Sound monitors were deployed in the Inverhuron Community, including locations within Inverhuron Park, and Lake Street. In 2019 an external acoustic analysis was conducted, concluding that the silencers installed on the Bruce B dearator vent lines effectively decreased the tonal sound occasionally observed at Lake Street in Inverhuron during periods of low background sound. This year’s monitoring is intended to enhance the existing data set, following 2020, sound level monitoring will move to a 3-5 year frequency.
In the summer of 2015, following public inquiries and complaints regarding noise detected by residents south of the Bruce site, Bruce Power engaged an external Acoustic Expert to investigate potential operational changes that could be causing a plausible sound. Sound level measurements were collected between 2015 and 2019.
The results of measurements indicated that sound levels of the Bruce Power site comply with the quantitative Ministry of Environment Conservation and Parks (MECP) limit of 40 dBA; as outlined within the Environmental Compliance Approval issued to Bruce Power. The study noted that there was occasionally an audible tonal sound within the Inverhuron community in the vicinity of Lake Street during periods of low background sound, prevailing meteorological conditions and all Bruce B deaerator vents operating actively.
Some types of sound have a special quality which may tend to increase their audibility and potential disturbance/annoyance. For tonal sound, MECP guidelines NPC-104 stipulates an adjustment of +5 dBA be added to a facility-total sound level measured at a point of reception. A tonal sound is defined as one which has a “pronounced audible tonal quality such as a whine, screech, buzz or hum”. Sound emissions from the unsilenced deaerator vents have been observed to be tonal in character and audible in the Inverhuron Park but not in the vicinity of 129 Lake Street.
Bruce Power’s Commitment
Bruce Power, while within limits, committed to install silencers on the four dearator vents by the spring of 2018 at an approximate investment value of $1 million. The initial timeline was modestly adjusted when further scoping took place and it was deemed much safer to install silencers on an offline unit.
2019 Reporting Results
By May of 2019 three silencers had been installed on Units 6 through 8, with the final on Unit 5 being installed during its outage starting August 16, 2019. Acoustic monitoring took place between August 9-23, 2019, capturing a few days prior to the shutdown of Unit 5 on August 16,as well as a week post shutdown.
The results of the report concluded that sounds of nature and of resident activities generally remain dominant in the Inverhuron Park and at 129 Lake Street. However the distinct tone that was clearly audible from all four deaerator vents prior to installation of silencers on Units 6 through 8 was completely inaudible following shutdown of Unit 5, which is a qualitative indication of the effectiveness of the installed silencers.
Decision on Methodology
Throughout this process Bruce Power has provided routine updates to the MECP, including written notification of each noise complaint received, and a discussion of mitigation measures and next steps. Following the MECP review of the noise monitoring study conducted by the external party, MECP concurred with the methodology used by HGC Engineering for the noise monitoring conducted for Bruce Power from May 25 to June 1, 2018.
Decision on Noise Control Measures
Following review of the noise monitoring report of 2018, the MECP communicated to Bruce Power that the methodology was appropriate and no further noise control measures were recommended.
Direction on approved Sound Analysis Equipment
Bruce Power sought guidance from the MECP on what was defined as adequate sound analysis instrumentation, following receipt of results taking via a cell phone app. The MECP indicated:
The use of cell phone apps to measure noise is not as reliable as compared to the Type 1 sound level meters (such as the ones used in this study). In addition to their lack of accuracy, cell phone apps usually measure linear (or Z-weighted) sound levels, which would give a higher numerical value than the A-weighted sound levels the ministry uses to regulate noise. Measurements taken by untrained persons too close to local sources of noise contribute to high results. Therefore, readings from these types of instruments cannot be used to verify compliance with the applicable noise limits. – MECP Communication 2018
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