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Manage dust with SiteHive

πŸ’¨ Managing dust with SiteHive

By monitoring dust levels, we can proactively identify any increases, determine their underlying causes, and take necessary action to prevent or mitigate their impact on stakeholders.

SiteHive Dust Direction of Arrival Graphic on Dashboard Map of Melbourne


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 πŸ€© Mastering dust monitoring with SiteHive: Key capabilities and functions



The purpose of dust monitoring

Managing construction dust is primarily about mitigating the impact of works on stakeholders. 


The main focus of dust monitoring is to identify:


πŸ‘€ Visual observations and record keeping are usually the primary method of managing dust, supported by dust monitoring.

Many Construction Environmental Management Plans (CEMPs) have dust compliance rules in the form of time-based limits for PM2.5 and PM10 levels, typically covering days, weeks, months and/or years. 

The table below shows an example from Western Sydney Airport Bulk Earthworks (see references to NSW EPA & NEPM-AAQ below under Relevant Policy):Table Displaying Air Quality Monitoring Criteria for Western Sydney Airport Bulk Earthworks

Compliance-based measurements are typically required to be undertaken using dust deposition gauges (DDGs), whereby samples taken over a period of time (usually a month) are sent to a lab to determine volume and type of dust over the previous period. 

The obvious downside of this approach is that any issues will only be identified weeks after they occurred, which doesn't enable proactive management to prevent issues from occurring. 

It is much more useful to know whether a site might exceed the dust limit in real-time, as this allows action to be taken to prevent potential issues from occurring. 

New technologies, such as optical particle counters (as used by SiteHive Hexanodes), make this possible and allow daily values to be calculated as often as required. 

Real-time dust monitoring


Real-time monitoring using this new technology allows management rules to be used throughout the day (e.g. rolling averages) to identify trends in the levels and enable remedial action before a dust event occurs. 


The below shows an example of management rules from the Sydney Football Stadium redevelopment, and the full plan is linked here: Sydney Football Stadium:

Outline of the Sydney Football Stadiums Reactive Management Trigger Levels for Air Quality (PM10). The trigger levels have been developed by considering the impact assessment criteria but also with short enough time scales to allow environmental managers to quickly respond to dust exceedances on site

Types of measurement


 Reference monitoring

There are several ways to express the amount of particles in the air. Most State-based Governments (e.g. NSW EPA, QLD EPA) run air quality monitoring stations, using approved sampling methods: https://www.epa.nsw.gov.au/your-environment/air/industrial-emissions/sampling-analysing-air-emissions/approved-methods-sampling-analysing-air-pollutants, to provide a network of air quality data.

The methods used at these sites are:

 All of these have filters that need maintaining/changing. These methods are also very expensive and usually require permanent facilities. For these reasons, they are not typically used for construction monitoring. 

However, construction projects can access and use the data. SiteHive makes it really easy to access this data by adding the nearest government reference station to each project site automatically, so the ambient reference measurements can be compared directly with onsite measurements.

The below shows an example from SiteHive Reporting, showing on site dust monitoring and nearby EPA reference monitoring on the same graphs: 


SiteHive reporting graph comparing measurements from the SiteHive Hexanode against reference dust monitors from the EPA


Construction monitoring

A reference grade station is a highly accurate and precise monitoring system used to measure various environmental parameters, such as air quality. 
As reference grade stations are too large and expensive, the methods usually used for construction monitoring are outlined below.


Lab-based analysis


Dust Deposit Gauges (DDG)

Dust settles in a container over a defined period (usually 14 or 30 days) and is sent to a lab for analysis that usually provides reporting on volume, mass, and type of dust deposited.


Gravimetric

The most commonly referred to method of dust sampling in the Australian and US standards is gravimetric sampling. This is a filter-based method, and gravimetric dust monitoring involves sampling a known volume of ambient air through a filter. The filters are sent to a lab to be weighed before and after exposure to determine the mass of particles. The collected dust sample is expressed as mass (mg) of dust per cubic meter (m3) of air.


Real-time monitoring

Real-time monitoring differs from the other types of measurement as it enables continuous and proactive monitoring of dust levels. It uses a variety of techniques (outlined below) that each have different price points and accuracy. The US EPA has run a number of field tests with emerging sensors, showcasing their performance against reference grade monitors: US EPA Evaluation of Emerging Air Sensor Performance. The following types of sensors are most often used for real-time construction monitoring. 

Light-based sensors

There are three types of light sensors generally used: 

Note that photometers and particle counters may also output mass concentrations, but in these devices they are calculated based on the device readings, not the actual raw readings. Also more expensive devices often have features such as a heated inlet, which adds cost and consumes more power, but can reduce erroneous data caused by periods of high humidity. 

Commercial real-time monitoring devices may include a combination of different light sensors. 

The relative costs of the different types of light sensors are identified by the $ ratings shown below:

πŸ€” How to: Calibrate dust with a K-factor


For construction monitoring, optical laser-based dust measurements offer a range of benefits when compared to reference grade instruments. In particular, their lower costs mean that more localised monitoring can take place by deploying more devices. 

Undertaking a field calibration can in some instances increase the usefulness of optical sensors by allowing the values to be adjusted based on local conditions. For example, when the type of dust being measured varies across projects undertaking road works, tunneling or cutting concrete. This process is often referred to as a K-factor calibration. 


Calibrating dust with K-Factor

The process for developing a K-Factor typically involves:


Example of calibration

Recently, for a major tunnel project in Victoria, a SiteHive Hexanode was co-located with a Victorian Government BAM monitoring station to undertake this calibration (see image below).   Over a 2 week period the results were compared, and a K-Factor was developed. 


SiteHive Hexanode co-located with a Victorian Government Beta Attenuation Monitoring System in Melbourne to determine a K-Factor Calibration for Dust


Over the period, the PM10 values correlated well with the reference BAM monitor:

Line Graph comparing SiteHive Hexanode Daily Average Dust PM10 Measurements against reference Beta Attenuation Monitor. Both lines feature the same shape and track fairly close together which demonstrates a strong correlation

Scatter plot comparing Hexanode Dust PM10 measurements to reference bam station results. A line of best fit runs through the middle of the plot tracking closely to the scatter plots which demonstrates the correlation between the SiteHive Hexanode readings and the BAM station. The formula for the line of best fit is shown which gives the K-Factor of 0.697 based on the slope. The R-Squared value of 0.868 shows that the deviation of scatter plots around the line of best fit or k factor is minimal



Results

Based on these results a K-Factor specific to the project was developed and applied, with an R2 value of 0.868. 

The SiteHive Hexanode is already close to the BAM monitor in terms of accuracy, and with the K-Factor applied, there is very little difference.

Comparisons like this provide confidence that lower cost, optical-based systems - such as the SiteHive Hexanode - can be relied on to provide valuable insight into project performance and impacts. As more of this technology is being used, projects are enabled to undertake proactive environmental management in real time. 

Dust spikes

Optical particle counters, such as the sensor used in the SiteHive Hexanode Multi, along with a range of other industry standard devices, have a range of benefits over traditional approaches including being more compact, lower cost, and able to measure in real-time. 

However, they also have some limitations, including producing measurements based on some assumptions (specifically particle density [weight] and refractive index [shape]), which can result in some conditions causing significant spikes in data that are not actual measurements of construction dust.

The Victorian EPA has published a useful guide explaining more about this: https://www.epa.vic.gov.au/about-epa/publications/1745

These are commonly seen in a few consistent scenarios: 



Calculating Direction of Arrival


Understanding the source of dust on your site can be a complex challenge, with local weather conditions often causing dust to be blown on and off site, impacting local stakeholders and communities. To make it easier to understand where dust is coming from, SiteHive shows indicative dust Direction of Arrival (DoA).

Taking inspiration from a traditional pollution rose, the SiteHive dust DoA plot shows the percentage of dust that has come from each direction, for the day so far.

The percentages are calculated based on PM2.5/PM10 readings and the wind direction at the time of the reading. So, for instance, if a PM10 mass of 180 is measured with a corresponding wind direction of North, and 20 is measured with wind blowing South, then 90% of the PM10 will be shown as coming from the North, and 10% from the South.GIF of the SiteHive dashboard map with the dust direction of arrival data layer turned on at Thomas Road WA. The data layer shows the pm10 and pm2.5 concentrations per direction over the course of a day for two separate hexanodes

The DoA plot is meant to be indicative, rather than definitive, and is designed to help you understand where dust may be originating. Having an anemometer (a device that measures wind) co-located with the SiteHive Hexanode will give the most accurate input to this plot. The source of the wind data is currently Openweathermap, but we’ll look to broaden this out to include alternative sources soon.

πŸ‘€ Other useful links


Kaiterra knowledge base, explaining context and methodology for how they measure pm2.5.

South Coast air quality management district 

The South Coast Air Quality Management District (South Coast AQMD) is the agency responsible for attaining state and federal clean air standards in the South Coast Air Basin in southern California. With a population of 14.6 million, the South Coast Air Basin covers an area of 6,745 square miles, which includes Los Angeles. In order to inform the public about the actual performance of commercially available ‘low-cost’ air quality sensors, the South Coast AQMD has established the Air Quality Sensor Performance Evaluation Center (AQ-SPEC) program, which characterises sensors under both field and laboratory conditions. AQ-SPEC field evaluations. 

Relevant policy


The standards in Australia are very specific to each method, and have not yet kept up with newer technology such as optical particle counters. If your management plan specifies that you need to comply with one of the standards below, then you must use that method. Where no standard is defined, or the management plan is more focused on real-time management, then optical particle counters are a great tool for the job. 

The National Environment Protection (Ambient Air Quality) Measure - NEPM aims to achieve National Environment Protection Standards as assessed in accordance with (set) monitoring protocol. The desired outcome of the NEPM is an ambient air quality that allows for the adequate protection of human health and well-being.

Each state also typically has their own approved sampling methods, which overlap with the NEPM. For example the NSW EPA approved methods for the sampling and analysis of air pollutants and the Queensland Government Environment department summary of methods for sampling particulates.

Standards referenced by the NEPM:

Particles as PM10

Particles as PM2.5

Glossary of terms


PM2.5 - Airborne particles less than 2.5 micrometers in diameter

PM10 - Airborne particles less than 10 micrometers in diameter

TSP - Airborne particles up to about 100 micrometers in diameter are referred to as TSP (total suspended particles).

TPS - Typical Particle Size, output from some optical laser particle counters

BAM - Beta Attenuation Monitor

TEOM - Tapered Element Oscillating Microbalance