Code of practice on surface water drainage
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| 4.3 Closed Drainage System 4.3.1 The internal width and clear depth of a roadside drain (including entrance culvert) shall beat least 600 mm. 4.3.2 The provision of gratings, openings and chequered plates for closed drains shall comply with Clause 9.11. 4.3.3 Culverts Across Roads Only box culverts shall be provided. The internal width and clear depth of a box culvert shall beat least 600 mm. For culverts across expressways and semi-expressways, the minimum size shall be 1.0 m x 1.0 m. 4.4 Internal Drainage System 4.4.1 Internal drains shall be designed with sufficient capacity and openings to intercept and discharge all runoff from the development site. 4.4.2 Internal drains shall be designed for safety and ease of maintenance. 4.4.3 Prior to discharging any storm water within the development site to the roadside/outlet drain, vertical gratings) shall be installed at the outlet discharge points) of the internal drains) located within the development site. 13 4.4.4 Internal Conduit Drain Where the open backyard area of each intermediate terraced development is not linked to the front yard by a corridor at ground level, a conduit drain for conveying surface runoff may run beneath the building itself. The conduit drain shall beat least 300 mm in diameter. The conduit drain shall be laid straight without any bend or sag in its alignment. At both the inlet and outlet ends of the conduit drain, maintenance sumps shall be provided with invert level drops of at least 150 mm deep. The conduit drain shall be fully supported along its entire length by (and not attached to) the ground beams of the building and shall form as part of the permanent structure of the building to ensure against settlement. 4.4.5 Drainage for Air Wells Courtyards Conduit drains serving the air wells or courtyards shall be designed to cater for the runoff and shall beat least 150 mm in diameter. Maintenance sumps) should also be provided. If the drainage of the air wells runs through more than one premises, the size of the conduit drain shall comply with the requirements of the common drain as stipulated in Clause 4.5.1. Download 3.37 Mb. Share with your friends:
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