A Guide to Particulate Monitoring after Implementation of SPG8: Construction and Demolition Sites

Introduction

Environmental particulates and NO2 are becoming an area of increased interest due to their effect on the health of large swathes of the population. Particulate matter is composed of non-gaseous material of varied chemical composition, which is categorised by its diameter. It is produced by a vast number of sources but can include engine emissions, brake wear, fires and construction activities. Particle size is directly linked to their potential for causing health problems. Those of less than 10 micrometers in diameter are linked to significant health problems due to their ability to infiltrate deep into the lung, with the smallest particulates crossing into the bloodstream.

This can cause significant problems with both your lungs and heart, with many studies having linked particulate pollution exposure to a variety of problems, which include:

The control of dust and emissions during construction and demolition - Supplementary Planning Guidance Greater London Authority (2014)

premature death in people with heart or lung disease
non-fatal heart attacks
irregular heartbeat
aggravated asthma
decreased lung function
increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing

In the UK the action to combat particulate pollution was initially instigated through the implementation of Part IV of the Environmental Protection Act 1995 and the Government’s UK Air Quality Strategy (1997). Guidance has also been published by the Environment Agency for local authorities, through Technical Guidance LAQM.TG(09) ‘Local Air Quality Management’.

Recently action on the control of particulates has been spearheaded by the Greater London Authority, culminating in

the publication of ‘The Control of Dust and Emissions during Construction and Demolition’ (July 2014) and the ‘London Local Air Quality Management (LLAQM), Policy Guidance 2016 (LLAQM.PG(16))

Authorities Focus on Construction and Demolition Activities

Construction and demolition activities can result in impacts on local air quality through:

Visible dust plumes;
Dust deposition;
Elevated PM10 and PM2.5 concentrations; and
Increased concentrations of nitrogen dioxide.

These pollutants can result from such on site activities as the breaking-up of materials, movement of soil, the exhaust of diesel powered machinery/vehicles and the movement of vehicles/people across site.

The increased focus on the control of particulate matter by local authorities has meant that construction and demolition activities have been identified as significant sources of particulate matter and subsequently targeted for emissions control. This has been implemented through the aforementioned, ‘The Control of Dust and Emissions during Construction and Demolition’.

Categorisation of Dust Emission Risk from Sites

In order to achieve control of these emissions it is necessary to measure the concentrations that are being emitted from a construction site. These are prescribed under the planning conditions of a local authority, and within London is dependent on the categorisation of the site. This is normally undertaken by the developer through a Dust Risk Assessment (DRA) that is submitted to the local authority, taking into account each phase of the works (demolition, earthworks, construction, trackout), identifying risks and suitable mitigation measures.

Sites are generically categorised as:

Low risk sites

Development of up to 1,000 square metres of land and;
Development of one property and up to a maximum of ten and;
Potential for emissions and dust to have small impact on sensitive receptors

Medium risk sites

Development of between 1,000 and 15,000 square metres of land and;
Development of ten to 150 properties and;
Potential for emissions and dust to have medium impact on sensitive receptors

High risk sites

Development of over 15,000 square metres of land
Development of over 150 properties or;
Major Development referred to the Mayor and or the London Development Agency;
Major development defined by a London borough or;
Potential for emissions and dust to have significant impact on sensitive receptors

Monitoring Requirements

Site monitoring protocols to be undertaken are dependent on the risk categorisation of the site, however:

‘all demolition and construction sites should be monitored for the generation of air pollution. It is essential to monitor for dust generation, including PM10. For smaller sites this can be simply visual monitoring. The need to monitor PM2.5 and NO2 will be determined on a case by case basis by the local planning authority. The need for monitoring will generally depend on existing air quality, air pollution risks from the development, the technical practicalities and financial implications of such monitoring.’

The Control of Dust and Emissions During Construction and Demolition: Supplementary Planning Guidance 2014 (SPG8)

Dependent on the risks posed, any one of three site categories can be determined; low, medium and high.

Low Risk

Low Risk Sites require the following activities to be undertaken:

Take into account the impact of air quality and dust on occupational exposure standards to minimise worker exposure and breaches of air quality objectives that may occur outside the site boundary, such as by visual assessment
Keep an accurate log of complaints from the public, and the measures taken to address any complaints, where they were required

It is notable that measurement of dust/particulate is not required, however subjective assessments are necessary.

Medium Risk

The requirement of Medium Risk Sites is slightly more involved with the local authority requiring the implementation of one or multiple monitoring regimes along the line of a site and/or at sensitive receptors. Assessments must be completed in the following manner:

All tasks required for low risk sites
Determine the prevailing wind direction across the site using long term weather data from a nearby weather station;
If a requirement is imposed for measuring air quality along a line of a site:
Set up a line across the site according to the direction of the prevailing wind
Operate a minimum of two automatic particulate monitors to measure PM10 levels at either end of the line - either inside or outside the site boundary. These instruments should provide data that can be downloaded in real-time by the local authority

The LPA may also require monitoring at sensitive receptors. If this is necessary then the following must be implemented:

Identify which location(s) need to be monitored and set up an automatic particulate monitor at each of these to measure representative PM10 levels. These instruments should provide data that can be downloaded in real-time by the local authority;
If applicable, supplement with automatic monitors or hand-held monitors, particularly focusing on any sensitive locations such as schools;
Carry out dust deposition and soiling rate assessments following recommended procedures
Carry out a visual inspection of site activities, dust controls and site conditions and record in a daily dust log;
Identify a responsible trained person on- site for dust monitoring who can access real-time PM10 data from automatic monitors (e.g., at hourly or 15 minute intervals). Ensure that adequate quality assurance/quality control is in place; and
Agree a procedure to notify the local authority, so that immediate and appropriate measures can be put in place to rectify any problem. Alert mechanisms could include email, texts or alarm systems.

High Risk Sites

For higher risk sites all the procedures outlined under medium risk sites must be followed. In addition it is necessary to:

Determine the prevailing wind direction from local weather stations or by setting up a weather station on site to measure local wind direction and speed.
If measuring along a line: Set up a line across the site according to the direction of the prevailing wind; and
Operate a minimum of two automatic particulate monitors to measure PM10 levels at either end of the transect - either inside or outside the site boundary. These instruments should provide data that can be downloaded in real-time by the local authority.

The LPA may also require monitoring at sensitive receptors, if this is the case it will be necessary to:

Identify which location(s) need to be monitored and set up an automatic particulate monitor at each of these to measure representative PM10 levels. These instruments should provide data that can be downloaded in real-time by the local authority;
If applicable, supplement with automatic monitors or hand-held monitors, particularly focusing on any sensitive locations such as schools;
Carry out dust deposition and soiling rate assessments following recommended procedures;
Carry out a visual inspection of site activities, dust controls and site conditions and record in a daily dust log;
Identify a responsible trained person on- site for dust monitoring who can access real-time PM10 data from automatic monitors (e.g., at hourly or 15 minute intervals). Ensure that adequate quality assurance/quality control is in place; and
Agree a procedure to notify the local authority, so that immediate and appropriate measures can be put in place to rectify any problem. Alert mechanisms could include email, texts or alarm systems.

As you can see from the above requirements, the monitoring of dust emissions from a site can require the use of dedicated instrumentation and personnel with appropriate levels of knowledge and training. Furthermore, there is a requirement for the local authority to have direct access to live results; meaning any system used must have telemetry and an easy to interrogate database that provides automated alerts for exceedance of trigger values.

Trigger/Threshold Values

Under SPG8 it is recommended that a trigger level of 250 ug m-3 is set as a 15-minute mean for concentrations of PM10 close to construction sites. The trigger level was derived from Fuller and Green, 2004. However, some PM10 reference instruments cannot measure a 15 minute mean. As an alternative 50 ug m-3 is suggested as a 1-hour mean having subtracted background concentrations (to account for regional pollution episodes etc). The one hour limit is designed to prevent any complaints from people living or working close to a site.

Where the site threshold for PM10 is being significantly breached, developers should stop work immediately and ensure best practice measures are in place before restarting. Where there are breaches of the PM10 threshold local authorities can use their powers to prevent the statutory nuisance.

On Site Monitoring Techniques

There are a wide range of monitoring techniques available for the measurement of airborne particulate matter, deposition and soiling rates. The techniques range from “active” samplers to measure specific dust fractions (e.g. TSP, PM10, PM4, PM2.5 and PM1) to simpler “passive” samplers that measure dust flux, dust deposition and soiling. We will quickly discuss the relative merits and disadvantages of each technique below:

Beta-attenuation Analysers

These instruments provide continuous real time data with a resolution of 1-hour. They demonstrate equivalence to the reference methods set out in EN12341 and EN14907, meaning they can be used to compare concentrations directly against objectives/limit values set out in EC Directive 2008/50/EC. However, their very high capital, operational costs, electrical power, site security and careful servicing/maintenance make them unsuitable for most commercial applications. These are only really suitable/practicable for sites where demonstration of compliance with the objectives/limit values are critical.

TEOM Analyser

The TEOM analyser provides continuous real-time data with intervals/reporting of less than 1 hour. Data acquired from the instrument can be corrected to account for loss of semi-volatile material that can be used to compare with the objectives/limit values set out in EC Directive 2008/50/EC. However, again the high capital, operational cost, electrical power, site security, careful servicing and maintenance requirements, make these instruments unsuitable for most commercial applications.

Optical Analysers

Optical analysers are more wide spread than any other type. They often have the ability to measure several size fractions simultaneously (e.g. TSP, PM10, PM4, PM2.5 and PM1) and continuously, providing data down to intervals of seconds. They have significant advantages over all other types with them being relatively lightweight, portable, battery operated or mains power operated. They can easily be attached at site boundaries and their low cost, low maintenance requirements mean that they are perfect for most commercial applications. They do not have the required level of accuracy necessary for demonstrating compliance with EC Directive 2008/50/EC but provide distinct advantages in that they provide information on effectiveness of mitigation measures and can be used to identify any periods of unexpectedly high levels of dust. They are classified as an indicative instrument defined under the Environment Agency’s MCERTS scheme. They carry a higher level of uncertainty than refe