Construction site dust suppression techniques - keeping dust under control.

Australia’s construction industry has some of the most stringent safety and environmental management laws in the world. And given our incredibly dry climate in parts of the country, dust suppression on construction sites can be a big issue, especially when working in built-up or residential areas. Below we talk about the laws, the different types of dust, health risks and the EPA’s best dust suppression techniques, so you can be fully equipped to handle dust on your site.

The law - dust suppression guidelines in Australia

Dust suppression is a big issue in construction and mining, but laws apply to the creation of dust across all industrial pursuits and every business needs to be aware of the Australian business guidelines on the subject. The problem is - the guidelines around dust suppression, particularly for construction sites, can be mandated by local councils, the EPA in each state and by Worksafe - and they can all be different, so it can sometimes be an issue you need to read widely on before you fully understand your rights and obligations.

Different types of dusts and dust suppression issues

Dust can be the by-product of many types of construction activities, so it depends on what toxic or non-toxic chemicals are present in the dust, to know how to best treat the issue and suppress dust on your construction site. You also need to be aware of the legal limits of exposure to certain dust types on your site, particularly in some mining activities, so you can keep people working on your site safe from long-term health issues.

Dust Suppression in Coal Mining

Dust suppression in coal mining Is a particular issue for the government to manage, given the array of harmful toxins and chemicals that are exposed (or used) during the process of coal mining. From November 2018, the occupational exposure limit for respirable dust in coal mines is 2.5mg/m3. This new increased limit means that everyone in the coal mining industry needs to be responsible for getting on top of dust at coal sites to ensure workers have a safe and healthy environment to work in.

Crystalline Silica (quartz) Dust

Silica is a natural mineral that occurs in many construction materials such as cement, concrete, mortar, sandstone, granite, sand and other myriad materials made with these inputs. It is the most dangerous type of dust produced by construction and mining activities and can cause a range of troubling health concerns in people who are exposed to either a very large amount in one dose or to smaller amounts and doses over longer periods of time.

Silica dust is created through activities such as concrete cutting, demolition, sandblasting, drilling, grinding and other activities, most common to work that involves shaping, removing or installing concrete. As such - if your site is conducting any of these activities - its needs to have dust suppression tactics in place prior to undertaking those activities to limit the harmful impacts to workers on the site, and surrounding residential areas, as well as using the best-in-class PPE to prevent workers from inhaling this dust.

Non-Silica Dust

Non-silica dust is harmful, but not as bad as silica dust, so different government guidelines apply to activities where non-silica dust is created. Non-silica dust is present in construction supply materials such as cement, dolomite, gypsum, limestone, plasterboard and marble. Non-silica dust is created from cutting, blasting or grinding the aforementioned materials.

Respirable Dust

Respirable dust is very fine dust which is able to be inhaled and reach the lungs. It is measured as smaller than 10 microns in diameter. There are respirable dust types that include silica, and ones without. Both types of dust, if respirable, need to be treated as very harmful to workers and those in the local communities. Special caution needs to be applied to suppress respirable dust.

Wood Dust

Wood dust occurs when you work with hard and soft woods - and is created from the process of sanding and cutting wood. This is very common in residential construction projects and a particular issue for carpenters.

Exposure to Dust - What are the health risks?

Most of the long-term harmful impacts of dust exposure involve people who have had lots of exposure to silica dust in their career, and that dust has settled in the lungs and caused one or many health issues. Lung disease and lung cancer can be common amongst construction workers, particularly older ones, that didn’t use as much PPE as modern construction workers use now.

Another condition is chronic obstructive pulmonary disorder (COPD). This occurs when the dust has settled at the base of the lung, and caused the formation of scar tissue which impedes proper lung function. Silicosis is a very specific condition (with three levels, acute, chronic and accelerated), which occurs only in people who have been exposed to large amounts of silica dust and can take 10-30 years to develop after exposure. This condition can greatly decrease the patient's quality of life, and shorten their lifespan.

EPA-Recommended Dust Suppression Techniques

1. Prevent generation of dust (in preference to managing dust when it happens)
2. Manage the project schedule to minimise land clearing in drier months
3. Pave and water haul roads
4. Water areas around haul roads
5. Ensure smooth surfaces are deep ripped and left rough and cloddy to reduce wind velocity
6. Construction wind fences
7. Never have access to less than 2,000 litres of water on your site
8. Manage contaminated runoff
9. Manage your stockpiles and batters

This really goes without saying (or maybe it doesn’t) that everything that can be done to avoid dust generation, should be done as part of your construction or mining project plan. This is particularly the case, as it relates to the creation of silica dust - because it's harmful to the construction site workers and the local community.

In an arid country like Australia, you need to be wary of undertaking massive land clearing activities during the summer or drought times. In planning your project, be mindful of the local climate, and either plan your construction to accommodate areas that haven’t seen rain for a while or have some water trucks and other dust suppression suppliers onsite at the ready to manage the impending dust cloud created by your bulk earthworks project.

It is common to regularly water haul roads on mine sites where there are dust issues impacting a local community, and it's becoming more common to pave them to prevent dust generation over the long-term. The frequency of watering haul roads will be determined by the local weather conditions and the erodibility of the soil or materials used in the haul road’s construction. Construction managers need to be mindful of the additives they include in the water that’s used for dust suppression (if the intent is that additives are included to increase the dust suppression qualities) because there are strong EPA guidelines around the management of contaminated water as a by-product of dust suppression activities. The best machine for haul road dust suppression is the dump truck mounted water truck hire , or moxy water cart or articulated water cart . Click on the links to find local suppliers and request a quote.

It can pay to extensively water areas around the haul roads, including the batters and any land areas that were disturbed or excavated in the construction of the haul roads. This is because loose dust and earth around the haul road can be as big a problem as the haul road itself.

Whatever you do, don’t Google ‘deep ripped’ without qualifying the query with ‘road surfaces’ because you’re going to get a hell of a fright (like I did writing this article). Deep ripping (as it relates to the construction industry and not that niche gear I just found on the internet) is an erosion management technique that involves breaking up layers of compressed aggregate (its most common practice in haul road construction) using strong tines (35 - 50cm) usually affixed to a grader or dozer (using a ripper attachment), roughening or corrugating the surface to increase water filtration, delay the formation of rilling and reduce dust generation. There are plenty of machines that can do this - including a grader with a ripper, a dozer with ripper, and even an excavator can be used to rip in a few extenuating circumstances.

Wind fence hiring or building is more common around infrastructure projects and commercial construction projects in built-up areas, more so than in the mining industry where projects are undertaken miles from local communities. Windbreak fences are usually built from chain mesh and farm mesh fencing, or really light-weight and pliable transparent plastics around the edge of a construction site, and with consideration for the direction of winds and the corresponding communities that are in the area. Depending on the size and scale of the job, these things can be massive and are usually erected at the ‘down-wind’ point of the construction, blocking any nearby highways, roads or residences from the harmful impacts of construction dust.

Dust is something you need to be permanently willing and planned to manage on your site at a moment's notice - a dust suppression incident can occur in a heartbeat, and you need to be able to react and solve the problem quickly before it negatively impacts a local community. As such, the EPA guidelines recommend that on your site - you never have access to less than 2000 litres of water at any one time. This might mean tapping into the local main, if you can, or storing an amount of water on your site in holding tanks for quick and easy access.

If you deploy a bunch of water trucks to your site to contain and suppress dust, then you need to be aware of the water run-off created by this activity - and ensure that if the water contains any harmful chemicals, it is subsequently treated and managed as contaminated water and the water runoff is not expelled into local waterways or the stormwater drainage system (at a minimum). You need to be fully aware of the content of the water runoff on your site, particularly when using thousands of litres in dust suppression activities and these risks should be managed as part of your broader site risk and environmental management strategies.

One of the big issues in dust suppression on major earthworks projects is how you manage stockpiles of dirt and soil within the site confines, and how you best control dust as you are building these things. The EPA of Victoria recommends:

• Locate the stockpiles away from drainage lines and protected from wind
• Minimise number and size of stockpiles
• Separate topsoil from underburden
• Construction the stockpile with no slope greater than a 2:1 vertical
• Mulch, roughen and seed with sterile grass
• Circle all unstabilised stockpiles and betters with silt fences or a drainage system
• Never locate a stockpile within 10m of a waterway if can be avoided
• Install sprinklers or hand water the stockpiles