Implementing an industrial mining project: noise challenges

Feasibility study

The purpose of a feasibility study is to determine project profitability. Capital costs are assessed based on the general design and the main equipment required. This study also aims at selecting the project location. However, at this stage, it is also important to consider noise challenges, as these can have a financial impact on the project. What is the legal framework for each of the proposed sites? The noise restrictions can vary by over 10 dBA depending on the selected location:

• The municipality’s urban plan (zoning and main use)
• Provincial guidelines (98-01 instruction notes or 019 Directive)
• National or international guidelines, (International Finance Corporation)

Are there sensitive receivers nearby? These can force developers to make noise corrections or implement environmental monitoring, the costs of which must be added to the project:

• Human environment (residential area, site used by Indigenous peoples)
• Natural environment (areas with fish, the presence of bats or a protected space)

The challenge can initially be quantified by assessing how the noise from main equipment travels toward the sensitive areas. By knowing which equipment is likely to produce a significant level of noise, developers can plan corrective measures and follow up, and include these costs in the project. Ideally, however, it would be best to configure each site in such a way as to prevent having to take corrective noise measures at all.

Engineering study

This step focuses in detail on project execution. It makes it possible to avoid having to make adjustments after the project has been completed (costly changes) or to prevent delays during construction work (exceeding allowed limits during the construction period). At this stage, it is important to assess the following aspects:

• What is the legal framework that will govern the work (operating hours allowed by municipal authorities and noise limits allowed under provincial or federal standards)?
• Were the construction methods and type of equipment chosen based on noise (soundproof equipment available)?
• What are the minimum control measures required to comply with environmental criteria (delays, fines)?

In some cases, regulations require demonstrating, through a noise assessment program, the steps taken to integrate acoustic aspects into the site planning. This program includes a noise dispersion simulation of construction steps, a site maintenance plan for equipment used and a noise monitoring plan at the receiving points near the construction.

• At the oprational phase, is the selected equipment likely to generate noise that will result in fines (tones, low frequencies, impact noises)? If so, are there alternatives or can it be mitigated?
• Does the planned equipment generate cumulative noise levels that exceed environmental limits? If so, is the equipment configured in such a way that it can be easily corrected and maintained economically?
• Are you planning an expansion phase for the project? It is important to give yourself room to maneuver when it comes to noise (aim for a sound criterion lower than the permitted limit, otherwise, several corrections may have to be made to the existing portion of the plant).

Québec’s Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques imposes a 5 dBA penalty on emergent noise or noise that can produce a surprise effect. In comparison, the obligation to lower noise levels by 5 dBA for ten identical machines amounts to having to shut down seven of the ten pieces of equipment. As a result, we understand that emergent noise can have a significant impact on the noise allowed for a project and requires adding many noise corrections. Planning the design for equipment that can potentially generate emergent noise (fan, funnel, water tower, etc.) can therefore prevent additional unexpected project costs.

Additionally, many factories are forced to add silencers inside stacks, because they were not considered during the engineering study. Adding a silencer in a confined space significantly restricts flow and thus generates increased power consumption. Moreover, placing a silencer at a higher level makes inspections and maintenance more difficult and expensive. Providing a space close to the ground makes maintenance easier (easy-to-clean baffles can be used and can be accessed with standard lifting devices) and allows developers to opt for an ideally sized silencer (drop in load losses).

Indoor acoustics

Standards and guidelines exists (Commission des lésions professionnelles, ASHRAE, LEED). Interior noise modelling anticipates the noise levels in various sections of the lant and provides solutions for creating a safe and efficient workspace. Additionally, designing a workspace that reasonably limits noise levels reduces the risk of occupational injuries while eliminating indirect costs associated with administrative and legal management for executive management.

Conclusions

Performing a noise assessment, both at the feasibility and at the detailed engineering phases, is a minor investment compared to overall project costs, but, mostly, to costs associated with addressing issues that were not dealt with initially, as shown in this article. It is therefore wise to entrust the review of your project’s noise challenges to an experienced person to prevent unwanted situations at project kick-off. This expert will also be able to guide you efficiently through the various legal obligations at all project stages.