2   National Spill Statistics and Trends

2.3   Summary Findings for Causes and Reasons for Spills in Seven Major Sectors

• 2.3.1 Causes of Spills in Seven Major Sectors
• 2.3.2 Reasons for Spills in Seven Major Sectors
• The ‘cause’ of a spill is ‘what went wrong’ while the ‘reason’ for a spill is ‘why it went wrong’. Examination of the seven sectors together indicates that pipe leaks account for the majority of causes (22%), followed by discharge (11%), process upset (11%) and overflow (9%).
  
• Unknown causes account for 13% and unknown reasons 17% of all reported causes and reasons for spills.
  
• Equipment failure (25%) and human error (16%) are included in the top three reasons for spills among all seven sectors. Corrosion accounts for 12% of all reasons given.
  
• Spills in the production field are one of the top sources for four of the top five reasons: equipment failure, corrosion, material failure, human error, and storm or flood.
  
• Seventy-one percent of spills attributable to a storm or flood are sewage spills from either a sewage treatment plant or from a sewer. Run-off during periods of major precipitation, particularly from storm and sanitary sewers, constitutes one of the major reasons for sewage spills.
  

2.3.1 Causes of Spills in Seven Major Sectors

This section explores the causes of spills for the seven selected sectors. The cause of a spill relates to how a spill happened. Industry sometimes refers to cause as the source of the spill, however, for consistency, standard NATES field names have been maintained. Examination of these causes by persons working in the various sectors can assist in preventing similar events from happening in the future. Upon examination of the seven sectors data, it is interesting to note that 13% of causes fall into the ‘unknown’ category, making it the second largest category. This indicates a need for better follow-up, as the cause and reason are often not known until after the spill is first reported. This would provide more accurate data for analysis and a better focus for spill prevention programs. In the figures that follow, the unknowns are included in the total number of spills.

Pipe leaks are the most common cause of spills in the seven sectors, representing 22% of total causes.

Table2.3.1 plots the spill cause against the seven chosen sectors, demonstrating that the leading causes of spills vary greatly from sector to sector. Process upset is the leading cause of spills in the chemical and metallurgical sectors, accounting for 39% and 25% of spills in those sectors, respectively.

Discharge is the most frequent cause of spills in the government and pulp and paper sectors, representing 28% and 15%, respectively, of all causes reported. Pipe leaks are the primary cause of spills in the mining sector (25%) as well as in the petroleum sector (33%). The most important cause of spills in the service industry is container leaks, accounting for 18% of the reported causes of spills in this sector.

2.3.2 Reasons for Spills in Seven Major Sectors

This section presents the main reasons (sometimes referred to as ‘root causes’) for spills in the seven selected sectors. In some cases the ‘unknown’ category is quite large, totalling almost 17% of all spills in the seven selected sectors. The percentages that follow are derived with the unknowns included in the total number of spills.

As stated previously, the selected sectors are of different sizes and report differently. Each sector is therefore examined independently. There are, however, some apparent trends visible when reasons for spills in the various sectors are compared. Equipment failure and human error are among the top three reasons for all seven sectors. Focused prevention efforts in these two areas may contribute significantly to a reduction in the number of reported spills in these sectors.

Thirty percent of all spills in the chemical sector are due to equipment failure, while 15% are attributed to human error and 13% to intentional discharge. Equipment failure refers to the failure of systems and machinery, not to failure of the actual containment material or from corrosion of containment materials in piping and tanks (Fig. 2.4.2).

In the government sector, the main reasons for spills are: storm, flood (25%), equipment failure (22%), and human error (10%). From a search of the database (not shown), the most frequent source of government-sector spills are waste water treatment plants, leading to the conclusion that ‘storm, flood’ is an important reason for sewage spills. This type of spill is often the result of overflow that occurs when rainfall exceeds the capacity of the treatment plant or sewer system.

Equipment failure accounts for 32% of the reasons for spills in the metallurgy sector, and human error for 11%. Similar percentages were determined for the mining sector, with 31% of the reasons for spills attributed to equipment failure and 14% to human error. Material failure and corrosion accounted for an additional 9% of reasons for spills in the mining sector.

Equipment failure (24%), corrosion (24%), and human error (18%) collectively account for two thirds of the reasons for spills in the petroleum sector.

Equipment failure is the reason for over one-third (37%) of reported spills in the pulp and paper sector. Human error accounted for 15% and power failure for 6%.

The service-industry sector, including businesses such as dry cleaning, construction and janitorial services, reported human error as the reason for 23% of all spills, with equipment failure accounting for another 15%.

In summary, the most commonly reported reason for spills in the seven sectors is equipment failure (25%), followed by human error (16%) and corrosion (12%). In all seven sectors, equipment failure and human error are included among the top three reasons for spills.