Appendix K Air Quality

Air quality assessment monitoring undertaken in 2014 indicated that 12 sites outside of the former Broughton Air Quality Management Area (AQMA) exceeded the annual mean Air Quality Strategy objective for NO2 in Chester. Dispersion modelling detailed assessment of the roads surrounding the City Centre was subsequently undertaken in 2016.

The area was modelled using the advanced atmospheric dispersion model ADMS-Roads (Version 4.0), with annual mean NO2 concentration output. The model suggests that the 40μg/m3 annual mean AQS objective is exceeded at a total of sixteen locations outside of the Broughton AQMA.

It can be concluded that the former Boughton AQMA did not cover all areas of exceedance within Chester City Centre and as such the AQMA was extended to incorporate the whole of Chester City Centre.

With respect to NOx, targeted intervention and local policy has the potential to have a significant influence on local NOx concentrations, with local road sources accounting for 59.0% of average NOx concentrations, and local background the remaining 30.7%.

For NOx and NO2, vehicle emissions represent the largest proportion of total concentrations at locations with NO2 concentrations greater than 40μg/m3, at 67.8% and 56.4% respectively. Considering road traffic only, cars represent the largest contribution for a specific vehicle type, at 32.8% of total vehicle emissions at locations where NO2 concentrations exceed the annual mean objective.

In summary, there are a number of areas in the settlement area that are affected by air quality issues. Chester has a designated city-wide AQMA that covers the City Centre and areas leading out of the city along Boughton and Liverpool Road. The air quality issues are a result of traffic / congestion along these routes. The Air Quality issue clearly highlights the need to reduce traffic flows into and out of the city centre and makes the case for projects which promote more sustainable modes of travel and bring about mode shift to walking cycling and public transport.

To protect future occupiers and reduce exposure to air pollution, development proposals located within an AQMA should include measures to mitigate the impact of poor air quality, where appropriate. Examples include:

On-site provision of electric vehicle charging infrastructure

Avoiding the creation of new “street canyon”, or building configurations that inhibit effective pollution dispersion;

Locating habitable rooms away from busy roads, or directing combustion generated pollutants through well sited vents of chimney stacks; and

Increasing the distance between the development façade and the pollution source.