1)
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To assist with Condition 3
The report provides no reference to the existing SuDS that were implemented on the site as part of the previous permission in 2018. It is understood that permeable paving was implemented for part of the paved area and a rainwater harvesting tank was installed with an overflow into the sewer network. Clarification is required to confirm what existing drainage infrastructure will be retained.
The proposed strategy will limit surface water runoff to the sewer network by over 50%. The strategy includes a 7m3 attenuation tank beneath the artificial lawn in the rear of the garden. The section provided in the rear of the submission specifies Tarmac above the attenuation tank. Although this is believed to be an error, it is important that the proposed surfacing of this part of the garden is clarified to avoid any confusion. A plan should be provided to set out the details for the proposed external surfacing for the entire property and identify which will be retained as or created permeable.
In addition, the section should demonstrate how the attenuation tank will interact vertically with the existing basement constructed under part of the rear garden. Detailed sections should be provided (as requested in Point 4 of Condition 3) to clarify the vertical profile of the entire drainage infrastructure.
Amended information should be secured through a new submission under Condition 3, and consulted upon etc, before it could be agreed that the requirements of Condition 3 have been adequately discharged.
2)
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To assist with Condition 8
The Indicative Drainage Layout contained in the appendices for the drainage assessment includes a sump pump for the surface water drainage and non-return valves in the surface water network. The foul sewage pipework is not shown and therefore does not adequately demonstrate that the property and proposed basement will be protected from sewer flooding in line with Condition 8. A comprehensive drainage plan, including foul and surface water connections, as well as the location of any pumped devices, should be provided.