Environmental Statement volume 4 - Chiltern Evergreen3

Waterbodies not Considered for the HSIA SurveyWaterbodies were not considered for the HSIA survey where major physicalbarriers, considered to prevent dispersal of great crested newts (such as majorroads including motorways and busy A roads) were present in between thewaterbody and the development boundary. Waterbodies were also excludedfrom the HSIA survey where they were on the limit of the 500 m buffer of thedevelopment boundary and where a known population of great crested newtoccurs closer to the development boundary.F4-2.3F4-2.3.1HABITAT SUITABILITY INDEX ASSESSMENT SURVEYIntroductionThe desk study and walkover survey initially identified the location ofpotential waterbodies for great crested newt. These waterbodies were thensurveyed to identify their suitability to support great crested newt. TheseHabitat Suitability Index Assessment surveys comprised one visit to eachwaterbody to record various ecological parameters which would then be usedto score their suitability for great crested newt.F4-2.3.2MethodFollowing the confirmation of the location of waterbodies within 500 m of thedevelopment boundary, an HSIA survey of 48 waterbodies was carried out inMarch and April 2009 by ERM and Keystone Environmental (see Appendix 1for the Keystone Environmental report and Appendix 2 for the ERM HSIA rawdata).The HSIA survey includes one visit to each waterbody to record 10 habitatcriteria taken from Oldham et al, 2000 which are then used to assess thehabitat quality. The 10 habitat criteria are as follows:pond size;surface area;water depth;water quality;% shade;% macrophyte cover;presence of fish and waterfowl;number of waterbodies wthin 1 km of survey waterbody;quality of terrestrial habitat surrounding ponds; andtype of marginal/aquatic vegetation.The HSIA then uses these ten key habitat criteria to produce an HSI score fora pond, which ranges between 1.00 (optimal suitability for great crestednewts) to 0.00 (unsuitable for great crested newts). Once this score isassigned, it can be used to define the suitability of the waterbody for greatENVIRONMENTAL RESOURCES MANAGEMENTF4-3CHILTERN RAILWAYS