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FERC Noise Compliance Assessment

This is Part 6 of The FERC 55 dB(A) Ldn Requirement series, where we learn the practical ins and outs of this requirement.

FERC Noise Compliance Assessment

In this post, we will consider what it takes to demonstrate compliance with the FERC noise requirement for natural gas compressor stations and LNG facilities. This is applicable after the project has been approved, the facility is constructed, and it is ready to be placed into service. (The process can also apply to non-FERC post-construction noise tests as well.)

Let us look at an actual statement from a FERC-issued Environmental Assessment, which is representative of what is typically recommended:

[Applicant] should file a noise survey with the Secretary of the Commission (Secretary) no later than 60 days after placing the additional compressor unit at the existing … Compressor Station into service. If a full power load condition noise survey is not possible, [Applicant] should file an interim survey at the maximum possible power load within 60 days of placing the additional compressor unit at the … Compressor Station in service and file the full load survey within 6 months. If the noise attributable to the operation of the additional compressor unit at maximum flow conditions exceeds 55 dBA Ldn at any nearby NSAs, [Applicant] should file a report on what changes are needed and should install the additional noise controls to meet the level within 1 year of the in-service date. [Applicant] should confirm compliance with the above requirement by filing a second full power noise survey with the Secretary no later than 60 days after it installs the additional noise controls.

The underlined portions are original to the statement (i.e., not my emphasis) and highlight the important time scales associated with each action. The key action items are as follows, in plain English:

  • Conduct a noise survey within 60 days of the in-service date
  • If the noise survey is not at full load conditions:
    • file interim results and
    • repeat the noise survey at full load conditions within 6 months.
  • If the full load test passes, then you file the report and are finished.
  • If the full load test does not pass, then
    • you have until the end of the first year in service to fix it (determine requirements, design mitigation, purchase, procure, and install) and to
    • complete a 2nd full load noise survey.

The form of the statement reflects an evolution of the process over the years and acknowledges one of the major challenges in conducting the noise survey – the full load requirement. It is not uncommon for new or additional compression to be built for a future case when more capacity will be needed. At start-up, the demand may not be there and may not be there in the near future. Because of this, it can take considerable planning and preparation to orchestrate the noise test so that enough gas is available (or in demand) to run the new compressor unit(s) at full load. The timing of the in-service date with respect to seasonal gas demands can also be a fly in the scheduling ointment. FERC recognizes this operational concern by allowing an interim report to be filed if the new compression can only be partially loaded. Also, extensions can be requested for mitigating circumstances.
In order for a post-construction noise survey to occur, several factors must come into alignment:

  • Availability of gas
  • Equipment is operational (sometimes there are issues during start-up)
  • The station is quiet otherwise (e.g. no construction or other loud activities)
  • Weather is favorable (no high wind or moderate precipitation)
  • Coordination of personnel: noise assessor (e.g. consultant), gas control, management, safety, operations, and maintenance.

The full-load requirement must be clearly understood by the owner/operator so that proper planning can be successfully implemented. An experienced noise expert can inform and guide the process. This is a good time for me to reiterate the benefits of considering and planning for proper noise control in the design phase. For FERC projects, this is baked into the process, because the applicant must demonstrate through design and analysis that the facility will meet the noise requirement as part of the certificate application process.

Note that potentially three sound level surveys could be required: interim, full load, and full load after remediation. Each survey has hard costs (e.g. consultant – thousands of dollars a pop), plus the opportunity costs of the distraction to normal operations of having to coordinate the noise surveys, and the potential disruption to gas control operations and maintenance schedules. This is another example where experience in FERC noise projects is advantageous; an experienced noise expert knows the pitfalls in design, implementation, and the post-construction compliance test and can raise concerns and solve problems before they surface.

To demonstrate compliance with the FERC noise requirement for natural gas facilities:

  • A sound level survey must be conducted while the equipment operates at full load.
  • The filing requirement time limit begins on the in-service date.
  • Scheduling can be difficult and there are many factors to consider.
  • There potentially could be three noise surveys required if loading is an issue or if the facility exceeds the 55 dB(A) Ldn limit.

About the Author - Tim Simmons, Ph.D. - USSI Director of Industrial Acoustics
Dr. Tim Simmons manages USSI's Industrial Acoustics Department. Tim comes to USSI with a wealth of Acoustical and Noise Control knowledge and real-world experience. Tim holds a Ph.D. in Physics from the University of Mississippi and a B.S. in Engineering Physics from the University of Tennessee.