Making State Gas Pipelines Safe and Reliable: An Assessment of State Policy

March 2011 
By Jacquelyn Pless

Natural Gas as an Expanding Industry

• Interstate vs. Intrastate
• Variation of Incidents Despite Similar Inspection Efforts
• Population Density and Pipeline Mileage per Square Foot of Land

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  In 2008, 72 percent of North America’s natural gas supply was produced in the United States, 21 percent in Canada and 6 percent in Mexico.⁷ The U.S. natural gas pipeline grid that delivers this supply encompasses:
• 305,000 miles of interstate and intrastate transmission pipelines with 1,400 compressor stations,
• more than 11,000 delivery points,
• 5,000 receipt points,
• 1,400 interconnection points,
• 400 underground storage facilities, and
• 24 hubs or market centers.

Two-thirds of the lower 48 states depend almost entirely on interstate pipeline systems for natural gas supplies.^8,9  Figure 1 illustrates this intricate network.

Figure 1. Natural Gas Pipeline Network—Lower 48 States (2009)

Interstate

About 71 percent of all U.S. natural gas transmission is made up of interstate natural gas pipeline. In Figure 2, the 31 states in grey obtain at least 85 percent of their natural gas from the interstate network.

Figure 2. Interstate Natural Gas Supply Dependency (2007)
 

Notes: EIA determines state’s relative dependence on the interstate natural gas pipeline network for suppliers by calculating the level of natural gas consumed within the State (2007) relative to the amount of natural gas produced within the state. If no natural gas is produced within the state, it is 100 percent dependent on the interstate network.
Source: U.S. Energy Information Administration, Form EIA176 “Annual Report of Natural Gas and Supplemental Gas Supply and Disposition,” About U.S. Natural Gas Pipelines, Transporting Natural Gas; http://www.eia.doe.gov/pub/oil_gas/natural_gas/analysis_publications/ngpipeline/dependstates_map.html.
 

Intrastate

 In the lower 48 states, more than 90 intrastate natural gas pipelines link producers to local markets and the interstate pipeline network. As the top natural gas consuming state, Texas’ intrastate pipelines account for 45,000 miles of its 58,000 miles of natural gas pipelines. California, ranked second for natural gas consumption, is dominated by only a few distribution companies, including Southern California Gas (SoCal) and California Gas Transmission Company (PG&E)—two of the nation’s largest distribution companies.

Variation of Incidents Despite Similar Inspection Efforts

All states except Alaska and Hawaii conduct natural gas pipeline inspections and report efforts as Inspection Person Days, the number of days spent in the field conducting inspections. Data reveal that, in 2009, Inspection Person Days varied from 62 in Maine to 4,368 in New York with a median of 499.¹⁰

Pipeline mileage varies substantially across states, however, and Inspection Person Days per mile of pipeline may be a more accurate reflection of inspection activity since it indicates how much time states spend inspecting comparable lengths of pipeline. Inspection Person Days per 1,000 Miles of Natural Gas Transmission Pipeline ranges from 26 in Montana to 1,305 in Rhode Island, a 50-fold difference, with a median of 107. To access this data, visit the chart below.  Alaska and Hawaii are omitted since the Office of Pipeline Safety (OPS) regulates, enforces and inspects all activity there, and the District of Columbia is not included.

NCSL’s analysis reveals that states that dedicate less time to inspections generally experience more significant incidents, which suggests that more inspection time results in less incidents. On average, states with less than 400 inspection person days a year experienced 1.55 significant accidents per 1,000 miles of pipeline, whereas states with more than 400 inspection person days experienced an average of 0.9 significant incidents, a 41 percent decrease. When an outlier state is omitted from the analysis, the decline is even more substantial—resulting in a seventy five percent decrease.

However, some states experience more incidents than those that devote similar amounts of time for inspections. For example, the 22 states dedicating less than 100 inspection person days a year experienced between 0.41 and 4.60 significant incidents per 1,000 miles of pipeline. Regulators in some states may want to consider ensuring proper inspection practices, possibly through more stringent rules and regulations rather than by allotting more time to inspection.

A graph illustrating the relationship between Inspection Person Days per 1,000 Miles of Natural Gas Pipeline and Gas Transmission Significant Accidents per 1,000 Miles of Gas Transmission Pipeline can be found below. 

  Population Density and Pipeline Mileage per Square Foot of Land

Data reveal substantial variation among the number of significant incidents involving all gas pipelines when compared to population density and pipeline mileage per square foot of land (pipeline density). A positive relationship exists, however, between significant incidents and natural gas transmission pipeline density, which indicates that states with higher pipeline density may require more stringent oversight. This relationship does not hold for population density.

To access this dataset, please see the chart detailing natural gas transmission pipeline mileage and incidents below. 

A graph illustrating the relationship between incidents and pipeline density can be found here.

⁷ Northwest Gas Association, Natural Gas Supply Serving the Pacific Northwest 5, no. 2 (West Linn, Ore.: NWGA, n.d.)

⁸ U.S. Energy Information Administration, About U.S. Natural Gas Pipelines (Washington, D.C.: EIA, n.d.); http://www.eia.doe.gov/pub/oil_gas/natural_gas/analysis_publications/ngpipeline/index.html.

⁹ U.S. Energy Information Administration, About U.S. Natural Gas Pipelines, Interstate Natural Gas Pipeline Segment, (Washington, D.C.: EIA, n.d.); http://www.eia.doe.gov/pub/oil_gas/natural_gas/analysis_publications/ngpipeline/interstate.html.

¹⁰Author’s calculations with data gathered by PHMSA from 2010 certification documents reporting activity for 12 months ending Dec. 31, 2009.