Healthy Environment, Healthy Community, Healthy Business

Environment Protection Authority

3 Mitigation

3.1 Introduction

Section 2 provides criteria that should be applied when the effects of vibration emissions from industry, transportation and machinery are evaluated and assessed. When the predicted vibration value exceeds the preferred value, then mitigation measures to meet the preferred value should be considered. The degree of vibration impact will determine the extent of mitigation required and the mix of vibration control measures to be adopted as a mitigation strategy. This policy focuses on achieving the desired environmental outcomes so that the vibration source manager is given maximum flexibility in controlling the vibration. Although no prescribed management or mitigation strategies are dictated, the sections below provide guidance on what might be appropriate.

Selecting an appropriate strategy for a proposed development or alterations to an existing development involves the following steps:

  1. Determine the vibration reduction required to achieve the preferred vibration values.
  2. Identify any project-specific or site-specific constraints or opportunities.
  3. Investigate mitigation strategies adopted by similar industries on similar sites.
  4. Consider the range of mitigation options available.
  5. Consider community preferences for particular strategies. This is especially important when the community has particular sensitivities to vibration.

There are essentially three main mitigation strategies for vibration control:

  • controlling vibration at the source (Section 3.2)
  • controlling the transmission of vibration (Section 3.3)
  • controlling vibration at the receiver (Section 3.4).


Vibration is generally treated by reducing the dynamic forces associated with the source or by isolation techniques. The source may be isolated from the ground or structure, thereby reducing the vibration propagating towards receiver buildings.
Alternatively, structures and buildings may be isolated from sources.

The actual values of building vibration induced by sources are a function of the vibration characteristics of the source, ground conditions, building foundations and building construction material and techniques.

The management of short-term exceedances for which mitigation is impractical is discussed in Section 3.5.

3.2 Controlling vibration at the source

The principles of 'best management practice' (BMP) and 'best available technology economically achievable' (BATEA) should be applied.

BMP is the adoption of particular operational procedures that minimise vibration impacts while retaining productive efficiency. Examples could include:

  • choosing alternative, lower-impact equipment or methods wherever possible
  • scheduling the use of vibration-causing equipment, such as jackhammers, at the least sensitive time of day
  • routing, operating or locating high vibration sources as far away from sensitive areas as possible
  • sequencing operations so that vibrationcausing activities do not occur simultaneously
  • isolating the equipment causing the vibration on resilient mounts
  • keeping equipment well maintained.

BATEA includes equipment, plant and machinery which incorporate the most advanced and affordable technology to minimise vibration output. Where BMP fails to achieve the required vibration reduction by itself, the BATEA approach should be considered. Examples of these strategies for various sources follow.

Blast vibration
Criteria for blast vibration are contained in ANZECC (1990). Blast vibration values may be controlled by careful attention to blast details and the application of correct techniques.

Roads
The most severe vibrations associated with road traffic result from heavy vehicles with stiff suspensions moving rapidly along roads with irregular surfaces. Mitigation techniques could therefore include the restriction of use of heavy vehicles on particular roads, limiting speed and reducing the occurrence of surface irregularities such as potholes and speed humps.

Railways
For railways, jointed rail could be replaced by continuous welded rail in rail lines passing near sensitive premises. Rail vibration isolation systems include resilient rail fastenings, ballast mats and floating slabs. Rolling stock controls include keeping wheels regularly maintained.

Construction
There are several strategies for managing vibration from construction sites:

  • inform neighbours about the nature of the construction stages and the vibrationgenerating activities-e.g. excavation and rock-breaking
  • use alternatives to impact piling-bored piling, grip jacking, or the use of a hammer cushion when driving steel piles that minimise the vibration generated
  • organise demolition, earthmoving and groundimpacting operations so as not to occur in the same time period
  • avoid night-time activities wherever possible to minimise impact on residential receivers
  • place as much distance as possible between the plant or equipment and the receivers
  • select demolition methods not involving impact where possible (e.g. hydraulic rock splitters rather than rock breakers).

Industrial plant
At the initial design stage it is preferable to select machines that are inherently free of vibration. Vibration-producing machinery should be supported on stiff structural components, and be provided with efficient vibration isolation systems.

Structural vibration caused by machinery could be caused by the rotation of poorly balanced parts such as fans, fly wheels, pulleys, cams and shafts. Measures used to correct this condition involve the addition of balance weights to the rotating unit or the selective removal of mass from the unit.

Inertia blocks can be used to add system mass to reduce vibration. They reduce motion, lower the centre of gravity, minimise the effect of unequal weight distribution and stabilise the assembly.

Mechanical vibration passes easily through rigid structures. Vibration isolators reduce vibration by acting as breaks in the vibration transmission path. For effective control, the vibrating unit must be isolated from any connective structures. The types of vibration isolators include:

  • resilient matting-pads made of neoprene or neoprene and cork. Typically used on air conditioners, business machines, transformers, pumps etc.
  • spring mounts-spring mountings are used where some limitation of horizontal movement is required, e.g. free-standing spring type with spring location cups at top and bottom and a ribbed neoprene acoustic pad bonded to the underside of the base. Typically used on refrigeration compressors, hydrant pumps, cooling towers and chillers
  • rubber mounts-typically used on fans, pumps and general industrial equipment
  • isolation hangers-typically used for piping, duct work, fans, packaged air conditioners, suspended ceilings etc.
  • floating floor-false concrete floors can be supported on integral jacking mounting systems to provide support and acoustical isolation. Typically used in plant rooms, theatres, multi-storey buildings and hospitals.

To reduce machine vibration, such as in engines, compressors, air conditioners and fan coil units, isolation mounting should be considered. The mountings should be located to prevent the machine from rocking excessively. The selection of the mounting will depend on the static weight of the equipment, the dynamic reaction force and the reaction forces at start up. Mountings should be installed so that there are no rigid connections between the equipment and the structure.

3.3 Controlling the transmission of vibration

Distance is one of the most effective mitigation measures against noise and vibration, although geological make-up and terrain also have an effect. For example, some studies have shown that annoyance from railway vibrations is inversely proportional to distance from railway tracks, with a rapid decrease in vibration disturbance as the distance increases from 25 to 150 metres and a slower rate of reduction over 200 metres, until no vibration disturbance is detected at 500 metres (DUAP, 1997).

3.4 Controlling vibration at the receiver

Land-use planning is a critical component in managing vibration impacts. Planning decisions can create or avoid vibration impacts. Decisions that do not consider vibration impacts (where they are present) will almost certainly create land-use conflicts. At the initial planning stage it may be feasible to reduce or avoid vibration impacts by locating less vibration-sensitive land uses (e.g. active recreation, industry) in the intervening land between the existing vibration- o o causing development and sensitive receivers. Alternatively, at the building stage, special building methods could be used to modify ground-borne vibration being transmitted into the building structure (e.g. isolation of foundation and footings using resilient elements such as rubber bearing pads or springs).

The economic viability of vibration control at existing receivers affected by an existing vibration source is dependent on the number of receivers to be treated and the degree of treatment required.
The cost-effectiveness may also depend on whether there are a large number of potential receivers who may require attenuation in the future.

3.5 Managing short-term exceedance of approved vibration values

From time to time, managing vibration at the source may require a short-term increase in vibration beyond the value approved. Such situations may include:

  • piling, demolition and construction
  • abnormal operations due to unforeseen breakdown or maintenance requirements.

Mitigation strategies may be impractical for such short-term events.

The vibration-source manager should demonstrate that all alternatives have been considered before seeking an accommodation from the relevant regulatory or consent authority to operate in excess of the agreed vibration values. If it is judged that such an accommodation for a shortterm operation is warranted, the following options could be considered:

  • confining vibration-generating operations to the least vibration-sensitive part of the day-which could be when the background disturbance is highest
  • determining an upper level for vibration impact also considering what is achievable using feasible and reasonable mitigation
  • consulting with the community regarding the proposed events.


3.6 Negotiation

Where maximum values in Tables 2.2 and 2.4 cannot be met after all feasible and reasonable measures have been applied, any unacceptable impacts may be dealt with through negotiation- either by improved mitigation or by trade-offs with benefits. Negotiation can occur between the operator and the regulator or between the operator and the affected community. In the latter case, negotiation should be made available to those people whose amenity is potentially affected by non-achievement of the relevant vibration criteria. This type of negotiation process, which leads to the determination of an achievable vibration limit, is additional to the type of direct consultation that typically occurs between the operator and the community throughout the impact assessment process in defining the important project parameters.

It is important that, as far as possible, the vibration assessment quantify any remaining or residual impacts that exceed the criteria. The acceptability of the residual vibration impacts should be evaluated by taking into consideration factors such as characteristics of the areas and receivers likely to be affected, characteristics of the proposal and its noise and vibrations, the feasibility of additional mitigation or management measures, and generational and community equity issues. For more detail, see the checklist in Section 8.2.1 of the NSW Industrial noise policy (EPA, 2000).

Representatives of the community could have equal status in the negotiating process with the operator, and with any other parties (such as DEC, councils, and the Department of Planning) acting in an advisory capacity.

Meetings could be chaired by an independent facilitator, depending on the circumstances.

Ideas for community consultation (DUAP, 2001) provides a useful resource on principles and methods of community consultation and negotiation.

 

Page last updated: 12 June 2013