Navigating Retrospective Planning Permissions: A Sustainable Drainage Solution for a Livestock Barn.

Livestock barn

Following a prior objection from the Greater Cambridge Shared Planning team, FPS Environmental Ltd assisted our client with gaining retrospective planning permission for the sustainable drainage element of their agricultural development. A single barn structure (stabling) which had been constructed to provide shelter for two pet alpacas, required a sustainable drainage solution that did not dispose of any water off site.

The barn had a roof area of 107m2 and was situated in a field with an area of approximately 0.975ha, in an agricultural setting. This rural site is located to the north-east of Oakington Road, approximately 5km north-west from Cambridge City centre. The Beck Brook, an EA designated Main River is located approximately 190m north-east of the site. Beck Brook confluences with the River Ouse (Main River), approximately 8km north of the site.

Cambridgeshire County Council as the Lead Local Flood Authority (LLFA) required any drainage strategy to follow their Surface Water Planning Guidance, July 2021 and Cambridgeshire Flood & Water Supplementary Planning Document (SPD), 2016 to ensure that new developments ensure that the discharge of surface water could be sustainably managed and not increase the risk of flooding on site or elsewhere.

After Consulting Cambridge County Council LLFA, our approach proposed was to harvest the rainwater for use on site, ensuring that the rainwater harvesting tank has a low enough permanent water level to allow for storage of the 1% AEP (100yr Return Period) plus an allowance of 40% climate change. It was proposed that unused/excess water would drain into either a soakaway or an infiltration blanket and the solution modelled using MicroDrainage 2020.1.3 software.

The drainage team discussed the current proposals and strategy with the LLFA and stated:

 After a careful review of the proposals, and taking into account there is no significant increase of impermeable area and part of the site has been partly developed and any exceedance flows would be manage on site we have no objection to the proposals.

Result: Permission Granted ✅

Reference: 23/01831/FUL

By working with FPS Environmental Ltd, our client smoothly secured the needed planning permission for their livestock barn’s drainage system. Our approach, balancing site specifics with local regulations, led to a sustainable solution that got the green light from authorities. This success showcases how our practical expertise can help others facing similar planning hurdles, making the path to approval less daunting while ensuring environmentally sound outcomes.

Our scope of works included:

  • Reviewing topographic survey of the site.
  • Obtaining catchment data for the site from the Flood Estimation Handbook (FEH) web portal.
  • Obtaining sewer record plans from Anglian Water.
  • Submiting Developer Services Enquiry to Anglian Water to understand the capacity of the local sewer network in relation to the surface water and foul water flows from the proposed development, and to determine allowable surface water discharge rates.
  • Calculate existing and proposed runoff rates and volumes at the site.
  • Producing an appropriate outline surface water drainage strategy, in-line with the drainage hierarchy, to include consideration for SUDS as appropriate. Storage requirements based on the total impermeable area of development and will be designed to attenuate surface water storage volumes up to and including the 1 in 100 year storm, with consideration for future climate change, in-line with national guidance and any supplementary local guidance
  • Producing a plan drawing of the surface water drainage scheme, outlining any methods employed to delay and control surface water discharge from the site and the measures taken to prevent pollution of receiving groundwater and/or surface waters.
Surface Water Drainage Design for Barn
Rainwater harvesting schematic

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