Natural Gas Storage: Actions Needed to Assess Inspection Workload and Progress toward Safety Outcomes

About 400 natural gas storage sites are important to the U.S. natural gas system, providing about 30 percent of the nation's energy. During a 2015 leak at a storage site near Los Angeles, about 8,000 families were temporarily relocated due to symptoms such as migraines, nausea, and respiratory problems. The leak raised concerns about health and safety risks from other storage sites. In 2017, GAO recommended that PHMSA take actions, including using baseline data to develop performance goals for its natural gas storage program.

GAO was asked to review the health and environmental effects of activities at natural gas storage sites. This report, among other objectives, (1) assesses the extent to which PHMSA has developed its natural gas storage inspection program and (2) describes what is known about the potential health effects from chemicals in stored natural gas. GAO reviewed available documents about natural gas storage incidents from 2000 through 2018; compared PHMSA research, goals, and plans against leading planning practices; visited sites representing the three types of storage sites; and interviewed agency officials.

In 2018, the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) set a goal for its natural gas storage inspection program to inspect all approximately 400 natural gas storage sites within 5 years, according to agency officials. PHMSA expected that all 25 eligible states would help inspect sites, but only 10 states agreed to partner with the agency. As a result, the agency's inspection workload increased by almost 60 percent from when it set its goal, according to PHMSA data. Because of the increase in its inspection workload over its preliminary estimate, PHMSA does not have assurance that it has enough resources to meet its inspection goal. Furthermore, PHMSA has not used a workforce analysis to inform its budget requests. PHMSA officials said that the agency does not expect to have enough data until 2022 or 2023 to further inform analysis of its workforce. By analyzing factors affecting states' willingness to partner with PHMSA and its workforce needs on an ongoing basis, the agency would have better assurance that it has the staff it needs to meet its inspection goal.

Health effects have been reported related to chemicals that may be found in stored natural gas. Several federal agencies—including the Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry—have documented potential health effects of chemicals that may be found in stored natural gas. In addition, some chemicals may be added to natural gas, such as sulfur odorants that give natural gas a distinct smell in case of leaks. The combination of such chemicals varies from one natural gas storage site to another, based on the attributes of that site such as its geologic type and the extent to which sulfur odorants are added to the natural gas before storage. Many of these chemicals have been linked to adverse health effects. However, research is limited on the health effects of exposure to stored natural gas in general and on the effects in particular from exposure to chemicals that may occur in natural gas storage leaks or be present at the storage sites. Reports linking health effects are available on specific chemicals but not in the context of natural gas storage, based on GAO's literature review.

GAO is making two recommendations, including that PHMSA should analyze factors affecting states' willingness to partner with PHMSA and analyze its workforce needs on an ongoing basis. The agency concurred with the recommendations.

Natural gas plays a vital role in the U.S. energy system. It provides about  30 percent of the nation’s energy and is widely used to generate  electricity, to heat and cool homes and businesses, and in a variety of  industrial processes, according to the U.S. Energy Information  Administration (EIA). As of July 2019, approximately 400 sites across the  country store natural gas in underground geological formations and use  wells at these sites to inject and withdraw natural gas, according to EIA.  These sites typically are near or have convenient pipeline access to major  metropolitan areas. This proximity helps to ensure that natural gas is  available for times of peak energy use—such as in winter to heat  homes—more quickly than would be possible if relying solely on pipelines  that transport natural gas from distant production fields. However, these  sites can pose risks.

In 2015, a natural gas leak from a well at the Aliso Canyon site near  suburban Los Angeles, California—the fourth-largest storage site in the  United States—raised concerns about the safety of the underground wells  used at storage sites and about potential adverse health and  environmental effects from natural gas releases. The leak released about  5.4 billion cubic feet of natural gas into the atmosphere, continued for  almost 4 months, and eventually led to the temporary relocation of about  8,000 families in the nearby Porter Ranch neighborhood. California  government officials identified two factors that contributed to the leak: (1)  the aging infrastructure of the well, which was drilled in 1953 as an oil  production well, and (2) the lack of redundant safety valves at the well.

After this emergency, the Protecting Our Infrastructure of Pipelines and  Enhancing Safety (PIPES) Act of 2016 was enacted. The act, among  other things, required the Secretary of Transportation to establish  minimum safety standards for all underground natural gas storage sites  by June 22, 2018. The Department of Transportation’s (DOT) Pipeline  and Hazardous Materials Safety Administration (PHMSA) is responsible  for setting and enforcing these standards for underground natural gas  storage sites. In 2017, PHMSA established an oversight and enforcement  program for natural gas storage sites. PHMSA's mission is to protect  people and the environment by advancing the safe transport of natural  gas, among other types of energy, and hazardous materials that are  essential to our daily lives.

In 2018, PHMSA collected data that showed approximately 10,000 of the  17,000 (about 59 percent) underground natural gas storage wells across  the country have design characteristics similar to the well at Aliso  Canyon. This could increase the risk of more natural gas releases,  according to a 2017 study by Harvard University researchers. According  to an analysis by the Department of Energy (DOE), more than 300 cities,  towns, and other populated areas are located within about 3 miles of a  natural gas storage site.

In November 2017, we reported that PHMSA had taken steps in its  recently established natural gas storage program, such as developing a  training program for inspectors and setting a performance goal for its  training program. However, we found that PHMSA had not yet followed  certain leading strategic planning practices for the program. For example,  PHMSA had not yet defined the level of performance to be achieved,  developed goals to address core program activities other than training, or  used baseline data to develop goals. We recommended that PHMSA (1)  define levels of performance and address all core program activities and  (2) use budget data to refine its performance goals for its gas storage  program. PHMSA officials concurred with these recommendations and  implemented the first recommendation. PHMSA officials told us in July  2019 that to address our second recommendation, they would strive to  add and refine performance goals as they continued to develop the  program.

You asked us to review issues related to the safety of natural gas storage  sites and potential environmental effects from site activities. This report  (1) assesses the extent to which PHMSA has further developed its natural  gas storage program since our November 2017 report, (2) describes what  is known about the potential health effects from chemicals in stored  natural gas, and (3) describes what is known about the potential  environmental effects of releases at natural gas storage sites.

To address these objectives, we reviewed documents from PHMSA, the  Environmental Protection Agency (EPA), DOE, the Agency for Toxic  Substances and Disease Registry (ATSDR), the National Institute for  Occupational Safety and Health (NIOSH), and the Occupational Safety  and Health Administration (OSHA), and met with officials from these  agencies to determine the extent to which chemicals in stored natural gas  have documented potential health effects. To identify releases of natural  gas from storage sites, we conducted a literature search to identify  releases such as leaks and explosions that occurred in the United States  from 2000 through 2018 and reviewed PHMSA’s list of natural gas  storage sites from 2017, the first year PHMSA collected such information.  We identified 93 releases of natural gas from storage sites; these 93  releases include incidents as defined by PHMSA regulations as well as  releases of natural gas that may not meet that definition.

We met with officials representing a nongeneralizable sample of seven  states to understand their perspectives on the natural gas storage safety  program and PHMSA's efforts to partner with states and conduct  inspections. We selected four of the five states with the largest amount of  working natural gas storage (Michigan, Texas, Louisiana, and California),  one state in which PHMSA was conducting an inspection (Iowa), and two  additional states that had considered partnering with PHMSA (Alaska and  Colorado). We visited sites representing each of the three types of  natural gas storage sites—Moss Bluff in Texas (a salt cavern), Aliso  Canyon in California (a depleted oil and gas field), and Redfield in Iowa (a  depleted aquifer). We reviewed documentation from each site and  interviewed officials representing these sites’ operators. We selected  these sites for specific reasons: Aliso Canyon because of the 2015 leak,  Redfield because it was scheduled to undergo an inspection by PHMSA  at the time of our visit, and Moss Bluff because it was readily accessible  from a major urban area (Houston, Texas). Our findings from the sites we  visited and officials we interviewed are not generalizable to sites and  officials we did not include in our review but provide illustrative examples  of such sites. We also met with officials from industry groups that  represent companies that operate natural gas storage sites—the  American Gas Association, the American Petroleum Institute (API), and  the Interstate Oil and Gas Compact Commission—to better understand  these groups’ perspectives on PHMSA’s natural gas storage safety  program.

To assess the extent to which PHMSA has taken action to continue  developing its program for natural gas storage since our November 2017  report, we reviewed documents related to the program, including strategic  plans, DOT annual performance reports, and inspection-related  documentation. We also met with PHMSA officials to discuss the  program. We visited the Redfield gas storage facility in Iowa during a  PHMSA storage safety inspection, and we met with officials from the Iowa  Department of Natural Resources to discuss natural gas storage safety.  We compared PHMSA efforts on its natural gas storage program’s  workforce planning against our prior work on best practices in workforce  planning. We compared PHMSA’s efforts on strategic planning against  leading strategic planning practices we identified in our prior work. For  example, we have previously reported that requirements of the  Government Performance and Results Act of 1993, as amended  (GPRA), such as performance goals, that apply at the departmental or  agency level can serve as leading practices for planning at lower levels,  such as component agencies, offices, programs, and projects within  federal agencies.

To describe what is known about the potential health effects from  chemicals in stored natural gas, we used literature search results that  identified releases from 2000 through 2018 to determine whether there  were any studies that empirically linked the releases of natural gas in  storage sites with health effects; we did not find any such studies. As a  result, we reviewed chemicals known to be found in stored natural gas,  some at trace levels. As previously mentioned, we reviewed documents  from and met with officials from EPA, ATSDR, OSHA, and NIOSH. We  also identified chemicals that may be found in stored natural gas by  reviewing the Safety Data Sheets from 12 operators with the largest  storage capacity. In addition, we reviewed documentation from  California agencies on reported health symptoms and chemicals that  were tested for during the Aliso Canyon incident. We also reviewed  agency documents and spoke with agency officials about the natural gas  storage program. Additionally, we reviewed reports from the Public Health  and Environment Subgroup of an interagency task force that studied the  Aliso Canyon incident and the California Council on Science and  Technology (CCST).

To describe what is known about the environmental effects of releases  from natural gas storage sites, we reviewed documentation from EPA on  greenhouse gas emissions, in general and specifically for the Aliso  Canyon natural gas leak in 2015. We also spoke with agency officials  knowledgeable about EPA programs that track emissions of greenhouse  gases. We obtained data from EPA that estimated methane emissions  from natural gas storage sites for 1995 through 2016, and we assessed  the reliability of these data by reviewing information about the data and  the methods EPA used to produce them. We determined that these data  were sufficiently reliable for our reporting objectives. We used our  literature search results that identified 93 incidents in 2000 through 2018  to identify potential environmental effects associated with releases at  natural gas storage sites. For the Aliso Canyon incident in 2015, we  reviewed reports related to the release of methane during the leak. For  more information about our scope and methodology, see appendix I.

We conducted this performance audit from December 2017 to October  2019 in accordance with generally accepted government auditing  standards. Those standards require that we plan and perform the audit to  obtain sufficient, appropriate evidence to provide a reasonable basis for  our findings and conclusions based on our audit objectives. We believe  that the evidence obtained provides a reasonable basis for our findings  and conclusions based on our audit objectives.

After it is extracted, natural gas—a colorless, odorless fossil energy  source—is stored in three types of underground geologic formations: salt  caverns, depleted aquifers, and depleted oil and gas reservoirs. Two  physical characteristics govern the suitability of each type of geologic  formation for storage, including: (1) its capacity to hold natural gas for  future use and (2) the rate at which natural gas can be withdrawn to meet  demand. As of July 2019, about 80 percent of the approximately 400  natural gas storage sites in the United States are depleted natural gas or  oil reservoirs because they are available in greater numbers than other  types of formations, according to EIA. Underground salt caverns and  depleted aquifers each account for about 10 percent of the sites.

Natural gas storage sites are located in 31 states. California, Louisiana,  Michigan, Pennsylvania, and Texas together contain natural gas storage  sites that provide more than half of the natural gas storage capacity in the  United States. Figure 1 illustrates the types of geologic formations used  for natural gas storage and the locations of natural gas storage sites in  the United States.

The wells that inject natural gas into, or withdraw it from, the underground  storage sites can extend thousands of feet underground. According to  information from PHMSA, about 17,000 wells are used to inject and  withdraw gas at approximately 400 natural gas storage sites, ranging  from a few wells per site to more than a hundred wells at some larger  sites. Wells are constructed with multiple layers of steel pipe, called  casing, which are cemented in place. The layers of steel casing are  intended to isolate the internal portion of the well from the outlying  geological formations, which may include underground drinking water  supplies. As a well is drilled deeper, progressively narrower casing is  inserted further down the well and cemented in place. The wells at natural  gas storage sites can be constructed to prevent leaks by installing  multiple control points at each well, according to API. If a well is not  constructed with such multiple points of control, it could be subject to a  single point of failure, in which the failure of a single component, such as  a casing or a safety valve, can lead to a large release of natural gas—a  factor that contributed to the Aliso Canyon incident, according to PHMSA  officials.

Aliso Canyon Underground Storage Facility Leak

From October 23, 2015, through February 11, 2016, the Aliso Canyon  Underground Storage Facility in Los Angeles County, California,  experienced a large and uncontrolled natural gas leak. The Aliso Canyon  natural gas storage site is a depleted oil field that was converted into a  natural gas storage reservoir in the 1970s and that is near the Porter  Ranch community, a residential community of about 30,000 people. It  provides natural gas to the Los Angeles region for residential heating and  cooling, commercial and industrial uses, and as fuel for electric power  plants. According to the Energy Information Administration, the Aliso  Canyon site has the fourth largest capacity among the approximately 400  underground natural gas storage sites in the United States. The leak  reportedly was caused by damage to a well casing approximately 500  feet underground. California state government officials identified the  damage as being caused by the aging infrastructure of that well, which  had been drilled in 1953, and a lack of redundant safety valves at the well  that prevented the leak from being stopped.

Across a 4-month period, the site operator made multiple attempts to stop  the leak. About 8,000 families near the Aliso Canyon leak were  temporarily relocated in November 2015 due to ongoing odors and  symptoms including headaches or migraines; nausea, vomiting, stomach  aches, or diarrhea; nosebleeds; respiratory or breathing problems; chest  tightness, coughing, or palpitations; and light-headedness and dizziness.  Various agencies, including public health and regulatory agencies from  state and local governments such as the Los Angeles County Public  Health Department and California’s Office of Environmental Health  Hazard Assessment, responded to the leak.

Additionally, several studies about the leak have been conducted or are  planned. CCST, a nonpartisan, nonprofit organization established in  response to a California state legislative resolution, published an  independent review of the viability of underground natural gas in  California, including an analysis of the health effects from stored natural  gas releases. An interagency task force established pursuant to federal  law, led by DOE and PHMSA, studied the Aliso Canyon incident and in  2016 provided a report to relevant congressional committees with  recommendations to enhance safety. According to the 2016 interagency  task force report, natural gas stored in geologic formations is under high  pressure, which can force the gas through underground fissures or  unplugged oil and gas wells and allow the gas to find its way to the  surface. Leaks can also occur if the wells lose integrity because of  cracking of the cement used to seal them, among other factors. Older  wells used for natural gas storage were often drilled for other reasons,  such as oil and gas production, and are more likely to have age-related  degradation. As part of its work, the interagency task force chartered a  Public Health and Environment Subgroup, led by EPA, to summarize the  actions taken by local, state, and federal agencies to monitor and mitigate  impacts to public health and the environment. The subgroup was to also  recommend actions to prepare local, state, and federal agencies if a  release from a natural gas storage facility should occur in the future.

Safety Regulations and Enforcement for Underground Natural Gas Storage Sites

When the Aliso Canyon leak occurred in 2015, federal safety regulations  applied to conventional surface pipelines and above-ground equipment at  all natural gas storage sites. Only state safety regulations applied to  underground natural gas storage sites at that time. The PIPES Act of  2016 significantly changed the regulation of natural gas storage. It  requires, among other things, that DOT establish minimum safety  standards for all natural gas storage sites. Within DOT, PHMSA's mission  is to protect people and the environment by advancing the safe  transportation of energy and other hazardous materials, and because  natural gas storage is a part of this mission, PHMSA is responsible for  natural gas storage safety. In response to the act’s requirement, PHMSA  issued an interim final rule in December 2016 that took effect in January  2017. The rule included minimum safety standards based largely on  recommended practices from API and generally required compliance by  natural gas storage sites by January 2018. PHMSA provided for a public  comment period, and after reviewing the public comments received on  the interim final rule, PHMSA may modify aspects of the interim final rule  by issuing a final rule. In August 2019, PHMSA officials told us they  planned to issue a final rule in October 2019.

PHMSA's interim final rule contains four different reporting requirements  for operators of all natural gas storage sites, including an annual report  with gas storage volumes, gas storage pressures, well depths, gas  injection and withdrawal rates, and maintenance information that is  conducted to ensure the safety of a facility. The interim final rule also  requires operators to develop emergency response plans, but the  required elements for such plans vary depending on the type of natural  gas storage site.

While PHMSA has authority for oversight of underground natural gas  storage facilities, the PIPES Act also authorizes states to participate in  such oversight by annually obtaining certification from or entering into an  agreement with PHMSA (which we refer to as partnering with PHMSA).  Authorized states are responsible for inspecting intrastate underground  natural gas storage facilities on sites fully within their borders. According  to PHMSA officials, 25 of the 31 states where underground natural gas  storage sites are located have such intrastate sites, and PHMSA  expected to partner with these 25 states by granting them oversight  authorization, according to PHMSA officials.

In addition, the PIPES Act requires PHMSA to set and charge user fees  for operators of underground natural gas storage sites. The act restricts  the use of these fees to activities related to natural gas storage site  safety. The act also prohibits PHMSA from collecting fees unless the  expenditure of these fees is provided in advance in an appropriations act;  as a result, PHMSA can only collect fees up to the amount provided in  advance in an appropriations act.

Public Health and Environmental Effects from Hazardous Chemicals

Human health can be affected by breathing hazardous chemicals in the  air; drinking water contaminated by such chemicals; or making skin  contact with contaminated soil, dust, or water. Chemicals that can affect  human health include several types of hazardous materials that pose a  risk to human health and safety. Environmental effects of chemicals can  include greenhouse gas emissions and groundwater contamination.

Several federal agencies have a role in assessing the public health and  environmental effects from exposure to hazardous chemicals, although  these efforts may not be specifically related to underground natural gas  storage as described in this report. For example, the Toxic Substances  Control Act authorizes EPA to review the environmental and health  effects of certain chemicals and regulate those that pose unreasonable  risks to human health or the environment. According to EPA's July 2018  Report on the Environment, relationships between environmental  exposures and health outcomes can only be established through well- designed epidemiological, toxicological, and clinical studies. Developing  evidence that environmental contaminants cause or contribute to the  incidence of adverse health effects can be challenging, particularly for  effects that occur in a relatively small proportion of the population or  effects with multiple causes. For example, there may be factors related to  both the exposure and the health effect—confounding factors—that can  make it difficult to detect a relationship between exposure to  environmental contaminants and disease.

In its 2018 report, EPA stated that it uses the results of scientific research  to help identify linkages between exposure to environmental  contaminants and diseases, conditions, or other health outcomes. These  linkages, in turn, identify environmental contaminants and health  outcomes of potential agency interest. Research has established a  relationship between exposure and disease for some environmental  contaminants, including  radon and lung cancer, arsenic and cancer in several organs, and  lead and nervous system disorders.

OSHA established the Air Contaminants Standard to limit employees’  occupational exposure to more than 400 chemicals. It also established  the Hazard Communication Standard, which requires employers to  provide information to their employees about the hazardous chemicals to  which they are exposed by means of Safety Data Sheets, among other  things. Other federal agencies have responsibilities related to the  human health effects of chemicals, including ATSDR and NIOSH.

ATSDR has authority to, among other things, perform health  assessments for releases or facilities where information was provided that  individuals were exposed to a hazardous substance for which the  probable source of such exposure is a release. NIOSH researches the  safe use of chemicals in the workplace and provides information on how  to measure chemicals in the work environment, among other things, for  understanding and managing chemicals safely at work.

2017 GAO Report Findings and Recommendations

In November 2017, we reported on PHMSA’s natural gas storage  program. At the time of our 2017 review, PHMSA was still establishing  its program, and we reviewed its planning efforts for developing the  program. We found that although PHMSA had established a strategic  goal for its natural gas storage program and set a performance goal for  training inspectors, it had not yet followed other leading practices for  strategic planning. PHMSA officials told us that the program would be  guided by one of PHMSA’s existing strategic goals: to promote  continuous improvement in safety performance. We found that PHMSA  had not defined the level of performance to be achieved and did not have  performance goals that addressed other core program activities, such as  conducting inspections. We recommended that PHMSA define levels of  performance, address core program activities, and use baseline data to  develop performance goals for its natural gas storage program. At that  time, we also found that PHMSA had not yet used initial baseline data it  gathered early in the program to inform the development of its  performance goal. We recommended that PHMSA use other data and  information about budgetary resources as they become available to  inform and refine its performance goals. PHMSA agreed with these  recommendations and in May 2018 established a performance goal for  inspections of natural gas storage sites. PHMSA officials told us in July  2019 that they were continuing to inform and refine agency performance  goals based on budgetary information.

Since November 2017, PHMSA Has Not Fully Evaluated Its Workforce Needs for the Program or Established Performance Goals That Reflect Efforts to Improve Safety

After our report in November 2017, PHMSA began inspecting natural gas  storage sites but has not fully assessed resource needs for its changing  workload or established a performance goal that measures PHMSA’s  progress toward its relevant strategic goal to improve safety. First,  because PHMSA has not used an analysis of its workforce needs to  inform its budget requests, the agency may not have assurance that it  has enough resources to meet its performance goal of inspecting all of  the approximately 400 natural gas storage sites within 5 years (from early  2018 through early 2023). Second, although PHMSA has established a  performance goal that focused on the number of inspections completed,  the goal does not reflect the agency’s contributions toward its strategic  goal to promote continuous improvement in safety.

Since 2017, PHMSA Has Established and Worked toward an Inspection Performance Goal but Has Not Used a Workforce Analysis to Guide Its Resource Decisions

In November 2017, we reported that PHMSA had established a strategic  goal for its natural gas storage program but had not yet set performance  goals that define the level of performance officials hope to achieve or that  address all core program activities, such as conducting effective  inspections. PHMSA's inspections of natural gas storage sites are  designed to determine the extent to which these sites meet PHMSA’s  2016 minimum safety standards for natural gas storage sites, according  to PHMSA officials and documents. In our November 2017 report, we  stated that our prior work had identified several leading practices for  strategic planning that PHMSA had not yet followed, such as setting goals  that define a certain level of performance and address all core program  activities. We recommended that PHMSA develop such goals, and the  agency concurred.

In 2018, PHMSA officials told us that the agency had established a  performance goal to inspect all of the approximately 400 natural gas  storage sites over 5 years (from early 2018 through early 2023), with the  expectation that state partners would help PHMSA inspect the sites. The  officials also told us the agency has started inspecting sites to meet that  goal. Currently, 10 states have agreed to partner with PHMSA to help  inspect natural gas storage sites, according to agency officials.

Natural Gas Storage Site Inspections  Conducted by the Pipeline and Hazardous  Materials Safety Administration (PHMSA)   At a PHMSA inspection of a natural gas  storage site in rural Iowa, we observed  PHMSA inspectors conducting visual  inspections of natural gas storage wells in the  field to ensure that the site operator's wells  matched the operator's documentation and  that the wells were operating within safe limits.  During the inspection, PHMSA's inspectors  also conducted a review of the storage site  operator's safety procedures, such as the  operator’s schedule for inspecting its wells for  potential leaks or pressure changes, its  emergency contact protocols, and its  procedures for ensuring the integrity of wells.  As part of the review, PHMSA inspectors  reviewed the site operator’s documentation to  evaluate the operator’s efforts to implement  the agency’s 2016 minimum safety standards  for natural gas storage sites.

To meet its performance goal, PHMSA set targets for each of the 5 years  (see app. II for details about PHMSA's annual targets for this performance  goal). For example, PHMSA set a target that its inspectors and state  partners would inspect a total of 41 sites in 2018. According to PHMSA  officials, the agency completed 35 inspections, and its state partners  inspected an additional 30 sites, for a total of 65 inspections in 2018. In  future years, according to PHMSA planning documents, PHMSA’s annual  site inspection targets will almost double from 41 total site inspections in  2018 to 80 total site inspections in 2019.

However, PHMSA's inspection workload for its natural gas storage  program has increased since November 2017, which may affect its ability  to meet its inspection performance goal. We reported in November 2017  that PHMSA had developed a preliminary estimate of the workforce it  would need to inspect half of the approximately 400 natural gas storage  sites. That estimate was based on the agency’s experience from its  pipeline safety program. Specifically, in 2017, agency officials said that  they expected 25 state governments would partner with PHMSA to  inspect about 200 of the sites and that six agency employees would  inspect the remaining approximately 200 sites. Specifically, in 2017  PHMSA estimated the inspections would require about 203 work weeks  of inspectors’ time. However, in October 2018, PHMSA officials told us  that their inspectors would need more time than previously estimated to  complete each natural gas storage site inspection, due to requirements  for operators in the 2016 minimum safety standards.

Furthermore, in its 2017 estimate, PHMSA assumed that all 25 state  governments eligible to partner with PHMSA on inspections would agree  to do so. However, as of June 2019, only 10 of the 25 eligible states had  agreed to partner with PHMSA, according to agency officials. PHMSA  officials told us that more states may decide to participate in the future.  However, there are a variety of reasons why states may be reluctant to  partner with PHMSA. For example, officials from two states told us that  PHMSA had not offered enough funding to cover the cost of partnering  with the agency. Officials from two states told us that partnering with  PHMSA required some lead time to obtain funds through their states'  legislative processes for such inspections. In addition, PHMSA officials  told us that some states are waiting until the interim final rule is issued as  a final rule before determining whether to partner. As a result, according  to PHMSA data, unless additional states partner with the agency, PHMSA  will need to increase the number of sites it inspects from about 200 to 322  in order for the agency to meet its performance goal of inspecting all of  the approximately 400 sites by 2023. This would increase PHMSA’s  inspection workload by about 60 percent, as shown in figure 2.

Because of the increase in its inspection workload over its preliminary  estimate, PHMSA does not have assurance that it has enough resources  to meet its inspection goal. Specifically, PHMSA has requested and  received the same budget authority for its natural gas storage safety  activities—$8 million—for each fiscal year from 2017 through 2019. Of  the $8 million, PHMSA requested $2 million for federal employees to  inspect about 200 of about 400 natural gas storage sites. PHMSA  requested the remaining $6 million for grants to authorized states to  conduct inspections of the remaining sites. However, of the 25 states  PHMSA expected to request such authority, only 10 did so and are  partnering with PHMSA to conduct inspections, according to PHMSA  officials. This means that the number of sites that states could inspect is  about 90 rather than about 200, as PHMSA had initially estimated. In  comparison, PHMSA's workload for its natural gas storage inspection  program is more than three times higher than the workload for PHMSA’s  pipeline inspection program.

We also recommended in November 2017 that PHMSA use other data  and information about budgetary resources to inform and revise its  performance goals. PHMSA concurred with our recommendation.  However, officials told us that as of July 2019, the agency had not yet  fully addressed this recommendation to use workforce data to inform and  revise its goals. In December 2018, PHMSA issued a strategic workforce  plan that indicates it represents a thorough analysis of the agency’s  current workforce composition as of 2018 and the collective viewpoints of  employees and senior leadership regarding the future. PHMSA stated in  this plan that workforce planning will allow the agency to respond to  emerging challenges and responsibilities and improve overall mission  effectiveness and efficiency. Specifically, the plan states that PHMSA  leadership recognizes that while the agency has implemented some  foundational elements of workforce management and the overall  workforce is staffed with skilled professionals, the agency’s workforce  planning has tended to be more reactive than proactive. The plan cites as  evidence underdeveloped succession plans, inconsistent hiring results,  increased turnover, and limited workforce analysis and forecasting. To  address these gaps, the plan identifies the following three high-level  strategies to supplement and expand agency capabilities: expand and enhance PHMSA’s recruitment and hiring plans,  conduct operational workforce planning and workload analysis by  program office, and  implement succession planning and develop leadership and staff.

PHMSA officials said that the agency has been assessing its workforce,  but they told us this assessment will not guide the agency’s budget  requests for its natural gas storage program. PHMSA officials told us  they did not plan to change the workforce levels reflected in the agency’s  budget requests until 2022 or 2023. This is because although PHMSA  has been collecting and assessing workforce data since March 2018, the  agency does not expect to have the workforce data it needs to further  inform workforce analysis until 2022 or 2023, according to PHMSA  officials. The officials indicated that the additional data they have begun  gathering may include variables such as the number of additional states  that may partner with PHMSA in the future; resources used, by region;  and the capacity of inspection teams of different sizes. In technical  comments PHMSA provided on a draft of this report, PHMSA officials  stated that the agency recently concluded a workforce assessment of its  pipeline inspection program—including its natural gas storage program— covering the 5 years from 2020 through 2024. PHMSA’s workforce  assessment indicated that the state of Texas is likely to partner with  PHMSA beginning in 2020, which would reduce the number of natural  gas storage sites PHMSA would need to inspect. Based on our  preliminary review of the information PHMSA officials provided, however,  PHMSA’s assessment does not address the reasons its inspectors’  workload increased by about 60 percent, such as the factors affecting  states’ participation in inspections. Moreover, PHMSA officials did not  indicate whether PHMSA would use this workforce information to guide its  workforce planning or budget requests.

We have reported that strategic workforce planning is an essential tool to  help agencies align their workforces with their current and emerging  missions and develop long-term strategies for acquiring, developing, and  retaining staff. Furthermore, we have reported that existing strategic  workforce planning tools and models and our own work suggest that there  are certain principles that such a process should address. These  principles include developing strategies tailored to address gaps in  number, deployment, and alignment of human capital to enable and  sustain the contributions of all critical skills and competencies. We also  have reported that workforce planning should include (1) identification of  the knowledge, skills, and abilities and other characteristics (i.e.,  competencies) needed by the future workforce; the competencies of the  current workforce; and gaps between the two; (2) development of a  workforce action plan designed to address these gaps; and (3) monitoring  and evaluation of the workforce planning actions taken. Furthermore,  we have found in our prior work that completing and regularly updating  staffing models in a timely manner can help support agencies’ activities  and decision-making. By analyzing the factors affecting states’  participation in inspections and analyzing the agency’s workforce needs  on an ongoing basis and using this information to guide its budget  requests, PHMSA would have more reasonable assurance that it has the  necessary staff to meet its inspection goal.

Since 2017, PHMSA Has Established a Performance Goal, but the Goal Does Not Reflect the Agency’s Contributions to Its Strategic Goal of Promoting Continuous Safety Performance

PHMSA has established a strategic goal for its natural gas storage  program to promote continuous safety performance but as of April 2019  had not established performance goals that reflect the agency’s  contributions to protecting human health and the environment. According  to PHMSA officials, PHMSA’s natural gas storage program is guided by  the agency’s strategic goal to promote continuous improvement in safety  performance. PHMSA officials acknowledged that the agency’s inspection  performance goal provides information about activities or outputs— specifically, the number of inspections. However, this goal does not  provide information on the outcomes or results of PHMSA's contributions  toward its strategic goal of improving safety at natural gas storage sites,  consistent with leading practices under GPRA. An example of an  outcome-oriented performance goal could be to measure reductions in  the volume of gas released from natural gas storage wells, which could  indicate that operators of natural gas storage sites are reducing safety  risks through improved maintenance.

Based on our previous work, measuring performance outcomes is an  important management tool for agencies, and leading practices indicate  that results-oriented performance goals focus on expected results to  show progress toward, or contributions to, intended results. By  establishing performance goals that demonstrate improvements to safety  outcomes, PHMSA would have better assurance that it can show its  progress toward meeting the agency’s strategic goal of continuously  improving safety performance.

In addition to the performance goal PHMSA established, agency officials  told us that DOT applied an outcome-oriented, department-wide  performance goal to its natural gas storage program. Based on our review  of DOT’s 2018-19 Annual Performance Plan—2017 Annual Performance  Report, PHMSA is responsible for meeting the department-wide  performance goal of reducing incidents involving death or major injury  resulting from the transport of hazardous materials by all modes,  including pipelines. While PHMSA officials told us this was an outcome-oriented goal, we believe it would not provide a meaningful measure of  safety improvements at natural gas storage sites because, according to  PHMSA data, there have been zero incidents involving death or major  injuries at natural gas storage sites since 2017, when PHMSA started  tracking incidents. While no deaths or major injuries have been reported  at natural gas storage sites since 2017, PHMSA reported seven  incidents—four in fiscal year 2017 and three in fiscal year 2018—that did  not result in death or major injury. These seven incidents resulted in  natural gas releases of 3 million cubic feet or more or caused estimated  property damage of $50,000 or more. By tracking reductions to these  incidents, PHMSA may have additional opportunities to measure  outcomes in safety improvements.

Federal Agencies Have Documented Potential Health Effects from Chemicals that May Be Found in Stored Natural Gas

Several federal agencies—including EPA, ATSDR, OSHA and NIOSH— have documented potential health effects of chemicals that may be found  in stored natural gas. These chemicals—some at trace amounts—are  known to cause health effects at specific levels of exposure. Stored  natural gas primarily consists of methane, and during large releases at  natural gas storage sites, downwind methane concentrations can be  higher than flammability or explosion limits, creating health and safety  concerns, according to CCST. In addition, other chemicals occur  naturally in natural gas or are residues from the storage site’s previous  use. For example, hydrogen sulfide, a flammable, colorless gas that  smells like rotten eggs, can occur in depleted oil and gas reservoirs.  Figure 3 shows a building containing a well at a natural gas storage site  with a notice that warns of hydrogen sulfide, which may collect in confined  spaces in amounts that are acutely toxic. Hydrogen sulfide can cause a  range of human health effects, from eye irritation to serious lung injury,  according to ATSDR.

In addition, some chemicals may be added to natural gas, such as sulfur  odorants that are added to give natural gas a distinct smell in case of  leaks. The combination of such chemicals varies from one storage site  to another based on the attributes of that site, such as its geologic type  and the extent to which sulfur odorants are added to the natural gas  before storage. Many of these chemicals have been linked to adverse  health effects. However, research is limited on the health effects of  exposure to stored natural gas in general and on the effects in particular  from exposure to chemicals that may occur in natural gas storage leaks  or be present at the storage sites. Reports linking health effects are  available on specific chemicals but not in the context of natural gas  storage, based on our literature review. Scientific studies are important for  establishing the association between chemicals in stored natural gas and  symptoms community members may experience during leaks to  determine health effects.

EPA, through its Integrated Risk Information System (IRIS) Program,  identifies and characterizes the health hazards of chemicals found in the  environment and has produced assessments on several chemicals that  may be present in natural gas. EPA established the IRIS Program in 1985  to help develop consensus opinions within the agency about the health  effects from lifetime exposure to chemicals. The IRIS database of  chemical assessments contains EPA’s scientific positions on the potential  human health effects that may result from exposure to various chemicals  in the environment. As of November 2018, the database included  information on 510 chemicals. To conduct an assessment of a chemical,  the agency follows a multi-step process that includes identifying credible  health hazards associated with exposures to a chemical and  characterizing the quantitative relationship between chemical exposure  and each credible health hazard. The program derives toxicity values  through this quantitative relationship. EPA has completed assessments  on several chemicals that may be in stored natural gas, including  hydrogen sulfide, benzene, toluene, ethylbenzene, and xylene. In its IRIS  assessment on benzene, EPA found that, as is the case with many other  organic solvents, benzene has been shown to produce neurotoxic effects  in test animals and humans after short-term exposures to relatively high  concentrations.

ATSDR develops toxicological profiles—summaries of its evaluations  concerning whether, and at what levels of exposure, adverse health  effects occur and levels at which no adverse effects occur—for several  chemicals that may be present in natural gas, including hydrogen sulfide, benzene, toluene, ethylbenzene, and xylene. For example, ATSDR has  found that inhaling benzene can cause drowsiness, dizziness, and  unconsciousness and that long-term benzene exposure affects the bone  marrow and can cause anemia and leukemia. Also, ATSDR found that  toluene may affect the nervous system and at low to moderate levels can  cause tiredness, confusion, weakness, memory loss, nausea, and loss of  appetite. However, these symptoms usually disappear when the  exposure stops.

NIOSH researches the safe use of chemicals in the workplace and  provides information on how to measure chemicals in the work  environment, engineering controls and personal protective equipment,  risk assessments, and communication tools for understanding and safely  managing chemicals at work. NIOSH publishes information on chemical  hazards in the workplace to inform workers, employers, and occupational  health professionals. For example, NIOSH reports on occupational  exposure limits for ethylbenzene. NIOSH’s Pocket Guide to Chemical  Hazards provides key facts on the health effects from exposures to  chemicals and recommends occupational exposure limits to chemicals  that can affect human health. In addition, NIOSH helped initiate the  International Chemical Safety Cards, a joint international agency effort.  The cards, which provide essential safety and health information in a  clear and concise way, are drafted and peer-reviewed by an international  group of scientists from institutions concerned with occupational safety  and health. The cards provide information about some chemicals that  can occur in natural gas storage sites, including hydrogen sulfide,  benzene, toluene, ethylbenzene, and xylene.

OSHA collects information on chemicals and occupational health effects  for workers and compiles that information into a database. OSHA  accumulates information from several government agencies, including  EPA, ATSDR, and NIOSH. This information includes chemical  identification and physical properties, occupational exposure limits, and  sampling information. OSHA’s Occupational Chemical Database provides  information on chemicals, including those that can be present in stored  natural gas, such as hydrogen sulfide, benzene, toluene, ethylbenzene,  and xylene. In addition, among other general information, OSHA  regulations require employers to maintain and make available to  employees Safety Data Sheets in the workplace for each hazardous  chemical they use.

Potential Environmental Effects of Releases at Natural Gas Storage Sites Include Greenhouse Gas Emissions and Some Risks to Groundwater

Releases at natural gas storage sites are known to emit greenhouse  gases—mainly carbon dioxide and methane—into the atmosphere,  according to EPA and CCST reports. In addition, we identified two natural  gas storage site releases from 2000 through 2018 that potentially  impacted groundwater, but information about such releases is limited.

Reports Reviewed Indicate that Natural Gas Storage Sites Emit Greenhouse Gases

Releases at natural gas storage sites emit greenhouse gases into the  atmosphere, according to data from EPA’s program on greenhouse gas  emissions. These can be major releases, such as the Aliso Canyon leak,  or other emissions, such as leaking pipes and valves. According to the  2019 EPA annual report Inventory of U.S. Greenhouse Gas Emissions  and Sinks, the main greenhouse gases released from natural gas storage  sites are methane, the largest component of natural gas, and carbon  dioxide, the main greenhouse gas produced by natural gas combustion.  Of the two, methane makes a greater pound-for-pound contribution to  climate change—the comparative impact of methane is more than 28 to  36 times greater than carbon dioxide over a 100-year period, according to  EPA officials who cited the Intergovernmental Panel on Climate Change.  As a result, leaks such as the Aliso Canyon incident contribute to climate  change, according to EPA. For example, the Aliso Canyon leak resulted  in the single largest release of methane in U.S. history, with a release of  78,000 metric tons of methane in 2015 and an additional 22,000 metric  tons in the first 2 months of 2016. The Aliso Canyon leak equaled the  greenhouse gas emissions from approximately 529,000 passenger  vehicles driven for 1 year, according to EPA data.

In most years since 1995, an annual average of 15,000 metric tons of  methane were released from natural gas storage, according to EPA data  on greenhouse gases. In 2015, however, due to the Aliso Canyon leak,  greenhouse gas emissions from all natural gas storage wells increased to  more than 92,000 metric tons of methane—about 6 times greater than the  release for an average year—according to EPA estimates. Figure 4  shows EPA‘s estimates of annual methane emissions from natural gas  storage sites from 1995 through 2016, including the estimated emissions  from the Aliso Canyon leak in 2015 and 2016.

Chronic releases during routine operations at natural gas storage sites,  such as small leaks from valves or from equipment exhaust, also emit  greenhouse gases into the atmosphere and may persist for long periods  of time. These chronic releases tend to be slow leaks from natural gas  wells, such as releases from seals and valves. Slow leaks can persist for  long periods because, unlike major leaks, they are less likely to be  detected, according to a CCST report. Moreover, slow leaks, if  identified, may not be prioritized due to a perception that they present few  implications for worker safety and public health, according to CCST’s  report. However, the CCST report also stated that chronic releases may  routinely occur, although the amount of the release is difficult to measure  since it may not be known when the release started, and these chronic  releases may lead to a significant release of greenhouse gas.

In 2016, California conducted an assessment of all its natural gas storage  wells across its 11 natural gas storage sites and found 229 chronic leaks.  Methane releases from these slow, chronic leaks generally represent a  small share of the statewide reported methane releases in California.  However, over a 10-year period, the cumulative impact of these releases  from routine operations in California can equal the amount of methane  released in the Aliso Canyon leak, according to CCST, using estimates  from the California Air Resources Board.

Evidence from Releases Indicates Some Risk to Groundwater from Natural Gas Storage, but Data Are Limited

In some instances, groundwater has been contaminated by the release of  natural gas from storage sites, but the extent of the risk to groundwater is  not known because data are limited. We identified two examples of  releases from 2000 through 2018 that potentially affected groundwater: a  2003 release at the Playa Del Rey storage site in California and a 2006  release at a storage site near Fort Morgan in Colorado.

Natural gas storage site releases can impact groundwater sources in  different ways. For example, these releases can impact groundwater  sources above the storage site when they involve the upward migration of  gas and other fluids mixed with the gas. According to CCST, this occurred  at the Playa Del Rey site, where stored natural gas has leaked into a  freshwater aquifer for a number of years. In other cases, faulty natural  gas well design and construction, such as inadequate cementing, can  allow natural gas to migrate through fractures and infiltrate overlying  groundwater sources or enter drinking water wells. For example, gas  infiltrated an aquifer that served drinking water wells in Fort Morgan,  Colorado, which led to an evacuation of about a dozen families until the  release was stopped. Subsurface leaks can also result from abandoned  wells in which the casings or cement have degraded over time or from  improperly plugged wells.

In January 2017, PHMSA started collecting data from operators on  incidents, including releases of natural gas from underground storage  sites that cause more than $50,000 of property damage; these incidents  could include leaks that harm groundwater resources, according to  PHMSA officials. Based on our review of PHMSA incident information, no  reported incidents have included groundwater contamination. Moreover,  PHMSA officials told us they are not aware of any incidents involving  groundwater contamination that meet reporting thresholds. PHMSA does  not require operators to submit information about groundwater  contamination unless that contamination meets the regulatory definition of  an incident.

Natural gas storage is an integral part of the nation’s energy system,  ensuring that energy is available to meet peak demands across the  nation. PHMSA’s safety program for natural gas storage fills a gap that  existed in the regulation of underground storage prior to 2017. PHMSA  met its inspection targets in the first year of its program, but it faces  challenges in meeting its performance goal to inspect 400 storage sites  by 2023 because fewer states agreed to partner with the agency on  inspections than PHMSA originally envisioned. Because of the increase in  its inspection workload from its preliminary estimate, PHMSA does not  have assurance that it has enough resources to meet its inspection goal.  PHMSA officials told us that while the agency has conducted a workforce  assessment, it will not have the data to complete a workforce analysis it  can use to guide its workforce allocations and budget requests until 2022  or 2023. The officials also told us that more states may decide to  participate in the future. By analyzing the factors affecting states’  willingness to participate in inspections and analyzing its workforce needs  on an ongoing basis, PHMSA would have more reasonable assurance  that it has the necessary staff to meet its inspection goal.

In addition, while PHMSA addressed one of the two recommendations in  our November 2017 report and has established a performance goal that  provides information about the number of completed inspections, this  performance goal does not provide information on the outcome of  PHMSA's efforts to improve safety at natural gas storage sites, consistent  with leading practices under GPRA. By establishing performance goals  that demonstrate improvements to safety outcomes, such as tracking  reductions in incidents ranging from releases of natural gas to death or  major injury, PHMSA would have better assurance that it can measure its  progress toward meeting its strategic goal to improve safety.

We are making the following two recommendations to PHMSA:  The PHMSA Administrator should analyze the factors affecting states’  participation in underground natural gas storage inspections and analyze  its workforce needs on an ongoing basis to guide its budget requests.  (Recommendation 1)

The PHMSA Administrator should establish performance goals that  demonstrate improvements to safety outcomes for the natural gas  storage program, such as tracking reductions to incidents.  (Recommendation 2)

We provided a draft of this report to DOT for review and comment. In  written comments, DOT concurred with the report’s recommendations  and provided additional information on steps it is taking or plans to take  as part of its implementation of the underground natural gas storage  program. In addition, DOT stated that it would provide a detailed  response to each recommendation within 180 days of our final report’s  issuance. The complete comment letter is reproduced in appendix IV.

If you or members of your staff have any questions about this report,  please contact me at (202) 512-3841, or gomezj@gao.gov. Contact  points for our Offices of Congressional Relations and Public Affairs may  be found on the last page of this report. GAO staff who made key  contributions to this report are listed in appendix V.

Appendix I: Objectives, Scope, and Methodology

This report (1) assesses the extent to which the Department of  Transportation’s Pipeline and Hazardous Materials Safety Administration  (PHMSA) has further developed its natural gas storage program since our  November 2017 report, (2) describes what is known about the potential  health effects from chemicals in stored natural gas, and (3) describes  what is known about the potential environmental effects of releases at  natural gas storage sites.

To address these objectives, we reviewed documents from PHMSA, the  Department of Energy, and the Environmental Protection Agency (EPA)  and met with officials from these agencies to understand their roles in  natural gas storage safety. Since there was no comprehensive list of  natural gas storage releases, we conducted a literature search for reports  of incidents that occurred in the United States from 2000 through 2018.  Later, we expanded our search to include reports of incidents related to  mercaptan, an odorant added to natural gas, regardless of whether these  incidents occurred at a natural gas storage site. We sought reports and  studies from news reports and trade and peer-reviewed journals. We  conducted searches in research databases such as Nexis’ All English  Language News, Elsevier’s Scopus, Ei EnCompassLIT, and Chemical  Safety Newsbase. We further expanded our search to include state or  county reports that had conducted studies or released reports on these  issues.

We also reviewed three reports referred to us by agency officials we  interviewed that compiled lists of natural gas storage releases to identify  those releases that occurred from 2000 through 2018 at underground  natural gas storage sites in the United States. The specific reports we  reviewed were: An Appraisal of Underground Gas Storage Technologies  and Incidents, for the Development of Risk Assessment Methodology;  “Analysis of Occurrences at Underground Fuel Storage Facilities and  Assessment of the Main Mechanisms Leading to Loss of Storage  Integrity”; and U.S. Natural Gas Storage Risk-Based Ranking  Methodology and Results. We also included a list of incidents at natural  gas storage sites in 2017, the first year for which PHMSA collected and  compiled these data for underground natural gas storage.

From these sources, we identified 93 releases of natural gas from storage  sites; these 93 releases include incidents as defined by PHMSA  regulations as well as releases of natural gas that may not meet that  definition. The releases we identified could include releases, leaks,  explosions, or fires that occurred at natural gas storage sites, and we  included these releases regardless of the severity of their impacts, such  as injury, death, cost associated with release, or volume of gas released  in the incident. We excluded releases at other types of storage, such as  aboveground storage or oil storage. This list may not represent the  complete universe of releases because not all releases may have been  documented, and no federal agency or independent source cataloged all  releases for this time period. We reviewed the list of releases to identify  any documented examples of health or environmental effects associated  with a release. We identified one example of reported health symptoms  associated with a natural gas storage release at the Aliso Canyon  Storage Site in 2015; the studies we identified did not empirically link the  release of natural gas at Aliso Canyon to health effects. The studies also  identified two examples of potential groundwater impacts from two other  natural gas storage leaks.

We visited natural gas storage facilities selected to represent each of the  three types of underground storage—for depleted fields, Aliso Canyon in  California; for salt caverns, Moss Bluff in Texas; and for aquifers, Redfield  in Iowa. We reviewed documentation from each site and interviewed  these sites’ operators. We selected these sites for specific reasons: Aliso  Canyon because of the 2015 leak, Redfield because it was scheduled to  undergo an inspection by PHMSA at the time of our visit, and Moss Bluff  because it was readily accessible from a major urban area (Houston,  Texas). Our findings from the sites we visited and officials we interviewed  are not generalizable to sites and officials we did not include in our review  but provide illustrative examples of such sites. We also met with officials  from industry groups that represent companies that operate natural gas  storage sites—the American Gas Association, American Petroleum  Institute, and Interstate Oil and Gas Compact Commission—to better  understand these groups’ perspectives on the natural gas storage safety  program. We also met with the Environmental Defense Fund to  understand its perspective on natural gas storage.

To examine the extent to which PHMSA has taken action since our 2017  report to continue developing its program for natural gas storage, we  reviewed documents related to the program, including strategic plans,  business plans, guidance and plans related to inspections, data on the  number of trained inspectors and completed inspection counts, and  workforce planning. We also met with PHMSA officials to discuss the  program. We selected a nongeneralizable sample of seven states: four of  the five states with the largest amount of working natural gas storage  (Michigan, Texas, Louisiana, and California), one state in which PHMSA  was conducting an inspection (Iowa), and two additional states that had  considered partnering with PHMSA (Alaska and Colorado). We met with  officials representing these seven states to understand their perspectives  on PHMSA’s natural gas storage safety program and their efforts to  partner with PHMSA and conduct inspections.

We compared PHMSA efforts on its natural gas storage program’s  workforce planning with our prior work on best practices in workforce  planning. We also compared PHMSA’s efforts on strategic planning with  leading strategic planning practices that our past work has identified. For  example, we have previously reported that requirements of the  Government Performance and Results Act of 1993, as amended—such  as performance goals—that apply at the departmental or agency level  can serve as leading practices for planning at lower levels, such as  component agencies, offices, programs, and projects, within federal  agencies.

To describe what is known about the potential health effects from  chemicals in stored natural gas, we used our literature search results that  identified releases from 2000 through 2018 to determine whether there  were any studies that empirically linked the releases of natural gas in  storage sites with health effects; we did not find any such studies. Since  no list of natural gas storage site composition exists, we took steps to  identify the components and chemicals that may be present in stored natural gas. First, we identified operators of natural gas storage sites  that represented 49 percent of the total storage capacity of all natural gas  storage sites within the United States. We identified these operators by  reviewing Energy Information Administration data on natural gas storage  working capacity from 2016. Next, we obtained and analyzed each  operator’s Safety Data Sheet for natural gas and identified the  components of natural gas. Also, we reviewed the interagency task  force report to identify any additional chemicals that may be present in  natural gas, and we reviewed reports to identify chemicals that had been  identified as present in the Aliso Canyon storage site release in 2015.

We then met with and obtained documents from federal agencies that  focused on public health and occupational health to determine the extent  to which chemicals within natural gas storage had documented potential  health effects. We reviewed databases from EPA and the Agency for  Toxic Substances and Disease Registry to identify the health effects that  may be caused by exposure to chemicals. We also reviewed documents  from and met with officials from the Occupational Safety and Health  Administration (OSHA) and the National Institute for Occupational Safety  and Health (NIOSH). To examine the health symptoms associated with  the Aliso Canyon storage site leak, we (1) visited the storage facility; (2)  met with officials from California state agencies, including the Los  Angeles Department of Public Health, Division of Gas and Geothermal  Resources, and South Coast Air Quality Management District to discuss  the Aliso Canyon natural gas leak; and (3) reviewed reports related to  potential health effects during and after the Aliso Canyon leak, including  results on community health (2016); indoor dust samples (2016); and air monitoring for methane, benzene, volatile organic compounds, and  sulfur odorants. Additionally, we reviewed reports from the Public Health  and Environment Subgroup of an interagency task force that studied the  Aliso Canyon incident and from the California Council on Science and  Technology (CCST).

To describe what is known about the potential environmental effects of  releases at natural gas storage sites, we reviewed documentation and  data from EPA on greenhouse gas emissions in general and specifically  for the Aliso Canyon natural gas leak in 2015, and we spoke with officials  from EPA knowledgeable about the agency’s greenhouse gas reporting  program and inventory program. In addition, we obtained data from EPA  estimating methane emissions from natural gas storage sites from 1995  through 2016. We assessed the reliability of these data by (1)  corroborating these data with other published sources, (2) reviewing  existing information about the data and the methods that produced them,  and (3) interviewing agency officials knowledgeable about the data. We  determined that these data were sufficiently reliable for the purposes of  our reporting objectives, specifically to illustrate the relative size of the  Aliso Canyon leak relative to estimated releases from natural gas sites.  We identified an EPA report summarizing the amount of air emissions at  the Aliso Canyon leak.

For the Aliso Canyon incident in 2015, we reviewed reports that we  identified through officials related to the release of methane, including  results from air samples for methane taken by California agencies. We  visited the Aliso Canyon storage facility and met with relevant California  state agency officials. Also, through our literature search, we identified  two examples of natural gas storage releases of chemicals into  groundwater: the Playa Del Rey storage site in California and a storage  site near Fort Morgan, Colorado. Additionally, we met with California  Council on Science and Technology officials and reviewed the council’s  report, Long-Term Viability of Natural Gas Storage in California, to better  understand how a natural gas storage incident could impact groundwater.  We also reviewed recommendations made in an October 2016 report by  the Interagency Task Force on Natural Gas Storage Safety.

We conducted this performance audit from December 2017 to October  2019 in accordance with generally accepted government auditing  standards. Those standards require that we plan and perform the audit to  obtain sufficient, appropriate evidence to provide a reasonable basis for  our findings and conclusions based on our audit objectives. We believe  that the evidence obtained provides a reasonable basis for our findings  and conclusions based on our audit objectives.

Appendix II: Annual Inspection Targets Set to Complete the 5-Year Goal Set by the Pipeline and Hazardous Materials Safety Administration

The Pipeline and Hazardous Materials Safety Administration (PHMSA)  has set a goal to inspect all of the approximately 400 storage sites over 5  years, from early 2018 to early 2023, according to PHMSA officials. To  meet this five-year goal, PHMSA divided its workload of approximately  400 inspections over the 5 years it planned to meet its goal. PHMSA  planned that its state partners would complete about one-quarter of the  inspections while its federal inspectors would complete the remaining  three-quarters of inspections. PHMSA’s targets for inspections, and its  actual inspections according to PHMSA officials, are illustrated in table 1  below.

Appendix III: Budget Request, Budget Authority, User Fee, and Obligation Information for the Underground Natural Gas Storage Program as of June 2019

The Pipeline and Hazardous Materials Safety Administration (PHMSA)  funds its enforcement activities, such as inspections by PHMSA  employees and grants to states, partially through user fees paid by  operators of natural gas storage sites. However, PHMSA cannot collect  user fees from operators unless expenditure of the fees is provided in  advance in an appropriations act. Annually, prior to the start of the fiscal  year, PHMSA submits a budget request to Congress that identifies the  amount of budget authority it needs for the underground natural gas  storage program. The annual appropriations act then provides for  expenditure of a certain amount of fees and PHMSA is authorized to  collect that amount in fees. PHMSA then obligates the fees it receives  either (1) for federal activities, such as inspections by PHMSA  employees, or (2) for grants to state governments, which carry out  inspections at some natural gas storage sites. Table 2 provides details  about the PHMSA’s budget request, budget authority, user fees, and  obligations.

Appendix IV: Comments from the Department of Transportation

Appendix V: GAO Contacts and Staff Acknowledgments

In addition to the contact named above, Diane Raynes and Janet Frisch  (Assistant Directors), Lee Carroll (Analyst in Charge), Ellen Fried, Cindy  Gilbert, Jennifer Gould, Rich Johnson, Jessica Lemke, John Mingus,  Katrina Pekar-Carpenter, Rebecca Parkhurst, Jeanette Soares, Sheryl  Stein, Sara Vermillion, and Kiki Theodoropoulos made important  contributions to this report.

A 2015 leak at a natural gas storage site near Los Angeles temporarily displaced about 8,000 families and raised concerns about other sites.

In 2018, the Pipeline and Hazardous Materials Safety Administration set a goal to inspect the roughly 400 natural gas storage sites in the country by 2023. It expected that 25 states would help, but so far only 10 have agreed to do so.

We made 2 recommendations, including that the agency examine the factors affecting states’ willingness to conduct inspections, which could help the agency determine whether it will have enough staff to meet its goal.