Drainage Strategy for Planning Applications
Fast & Reliable Reports to Accompany your Planning Submissions
Chartered Drainage Engineers Experts in Drainage Strategies
Our drainage strategy assesses the most sustainable way to discharge water safely whilst complying with the Local Drainage guidelines and the National Planning Policy Framework (NPPF). We also evaluate the management of foul water and determine whether the existing public sewer network requires upgrade.
Our experience allows us to manage water in difficult sites such as flood zone areas, contaminated land, steep or flat slopes or areas located within groundwater protection areas. Our drainage assessments take into consideration the results of the flood risk assessment and drainage strategy guidance.
Our Drainage Strategy Report
Our reports comply with the lead local flood authority standards, the national guidelines, the CIRIA Sustainable Drainage Systems Manual and Sewer for Adoption 8. See below for a list of our pricing:
How Do We Work?
We will get the available soil information from online databases and (if required) scope the soakaway tests.
You receive our drainage layouts based on expected infiltration rates and public sewer capacity.
You will be able to utilise our report to register or validate your planning application. We will support you through the planning process.
We will obtain quotes for soakaways, contact the local water company and agree the drainage design with the lead local flood authority.
Fully Approved by the LLFA
Compliant with the water company standards
Exceedance paths assessed
Water quality assessment
All the network modelled using Windes.
Our Sustainable Drainage Strategy Methodology
Our ethos of working in partnerships allows us to incorporate benefits into the design at a very early stage. We have worked with developers, contractors, architects and planning consultants to create sustainable developments in which water plays a fundamental part.
We obtain your development’s drawings and topographical survey levels in mAOD and site location.
We consult the local water company, the lead local drainage authority and the local council and obtain their records to give the development more certainty on the approval.
We scope the soakaways. When required, we obtain quotes from our recommended contractors.
Our designs reflect the most suitable and sustainable drainage system for the soil type, and the quantity and quality of water.
We are proactive engineers who have an in-depth understand of the need for efficient and sustainable drainage solution within developments. As drainage strategy consultants we create long standing partnerships with architects and developers.
Frequently Asked Questions
What is a drainage strategy?
The lead local flood authority requires the provision of a drainage strategy for all major developments in England. The aim of a drainage strategy is to determine the most sustainable way to disperse and discharge water without causing flooding to others and the development. A drainage strategy includes the assessment of the soil conditions, the discharge points and of the suitability of multiple sustainable drainage systems such as swales, ponds, block paving and water butts.
How do you manage a drainage system?
SuDS should be designed according to the following standards:
- Designed and located to facilitate maintenance.
- Suitably surfaced access tracks for access to the SuDS.
- Controls and de-silting features should be easily accessible from the surface.
- Silt traps should be accessible for manual clearance or suction vehicles.
- Separator should not require man-entry for inspection or emptying.
The maintenance activities for the Sustainable Drainage Systems (SuDS) are fully paid for by the developer, unless they have been adopted by an statutory authority such as the local council. This adoption can be achieved through the use of the Section 106 agreement/separate agreement with the City, district, town or parish council. As part of this agreement, a service management company or private individual/individuals pay Commuted Sums for maintenance.
Sustainable drainage systems SuDS can also be maintained by the local water company using an adoption process. The sustainable drainage system design must follow the rules given in the Design and Construction Guidance (DCG) document. These rules apply to all water and sewerage companies in England from 1 April 2020.
What is a drainage assessment or SuDS report?
A drainage assessment is a specific requirement set out by the lead local flood authority for all major applications. The Drainage Assessment may be part of the Flood Risk Assessment or vice versa. A drainage assessment includes the best practice design for the safe disposal of surface water run-off and includes information on the detailed design, management and maintenance of surface water management systems.
For some councils, soakaway tests to BRE365 need to be undertaken at planning stage.
Are Thames Water responsible for my drains?
It depends. As a rule, a public sewer becomes public when two pipes from different sites/dwelling areas joint into a manhole. If the manholes at which the two pipes join and the pipe downstream is a public sewer then Thames Water is responsible for its maintenance.
Thames Water shares maintenance responsibility of the pipe from the boundary chamber (the last chamber within your property) and the public sewer.
What are surface water drainage systems?
Surface water drainage systems are a group of structures that act to manage and dispose of rainwater falling onto a development. Rainwater is managed as close as possible to the roofs or surface, permitting water to evaporate, retain or soak into the ground. For example, by using green roofs and permeable surfaces that allow infiltration. The extra runoff water can be either discharged using ponds or drained to the nearest watercourse. This extra run-off should be discharged at the same rate and volume or lower as would naturally have occurred prior to development.
In the past (and still today) underground piped systems were used to rapidly divert and move surface water runoff to local watercourses or the sewer system. This process did not allow for water to soak into the ground and enter the natural water cycle. The use of this system reduces the capacity of the environment to easily recharge the groundwater aquifers, which results in the disruption of base flow in streams and rivers. Moreover underground piped systems moves water faster which can increase the risk of downstream flooding and lead to a deterioration of water quality.
Can Sustainable Drainage Systems (SuDS) be adopted?
Yes. There are four options for developers to adopt and maintain surface water drainage systems SuDS:
- The local sewerage undertaker or water company could adopt and maintain all SuDS except permeable surfaces, water butts, green roofs and rainwater gardens.
- Adoption could be agreed through a Section 106 (of the Town and Country Planning Act 1990) agreement/separate agreement with the city, district, town or parish council and pay the Commuted Sums for the maintenance.
- The developer can set up or use a service management company.
- The SuDS can be adopted and maintained by private individuals when the SuDS serve individual properties.
- The highways authority can adopt and maintain SuDS that serve only the highway.
The adoption and maintenance of all surface water drainage within a development would have to be discussed and agreed with the local planning authority and the lead local flood authority.
How do sustainable urban drainage systems work?
Sustainable urban drainage systems work by making water closer to people and creating streetscapes where people and communities can interact.
The SuDS in urban environments also work by achieving the principles of controlling water volumes, reducing temperatures of surfaces, and making stable urban environments that are more resistant to drought and flooding.
To achieve these principles, places where water interaction is possible should be introduced. For example: green walls, rainwater gardens, street water gardens, reflective ponds, water playscapes and plant drills.