Marcus Li, B.Sc., P.Eng.
Principal, Acoustics Noise and Vibration
Guelph, ON, Canada
The requirement to complete a Third-Party Acoustic Audit may be included with an Ontario Ministry of Environment Conservation and Parks (MECP), environmental approvals. When we’re approached, some clients aren’t sure what’s involved in having an audit completed. Well, the main focus is to confirm that the actual facility noise levels (typically measured), match with the predicted facility noise impacts (modelled), and ultimately, to confirm that the facility noise levels comply with the applicable guideline limits. The following are the key steps of how an audit is typically conducted.
Step 1: Review of the approval and Acoustic Assessment Report
The first thing we need to do is understand what the basis is for demonstrating compliance. This could include any number of mitigation measures, operational restrictions, relaxed limits from increased background noise (road traffic), etc. A review of the approval and the Acoustic Assessment Report will cover off these items.
Occasionally, there is additional correspondence between the Acoustic Assessment Report author and the MECP on something that may have required clarification. This is usually documented in the approval. It’s a good idea to review this additional correspondence. But, more often than not, the approval and Acoustic Assessment Report itself will set out the requirements for demonstrating compliance.
Once the conditions/scenarios are understood, we try to coordinate our site visit/noise measurements around the regularly scheduled occurrences of an activity. This could include items such as testing of the facility’s generator, capturing frequent deliveries using pneumatic delivery trucks/pump trucks, and/or completing measurements during the summer months when cooling units are in heavy use.
Step 2: Site Visit Review
Next, we complete a walk-through of the facility. During the walk-through we’ll take a look at the mitigation measures installed as a requirement of the approval (e.g. silencers, barriers, enclosures, etc.). Any differences are noted and commented on in our audit report. This is more for information purposes, since our main focus is whether or not the facility sound levels are in compliance. We have been involved in situations where mitigation was not installed, and the facility was found to be in compliance. In the end, these mitigation items were inconsequential.
We’ll also coordinate with the facility staff to ensure the facility is operating under the “worst-case” conditions/scenarios outlined in the Acoustic Assessment Report. A line of communication is also kept open in case operations change. We have had entire lines go down in the middle of a measurement period, in which any measurements following that event would no longer be considered representative of the facility impacts.
Figure 1: Site visits are key components to the acoustic audit processes.
Step 3: Review of the Surroundings
Before getting to the measurements, the surroundings also need to be reviewed. We’re interested in determining if the area classification (Class 1, 2, 3, or 4) in the report is appropriate for the actual site area. For example, a rural area (Class 3 area) could be classified as a more “urban” setting (Class 1 or 2 area), due to frequent road traffic. This allows us to apply more relaxed guideline limits associated with a Class 1 or 2 area for determining compliance. Additionally, we’ve encountered situations where the existing background noise levels are higher than the default sound level limits applied in the approval for the facility, which allows for some flexibility if the facility levels are higher than predicted.
Traditionally we have also checked that the noise receptors are in the correct locations. But, this was more of an issue before aerial photography was so readily available, and is usually not a necessity for the audit.
Step 4: Measuring the Facility Noise Level Concentration
Measurements are completed for each of the conditions/scenarios outlined in the Acoustic Assessment Report submitted during the application process. These measurements are required to be completed in accordance with the MECP NPC-103 publication.
Wherever possible, we complete measurements at each receptor location specified in the Acoustic Assessment Report. The locations are permitted to be changed, particularly if the worst-case locations are observed to be different from those used in the assessment.
We generally find the measurements are best completed during the overnight period (11 pm to 5 am). The background levels (roadway noise) are the lowest during these periods, and are the least likely to contribute to a false conclusion of non-compliance. In general, we try to complete measurements either on-site for the facility, or within publically accessible areas. In some situations measurements may require appropriate permissions for access and security reasons.
Other tasks considered during the measurements include confirming increased guideline limits are in the right sound level range, or confirming the presence/absence of any acoustical penalties (e.g. tonality, cyclical, etc.).
Figure 2: A sound level meter used in an acoustic audit to measure outdoor environmental noise.
Step 5: Preparing the Report
After completing the measurements, observations, confirmations, etc., we’ll know if the facility noise levels comply with MECP requirements. A report then follows, which supports the conclusions of the audit.
|Marcus is a specialist in acoustics, noise and vibration, he often assists with conducting audits, peer reviews, and complaint investigations.|
|Acoustic Audit, Environmental Compliance Approval, Facility Noise Levels, MECP, Renewable Energy Approval|