Detailed Assessment 2005

Conclusions and recommendations

Annual mean NO2 concentrations have been predicted along the A325 and A3 in East Hampshire with specific focus on Bramshott and Bordon. The model has been verified against the continuous monitor at Horndean and concentrations monitored by diffusion tubes at Bramshott and Bordon.

Predicted annual mean NO2 concentrations are below the AQS annual mean objective and the EU limit value in all years at Borden, Bramshott and Horndean. However monitoring at Bramshott (Ferndene) suggests a potential exceedence of the objective. It is recommended that the monitoring is continued in order to provide an annual average estimate for 2005 and the diffusion tube bias for 2005 should be determined. Should the 2005 concentration be above the objective, the model results can be re-verified based on this longer term monitoring and an AQMA would need to be declared. However, it is recommended that further monitoring is undertaken in order to demonstrate the requirements for an AQMA as the modelling indicates that the air quality objectives would be met.

There is good agreement between monitoring and modelling at Bordon apart from one location at the junction of Chalet Hill where the model under predicts. The diffusion tube is at a worse case location at a commercial property. A continuous monitor has been located at the junction in order to provide information on NOx and NO2 concentrations and to establish a local bias adjustment factor for diffusion tubes. At other locations in Bordon both monitoring and modelling indicate that the air quality objective is currently met and no AQMA is required.

EHDC should review monitoring for 2005 and include an updated estimate for  diffusion tube bias. Where possible, worse-case monitoring locations which do not reflect the exposure at relevant receptors (such as residential properties) should be avoided.