Our client from Richmond upon Thames, in London, approached us because their basement extension application had been refused previously, owing to new planning guidance launching the week before their application was considered. The proposed redevelopment included a finished floor level of -2.6 m below the existing ground floor.
Richmond’s guidance states that “planning applications which feature basements will need to provide supporting information regarding the potential level of impact the proposed development will have. The applicant will need to show that the proposal will not adversely impact the site, neighbouring properties, and the wider natural environment. This includes impacts to groundwater and water transferred via throughflow.” The latest guidance can be found here.
H Fraser Consulting interrogated the new guidance (which is quite different from that of other London Boroughs), seeking advice from the Local Authority where necessary. We undertook a groundwater Basement Impact Assessment (BIA) incorporating the latest planning guidance and the planners comments. The study included the following elements:
- Desk Study;
- Screening;
- Scoping;
- Site Investigation, monitoring, and interpretation of findings;
- Impact Assessment
The H Fraser Consulting Team applied a logical conceptualisation of the site based on a common sensical approach. Whilst further monitoring is often recommended in the guidance, it was realised that the information collated as part of the desk study was sufficient to demonstrate that whilst there was a groundwater flood risk, the worst case potential groundwater flooding scenario could be mitigated against.
Planning was successfully granted, and quickly too! For more information about our basement redevelopment support services and BIA assessments in London, you can visit our dedicated page here.
