Sacramento Municipal Utility District


INNOVA was selected by Sacramento Municipal Utility District (SMUD) to conduct a noise level survey in accordance with the California Energy Commission (CEC) NOISE-5 Conditions of Certification on the existing Consumnes 550MW combined cycle, natural gas-fired power plant in rural California. The plant’s power sources are two GE 7FA turbines and one MHI TC2F-40 steam turbine.


NOISE-5 requires the plant operator to investigate reasons for a noise complaint. In the case of the Consumnes Power Plant, several nearby residences submitted complaints about noise, while measurements by third party acoustical consultants revealed the plant was in compliance with noise regulations. Though evidence suggested noise should not be an issue, the complaints persisted until SMUD contacted INNOVA. In its investigation, INNOVA monitored noise levels at four (4) residential locations, the nearest at 3,500 feet away. Short-term measurements at 400 feet all around the plant were also taken, and a weather station was set up to collect meteorological data. The investigation by INNOVA found temperature inversions in the early morning hours caused noise levels to exceed the regulatory limit. In conjunction with the environmental survey, INNOVA was asked to determine the source of the noise by measuring the sound levels of the major pieces of plant equipment. 


INNOVA designed the power plant to meet the CEC’s noise requirement of 39 dBA at the nearest residence 3,500 feet away.


The main sources of noise were:

  • Breakout from the steam turbine condenser
  • Main transformers
  • HRSG inlet transition
  • Breakout from the gas turbine combustion inlet duct and generator housing


The solution was self-supporting noise barriers able to shield noise from each of the noise sources. The barriers did not impinge on the equipment nor void warranties while they lowered noise to the CEC compliance level. All barriers were designed, supplied and installed by INNOVA. Compliance with the CEC limit was also guaranteed by INNOVA.


The main challenge was the speed at which SMUD required mobilization for the noise surveys, production of reports to be provided to the CEC and resolution of the noise issues. To meet the timelines, INNOVA deployed a team consisting of acoustical and construction engineers to work round the clock. Another significant hurdle was how to design noise control measures so that they did not affect the structural integrity or the warranties of the existing equipment.


The customer was very satisfied with INNOVA’s responsiveness throughout the project, writing at one stage “… with this message I’d like to thank INNOVA for doing what it took to meet our request for a repeat 25-hour community noise survey. Based on INNOVA’s performance to date, I have every reason to believe you will meet our next deadline and, again thank you… for the hard work, professionalism, and dedication to duty that it (has) taken to accomplish this goal.”