Key Market
Mining
Highlights
A global mining company plans to develop a large open-pit gold mine in Eastern Canada.
Wood was hired to conduct environmental noise and vibration studies for the Impact Assessment Agency of Canada (IAAC).
29
sensitive receptors assessed (homes, cabins, properties)
24/7
remote noise and vibration monitoring conducted
100%
noise and vibration compliance achieved
Scope
This study assessed the potential noise and vibration impacts of the mining project's construction, operations and closure phases.
According to IAAC guidelines, the following impacts must be evaluated during pre-consultation using specified criteria:
Noise emissions
- Impact at dwellings [1], [2]
Blasting vibration and overpressure emissions
- Overpressure – fisheries [3], [4]
- Overpressure – structures [5]
- Groundborne vibration – fisheries [3], [4]
- Groundborne vibration – structures [5]
Noise and vibration must be assessed and controlled in design and monitored during construction and operations.
Figure A: Daytime noise contours for early operations phase (illustrative example)
Solution
Noise assessment
Environmental noise is emitted by mobile equipment, generators and processing equipment. Noise from these sources was assessed using a sound prediction software package, Cadna/A and ISO 9613-2 propagation algorithms [6].
Noise modelling considered source sound power level and directivity, distance attenuation, tomography, shielding effects of the building, sound reflections off buildings and ground and atmospheric attenuation.
Noise measurements were collected on-site once the equipment began operating to update the noise source definitions and improve model accuracy.
Blasting assessment
Blasting vibration is caused by the rapid release of energy during detonation, which sets off waves of motion through the ground. These waves, expressed as the speed of ground particle movement or peak particle velocity (PPV), weaken with distance as they travel through the earth. In addition, blasting also produces an airborne shock wave (or air overpressure) that travels through the atmosphere from the detonation point.
While it behaves similarly to ground vibration in that its intensity decreases with distance, air overpressure tends to dissipate more gradually. Vibration and overpressure were predicted at receptor sites based on general propagation models and specific blast parameters.
Where blasting occurs near water, protecting fish habitats becomes a critical consideration. The regulator outlines criteria to safeguard aquatic life, including limits on underwater overpressure and ground vibrations during sensitive periods such as egg incubation. These guidelines were used to calculate minimum setback distances for confined explosives, ensuring compliance with regulatory requirements.
Noise monitoring
Wood completed pre-construction baseline noise monitoring and is currently running a monitoring program during the construction and operation of the advanced exploration (AEX) phase of the main Project. Wood was contracted to provide self-powered monitoring systems and deploy packaged noise and vibration monitoring stations.
The monitoring data will be used to ensure the site remains in compliance and identify opportunities for mitigation. Continuous long-term noise and vibration monitors were deployed at various locations in the vicinity of the site. The monitoring locations were selected based on proximity to the site and directional relationship to noise sources and blast areas.
Assessment criteria
Noise
Table 1 outlines the main criteria used to assess the acoustical impact of mining activities.
Table 1: Noise impact guidance
Show Table ▾| Regulator | Type of impact | Assessment metric | Guidance |
|---|---|---|---|
| Ontario Ministry of Environment (MECP) | Steady noise – Daytime (7 am – 7 pm) | One-hour sound levels, Leq-1hr | ≤ 45 dBA [1] |
| Ontario Ministry of Environment (MECP) | Steady noise – Nighttime (7 pm – 11 pm) | One-hour sound levels, Leq-1hr | ≤ 40 dBA [1] |
| Health Canada (HC) | Interference with speech comprehension | Daytime LAeq-1hr | 55 dBA [2] |
| Health Canada (HC) | Noise-induced sleep disturbance | Nighttime LAeq-1hr | 45 dBA [2] |
| Health Canada (HC) | Long-term community annoyance | Nighttime LAeq-1hr | 6.5% [2] |
Blasting
Table 2 summarizes the criteria used to assess the impact of blasting activities. The project’s predicted levels at a sensitive receptor are compared against the guidance values.
Table 2: Blasting impact guidance
Show Table ▾| Regulator | Type of impact | Assessment metric | Guidance |
|---|---|---|---|
| Ontario Ministry of Environment (MECP) | Air overpressure | Peak pressure level (Lpeak) | ≤ 128 dBL [5] |
| Ontario Ministry of Environment (MECP) | Ground vibration | Peak particle velocity (PPV) | ≤ 12.5 mm/s [5] |
| Health Canada (HC) | Air overpressure | Peak pressure level (Lpeak) | ≤ 140 dBL [2] |
| Canadian Department of Fisheries and Oceans (DFO) | Underwater overpressure | Peak pressure (Ppeak) | ≤ 50 kPa [4] |
| Canadian Department of Fisheries and Oceans (DFO) | Waterbed ground vibration | Peak particle velocity (PPV) | ≤ 13 mm/s [3] |
Receptors
This project is located in a remote area near a small town, where mining is the primary economic driver.
For the assessment, twenty-nine (29) sensitive points of reception (PORs) were identified, including seasonal cabins/outfitters, family cottages and unoccupied private properties. Based on the fisheries waters near the blasting area, the nearest watercourses and waterbodies were identified.
Results
Noise
The periods were assessed for both daytime and evening/nighttime as per provincial and federal guidelines. Given that the site and associated activities are planned to operate 24 hours per day, it is expected that the Project's noise emissions will be similar during evening and nighttime. The noise contours at 1.5m above ground for the predicted worst-case hour are shown in Figure A, representing the early operations phase during daytime hours.
The noise prediction modelling indicates that noise levels at all 29 receptors meet provincial and federal guidelines for all assessed periods.
Ground vibration
The predicted PPV at the closest receptor (5 km away) is 0.09 mm/s, significantly below the 12.5 mm/s criterion. Figure C below shows the predicted ground vibration decay with increasing distance from the blasting points at the open pit, for explosives of varying weight.
Air overpressure
Air overpressure at the closest receptor location is predicted at 93 dBL, which is below the MECP and HC guidance of 128 dB(L) [5] and 120 dB(L) [2], respectively. Figure D indicates the predicted air overpressure propagation, attenuation and decay with increasing distance from the open pits during blasting operations.
Effects on fish habitats
Vibration and overpressure were assessed at waterbodies throughout the study area. Minimum setback distances were established based on the explosive charge weight (kg) for a rock substrate, summarized in Table 3. Lower explosive charge implies lower vibration and overpressure levels at a receiver and permits smaller setback distances.
Noise monitoring
Each noise monitoring station is equipped with a Class 1 integrating sound level meter logging continuously 1/3‑octave band data at 1-second intervals, and weather stations were installed at two locations to account for local meteorological effects on sound propagation. The vibration stations are equipped with a geophone and an overpressure microphone to characterize blast impacts.
These monitoring stations were designed to be self-powered using a battery and solar panel system that Wood provided, along with the respective maintenance instructions and calibration schedules. Figure B shows the noise and vibration monitoring stations packaged by Wood to operate during extreme weather conditions.
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Figure B: Noise monitoring station (left) and vibration monitoring station (right)
Mitigation measures
Noise modelling results indicate that noise levels at all receptors comply with applicable provincial and federal guidelines for all assessed periods. It is recommended that an updated noise prediction model be prepared if any significant changes to the equipment occur, particularly regarding impulsive or non-impulsive sound sources. In addition, an acoustic assessment is recommended to validate the modelling results.
For blasting impacts, Wood provided the client with setback distances and the required explosive charges to remain in compliance with regulations. In addition, the client has committed to preparing a detailed blasting management plan prior to blasting operations commencing, reviewing all potential blast locations, defining mitigation measures and detailing the inspection and record-keeping required to demonstrate that impact levels are being effectively managed.
This plan will include opportunities for adaptive management, in which the intensity of the control measures would be increased if site inspections and continuous monitoring indicate that implemented measures are insufficient.
Figure C: Ground vibration propagation curve (illustrative example)
Figure D: Air overpressure propagation curve (illustrative example)
Conclusions
Blasting vibration and overpressure from the project were assessed using prediction equations based on Ontario MECP, Health Canada and DFO guidelines.
Wood developed technical documentation on the noise and vibration impacts for the Impact Statement and will update the assessment as new noise sources become operational.
Noise, vibration and overpressure monitoring was completed to establish a baseline and will continue through construction and operation to ensure compliance and identify mitigation options.
Environmental noise assessments and monitoring
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References
[1] Ontario Ministry of the Environment and Climate Change (MOECC), “Publication NPC-300: Noise Assessment Criteria for Stationary Sources and for Land Use Planning,” Aug. 2013.
[2] Health Canada, “Guidance for Evaluating Human Health Impacts in Environmental Assessment: Noise,” 2017.
[3] G. Hopky and D. Wright, Guidelines for the Use of Explosives In or Near Canadian Fisheries Waters, Ottawa, ON: Department of Fisheries and Oceans, 1998.
[4] P. A. Cott, “Monitoring Explosive-Based Winter Seismic Exploration in Waterbodies, NWT, 2000–2002,” in Proceedings of the Offshore Oil and Gas Environmental Effects Monitoring Workshop, Columbus, OH, 2005.
[5] Ontario Ministry of the Environment, Noise Pollution Control (NPC) Publication 119: Model Municipal Noise Control
By-law, Toronto, ON, 1982.
[6] International Organization for Standardization, ISO 9613-2: Acoustics — Attenuation of Sound During Propagation Outdoors — Part 2: General Method of Calculation, 1996.
[7] World Health Organization, Guidelines for Community Noise, 1999.
