The construction phase section of an air quality assessment

The construction phase section of an air quality assessment is judged on whether the risk category matches the site and whether the mitigation follows from it. Most of this section is written to the Institute of Air Quality Management method for assessing dust from demolition and construction, which asks you to categorise four activities against the sensitivity of the surrounding area and then to specify mitigation proportionate to the result. Where it goes wrong is not usually the method. It is the template, reused from a previous scheme with the receptors and the risk categories left unchanged.

What the construction section assesses

Two separate things sit in this section, and they need separating on the page.

Dust and particulate matter from site activity, which is assessed qualitatively by risk category rather than by modelling, because dust deposition does not model reliably at this scale.

Exhaust emissions from construction plant and from vehicles travelling to and from the site, which matter where a site is large, long running, or close to receptors already exposed to poor air quality.

The assessment covers demolition, earthworks, construction and trackout, which is dust carried onto the public highway on vehicle wheels and then resuspended. Each of the four is categorised separately, and a site with no demolition simply says so rather than carrying an inherited paragraph about it.

Activity risk categories and site sensitivity

The method produces a risk category by combining the scale of each activity with the sensitivity of the surrounding area.

Activity scale is driven by measurable things: the volume of the building being demolished, the area being excavated, the total building volume, the number of heavy vehicle movements. State the figures rather than the conclusion, because a reviewer checking the category needs the inputs.

Area sensitivity depends on the number of receptors and their distance from the boundary. Dust effects are generally assessed for receptors within 350 m of the site boundary, and for trackout within 50 m of routes used by construction vehicles up to 500 m from the site exit. Human health receptors, ecological receptors and dust soiling receptors are counted separately, and a designated site within range raises the sensitivity for the ecological category regardless of how many houses there are.

Identify the receptors on a plan with distances. A list of street names is not enough, and it is the single quickest way for an environmental health officer to tell that the section has been copied.

Non-road mobile machinery emission standards

In Greater London, machinery with engines in the range covered by the Mayor's low emission zone for non-road mobile machinery has to meet a minimum emission stage, with tighter requirements inside the central activity zone and opportunity areas, and qualifying plant has to be registered before it comes to site.

The required stage has been tightened over time, so state the current standard and the date you checked it. Contractors plan fleets months ahead, and a condition referring to a superseded stage creates an argument at discharge.

Outside London there is no national equivalent, though a growing number of authorities impose similar requirements by condition where a site sits in an air quality management area. If your assessment proposes an emission standard for plant, say who will verify compliance and how, because an unverifiable commitment is worth little.

Monitoring during construction

Monitoring should be proportionate to the risk category the assessment produced.

For low risk sites, daily visual inspections of the site and the surrounding highway, recorded in a log, are usually sufficient. For medium and high risk sites, the expectation moves towards deposition gauges or directional gauges at agreed locations, and for the highest risk sites real-time particulate monitoring with an alert level and a defined response.

Where real-time monitoring is proposed, specify the alert and action thresholds, who receives the alert, and what happens when it triggers. A monitor with no response protocol behind it produces data nobody acts on.

Set the baseline before work starts. A month of pre-construction monitoring turns later complaints into a question of evidence rather than of assertion.

Agree the locations with the council rather than choosing them yourself. Gauges positioned on the downwind boundary nearest the closest houses answer the question people are actually asking, while gauges tucked behind a hoarding on the far side of the site answer nothing and are treated accordingly. Where a school, a hospital or a care home sits within the assessment distance, expect the authority to ask for a location facing it and to ask for the results to be shared.

Mitigation secured by condition

The method sets out mitigation by risk category, and the assessment should carry the measures that apply to your categories, not the full list.

The measures that do the work are unglamorous. Hard surfacing and regular damping of haul routes, wheel washing with a hard standing approach road, sheeting of loads, enclosure of cutting and grinding, a prohibition on burning waste, covered or damped stockpiles sited away from the boundary, and a designated site manager responsible for air quality with their name on the site notice board.

These are normally secured through a dust management plan or through the air quality section of the Construction Management Plan, submitted and approved before works begin. The wider construction phase sections of a management plan carry the same measures alongside noise, traffic and ecology, and duplicating them across two documents with different wording creates confusion on site.

Write the measures as instructions a site manager can follow. A commitment to employ appropriate dust suppression is not an instruction.

Reporting and complaints

Every construction dust regime needs a complaints route, and councils increasingly ask for it in the condition.

Specify a named contact with a telephone number displayed at the site entrance and on the site hoarding, a log recording each complaint with the date, time, weather conditions and activity underway, a response time, and a reporting arrangement to the council's environmental health team.

Weather recording is the part people skip and the part that settles disputes. Wind direction and speed at the time of a complaint frequently show whether the site could have been the source.

Noise complaints tend to arrive through the same channel, so align the procedure with the one in the Noise Impact Assessment rather than running two.

Where the section reads as a template

Four signs give it away, and all four are checked.

Receptors that do not exist at the site, or distances that do not match the plan. Risk categories asserted without the input figures. A mitigation list that includes measures for activities the project does not involve. And a monitoring proposal at a level that does not match the stated risk.

Fixing it takes an afternoon. Walk the boundary, list the real receptors with distances, recalculate the categories from the actual demolition volume and excavation area, then cut the mitigation list down to what applies. The section gets shorter and considerably more credible.

A full Air Quality Assessment covering the operational phase sits alongside this and answers a different question, and councils usually expect a suitably qualified author for both. Professional review before submission is strongly advised.

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