PST’s Data and GIS Analyst James Eager walks us through one state’s pipeline safety track record each month. Click on the “State of Safety” tag at the bottom of the post to see all of James’s entries to date.
Last month, we covered a state with some standout incident characteristics in North Dakota. This month, our focus shifts to a state remarkably close to the national average over the past 11 years of pipeline incidents: Minnesota.
|Rest of U.S.||12.4||47.5%||4.7%||5.0%||14.2%||$664,957.4||13.4||59.9||2.1||2.2||7.5|
Just how “average” is Minnesota, then? The table above presents some commonly-referenced incident characteristics comparing Minnesota to the Rest of the U.S. With few exceptions, Minnesota tracks pretty closely to the mean of the other states. In a couple of instances, such as the cost of damage and the number of fatalities, Minnesota outperforms the national mean. The GD (Gas Distribution), GT (Gas Transmission), and HL (Hazardous Liquids) columns denote the mean annual incidents in each system, and demonstrate another category where Minnesota closely follows the national average.
Plot 1 shows the actual distribution of these characteristics among all states, and reinforces the notion that Minnesota tracks pretty close to average. Note that the variables have been scaled so that 0 is the mean, and values are presented as a relative distance from that mean. This scaling allows us to compare the relative distribution of characteristics against each other on the same scale. The boxplot behind the points offers a glimpse at how that variable is distributed among the states, where the box itself contains the middle 25 values and the line bisecting the box shows the median value. Minnesota sits comfortably inside every box, confirming its nearly-average credentials.
- 136 Total Incidents including:
- 81 Hazardous Liquid Incidents
- 20 Gas Transmission Incidents
- 35 Gas Distribution Incidents
- 66 Significant Incidents
- 1 Incident ending in fatalities, resulting in 2 fatalities
- 2 incidents ending in injuries, resulting in 3 injuries
- 27 Incidents resulting in fire and 6 resulting in explosion
- 1,151 Members of the public evacuated
- Incidents have released:
- 359,357 thousand cubic feet (mscf) of gas
- 301,745 gallons of liquids
Now let’s dig into what a nearly-average state’s incident rates look like. Plot 2 compares the incident rates of Minnesota to its adjacent states and the rest of the U.S. over the 2010 to 2021 period. Generally, the state’s incident rates are falling, with a brief exception in 2019. Regardless, Minnesota’s rates usually track slightly above its neighbors and slightly below the rest of the country.
The significant incident rates in Plot 3 follow a somewhat similar trend, although these rates are a bit more volatile in Minnesota. While the rate is lower in 2021 than it was in 2010, the road to get there has not been quite as clear as with all incidents.
Plot 4 maps out the incidents and their costs across the state, and highlights how few of Minnesota’s incidents are relatively high cost. However, those that are relatively high-cost tend to be distribution incidents in the Saint Paul metropolitan area.
There are 21 independent operators in Minnesota, operating under 18 primaries, which registered at least one incident since 2010. In total, 93 uniquely-named operators were responsible for some mileage in Minnesota between 2010 and 2021. The table below presents the 3 or 4 operators with the most incidents for each system in the State of Minnesota over the 2010 – 2021 period. The trend column displays their annual incident rate from 2010 to 2021, with a green point at their maximum and an orange point at their minimum. The row labeled “Other” is an average of the other parent operators for each given system in Minnesota – including those without any incidents during this period. Significant incidents are presented as a percent of total incidents, and incident rates are given as incidents per 1,000 miles. Finally, releases are reported in thousand standard cubic feet (mscf) for gas incidents and gallons (Gal.) for hazardous liquids.
|Parent Operator||Total||Percent Significant||per 1K Miles||Trend||Total||per Incident||Total||per Incident|
|Flint Hills Resources, LC||14.0||43%||12.39||7,283||520||2,313||165|
|VANTAGE PIPELINE US LP||2.0||100%||7.87||165||83||966||483|
|8 Others (HL, avg.)||0.1||0%||0.53||7||7||31||31|
|NEW ULM PUBLIC UTILITIES COMMISSION||2.0||0%||19.80||77||38||160||80|
|46 Others (GD, avg.)||0.1||0%||2.25||4||4||6||6|
|NORTHERN NATURAL GAS CO||9.0||44%||2.69||1,021||113||89,506||9,945|
|12 Others (GT, avg.)||0.0||0%||0.00||0||0||0||0|
At first glance, it may appear difficult to single out any operator as the most unsafe in this list. OneOK could qualify for the most gas releases per incident, Enterprise for the most liquid releases per incident, Centerpoint Energy for the greatest damage cost per incident, Enbridge for the highest total number of incidents, or Magellan for the highest incident rate. Many operators on this list show peak incident years in the first half of the period studied, between 2010 and 2015, and some operators like Xcel Energy and OneOK have gone several years without required incident reports. Others, such as Flint Hills Resources, show a steady rate of incidents over the years, without any notable dips or peaks.
Plot 6 sheds some more light on which operators are responsible for some of the state’s worst incidents during this period. Using a grouped z-score of incident releases, we can identify which release sizes were well above average in the state during this period – as a z-score of 0 denotes the mean release size. There were 2 serious incidents in the past 12 years, both under the purview of Centerpoint Energy. The most recent of which occurred in 2017 at a Minneapolis school, killing 2 and leaving several hospitalized. Other standout incidents include a 2010 Enterprise liquid spill in Trimont, totaling over 196,000 gallons of highly volatile liquids (HVLs) spilled. OneOK’s Viking Gas Transmission line caught fire and released 80,000 MSCF of natural gas in May 2014, making it the highest-releasing gas incident of the period.
In addition to highlighting the biggest releases, we can also look at which causes led to the most incidents per operator. Plot 7 details the percentage of each operator’s incidents due to each specific cause in the PHMSA incident data. Included in this plot are the operators highlighted in the table, no longer grouped by system. During this time period, only Magellan was responsible for incidents attributable to each unique cause in the data. Magellan coincidentally was also responsible for the most incidents in this time period overall, and the most frequent cause of these was equipment failure. Similarly, Enterprise, Flint Hills Resources, and Northern Natural Gas Co can point to the same failure as their most frequent incident cause. In Minnesota overall, equipment failure accounts for about 34.6% of all incidents, and 36% of all incidents nationwide, so these results tend to fall in line with those trends.