The Northumberland County Council (A1 – South East Northumberland Link Road (Morpeth Northern Bypass)) Development Consent Order 2015

Drainage and water pollution post-construction

11.—(1) The authorised development must not be commenced until a surface water drainage scheme detailing how flood risk will be managed, how highway runoff will be treated before being discharged to a watercourse and the spillage protection measures to be provided has been submitted to and approved by the relevant planning authority in consultation with the Environment Agency.

(2) The measures stipulated in the approved surface water drainage scheme must be completed before the link road is opened to public traffic, and subsequently retained.

(3) The surface water drainage scheme must include—

(a) compliance with the Flood Risk Assessment and the following—

(i) a 1 in 2 year return period storm, with storage and attenuation to accommodate a 1 in 100 year return period storm without flooding outside the system or the designated storage areas;

(ii) discharges to watercourses to be greenfield runoff rates not greater than 4 litres per second per hectare; where they coincide with existing flows then the discharge rate must be the sum of the greenfield runoff and the existing flow; and

(iii) climate change allowance of +30% for the scheme lifetime;

(b) details of the drainage measures to be provided to manage flood risk;

(c) details of measures to treat highway runoff from the authorised development to avoid pollution of receiving watercourse;

(d) details of measures to protect receiving watercourses from spillages of pollutants on the link road;

(e) measures to prevent the infiltration of highway runoff into the ground;

(f) details of measures to manage overland flow intercepted by the authorised development; and

(g) details of how the measures in the surface water drainage scheme are to be maintained and managed after completion of the authorised development.

(4) For the purposes of this requirement, the expression “highway runoff” means water runoff from the surface of the completed link road, A1 trunk road within the Order limits, and their embankments.