Environmental Statement volume 4 - Chiltern Evergreen3

Evaluation Criteria4.5.7 With particular regard to the water environment, the assessment process willtake account of the following factors.• The magnitude of the effect, as determined by its intensity and by itsextent in space and time.• The sensitivity and vulnerability of the surface and groundwater bodies inthe vicinity of the scheme, taking into account current flow characteristics,water quality and considering pathways through which secondaryimpacts may result (eg within water body and watercourse catchmentareas, any groundwater recharge zones and throughout the length ofwatercourses).• The sensitivities of, and effects upon, surrounding and dependentenvironments, including the effects upon flood plains, storm water storageareas and related developments and environments, initiatives (eg existinginitiatives to improve water quality) and users of the water environment(eg abstractors, fisheries and recreational users).4.5.8 Significance is derived as a function of two main factors: the magnitude ofchange and the sensitivity / vulnerability of the receptor/resource that isaffected. The assessment of the impact will largely be based uponprofessional judgement, experience and site-specific hydrological andhydrogeological characteristics.4.5.9 Impact significance will be reported using the terms Minor, Moderate or Major,adverse or positive. Negligible or no impact ratings will assigned where animpact would not be considered to be significant enough to be discernablefrom natural baseline variation.4.5.10 Impacts which are graded as being major are those which the EIA teamconsider should be given greatest weight, relative to other levels of impact tothe water environment, in decision making. They usually concern keyactivities or risks, such as those that have the potential to cause a level ofdegradation in biological, chemical or aesthetic quality that endangers theclassification of the surface water or groundwater feature, compromisesdependent ecological habitats or associated flora and fauna, or preventssignificant abstractions or discharges from occurring.4.5.11 Moderate and minor levels of impact will also be reported. An example of amoderate impact would be a significant effect on shallow drainage pathwaysduring construction (due to excavation, compaction etc), over a wide area, butone not directly linked to sensitive surface waters, groundwaters or habitats.An emphasis on moderate impacts is to demonstrate that the impact has beenreduced to the extent practicable. This does not necessarily mean thatmoderate impacts have to be reduced to minor impacts.ENVIRONMENTAL RESOURCES MANAGEMENT 57 CHILTERN RAILWAYS LTD