An emerging alternative to domestic natural gas pipelines is shipping natural gas by rail, creating what some refer to as "virtual pipelines." On
The federal agencies with principal oversight of LNG shipments by rail are PHMSA and FRA, both within the
Federal safety requirements apply to any train operating in
Vessels have shipped
Natural gas is combustible, so an uncontrolled release of LNG poses a hazard of fire or explosion. LNG also poses hazards because it is so cold. Key safety issues include risk differences between trains carrying only LNG versus trains carrying LNG and other cargo, derailment risks, tank car crashworthiness, routing near populated areas, and emergency response capabilities, especially among local first responders. The security implications of LNG shipments by rail are also a consideration, as LNG shipments and facilities could be targeted by individuals with malicious intent, but also could provide backup natural gas supplies if pipelines were disrupted.
A 2019 House appropriations bill amendment (H.Amdt. 468 to H.R. 3055) would have prohibited appropriated funds from being used to carry out the LNG-by-rail provisions of the executive order or to authorize LNG transportation in rail tank cars by issuance of a special permit or approval; the amendment was not adopted.
It would rescind any special permit or approval for the LNG transportation by rail tank car issued prior to enactment and would prohibit any regulation, special permit, or approval prior to the conclusion of a specified study period.
Domestic transportation of natural gas occurs mainly by pipeline, but some parts of
Large marine vessels have shipped LNG between
Characteristics of LNG
When natural gas is cooled to temperatures below minus 260 F it condenses into a liquid form, generally referred to as "liquefied natural gas," or LNG. As a liquid, natural gas occupies only 1/600th the volume of its gaseous state, so it is stored more efficiently in a limited space and is more readily transported. At warmer temperatures LNG becomes gaseous again and can be pumped into local natural gas distribution systems, or fed directly into power plants or industrial facilities.
Safety Hazards of LNG
Natural gas is composed primarily of methane, which is combustible, so an uncontrolled release of LNG poses a hazard of fire or explosion. LNG also poses hazards because it is so cold. The possibility of catastrophic releases at LNG production, transfer, and storage facilities, and from LNG marine tankers, has long been the subject of technical research and congressional interest.6 LNG transportation by rail poses similar hazards, although at smaller scale.
Flammable Vapor Clouds
In the event of an uncontrolled LNG release directly from a tank container or tank car, some of the LNG will regasify in the warmer, ambient air and form a natural gas vapor cloud. If the incident causing the release creates a source of ignition (e.g., a spark), the vapor cloud could begin to burn immediately at the point of release. Burning LNG poses a significant thermal hazard as it is hotter and burns more rapidly than oil or gasoline fires.7
Its thermal radiation may injure people and damage property a considerable distance from the fire itself. Emergency responders are generally unable to extinguish LNG fires, except very small ones. As a 2019 study commissioned by PHMSA reported LNG releases do not allow first responders to cap off a leak or interact with the container.
LNG releases involving cryogenic gas would result in an immediate evacuation of the area and securing the adjacent facilities. Given the warming effect of water on cryogenic gases, putting water on a cryogenic release is not recommended.8
In most cases, therefore, an LNG fire will continue to burn until all the LNG feeding it is consumed. If the natural gas vapor does not ignite immediately upon release, the vapor cloud may drift from the site. If the cloud subsequently encounters an ignition source, those portions of the cloud with a combustible gas-air concentration may burn.9 The nature of such a fire would depend upon local conditions. Whether an LNG vapor cloud can explode, potentially posing greater risks to people on the ground, is an open technical question.10
If LNG spills on land without igniting, it will flow away from the source, potentially pooling in ditches, culverts, sewers, or other lower-lying areas. LNG spilled on water will spread out in a pool on the surface of the water. The LNG will continue evaporating as it travels, creating a vapor cloud over these areas. Any resulting fire could spread farther outward as the LNG flow expands away from its source and continues evaporating.11
Boiling Liquid Expanding Vapor Explosions
One hazard of particular concern for transportation of combustible fuels in tank containers or rail tank cars is the possibility of a boiling liquid expanding vapor explosion (BLEVE). As a Canadian study explained in 2015
This type of accident occurs when a tank car is heated (typically by fire) until rupture, at which point the vapour suddenly expands and the liquid contents boil rapidly due to the pressure drop. BLEVEs can result in a blast wave, projection of tank fragments and/or a fireball.12
Because experience with LNG transport by rail is limited and few experimental studies have focused specifically on LNG releases from tankers, there are significant uncertainties about the risk of a BLEVE from an accident involving an LNG tank container or rail car.13 Furthermore, the assessment of risk must take account of the safety measures (e.g., pressure relief valves) incorporated into tank and tank car designs, which may vary. Such incidents may not be ruled out entirely, however, as a BLEVE apparently occurred in
Other LNG Safety Hazards
LNG vapor clouds are not toxic, but they could cause asphyxiation by displacing breathable air.
Such clouds may begin near the ground (or water surface) at a spill site when they are still very cold, but rise as they warm because natural gas is lighter than air, diminishing the threat to people. Extremely cold LNG could injure people or damage equipment (e.g., by brittle fracture) through direct contact.
As noted above, LNG is composed principally of methane. In 2009, the
After the terror attacks of
While LNG shipments by rail may increase security risks to local communities and infrastructure, they may increase the resiliency of the energy sector more broadly. In particular, transporting LNG by rail may serve as a potential backup for pipeline natural gas supplies. In a
disruptions could interrupt gas supplies to power plants, but LNG transport by rail potentially could provide emergency fuel supply to critical end users until pipeline supplies could be restored.21 LNG shipments by rail also could be targeted, but an attack which could shut down a natural gas pipeline and simultaneously block rail shipments of LNG would be far more difficult to execute successfully. The effectiveness of LNG backup supplies could be limited, however, due to the time required for rail deliveries, the scale of rail equipment to handle the required LNG volumes, and the ability of end users to access such supplies.
Federal Agency Roles
Several federal agencies are involved with the safety and security regulation of LNG shipments by rail.
PHMSA, also within DOT, issues regulatory requirements for the safe transport of hazmat, including LNG, by all modes of transportation.23 FRA enforces PHMSA's hazmat regulations with respect to railroads.24 FRA and PHMSA work together on rail hazmat safety but FRA's core focus is with train operations while PHMSA's core focus is on hazmat packaging requirements, such as the design of tanks used in LNG transportation. PHMSA also regulates the safety and security of certain LNG facilities which may be involved in rail transportation.25
Rail incidents are investigated by the
Under the Aviation and Transportation Security Act (P.L. 107-71) and the
Other Federal Agencies
Federal Approval of LNG by Rail
Federal hazardous materials regulations prohibit rail shipment of LNG except with either FRA approval or a PHMSA special permit.34 FRA may allow LNG shipments in specialized, multimodal tank containers of the type already approved for transporting LNG in general commerce (i.e., by truck or container ship). These intermodal tank containers have been approved by PHMSA and are built to specifications set by the
FRA granted its first LNG-by-rail approval in 2015 to the
Executive Order 13868
The Secretary of Transportation shall propose for notice and comment a rule, no later than 100 days after the date of this order, that would treat LNG the same as other cryogenic liquids and permit LNG to be transported in approved rail tank cars. The Secretary shall finalize such rulemaking no later than 13 months after the date of this order.43 Based on the date of the order, issuance of the final rule was required by
PHMSA LNG by Rail Rulemaking
In response to Executive Order and the AAR petition, on
PHMSA's proposed rule would allow LNG to be carried in DOT-113C120W specification tank cars (Error! Reference source not found.), which are designed to carry liquefied ethylene, " another flammable cryogenic liquid which shares similar chemical and operating characteristics with LNG."47 In PHMSA's rulemaking, the agency, in conjunction with FRA, is examining potential limitations for routes and train length specifically for LNG shipments in rail tank cars.
Speed restrictions and requirements that cars be equipped with specialized brakes (further discussed below) are also under consideration. The proposed rule does not discuss specific tank car features designed to reduce the chances of tank car punctures during derailment, such as those newly required of cars carrying crude oil.
Selected Policy Issues
The federal government's issuance of the PHMSA rulemaking and its approvals of LNG shipments by rail have drawn both support and criticism. Consistent with the AAR's initial petition for PHMSA to allow LNG by rail, the association and other industry groups also support the broader rulemaking. However, the
Safety of Unit vs. Manifest Trains
An important safety aspect of the proposed rulemaking is how much LNG by rail would be carried in unit trains versus manifest trains. A manifest train carries a varied mix of products, usually in various different car types (e.g., box car, flatbed, tank car). A unit train comprises just one car type carrying a single commodity to a single destination, usually returning empty to its point of origin. Ethanol was the first hazardous material to be carried in unit versus manifest train formations in
PHMSA's final environmental assessment for the ETS special permit states that the applicant "seeks authorization to ship LNG via rail ... in shipment configurations that could range from single to multiple tank cars (blocks) in general manifest trains ... up to dedicated train configurations consisting of up to 100 tank cars (unit train)."50 The assessment further evaluates a "baseline case" in which ETS would ship between two and four unit trains of LNG per day.51 In its NPRM, the agency states
While PHMSA expects LNG will initially move in smaller quantities (i.e., a few tank cars) as part of manifest trains, it is uncertain whether LNG will continue to be transported in those quantities or if LNG by rail will shift to be transported using a unit train model of service, and if so, how quickly that shift will occur.52
Therefore, while PHMSA's proposed rule does not predict future numbers of LNG unit train shipments, it would allow them. Whether LNG is carried in a manifest or unit train configuration has risk implications because of the placement of the cars relative to the location of crews and possible flaws in the tracks, discussed below.
Derailment Risks and Safety Measures
According to the
In a loaded unit train, any derailed cars will be carrying the hazardous material. Given some of the large fires and explosions that have occurred when crude oil and ethanol unit trains have derailed in the past,58 DOT has mandated a number of specific measures for these trains to reduce the chances of derailment and mitigate the consequences of a derailment. Most of these measures are not being proposed as requirements in PHMSA's LNG-by-rail rulemaking, as further discussed below.
FRA has stated in past regulatory correspondence that "the transportation of large quantities of LNG in a single train presents unique safety risks."59 Stakeholders have identified the potential for "cascading failure" as one of these risks. In this kind of event, an uncontrolled LNG release and fire from one failed tank would cause successive cars to fail due to heat exposure, thereby increasing the overall quantity of LNG released in the incident. Such failures have occurred in rail accidents involving shipments of crude oil and ethanol.60
PHMSA's NPRM discusses the possibility of cascading failure in an accident involving LNG tank cars. The NPRM concludes that, due to the design of the DOT-113 tank cars "the risk of tank car failure and ignition" due to heat exposure "is low."61 The NPRM states that the "special design of the DOT-113 tank car reduces the probability of cascading failures of other undamaged DOT-113 specification tank cars being transported in a block or unit train configuration." It further states that exposure to heat or cryogenic temperature from a damaged LNG tank car "could potentially lead to the release of material or failure of otherwise undamaged tank cars," but "an undamaged DOT-113 specification tank car exposed to a radiant heat source could eventually ... trigger the activation of the tank car's [pressure release device]" which "would result in the controlled venting of LNG vapor" creating a significant risk of fire.62 The NPRM also cites AAR Circular OT-55 provisions related to unit trains as sufficient for addressing the safety risks of LNG unit train shipments.63 The proposed rule, therefore, does not propose additional restrictions on the number of tank cars carrying LNG in one train. Related to this issue, FRA conducted fire safety tests in 2017 demonstrating that the pressure relief devices on a multimodal ISO container (filled with nitrogen), which are similar in design to those on a DOT-113 tank car, worked as expected.64
PHMSA's assertion that the design of DOT-113 tank cars makes it safe to carry LNG in configurations of multiple tank cars, including unit trains, is disputed. In particular, critics question PHMSA's conclusions regarding the risk of cascading failures in an accident involving unit trains.65 FRA is conducting additional rail safety testing of multimodal ISO tank containers filled with LNG, but has not yet reported results.66 With limited domestic experience of LNG-byrail shipments in multiple car configurations, the risk implications of increasing the number of LNG cars in a shipment may continue to be the subject of disagreement.67
Reducing the chances of derailment requires more frequent track and rolling stock inspections.
Reducing the consequences of a derailment--including cascading failure--involves the crashworthiness of tank car design standards, braking systems, train speed, routing analysis, and the preparedness of emergency responders. While the proposed rulemaking mentions AAR Circular OT-55, the industry safety standard for trains carrying 20 or more cars of hazardous material (referred to by the rail industry as "key trains"), it does not incorporate these standards into the rulemaking.68 Circular OT-55, among other things, limits the speed of key trains to 50 miles per hour and specifies the frequency of inspections of tracks and rail cars supporting their movement.
Tank Car Safety Design and Safety Record
In a derailment, the forces applied as rail cars ram into one another (or into a significant fixed structure along the track) are so great that it is impracticable to build a tank car that is puncture proof in these scenarios. The strategy, instead, has been to reduce the number of cars being punctured with practical design elements.
Safety design elements for rail tank cars include increasing the metal thickness of the outer tank
In addition to increasing the
PHMSA's proposed rule would allow the existing DOT-113 tank car design to be used for LNG.
The existing fleet of DOT-113 tank cars consists of 405 cars and most of them are used to carry a non-flammable material (refrigerated carbon dioxide). Fewer than 3% of shipments using DOT113 tank cars carry a flammable material (refrigerated ethylene).70 The
The Railroad Tank Car Committee
The Railroad Tank Car Committee (TCC) is a long-standing industry group which evaluates and sets industry standards for tank car designs.74 Its members represent railroads, tank car leasing companies, and shippers (rail customers, such as chemical or petroleum companies that own the cargo). Under the Hazardous Materials Transportation Act (P.L. 93-933) and DOT regulations, the TCC has authority to review the "designs, materials and construction, conversion or alteration of tank car tanks" and to review "proposed changes in or additions to specifications for tanks."75 The TCC may make recommendations for DOT to consider, although it has no authority, itself, to regulate tank car specifications. Thus, the DOT relies on the TCC in an advisory capacity with respect to regulating tank cars. The TCC is evaluating the DOT-113 tank car design and is expected to provide its recommendation on any safety design improvements to DOT in the summer of 2020.76
Most often, in the tank car segment, shippers rather than the railroads either own or lease the tank cars from tank car leasing companies. Since rail shippers provide the tank cars while railroads provide the track and train operations, there can be disagreement between railroads and tank car shippers about how much emphasis should be placed on tank car safety versus track inspections and train operating parameters.77 Railroads, which have the majority vote in the TCC, want to increase the thickness of the outer
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1 Executive Office of the President, Economic Report of the President,
2 Executive Order 13868, "Promoting Energy Infrastructure and Economic Growth," 84
5 See, for example,
6 Walter Chukwunonso Ikealumba and
9 Methane, the main component of LNG, burns in gas-to-air ratios between 5% and 15%.
10 PHMSA states that it "is not aware of any reliable reports of explosions of outdoor vapor clouds of natural gas and does not believe that there is a risk of vapor cloud explosions (VCEs) due to a release of methane in an open area." PHMSA, "LNG Safety," accessed
11 In a 1944 accident with
13 Nilambar Bariha,
16 A related issue of debate is the potential environmental impact of greenhouse gas emissions from natural gas production and transportation prior to rail shipment and from natural gas combustion by consumers. Analysis of this issue is outside the scope of this report.
17 See, for example:
18 See, for example, Representative
19 Volpe Center, U.
20 Government Accountability Office, Critical Infrastructure Protection: Actions Needed to Address Significant Weaknesses in
21 For further discussion of pipeline security, see CRS Insight IN11060, Pipeline Security:
22 FRA, "
23 Through its
24 DOT has the emergency authority to restrict or prohibit transportation that poses a hazard of death, personal injury, or significant harm to the environment. See 49 U.S.C. Sec.20104.
25 49 C.F.R. Sec.193.
26 For rail examples, see
27 Executive Office of the President, "Presidential Policy Directive--Critical Infrastructure Security and Resilience," PPD-21,
28 PPD-21; Sector-specific agencies' responsibilities are further elaborated in
30 49 C.F.R. Sec.Sec.172.800 et seq.
31 15 U.S.C. Sec.Sec.
32 15 U.S.C. Sec.717b(a);
34 Hazmat regulations are at 49 C.F.R. Sec.172 et seq. PHMSA special permits are authorized under 49 U.S.C. Sec.5117; special permits may be issued to any applicant performing a regulated function, including, a "person who--(i) transports hazardous material in commerce; (ii) causes hazardous material to be transported in commerce; (iii) designs, manufactures, fabricates, inspects, marks, maintains, reconditions, repairs, or tests a package, container, or packaging component that is represented, marked, certified, or sold as qualified for use in transporting hazardous material in commerce; (iv) prepares or accepts hazardous material for transportation in commerce; (v) is responsible for the safety of transporting hazardous material in commerce" (49
35 49 C.F.R. Sec.178.274.
37 PHMSA, Risk Assessment of
40 Energy Transport Solutions, "Application for a Special Permit, to Transport Methane, Refrigerated Liquid, in DOT 113 Tank Cars," before the
41 PHMSA, Special Permit DOT-SP 20534, granted to
42 Executive Order 13868, "Promoting Energy Infrastructure and Economic Growth," 84
44 This is the rail car approved for use in the PA-NJ route mentioned above. PHMSA, "Hazardous Materials:
45 Ibid, p. 56965.
47 PHMSA NPRM, p. 56967.
49 For further discussion of crude oil shipment by rail, see CRS In Focus IF10727, Rail Transportation of Crude Oil and the FAST Act: An Update, by
50 PHMSA, SP 20534 Special Permit to Transport LNG by Rail in DOT113C120W Rail
51 Ibid., p. 23.
52 PHMSA NPRM, p. 56969.
55 See, for example,
56 This occurred, for example, in the 2018
60 See, for example
61 PHMSA NPRM, p. 56974.
63 PHMSA NPRM, p. 56973.
64 The FRA has reported the results of a fire safety tests conducted in 2017 on a multi-modal tank container filled with liquid nitrogen (a non-flammable cryogenic liquid) loaded on a rail flat car over a propane pool fire to evaluate the pressure relief valves. In the tests, the relief valve system successfully vented the evaporating nitrogen before the pressure became high enough for a BLEVE to occur (tank failure). See FRA, Fire Performance of a UN-T75 Portable Tank Phase 1: Loaded with Liquid Nitrogen, DOT/FRA/ORD-20/02,
65 See, for example, Earthjustice, "RE: Comments Objecting to the Proposed Rulemaking to Authorize the Transportation of Methane, Refrigerated Liquid by Rail, Docket No. PHMSA- 2018-0025 (HM-264), letter to PHMSA,
66 PHMSA, Hazardous Materials:
67 Japanese operators began shipping LNG by rail (in ISO containers) in 2000. Other countries, such as
68 AAR Circular OT-55, at https://public.railinc.com/sites/default/files/documents/OT-55.pdf.
69 The enhancements distinguish the older DOT-111 tank car design from the newer DOT-117 design (49 C.F.R. Sec.179.202-12) for carrying crude oil and ethanol.
73 PHMSA, Preliminary Regulatory Impact Analysis, p. 13, at https://www.regulations.gov/document?D=PHMSA2018-0025-0001.
74 Rail cars often traverse the track of more than one railroad. Therefore, industry has needed to set design standards for many rail car components to ensure interoperability; for instance, general elements like axle width and coupler height, and very detailed car specifications. These design standards enable railroads to maintain and repair cars interchanged among them.
75 49. C.F.R. Sec.Sec.179.3-179.4. In addition to defining this "delegated authority," Sec.179 refers to the TCC's specifications for tank cars in discussing more detailed aspects of tank car design in over 60 subparts of the code.
76 Comments of the
78 AAR and ASLRRA,
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The tables and figures can be viewed at: https://crsreports.congress.gov/product/pdf/R/R46414
The complete document can be viewed at: https://crsreports.congress.gov/product/pdf/R/R46414
(Continued with Part 2 of 2)