The Daventry International Rail Freight Interchange Alteration Order 2014

Flood Risk and Surface Water Drainage

23.  No phase of the authorised development is to commence until a surface water drainage scheme for that phase based on sustainable drainage principles and an assessment of the hydrological and hydrogeological context of the development in accordance with the Surface Water Drainage Strategy submitted with the application at appendix E1 of the environmental statement (Document 6.2) has been submitted to and approved in writing by the relevant planning authority or in accordance with such other approval process that may be prescribed under the Flood and Water Management Act 2010. The scheme must include:

(a) provision for limiting the surface water run-off generated by all rainfall events up to the 1:100 year plus 20% (for climate change) critical rain storm so that it will not exceed the run-off from the undeveloped site and not increase the risk of flooding off-site;

(b) provision of surface water run-off attenuation storage to accommodate the difference between the allowable discharge rates and all rainfall events up to the 1:100 year plus 20% (for climate change) critical rain storm;

(c) detailed design (plans, cross sections and calculations) in support of any surface water drainage scheme, including details of any attenuation system, and the outfall arrangements; and

(d) details of how the scheme is to be maintained and managed after completion.

The scheme must subsequently be implemented in accordance with the approved details or in accordance with any variations to the details agreed in writing by the relevant planning authority prior to the completion of the authorised development.