Drainage Design

Drainage Design


Sustainable Urban Drainage Systems (SuDS) design is at the core of stormwater management aiming to mimic natural performance while managing rainfall locally. We use infiltration options, attenuation systems and innovative layout arrangements to ensure maximum value is derived for the asset life.

We also produce comprehensive wastewater and foul sewer designs for efficient management of wastewater, ensuring the maximum benefit is derived from the system. In summary we produce the following :

  • Drainage strategy reports;
  • Drainage Design for stormwater management 
  • Drainage design for waste and Foul 
  • Sustainable Urban Drainage Systems Design (SuDS Design)
  • Flood Risk Assessment reports (FRAs),

The Need For Drainage Design


A well-considered solution for the discharge of unwanted water is a criterion often poorly considered during the early stages of projects in both building and transport infrastructure. A drainage system will only be effective if sufficient effort is put into the planning stage. A well thought through, practical and sustainable drainage strategy can be the key to unlocking development potential and or overcoming planning obstacles. What is involved will vary from site to site and our highly experienced Engineers are experts in developing well-balanced drainage strategies and designs towards providing cost effective solutions to discharge planning conditions and meet project requirements.


Surveys Required For Drainage Design


It is important to get surveys commissioned earlier in the design process and different site will have different requirements. Typical surveys for a drainage project are as follows: 


Topographical Survey

This is usually available as its one of the first considerations for Architects and Engineers when developing a site for any building or transport infrastructure. Topographical surveys involve the production of maps and plans to accurately represent the details of the natural and built environments.  For drainage purposes the survey scope needs to include cover levels and invert levels to any drainage chambers on the site. This information and wastewater and surface water stats plans should be used 


Drainage CCTV Surveys

The drainage survey picks up detailed information about the drainage infrastructure  such as invert levels, drainage network (Verified with foul and storm water Stats information), gully and manhole details, SUDS details focusing on location and condition of the existing drainage system. 


Statutory undertaker Information (STATS) 

 Details of existing statutory services in and around the site will be needed and can be procure via the C2 utility enquiry process. This helps gather all the information about the presence of underground utilities. A Ground penetrating radar (GPR) survey is also recommended subject to the scale of the development. A GPR Survey is a geophysical locating method that uses radio waves to capture images below the surface of the ground in a minimally invasive way that enables identification of underground utilities within reasonable level of accuracy (PAS 128 GPR Survey).


Soil Investigation

A soil investigation is usually carried out for structural and geotechnical engineering purposes, but it gives the opportunity to include tests for percolation rates. This test is used to determine the infiltration rate for SUDS options such as Soakaways or rain gardens. The BRE 365 test is the industry standard for infiltration tests, the video shows how to undertake the BRE365 test to determine the infiltration rate for a sustainable drainage system design.

Geo environmental surveys are also undertaken to confirm the presence of contaminants on site.  Some sites may contain contamination, and this may affect the drainage design options and layout. For instance, soakaways cannot be installed in contaminated land. 


Working Closely With You


We have vast experience dealing with Drainage Design covering many different types of proposed developments and highway infrastructures for our clients. We provide innovative, technically sound and robust solutions that are also cost-effective and would welcome the opportunity to provide the support you require on your project. 


Highway Engineering


We understand the importance of highways for both connectivity and economic growth and it forms the basis of our civil engineering offering. We design complex highway schemes using cost-effective and sustainable solutions from concept design to detailed design. Our work includes geometric design, pavement design, drainage design and other associated elements of highways infrastructure.  New developments generally requires, new access road, car park, hard landscaping and dropped kerbs where necessary in support of the architectural layout plan. 

SECTION 278 / SECTION 38 planning support: As specialists in the design of highways and associated Section 278 & S38 agreements for private developments, our work is tailored to match up the Developer & Council’s requirements to ensure an efficient design output.

Flood Risk Assessment


Drainage design and flood risk assessment are integral to successful planning applications with great emphasis on Sustainable Drainage Systems (SuDS) for stormwater management. SANDS Engineers are highly experienced in developing well-balanced drainage strategies and designs towards providing solutions to discharge planning conditions and project requirements.

Flood risk assessments are used to assess risks of all forms of flooding to a development and our drainage designs demonstrate how these flood risks are to be managed as part of the development while taking climate change into consideration. Our flood risk assessment provides a detailed analysis of multiple sources of flood risk proving specific mitigation strategies that apply to your development. Meeting all planning policies and being cost-effective in the easing of flood risk.

Road Safety Audits

Road Safety Audit is often required by highway and planning authorities when changes are proposed to an existing highway or in the creation of a new one. The objective of Road Safety Audits (RSA) is to identify aspects of engineering interventions that could give rise to road safety problems and to suggest modifications that could improve road safety. It is a process that is undertaken by Road Safety Auditors independent of the design team.

Traffic Management Plans

Traffic Management Plans during construction are one of the most significant elements to consider. We produce Chapter 8 traffic management plans for construction activities involving the highway network and construction site movements.  We work in conjunction with the local approving authority for TMAN approvals with designs aimed at minimising the impact on the network, road users, residential and business premises in proximity of the proposed works.