2009 Air Quality Update: Shortened Detailed Assessment of Nitrogen Dioxide in Bordon

Executive Summary

This report reviews nitrogen dioxide data that East Hampshire District Council has collected in Bordon between 2000 and July 2009. The purpose of the report is to determine whether or not it is likely that the annual mean air quality objective for nitrogen dioxide will be achieved in Bordon at the A325/Chalet Hill junction.

The 2008 Detailed Assessment predicted that exceedences of the annual mean objective for nitrogen dioxide at relevant receptors in Bordon were unlikely and therefore concluded that an Air Quality Management Area (AQMA) was not necessary at this location. Modelling predicted significantly lower concentrations at relevant receptors located at first floor level than ground floor level with no relevant exposure.

Following communication with DEFRA regarding concentrations of nitrogen dioxide measured with diffusion tubes along the A325/Bordon, it was agreed that the results of the 2008 Detailed Assessment may be optimistic due to increases in the bias adjustment factors used to correct the 2007 data.

The information that is provided in this report is intended to supplement and update that given in the 2008 Detailed Assessment, to enable East Hampshire District Council sufficient data to determine whether declaring an Air Quality Management Area (AQMA) is justified.

In January 2009 additional monitoring tubes were placed at first floor level to investigate whether ground floor concentrations measured at commercial premises are representative of higher floors with residential use. Initial results of the 2009 survey suggest that ground floor concentrations of nitrogen dioxide are not representative of higher floors. However despite reductions in concentrations at first floor level, it appears likely that an exceedence of the 40ug/m3 objective exists at the façade of the residential properties adjacent to tube BR7 located above Corals, High Street, Bordon.

In light of the review of monitoring data for Bordon and the initial results for the 2009 survey at height which suggest a likely exceedence of the annual mean objective for nitrogen dioxide at one location, East Hampshire District Council will need to declare an AQMA in Bordon which includes the residential properties above Corals, High Street, Bordon.

At this time it appears likely that the boundary of the AQMA will cover the residential properties above the Corals building only (1 - 5 High Street, Bordon). Provisional 2009 results for another first floor level monitoring tube BR8 indicate that although concentrations of nitrogen dioxide exceed the 40ug/m3 air quality objective at ground floor level, concentrations of nitrogen dioxide at first floor level are likely to fall below the air quality objective.

East Hampshire District Council recognises the results for 2009 are indicative only and therefore proposes to review this position and determine the extent of the AQMA in January 2010 when a complete dataset for 2009 is available.