Kensington & Chelsea
Basement Impact Assessment (BIA)
Planning is a legal procedure to which standard questions are applied. Croft Structural Engineers has developed and continues to evolve its documents to ensure that they meet the Council’s planning requirements.
The driving document in K&C is the Subterranean Planning Document (SPD). This is linked closely to the SPD supplements Unitary Development Plan Policy CD32.
There are numerous areas that are covered in our BIA. As the Council develops its SPD requirements our BIA’s are evolving. Recently RBKC has added an Engineering Design and Construction Statement (EDCS). The EDCS was something that Croft Structural Engineers included in its original BIA.
Our standard BIA for a single storey basement is typically 80-90 pages long. Croft Structural Engineers provides a service and this covers:
- Site Inspection
- Meeting with an engineer to discuss the needs of the projects and specific requirements
- Walk over survey to determine what the requirements of the site are
- Review of local trees (not a full arboricultarlist report, but one can be commissioned)
- Review of adjacent buildings where access is available
- Are there signs of subsidence locally
- Testing
- Arranging soil investigation report
- Bore holes to confirm ground and water tables
- Reports by a geotechnical engineer
- Arranging Hydrology report
- Desk Study – This forms the bulk of the BIA and will cover
- Structural Schemes of internal layouts
- Proposed use and loadings
- Retaining wall designs
- Anticipate deflections of retaining walls.
- Local Stability
- Highway loadings
- Ensure that the scheme “Maintains Structural Stability of the building & Neighbouring Properties”.
- Suggestions for monitoring during the works of neighbouring buildings.
- Are there slopes that may slip?
- Are landslides a concern?
- Are there signs of subsidence locally?
- Is network rail of the underground near?
- Are there listed buildings close to the site that may be affected?
- Water Flow and Hydrology
- Review of local water tables.
- Will the development affect London’s Main aquifer
- Will drinking water supplies be affected.
- Local water course reviewed within 100m
- Are we close to drift deposits – springs are likely to occur near changes in ground from sands to clays.
- Flood Risk Assessment
- Review on flooding
- Comment on whether the development may affect the Hampstead Heath Swimmers.
- Avoid Adversely Affecting drainage and Run off.
- Review of environment agency information
- Loss of Open Space or Trees
- Review of local trees, their location and the affect the basement may have.
- Arrange appointment of Arboricultarlist if many or impart trees are to be affected.
- Construction Process
- Method statement on how the contractor should approach the work to safely complete the design.
- Recently added is the initial temporary design details for the basement.
There are other items that may be required to complete the planning procedure and our BIA will not be the only document. You will need a planning drawings and design and access statement. If buildings are listed or near listed building then a Historic planning consultant may be necessary. On specific sites additional geotechnical advice is necessary to confirm soil movements to adjacent properties. We are here to help with the process where we can and will advise and bring people on board where appropriate.
RBKC also requires that the building should comply with ecological requirements for the entire building: With particular reference to water recycling and power.