London Borough of Hillingdon February 2016 ​ Appendix 1 List of SSSI SSSI Site Natural Description Main habitat Unit Condition Name England Type Site Information System (ENSIS) ID Denham 1001883 Denham Lock Wood is a Broadleaved, 1 Favourable Lock diverse area of open mire mixed and Wood and wet woodland which yew shows a zonation of woodland ­ wetland habitats occurring lowland rarely in Greater London. Fray's 1002024 Fray's Farm Meadows are Unfavourable 1 Neutral Farm one of the last remaining recovering grassland ­ Meadows examples of relatively lowland unimproved wet alluvial grassland in Greater London and the Colne Valley Harefield 1001658 Harefield Pit provides a Earth 1 Unfavourable Pit key section in the London heritage no change Basin for a sequence through the Upper Chalk,Reading Beds and London Clay. It is also the only known site for calcareous floral remains in the Reading Beds. Mid Colne 1003469 The Mid Colne Valley is of Calcareous 1 Unfavourable Valley significant ornithological grassland ­ recovering interest, particularly for the lowland diversity of breeding woodland and wetland Standing 2 Unfavourable birds, and for the numbers open water declining of wintering wildfowl. On and canals the eastern valley slope is one of the last remaining Standing 3 Favourable examples of unimproved open water chalk grassland in Greater and canals London. Standing 4 Unfavourable open water recovering and canals Local Flood Risk Management Strategy Strategic Environmental Assessment screening Appendix 1 Page 1 of 2 London Borough of Hillingdon February 2016 ​ Old Park 1003546 Old Park Wood comprises Broadleaved, 1 Favourable Wood some of the most mixed and floristically rich ancient yew woods in Greater London woodland ­ and contains complex lowland transitions through examples of widely Broadleaved, 2 Favourable differing woodland types. mixed and yew woodland ­ lowland Broadleaved, 3 Favourable mixed and yew woodland ­ lowland Fen, marsh 4 Favourable and swamp Ruislip 103633 The Ruislip Woods form an Broadleaved, 1, Favourable Woods extensive example of mixed and 3­8 ancient semi­natural yew woodland, including some woodland ­ of the largest unbroken lowland blocks that remain in Greater London. Acid 2 Unfavourable grassland ­ recovering lowland Local Flood Risk Management Strategy Strategic Environmental Assessment screening Appendix 1 Page 2 of 2 .