrels of oil and oil products, millions of cubic feet of natural gas, and tons of chemicals and other toxic material were released into the area surrounding Houston, Texas.

The changing nature of petroleum extraction, with an increased reliance on dry-land techniques such a hydraulic fracturing, requires that the industry and governmental authorities update their preparedness and response framework to focus on new threats. Global political and legislative developments come into play as well, requiring levels of response beyond the realm of heavy equipment and response teams. IPIECA periodically issues updated guidelines in an attempt to keep up with such developments.