Detailed Assessment Addendum

April 2008

Executive Summary

Part IV of the Environment Act 1995 places a statutory duty on local authorities to review and assess the air quality within their area. For local authorities that have identified areas, within their Updating and Screening Assessment (USA), where there is a potential risk of exceedence of Air Quality Strategy (AQS) objectives, a Detailed Assessment is required. Thanet District Council’s Detailed Assessment (April 2007) was a requirement resulting from the third round USA undertaken in 2006. The Detailed Assessment recommended further investigation of predicted exceedences of the nitrogen dioxide (NO₂) annual mean objective at Hereson Road, Ramsgate and High Street, St Lawrence. This Detailed Assessment Addendum considers new monitoring data near to the modelled exceedences. The assessment has been undertaken in accordance with the Technical Guidance LAQM.TG (03).

Between 1998 and 2001, Thanet District Council undertook its first round of review and assessment of air quality. The first round concluded that all air quality objectives were likely to be met in Thanet and there was no need to declare any Air Quality Management Areas (AQMAs).

The first phase of the second round of review and assessment of air quality, the USA, was completed in July 2003 with the conclusion that all air quality objectives would be met. The 2004 Annual Progress Report, however, considered the latest monitoring data from 2003 and highlighted seven areas where exceedences of NO₂ and fine particulates (PM₁₀) objectives may be occurring. These were considered in the 2005 Detailed Assessment, which concluded that The Square, Birchington should be declared an AQMA for NO₂ and PM₁₀ on the basis of predicted exceedences of the NO₂ annual mean objective and 24-hour mean PM₁₀ objective. The area was subsequently declared an AQMA in March 2006 and a continuous monitoring station was installed in 2007 to more accurately monitor changes in pollution levels. A Further Assessment and Action Plan for the AQMA were completed in 2007.

The third round USA was completed in June 2006, with the conclusion that a Detailed Assessment was required for NO₂ due to emissions from road traffic on Hereson Road, Ramsgate and on High Street, St Lawrence. The detailed assessment model results predicted exceedences of the annual mean NO₂ objective at both sites, but this was based on model verification that was limited to single roadside diffusion tube sites. The Council installed additional (triplicate) diffusion tube monitoring sites at relevant worst-case receptor locations to assess compliance with the annual mean objective.

Detailed dispersion modelling has been undertaken using the ADMS-Roads dispersion model. Annual mean NO₂ concentrations have been predicted at specific receptors along Hereson Road, Ramsgate and High Street, St Lawrence, where exceedences were predicted in the Detailed Assessment (April 2007). The selected receptors represent relevant exposure locations for the annual mean objective. The model has been verified

against the NO₂ diffusion tube sites in the assessment area.

The model results suggest that the annual mean objective for NO₂ is likely to met at all receptors at Hereson Road, Ramsgate. There are a small number of exceedences predicted at receptors on High Street, St Lawrence.

Based on this Detailed Assessment Addendum and review of monitoring data in the assessment areas the following recommendations are made for Thanet District Council:

• To continue to monitor NO₂ concentrations along Hereson Road, Ramsgate at relevant receptor locations to demonstrate continued compliance with the annual mean objective.
• To consider the declaration of an Air Quality Management Area along High Street in St Lawrence, on the basis of NO₂, where exceedences are predicted at relevant receptor locations as reflected in local monitoring results.
• To consider installing a continuous monitoring site at High Street, St Lawrence where exceedences of the NO₂ annual mean objective are predicted to provide more robust and accurate data for further review and assessment.

Next: Introduction

• Executive Summary
• Introduction
• Baseline Information
• Dispersion Modelling Methodology
• Results
• Conclusions
• Model Verification
• ADMS-Roads Modelled Results
• Mapped ADMS Results

E-mail:

airquality@thanet.gov.uk 

Tel: 01843 577580

Fax: 01843 290906