Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening Figure 3.6: Eversden & Wimpole Wood SSSI and SAC 3.7 Figure 3.6 above demonstrates that whilst the bulk of Eversden Wood is located in excess of 200m from local roads, elements of the SAC, namely ‘The Belts’ are located adjacent to an unnamed road which links local farms. Therefore, the potential for development related affects associated with this road has been further assessed. Page 10 Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening 4 SSSI Citations for Pre-Screened Sites 4.1 SSSI are declared as a result of their specific fauna, flora or geological or physiological features and usually as a result of a combination of all of these factors. The declaration of a SSSI is associated with the production of a ‘citation’ for the site, which sets out those attributes for which the site is of ‘special scientific interest’. Extracts of the citations for each of the sites of interest and their formal ecological classifications are provided below. Caldecote Meadows SSSI 4.2 Caldecote Meadows is a 3.19 hectare area of herb-rich grassland of a calcareous loam type, holding plant communities which are of nationally restricted distribution. Meadows of this type were once widespread throughout Cambridgeshire but are now scarce in the county. Condition: Favourable Main Habitat Classification: Neutral Grassland - Lowland Overhaul Grove SSSI 4.3 Overhall Grove is a 17.3 hectare site of ancient secondary woodland now dominated by small-leaved elm Ulmus minor and represents a woodland type which is nationally restricted in its distribution. The wood overlies the site, fields and ponds of a medieval manor house and was well established by 1650. The break, or discontinuity, in tree cover with no primary woodland nucleus remaining has resulted in a classic example of the long-lasting effects on the ground flora of the removal of woodland cover. Condition: Unfavourable Recovering Main Habitat Classification: Broadleaved, Mixed and Yew Woodland Page 11 Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening Maddingley Woods SSSI 4.4 Madingley Wood is a 15.4 hectare example of the ash-maple woodland type characteristic of the chalky Boulder Clay of eastern England. The western sector of the wood is of ancient origin whilst the eastern half is of relatively recent origin thus providing valuable opportunities for study into colonisation processes and historical ecology generally. 4.5 The site is of particular educational and research value in view of its long association with the University of Cambridge. Condition: Favourable Main Habitat Classification: Broadleaved, Mixed and Yew Woodland Eversden and Wimpole Wood SSSI and SAC 4.6 Eversden Wood has been declared as a SSSI as a result of its status as important ancient semi-natural woodland of a type now localised in extent, and rare in lowland England. It has also been declared an SAC as a result of the presence of a summer maternity roost for the barbastelle bat, Barbastella barbastellus. Wimpole Wood is considered to be of more recent origin. Condition: Unit 003 Unfavourable Recovering. Unit 004 Favourable Main Habitat Classification: Broadleaved, Mixed and Yew Woodland Page 12 Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening 5 Further Assessment Criteria 5.1 The pre-screening presented in Section 3 has identified Caldecote Meadows, Overhaul Grove, Madingley Wood and elements of Everston & Wimpole Wood as requiring further assessment by virtue of their distance from potentially affected roads. This further screening stage has necessitated a review of the likelihood that traffic volumes associated with the Application Site, in combination with other local development, may travel passed the identified SSSI and SAC at levels which could potential effect the integrity of the habitats for which their designations have been given. This is further discussed below. Critical Loads 5.2 Critical Loads are defined on the Air Pollution Information Systems (APIS) website 3 as “ a quantitative estimate of exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge ” 5.3 Therefore, it is reasonable to assume that if exposure above the critical load will have ‘... harmful effects on specified sensitive elements of the environment ...’ then the integrity of the site is thus affected. 5.4 Nutrient Nitrogen deposition is identified within Annexes A and B as the main pollutant of concern within these habitats. The Critical Loads of Nutrient Nitrogen across the potentially affected habitats identified range from 10 – 30(kg/N/ha/yr), therefore for the purpose of this further screening a worst value of 10 (kg/N/ha/yr) has been applied. 5.5 A full examination of the Nutrient Nitrogen critical loads used within this assessment is contained within Annex C. 3 www.apis.ac.uk/overview/issues/overview_Cloadslevels.htm Page 13 Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening Significance 5.6 In accordance with the Annex F of the EA’s Horizontal Guidance on Air Emissions, the significance of impact has been derived from an examination of whether an air quality impact is likely to constitute more than 1% of the critical load for Nitrogen deposition 4. Traffic Data 5.7 Previous HRA Screening work 5 undertaken by Mayer Brown identified that Annual Average Daily Traffic (AADT) Flows of 120 were associated with Nutrient Nitrogen deposition levels within 10m of the road that were likely to be 0.5% of the critical load of 10 kg/N/ha/yr. Therefore, this has been used as the trigger level for traffic flows to be assessed within this HRA air quality screening exercise. 5.8 Therefore, the need for detailed assessment is proposed where any roads located within 200m of the SAC are subject to increases of Annual Average Daily Traffic of more than 120 as a result of the development either alone or in- combination with other foreseeable development. 5.9 The transport assessment has concluded the following: Caldecote Meadows SSSI 5.10 AADT Traffic flows associated with the Application Site within 200m of this SSSI are anticipated to be around 56 in the development year of 2031. AADT traffic flows for the same location and in combination with other plans or projects for the development are anticipated to be approximately 97. 5.11 Therefore, this level of traffic is not considered to be of a level which would result nutrient nitrogen disposition within the SSSI which is above 0.5% of the critical load. 4 Environment Agency (2011) Horizontal Guidance – H1 Annex F - Air Emissions. EA. Bristol 5 Mayer Brown (2015) Horton Heath HRA Screening Addendum. MB. Woking Page 14 Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening Overhaul Grove SSSI 5.12 Given that traffic approaching Overhaul Grove would be required to take the same route as that approaching Caldecott Meadows, the same conclusion can be drawn. This is that AADT traffic either alone or in combination with other plans and projects would not be considered to be of a level which would result nutrient nitrogen disposition within the SSSI which is above 0.5% of the critical load for this site. Maddingley Woods SSSI 5.13 The transport assessment has concluded that AADT Traffic flows associated with the Application Site and other plans and projects, travelling to the east along with the A428 would be approximately 12891. In addition, AADT Traffic flows associated with the Application Site and other plans and projects travelling adjacent to the woods on the A1303 would be approximately 8,336. As a result, this exceeds the identified trigger level and further assessment is required of this potential impact. Eversden and Wimpole Wood SSSI and SAC 5.14 In order to reach the Eversden and Wimpole Wood SSSI and SAC, traffic associated with the Application site would be required to travel south along Broadway before joining the A1198 and then taking Old Wimpole Road to the east. The Transport Assessment has concluded that less that 1% of the Application Site AADT and that of other plans and projects, would take this route from the Broadway South. This equates to an AADT of approximately 15. Therefore, it can also be concluded that this level of traffic is not considered to be of a level which would result nutrient nitrogen disposition within the SSSI which is above 0.5% of the critical load. Page 15 Countryside Properties (UK) Ltd Bourn Airfield, Bourn, Habitat Regulations Assessment Air Quality Screening 6 Detailed Assessment Assessment Model 6.1 A quantitative assessment of traffic related air quality impacts on the Maddingley Wood SSSI has been undertaken. The modelling tool which has been used is the dispersion model ADMS Roads, which has been developed by the Cambridge Environmental Research Consultants. It is one of the screening models referred to within the Local Air Quality Management Technical Guidance document TG (09) Annex 2: Estimating Emissions 6. 6.2 This model uses the following input data: • Hourly Average Traffic Speeds - derived from diurnal traffic counts and provided by the transport consultants; • Latest relevant Emission Factor Toolkit (Version 8); • Geo-referenced mapping data; and • Hourly