Rural Barn Conversion Development.

This case study reviews a surface water and off-mains sewer design for a redevelopment of a Grade-2 Listed barns site in Shropshire, to provide three new dwellings, an office and a gym. A sustainable drainage (SuDS) scheme was designed to provide an attractive feature as part of the development.

Site Constraints

As the site is located in a remote rural location, no public foul sewers were available to connect to and therefore a design for a private ‘off-mains’ sewer network was required. The site had poor infiltration rates for surface water and failed the BRE Digest 365 test, so a pond was required. Also, as a group of listed buildings as part of a historic farm, care was required to place below ground pipe networks to avoid intrusive work to the buildings were possible.

How We Approached the Design

The Berrys engineering team always approach the design of infrastructure holistically, so that integrates well with the wider site design and maximises the planning benefits. This is how we approach the SuDS scheme for this site, so we designed an attractive attenuation pond that suited the rural character of the development and provide wetland and aquatic habitat. The attenuation pond also provides a treatment stage to the site surface water runoff, so water is cleaned prior to flowing to a receiving watercourse. This drainage system was also cheaper to construct than an equivalent storage tank type solution.

Berrys designed a foul sewer system for the site which flows to a ‘packaged’ sewage treatment plant, before flowing to a drainage field soakaway. The latest type of treatment plan was specified, which has no moving parts and uses an air pump to aid anaerobic digestion of wastewater, ensuring that the effluent is cleaned beyond the statutory requirements.

Calculations were made for the drainage elements and the designs were modelled using the latest Causeway Flow hydraulic design software.

The drainage design was expediently approved by the Local Lead Flood Authority with no queries raised.

For information and assistance with your development drainage designs please contact Richard Harman.