I have severe problems breathing when I am on the hill adjacent to your Aliso Canyon facility. Please tell me what chemicals are escaping into the air so I may give to my Pulmonologist.


The Safety Ombudsman received the following request for assistance on July 14, 2020: “I have severe problems breathing when I am on the hill adjacent to your Aliso Canyon Facility. Please tell me what chemicals are escaping into the air so that I may give to my pulmonologist. Thank you”.

Chemicals which may possibly result in some degree of respiratory irritation include both current natural gas emissions (which is predominantly methane but also contains trace amounts of mercaptans as an odorant for leak detection purposes), and chemicals which may have been emitted at some prior point in time and were deposited on the surface and possibly remain persistent.

After the gas leak from the Aliso Canyon SS-25 well, SoCalGas installed equipment at the Aliso Canyon Facility (Facility) to detect the leakage of natural gas using three different independent systems. These include:

  1. SoCalGas’ “fence line” monitoring system, which consists of eight stations where methane emissions are monitored and recorded using a laser-based system. This system records methane emissions in parts-per-million (ppm) and the data is posted to a website where anyone can access the data via this link: https://sem.secmcs.com/MethaneMonitoring/;
  2. An ambient air monitoring system which includes five different stations, three of which are located on the south side of the Facility and two on the north side. This system also monitors and records methane emissions in ppm using laser-based detection technology; and
  3. Methane monitoring equipment at each active well and its connecting pipeline lateral. This system also monitors and records methane emissions in ppm, but utilizes infrared-based technology. 

Another potential source of contaminants relates directly to the leak event itself and the fluids that were released into the atmosphere during that period. Based on records SoCalGas provided to the California Public Utility Commission (CPUC), it is possible, though perhaps unlikely, that some of the chemicals released into the atmosphere during the leak were deposited on the ground and remain persistent.

A data request was subsequently submitted to SoCalGas to obtain information related to the three methane monitoring systems and the chemicals and fluids used during attempts to bring the SS-25 well under control after it blew out. This data may identify chemicals associated with the Facility and which may result in some respiratory irritation. This data may, in turn, assist in resolving this issue. The information requested from SoCalGas included the following:

  1. Please provide me with the dates on which SoCalGas’ fence line methane monitoring system detected any methane emissions since October 14, 2019; please include with the dates the actual emission levels for each of the eight monitoring stations, including those below the threshold reporting level of 25 ppm averaged over 30 minutes.
  2. Please provide me with the dates on which any of the five area methane monitors (3 on the south side of the Aliso Canyon property and 2 on the north side) registered methane emissions since these monitors were placed into service on August 6, 2019. Please include the actual emission levels for each monitor and for the duration of the emission period.
  3. Please provide me with a listing of any well which detected methane emissions from either the wellhead lower explosive limit (LEL) sensor or the adjacent lateral pipeline LEL sensor since the date of installation of these wellsite monitors. Please include the actual LEL readings to the extent those readings are recorded.
  4. Please provide me with a copy of all material safety data sheets (MSDS) for all chemicals, additives, and materials (both solid and liquid) that were used in making any fluids which were pumped into the SS-25 well during the seven attempts to kill that well between October 23, 2015 and February 11, 2016, and any fluids which were pumped into the P-39A relief well for the purpose of killing the SS-25 well.

SoCalGas provided a response to each of the above four questions on October 6, 2020. In reviewing their response, particularly the data they supplied as part of their response, it became clear that additional questions would need to be addressed to clarify what the data reflect. Thus, a subsequent request (Data Request 7A) was made to SoCalGas seeking such clarification. That request was made on October 16, 2020 and a response was received on October 30. A copy of their response to Data Request 7A may be viewed via these two links: Click Here and Click Here. The data supplied by SoCalGas in response to each question is discussed in some detail below. 

Question 1 – Fence Line Methane Monitoring Data

SoCalGas provided the requested data from all eight of the methane monitoring stations at the Facility. The requested data includes all events where methane emissions exceeded normal background level, which is about 2 ppm, and covers the period from October 14, 2019 through August 4, 2020 (methane emission events prior to October 14, 2019 are addressed below). Normal background level was established independently by studies performed by the California Air Resources Board (CARB). There were 35 events during this period when methane emissions exceeded normal background level. In all instances, the peak exceedance was well below the regulatory reporting threshold (which includes readings in excess of 25 ppm averaged over 30 minutes) and the duration extended over a relatively short period of time – typically 10-15 minutes – though several events lasted between 25-65 minutes. A copy of the data supplied by SoCalGas may be viewed via this link: Click Here. The “Peak Methane Value” is, as the heading suggests, the highest methane level that was recorded during the time interval when the methane level exceeded background level.

As noted above, SoCalGas is required to report methane emission events to CARB when emission readings exceed 25 ppm averaged over 30 minutes. SoCalGas is also required to provide notice to the public of all such events and maintains a website, which is available to the public, for documenting such events. The link to the website is: https://www.socalgas.com/stay-safe/pipeline-and-storage-safety/natural-gas-storage-facility-notifications/aliso-community-notifications

The methane monitoring system was installed and became operational in July 2017. From August 2017 through October 13, 2019 there were seven events when methane emissions temporarily spiked above normal background level. These include the following:

DATE Reported Concentration – ppm 
August 11, 2017  10 ppm
September 3, 2017 7 ppm
October 13, 2017 25 ppm & 18 ppm
December 1, 2017 minor elevated reading
December 18, 2017 66 ppm
June 21, 2018  8 ppm
October 11, 2029 68 ppm

Several of these exceedances were attributed to high humidity/fog at the time of the event. The October 11, 2019 event was attributable to heat and smoke associated with the Saddle Ridge fire which burned through a portion of the Facility. The methane sensors can and sometimes do indicate false methane emissions due to high humidity/fog. During these events, SoCalGas conducts manual confirmation readings by deploying crewmembers to survey the affected area using infrared sensors.

In summary, methane emissions recorded by the fence line monitoring system at the Facility generally indicate emissions which are at or only slightly above background level. While there have been numerous events registering methane readings above background level, peak levels have remained well below threshold reporting levels for the most part, and in several instances, the methane readings were not, in fact, due to methane leakage but rather to high humidity/fog.

Question 2 – Ambient Methane Monitors

SoCalGas provided the requested data from all five of the ambient methane monitoring stations at the Facility. Three of the monitors are located on the south side of the facility property and the other two on the north side. These monitors utilize the same technology (laser-based) as the fence line methane monitoring system. This system was installed in August 2019. The system records methane levels on a continuous basis in ppm. SoCalGas reported the figures as a 60-minute average. As with the fence line monitoring system, background methane level is approximately 2 ppm. The data provided by SoCalGas may be accessed via this link: Click Here. Raw data from each of the monitors is presented graphically on five separate tabs to better illustrate methane emission levels over time. With few exceptions, all readings for each of the five monitors remain at or near background levels. While each monitor has recorded elevated readings for very brief periods, peak levels have remained below 10 ppm in all instances.

Question 3 – Wellhead and Lateral Line Methane Sensors

There are two wellsite monitors at each active well; one adjacent to the wellhead and the other adjacent to the lateral line which connects to each well. The wellsite monitors utilize infrared technology to detect the concentration of methane emissions in ppm. This equipment was installed beginning in July 2019 and was operational shortly thereafter. SoCalGas provided an Excel file containing the requested data, which included any methane emissions from the time of installation up through the date of the data request. The data may be accessed via this link: Click Here.

The readings are recorded on a continuous basis and are reported as a five-minute average in ppm except when the readings fall to zero, in which case no reading is recorded for that five-minute period. A graph of the historical data has been prepared for each well and lateral to show graphically the trend in methane emissions in ppm as a function of time; the graphs are immediately above the columns which contain the emission readings. As can be seen from the graphs, there is considerable variability in emission levels from well-to-well. Some wells tend to show relatively low emission levels while others, during the same period show higher levels. Also, there does not appear to be any correlation of leakage levels at any specific wellhead and its associated lateral line connection. Sharp declines in readings may be attributable to leakage repair efforts, although in several instances wells which experienced a sharp decline often exhibit a sharp increase later.

As of January 1, 2020, CARB instituted new reporting thresholds for methane emissions. For emissions of 1,000 – 9,999 ppm, repairs must be made within 14 calendar days; for those of 10,000 – 50,000 ppm, repairs must be made within 2 calendar days.

Question 4 – Materials Used in Making Well Kill Fluids Pumped into the SS-25 Well

Seven attempts were made to kill the SS-25 well between the period of October 2015 – December 2015 by pumping water-based fluids into the well. The well was finally killed during an eighth attempt via a relief well drilled specifically for that purpose in February 2016. A variety of different chemicals and additives were used to formulate the kill fluids. According to SoCalGas’ records, the chemicals used in formulating the kill fluids include the following (some of which are trade names):

  • Amberguard-215
  • Desco CF
  • DrisPac SL
  • GeoZan
  • Polytek+
  • Calcium chloride
  • Calcium carbonate
  • Potassium chloride
  • Barite
  • Caustic Soda
  • Nut shells
  • Saw dust

Some of the kill fluids were ejected into the atmosphere during at least one kill attempt and so there is a question as to whether the ejected fluids may have presented a health hazard to nearby residents. In response to a data request from the CPUC dated July 25, 2017, SoCalGas provided a copy of the MSDS sheets for all chemicals/additives used in formulating the kill fluids. SoCalGas provided a link to that same data in response to the Safety Ombudsman’s request for information concerning this issue. That data may be accessed via this link: ftp://ftp.cpuc.ca.gov/Aliso. The link to the MSDS sheets themselves may be accessed via the following links: Click Here and Click Here.

According to a report dated May 22, 2018, issued by the Office of Environmental Health Hazard Assessment (OEHHA), California Department of Conservation Geologic Energy Management Division (CalGEM) inspectors who were on site during kill attempts on the SS-25 well observed that some of the injected kill fluids migrated back to the surface via a vent that formed close to the well-bore and were ejected into the air. OEHHA aided state and local agencies during the leak event; they evaluated the potential public health impacts from exposure to the natural gas plume and its trace organic constituents including benzene, mercaptan, and residual hydrocarbons. A copy of the OEHHA report may be accessed via this link: Click Here.

In their report, OEHHA notes that the Los Angeles County Department of Public Health (LADPH) was alerted by Porter Ranch residents of oily brown spots on outdoor surfaces around their homes in December 2015. The oily spots were attributed to oily mist escaping from the leaking well and transported via wind currents. The highest concentration of oily spots was found north of the Highlands neighborhood of the Porter Ranch community. SoCalGas collected surface-wipe samples from affected cars and tested them from the presence of hydrocarbons and benzene, toluene, ethybenzene, and xylene (BTEX). The samples indicated the presence of heavy hydrocarbons consistent with crude oil; however, BTEX was not detected in any of the samples.

A section of the OEHHA report also addresses potential toxic hazards from inhalation and oral exposure to the chemicals used in the well kill fluids. The report states that most of the chemical additives are non-volatile substances and would not be expected to have a significant exposure hazard to downwind residential areas, given the relatively small quantities of material that were used. One additive, glutaraldehyde, was noted as being semi-volatile with short-term exposure of the vapor to humans resulting in eye, nose, and respiratory tract irritation. OEHHA indicated that if glutaraldehyde were present in air emissions during well control operations it may have contributed to respiratory and other symptoms reported by some residents residing downwind of the leak. However, they concluded that since it is reactive and readily biodegradable, glutaraldehyde would not be expected to persist in surface deposits and would not represent an ongoing oral exposure hazard.

OEHHA concludes their report by indicating that no long-term health consequences would be expected from exposure to the constituents used in the well kill fluids; rather, that sustained release of odorants (specifically mercaptans) in the natural gas during the leak appears to have been more likely to cause respiratory issues for exposed residents. Footnote 16 in the report includes this link to an earlier OEHHA gas-leak hazard assessment which addresses the natural gas plume and trace organic chemicals – https://oehha.ca.gov/air/general-info/aliso-canyon-underground-storage-field-los-angeles-county. There are several other useful links embedded within this earlier assessment, including a summary of expert advisor input regarding public health measures.