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.
This month, we’re taking a look at incidents in the state of Tennessee. In light of the possibility of new pipelines in the area, we’ll dig into Tennessee’s incident rates, mileage, and look at some maps.
Quick Facts
From 2010 to present Tennessee pipelines caused:
- 60 total incidents including:
- 12 Hazardous Liquid incidents
- 26 Gas Transmission incidents
- 22 Gas Distribution incidents
- 35 significant incidents
- 11 incidents ending in injury and/or fatality causing:
- 13 hospitalized injuries
- 3 deaths
- 21 incidents resulting in fire and/or explosion
- 786 total members of the public to be evacuated
- Incidents have released:
- 301,745 gallons of hazardous liquids
- 491,273 thousand cubic feet (mscf) of gas
Incident Breakdown
In general, Tennessee’s incident rate is lower than its neighbors and the national average (Plot 1). Aside from an unusually high spike in the late 2010s, this trend appears to span the 12-year span of the data. This generally remains true when only looking at significant incidents (Plot 2), although the state did see a bit more volatility given spikes in 2012 and 2019. Impressively, Tennessee operators avoided a single significant incident in 2021.
We also looked at the map of incidents and the total cost of their damage (Plot 3) and found that unlike states such as Minnesota, Tennessee had much higher cost incidents on liquid pipelines than distribution lines. This is marked by the costliest incident in the state: a Colonial Pipeline spill on April 4, 2019, which released over 14,000 gallons of gasoline and caused over $9 million in damage.
Operator Analysis
Of the 142 operators in Tennessee between 2010 and 2021, 24 have been responsible for at least one incident. Nine of these 24 companies operate integrity management programs under a different primary operator. For example, Tennessee Gas Pipeline Company operates integrity management under Kinder Morgan, suggesting that Kinder Morgan is their primary operator.
The table below presents the 3 or 4 operators with the most incidents for each system in the state of Tennessee 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 Tennessee – 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.
Incidents |
Cost (K, USD) |
Releases |
||||||
|---|---|---|---|---|---|---|---|---|
| Parent Operator | Total | Significant | per 1K Miles | Trend | Total | per Incident | Total | per Incident |
| Hazardous Liquids | ||||||||
| COLONIAL PIPELINE CO | 5.0 | 80% | 10.33 | 14,560 | 2,912 | 18,185 | 3,637 | |
| MARATHON PIPE LINE LLC | 2.0 | 50% | 9.05 | 290 | 145 | 105 | 52 | |
| 12 Others (HL, avg.) | 0.0 | 0% | 0.00 | 0 | 0 | 0 | 0 | |
| Gas Distribution | ||||||||
| CHATTANOOGA GAS | 4.0 | 100% | 2.43 | 1,218 | 305 | 51,920 | 12,980 | |
| Atmos | 3.0 | 100% | 0.87 | 580 | 193 | 78 | 26 | |
| MEMPHIS LIGHT GAS & WATER DIVISION | 3.0 | 67% | 0.63 | 121 | 40 | 3,586 | 1,195 | |
| LAWRENCEBURG GAS DEPT, CITY OF | 2.0 | 100% | 6.26 | 816 | 408 | 247 | 124 | |
| MIDDLE TENNESSEE NATURAL GAS UTIL DIST | 2.0 | 50% | 0.53 | 224 | 112 | 5 | 3 | |
| 103 Others (GD, avg.) | 0.1 | 5% | 0.28 | 7 | 7 | 20 | 20 | |
| Gas Transmission | ||||||||
| Enbridge | 11.0 | 36% | 11.39 | 3,992 | 363 | 102,793 | 9,345 | |
| Kinder Morgan | 6.0 | 25% | 11.77 | 447 | 37 | 151,834 | 12,653 | |
| Energy Transfer | 1.0 | 100% | 8.54 | 58 | 58 | 21,900 | 21,900 | |
| OneOK | 1.0 | 0% | 30.01 | 11 | 11 | 4,650 | 4,650 | |
| 29 Others (GT, avg.) | 0.0 | 0% | 0.00 | 0 | 0 | 0 | 0 | |
To offer a holistic view of the relative responsibility of operators in Tennessee, this table can be referenced in conjunction with Plot 4, which looks at each operator’s incident causes. One trend that sticks out is how some of the larger operators – such as Energy Transfer and Kinder Morgan – are seeing incidents due to equipment failure at a higher rate than average. For context, about 36% of all incidents nationwide are due to equipment failure. Interestingly, all of the state’s operators are below average in terms of incidents due to corrosion failure. Nationwide, 17% of incidents are due to corrosion, in Tennessee only Energy Transfer comes close at 16.7%.
Plot 5 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. The largest relative incident in the state was a Gas Transmission incident on November 18, 2019 in Maddox, TN on a Kinder Morgan line operated by Tennessee Gas Pipeline Company. This incident released 116,172 mscf, twice as much gas as the next largest gas incident. The largest liquid incident was the aforementioned Colonial PIpeline incident, releasing 14,313 gallons of gasoline.
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