CODE OF PRACTICE FOR SUBDIVISION AND DEVELOPMENT

Part 4 – Drainage4.2.7 The Hydraulic Design of PipelinesThe hydraulic design of storm water pipelines shall be based on HR Wallingford’s “Tablesfor Hydraulic Design of Pipes, Sewers, and Channels” or on graphs or otherrepresentation of the same or similar accepted method.The pipe roughness co-efficient k s used in the hydraulic design shall be nominated by, oragreed upon, with the Engineer on the basis of commonly adopted modern engineeringdesign practice, and will take into account the increased roughness resulting from age.The co-efficient k s shall not be less than 0.6mm. As a guide k s should be taken as 1.5 forpipes up to 750mm diameter and 0.6 for pipes greater than 750mm diameter.The hydraulic gradient shall be the pipe gradient at design flow (20% AEP), with nosurcharging at manholes.The design shall provide that:(c)(d)(e)No storm water sewer other than connections is less than 150mm internal diameter.Road catchpit outlets shall be not less than 225mm internal diameter; or exceed25m in length.Catchpit leads shall not be connected to other catchpits.A minimum velocity of 0.7m/s at 50% of design flow is desirable but lower velocities are attimes unavoidable and may be permitted by the Engineer.Special measures to dissipate energy may be required at connections and outfallstructures.Pipe entry conditions are to be considered at all pipe entries and entry and exit lossescalculated.4.2.8 Location of PipelinesStorm water drainage pipelines shall generally be sited clear of buildings and fences,0.5m to 1.0m from boundaries in front, side or rear yard areas of development sites or inreserve areas.In cases where pipelines are laid within the building area on lots, the Council will requireConsent Notice pursuant to RMA Section 221 restricting the erection of buildings over orwithin 1m of the pipeline, requiring specific design of building foundations located within ahorizontal distance of the pipeline equal to the invert depth of the pipeline. Pipelinesgreater than 450mm diameter shall generally be located within overland flow paths.If storm water pipelines are required to be laid within the road reserve they should be laidwithin the road berms wherever possible.Road crossings to be at 90 o wherever possible and in no case less than 45 o .Crossing of other services shall be at not less than 45 o .Code of Practice for Subdivision and Development – Edition 5 October 2010 Page 60