The Company commissioned ECOSA based in Winchester, Hampshire, to carry out an ecological survey of all its sites. This was carried out in summer/autumn 2000 and supplemented by further particular survey work in spring 2001. Based on that work, this Plan reviews the various habitats and species to be found on these sites and examines the issues affecting their biodiversity. The sites are generally of limited size and range from 0.1 hectares at Slindon Service Reservoir to 30 hectares at the Company's Head Office and Source Works at Havant.
The survey concentrated on establishing the habitat value of the sites, identifying scarce, protected and Biodiversity Action Plan species. Each site was evaluated based on the species and habitat types present and graded low, medium or high conservation value, where high conservation value equates roughly to SINC (Site of Importance for Nature Conservation) quality. In total 5 sites were identified as being of high value, 16 of medium value and 21 sites of low value.