Low Emission Strategies

Sefton Council: Intensive Road Cleaning to reduce particulates

October 2011

‘Resuspension’ of particulate air pollution (PM₁₀) occurs when dust which has settled on a road or pavements subsequently becomes airborne due to wind or moving traffic on the carriageway. One Air Quality Management Area (AQMA) in Sefton, which has been declared for PM₁₀, is adjacent to a number of industries that will generate particulate pollution both from the industries themselves and the vehicles transporting their products. As a result of this, dusty material can be deposited on road and pavement surfaces in these areas. Investigations carried out as part of Sefton Council’s Detailed Assessment and Further Assessment of air quality suggested that resuspension is an important source of particulate matter.

Recent studies in Düsseldorf have shown reductions in particulate matter when road washing is introduced, indicating that that reductions of 6% in the number of ‘exceedence days’ were achievable.

Purchase of the necessary equipment is expensive and would not be justifiable unless evidence could be produced that the introduction of road washing would be effective in Sefton. Defra funded a project in Sefton to investigate the potential benefits that road washing could bring. The Council was unable to hire a road washing vehicle on a short term contract, so a programme of manual ‘digging out’ and washing of pavements and more intensive sweeping of the roads was developed. Manual pavement and carriageway washing at the Millers Bridge AQMA was conducted by Sefton Council’s Operational Service department during 2010. To take account of variations due to meteorological conditions, the ratio of daily mean PM₁₀ in the AQMA to an urban background site was compared for 2009 and 2010. This trial has indicated reduced PM₁₀ levels during 2010 spring/summer months (blue line on graph), see Figure 1. From analysis of the results the measure is most effective during drier conditions but is less effective during the winter months due to the wetter weather/snow experienced during this season.

The trial has been continued in 2011 and extended to another AQMA. For more information,
contact Gary Mahoney at Sefton Council.

Figure 1: Effect of Road Sweeping and Manual Pavement and Carriageway Cleaning and Washing on PM₁₀ Concentrations (daily mean)

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