Drainage Design from Planning to Construction

Common Sense Designs

Chartered Drainage Engineer Experts in Sustainable Drainage System Design (SuDS) and Highway Drainage Design

We work closely with our clients throughout the entire process: from design outline to construction. Our designs include drainage strategies, tender drainage drawings, detailed drainage drawings, sewer permit applications such as sewer requisition, adoptions and connections, and detailed designs of pumping stations.

Our designs aim to maximize the use of sustainable drainage solutions where use of material and energy is minimized.

We have extensive experience in dealing with water companies and the lead local flood authority standards for the adoption of sewerage systems.

We use the latest WINDES micro-drainage software and 2D modelling of surface water run-off to evaluate the foul and surface water designs.

Detailed Drainage Design Services

Our detailed drainage design services are fully compliant with building regulations, Sewers for Adoption: A Design and Construction Guide for Developers, lead local flood authorities guidance and the CIRIA SuDS Manual.

Drainage Strategy
Drainage report for planning applications in full compliance with local and national regulations at competitive prices. 
Foul Water Drainage Design
Foul sewer design from feasibility to construction. Designs are fully adoptable and in compliance with building regulations.
Sustainable Drainage System
SuDS Designs that take into account the needs of your development and are fully adoptable and modelled to safely manage the surface water run-off.
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Our Benefits

Experience

We are proactive in following up with the water companies and the lead local flood authority to get your development underway.

Expertise

We are fully up to date with legislation and guidance from the water companies and the lead local flood authorities in England.

Success

We have 100% success in designing drainage systems and obtaining approval from the water companies, lead local authorities and building control.

No Extra Fees

Our prices are competitive and fixed.

Our Methodology for Drainage Design

We have worked with developers, contractors, architects and planning consultants to design drainage at different stages of the project. During the planning stages we work with planning consultants and developers to get planning approval. In order to create our designs we work with architects, developers and contractors to produce the best designs for the development.

Our ethos of working in partnerships allow us to  incorporate benefits into every stage of the design process.

urban-water-location-flood-risk
Obtain project Details

Obtaining your development’s drawings and levels in mAOD.

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Consult Authorities

We consult the local water company, the lead local drainage authority and the local council and obtain their records to give the development a better chance of being approved.

urban-water-submit-report-flood-risk-drainage
Scope Investigations

We scope the site using CCTV surveys, Topographical and service information, and complete an initial model to check the location of the main infrastructure and how it fits within the development.

urban-water-report-flood-drainage
Create a Drainage Design

We work together with multidisciplinary teams to get the most sustainable and cost effective drainage design for your development.

We strive to maintain ongoing partnerships with architects and developers.

Let's Get Your Project Started

Other Services

Climate Change Adaptation
Green infrastructure and nature-based solutions to Zero Carbon for the protection of communities.
Flood Risk Assessment
We implement detailed flood risk assessments that your planning application can rely on.
Sustainable Drainage System
Our detailed Sustainable Drainage Designs are council-approved and fully adoptable. 
Sequential-Test

Sequential and exemption reports in compliance with the local councils. 

Let's Get Your Project Started

Frequently Asked Questions

What is the minimum slope for drainage?

The minimum slope for surface water drainage in a house is: 1:100 (1%) for a 100mm pipe. Foul Sewer drainage is 1:40 with a 100mm pipe for a single connection that carries a flow less than <1l/s (this is usually a combination of a WC, sink and shower).If there are more fittings discharging to the pipe then the slope is 1:80.

For more than one house and industrial areas, the minimum slopes for a pipe should be able to carry the design flows without surcharge and maintain a self-cleansing velocity when carrying the design flow. A self-cleansing velocity is one that is able to carry away any solids within the water and prevent sediment or scaling and eventual blockage.

Foul flows are relatively low and can on most small sites be conveyed in 100mm diameter pipework. It is however considered good practice to provide a minimum size of 150mm for main drainage runs where a number of WC’s may be connected as this helps prevent blockages. The individual branch runs or laterals installed can remain at 100mm diameter. Anything over the flow from 10 houses should connect to a DN150 with a minimum slope of 1:150. If there are less than 10 houses connected the pipe size should be 100mm and have a slope of 1:100. This needs to be agreed in advance with the water companies at the design stage.

How deep should drains be?

The minimum depths for drains without protection should be as follows:

  • 0.35m for domestic gardens or pathways without car loading.
  • 0.50m for domestic driveways and areas where the gross vehicle weight is less than 7.5 tonnes.
  • 0.9m for domestic driveways, parking areas and narrow roads with limited access to gross weight higher than 7.5 Tonnes.
  • 0.9m for agricultural land and public spaces.
  • 1.2m for other highways and parking areas with unrestricted vehicle access.

What is a drainage structure?

A drainage structure is a structure that aids the movement and management of water. These structures can be manholes, pipes or any sustainable drainage system and outfall.

What surveys and investigations are required for the drainage design?

It is important to get surveys and investigations commissioned at an early stage to provide information to develop the drainage design.

  • Topographical Survey – If not already available, this needs to be organized and the surveyors should be asked to record both cover levels and invert levels to any drainage chambers on the site. They should also be asked to plot the routes of drainage runs where possible. Quite often the survey information relating to drainage is limited and it will be necessary for the drainage engineer to carry out their own additional survey.
  • Services Information – Details of existing statutory services in and around the site will be needed. This information may be provided as part of the topographical survey or can be provided by the mechanical or electrical engineer. If this is not the case then searches will need to be arranged with the various service providers. It is important to know the positions and depths of existing services to avoid clashes with any new drainage.
  • Soil Investigation – A soil investigation is usually carried out for structural engineering purposes but it gives the opportunity to include tests for percolation rates. If soakaways are thought to be an option for surface water disposal then a test to BRE 365 should be requested and if the site requires treated effluent to be discharged to ground, then a test to BS 6297 should be requested. Likewise, if a new road is to be built CBR tests are appropriate.
  • Contamination – Some sites may contain contamination and this may affect where drainage is installed or what materials are used. Generally soakaways cannot be installed in contaminated land. The parameters of any investigations for contamination will come under the scope of the environmental engineer. It is critical that both engineers work together closely, as one element leads the other and vice versa.
  • CCTV Surveys – Closed circuit television surveys may be needed to ascertain the position or condition of existing drainage. Where information on existing systems is limited it may be necessary to commission a CCTV survey to establish exact routes. If it is the intent to reuse existing drainage as part of a new scheme, the CCTV survey is useful to establish the condition of the drainage and if it is able to provide suitable long term use or if any remedial works should be carried out.
Let's Get Your Project Started

What are the consultations with the water companies?

The initial consultations with the water authorities are:

  •  Sewer Plans: these must be acquired from the local water authority. An annotated street plan must be provided to indicate the specific area for which the information is required. The results are usually received within a week.
  • Capacity Checks: If it is possible that a proposed development will increase flows to a sewer, then it is a requirement to get a capacity check carried out by the local water authority. The process does vary across the different authorities and it usually requires a form to be filled out and returned. These capacity checks can incur a fee from the local water authority.
  • It is also important to obtain the baseline discharge flows, as well as to ascertain the potential for the adoption of sections of the sewerage system. 

What are the consultations with the Environment Agency?

 The Environment Agency are responsible for the many aspects of a development. The common issues relating to drainage design are:

  • Consent to discharge: This is an application that is required if sewage treatment and disposal is to take place on the site and necessitates a great deal of information for completion. This will require details such as borehole logs, percolation tests and local environmental information etc. The approval process for a consent to discharge has a statutory limit of 4 months but can often exceed this.
  • Light Liquid Separators: Petrol interceptors are needed wherever there is a risk of oil or petrol pollution. They are usually provided as a matter of course in large car parks and where oils or fuels are stored or delivered. Consultation may be needed with the EA in some specific installations. Most small car parks are best treated using source control sustainable drainage methods. A small car park is generally defined as having under 20 spaces.
  • Planning Consents: On the majority of projects the EA will be consulted by the local planning authority to gain their input on environmental matters that may be relevant to the development. The Environment Agency’s feedback is usually incorporated into the planning conditions which are not always available to the design team until after the project has begun. It is therefore important to speak to the EA at an early stage to avoid any surprises when the planning conditions are released.
  • Flood Risk Activities Permit: If the design involves connecting to a water course or carry out works within 8 metres of a water course then a flood risk activities permit may be needed and the Environment Agency should be consulted to determine if your proposals require a formal application.

What are the design standards used for the design of underground drainage?

  • Building Regulations: Part H
  • British Standard EN 752 2008: Drain and Sewer Systems Outside Buildings. This will provide information on the design of both small and large scale drainage systems.
  • BS 12056 2000: Gravity Drainage Systems Inside Buildings. This document essentially covers above ground drainage systems and contains detailed information on the sizing of soil and waste pipes together with rainwater pipe and gutter sizing.
  • Sewers for Adoption: A Design and Construction Guide for Developers: This is a design and construction guide for drainage and pumping stations to be adopted by water authorities. If drainage on your site is to be considered for adoption then it will need to meet the requirements of this document. The local water authority may also have its own additional requirements and this should be checked with them to see if they have a supplementary document.
  • The SUDS Manual: This is a very comprehensive document that explores in detail the best practice methods for the design of sustainable drainage systems.

Sequential Test – District

Sequential Test City District - Urban Water

Our Benefits:

  • Immediate communication with council to determine study area
  • Report in accordance with the local guidelines
  • Assess multiple resources of planning information as per agreed with the council
  • Give preliminary advice on potential sites
  • Recommend appropriate site for assessment
  • Allows for one set of consolidated comments/amendments following the first issue of the report 

What we need from you:

  • Site Address
  • Development Plans
  • Local Planner Contact Details

Single House

Sustainable Drainage Systems Single House

Key Benefits:

  • Design compliant with Building Regs and local water company
  • Scope of site investigations
  • Capacity Assessments from Water Companies
  • Undertake Detailed Hydraulic Modelling
  • Clear Planning Conditions
  • Produce Construction Drawings
  • Providing drawings in .pdf

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Minor Development

Flood Risk Assessment Single House

Key Benefits:

  • First draft in 48 hours with the final report in 20 days (dependent on ea information)
  • Report in accordance with the environment agency and with national policy planning framework
  • Allows for one set of consolidated comments/amendments following the first issue of the report

What we need from you:

  • Site address
  • Development plans
  • Topographical ground levels

Major Development

Flood-Risk-assessment-Major-Development

Key Benefits:

  • First draft in 48 hours with the final report in 20 days (dependent on ea information)
  • Report in accordance with the environment agency and with national policy planning framework
  • Allows for one set of consolidated comments/amendments following the first issue of the report

What we need from you:

  • Site address
  • Development plans
  • Topographical ground levels

Strategic Development

Flood Risk Assessment Strategic Development

Key Benefits:

  • First draft in 48 hours with the final report in 20 days (dependent on ea information)
  • Report in accordance with the environment agency and with national policy planning framework
  • Allows for one set of consolidated comments/amendments following the first issue of the report

What we need from you:

  • Site address
  • Development plans
  • Topographical ground levels

Single House

Drainage Strategy Single House

Key Benefits:

  • The drainage strategy will inform the flood risk assessment
  • Assessment of available geological records or site investigation if available
  • Obtain and review sewer plans
  • Evaluate potential use of suds applicable to site
  • Determine climate change allowances
  • Undertake basic hydraulic modelling of foul and surface water
  • Calculate storage volumes to comply with suds guidance
  • Indicate discharge points and rates for foul water
  • Indicate applicable suds and volume distribution at a principle level
  • Provide single sketch concept of the drainage strategy
  • Allows for one set of consolidated comments / amendments following first issue of report

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Minor Development

Drainage Strategy Minor Development

Key Benefits:

  • The drainage strategy will inform the flood risk assessment
  • Assessment of available geological records or site investigation if available
  • Obtain and review sewer plans
  • Evaluate potential use of suds applicable to site
  • Determine climate change allowances
  • Undertake basic hydraulic modelling of foul and surface water
  • Calculate storage volumes to comply with suds guidance
  • Indicate discharge points and rates for foul water
  • Indicate applicable suds and volume distribution at a principle level
  • Provide single sketch concept of the drainage strategy
  • Allows for one set of consolidated comments / amendments following first issue of report

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Major Development

Drainage Strategy Major Development

Key Benefits:

  • The drainage strategy will inform the flood risk assessment
  • Assessment of available geological records or site investigation if available
  • Obtain and review sewer plans
  • Evaluate potential use of suds applicable to site
  • Determine climate change allowances
  • Undertake basic hydraulic modelling of foul and surface water
  • Calculate storage volumes to comply with suds guidance
  • Indicate discharge points and rates for foul water
  • Indicate applicable suds and volume distribution at a principle level
  • Provide single sketch concept of the drainage strategy
  • Allows for one set of consolidated comments / amendments following first issue of report

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Single House

Foul Drainage Design Single House

Key Benefits:

  • Design compliant with Building Regs and local water company
  • Scope of site investigations
  • Capacity Assessments from Water Companies
  • Undertake Hydraulic Modelling
  • Treatment Plant Sizing
  • Drainage Field Calculations
  • Providing design in .pdf
  • Clear Planning Conditions
  • Produce Construction Drawings

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Major Development

Foul Drainage Design Major Development

Key Benefits:

  • Design compliant with Building Regs and local water company
  • Scope of site investigations
  • Capacity Assessments from Water Companies
  • Undertake Hydraulic Modelling
  • Pumping Station Calculations
  • Rising Main Design
  • Provide design in .pdf and .dwg
  • Clear Planning Conditions
  • Produce Construction Drawings

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Minor Development

Foul Drainage Design Minor Development

Key Benefits:

  • Design compliant with Building Regs and local water company
  • Scope of site investigations
  • Capacity Assessments from Water Companies
  • Undertake Hydraulic Modelling
  • Pumping Station Calculations
  • Rising Main Design
  • Providing design in .pdf and .dwg
  • Clear Planning Conditions
  • Produce Construction Drawings

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Minor Development

Sustainable Drainage Minor Development

Key Benefits:

  • Design compliant with Building Regs and local water company
  • Scope of site investigations
  • Capacity Assessments from Water Companies
  • Undertake Detailed Hydraulic Modelling
  • Clear Planning Conditions
  • Produce Construction Drawings
  • Providing drawings in .pdf and .dwg

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Sequential Test – City

Sequential Test City Borough - Urban Water

Our Benefits:

  • Immediate communication with council to determine study area
  • Report in accordance with the local guidelines
  • Assess multiple resources of planning information as per agreed with the council
  • Give preliminary advice on potential sites
  • Recommend appropriate site for assessment
  • Allows for one set of consolidated comments/amendments following the first issue of the report 

What we need from you:

  • Site Address
  • Development Plans
  • Local Planner Contact Details

Major Development

Sustainable Drainage Major Development

Key Benefits:

  • Design compliant with Building Regs and local water company
  • Scope of site investigations
  • Capacity Assessments from Water Companies
  • Undertake Detailed Hydraulic Modelling
  • Clear Planning Conditions
  • Produce Construction Drawings
  • Providing drawings in .pdf and .dwg

What we need from you:

  • Site address
  • Site Layout
  • Topographical survey

Zero Carbon Design

Zero Carbon - Climate Change Adaptation

Key Benefits:

  • Complete Cycle Assessment
  • Early Design Optimization
  • Embodied Carbon Calculation
  • Circularity Assessment
  • Carbon Benchmarking
  • Our calculations are based on the LCA standards (CEN/TC350, ISO 218930)
  • It follows the RICS building stages
  • All CO2 values taken from the verified EPD database
  • Compliant with BREEAM UK and CEEQUAL Standards

What we need from you:

  • External Work Layout
  • Initial Drainage Design
  • Site Layouts

Zero Carbon Design

Nature-Based-min.jpg

Key Benefits:

  • Tackle Climate and Nature Crises in Master Planning
  • Example of Using Nature-Based Solutions around the world
  • Utilize the Government’s Research to identify area in which Local and Regional Nature-Based Solutions can be implemented.

Urban Areas

Hydraulic River Modelling - Urban Water

Our Benefits:

  • Models fully approved by the Environment Agency
  • Obtain LIDAR data
  • Produce Hydrological and hydraulic assessment
  • Model Climate Change
  • Site Visit
  • Scope Topographical and measurement survey

What we need from you:

  • Site Location Plans
  • Topographical survey of the site
  • All correspondence with the Environment Agency

Rural Areas

Hydraulic Modelling of River Flow

Our Benefits:

  • Models fully approved by the Environment Agency
  • Obtain LIDAR data
  • Produce Hydrological and hydraulic assessment
  • Model Climate Change
  • Site Visit
  • Scope Topographical and measurement survey

What we need from you:

  • Site Location Plans
  • Topographical survey of the site
  • All correspondence with the Environment Agency

Exception Registration

Flood Risk Activity Permit Exception Application - Urban Water

Our Benefits:

  • Fast assessment on the required exception application
  • Follow up on the Environment Agency
  • Review of your design
  • Review of the contractor’s method statement
  • Assess  the environmental risk for the site

What we need from you:

  • All detailed drawings
  • RAMS
  • Flood Risk Assessment
  • Construction Phase Plan

Standard Rules Permit

Flood Risk Activity Permit Standard Application - Urban Water

Our Benefits:

  • Fast assessment on the required exception application
  • Follow up on the Environment Agency
  • Review of your design
  • Review of the contractor’s method statement
  • Assess  the environmental risk for the site

What we need from you:

  • All detailed drawings
  • RAMS
  • Flood Risk Assessment
  • Construction Phase Plan

Bespoke Permit

Flood Risk Activity Permit Bespoke Application - Urban Water

Our Benefits:

  • Fast assessment on the required exception application
  • Follow up on the Environment Agency
  • Review of your design
  • Review of the contractor’s method statement
  • Assess  the environmental risk for the site

What we need from you:

  • All detailed drawings
  • RAMS
  • Flood Risk Assessment
  • Construction Phase Plan

Sequential Test – Village

Sequential Test Village- Urban Water

Our Benefits:

  • Immediate communication with council to determine study area
  • Report in accordance with the local guidelines
  • Assess multiple resources of planning information as per agreed with the council
  • Give preliminary advice on potential sites
  • Recommend appropriate site for assessment
  • Allows for one set of consolidated comments/amendments following the first issue of the report 

What we need from you:

  • Site Address
  • Development Plans
  • Local Planner Contact Details

Sequential Test – Town

Sequential Test Town - Urban Water

Our Benefits:

  • Immediate communication with council to determine study area
  • Report in accordance with the local guidelines
  • Assess multiple resources of planning information as per agreed with the council
  • Give preliminary advice on potential sites
  • Recommend appropriate site for assessment
  • Allows for one set of consolidated comments/amendments following the first issue of the report 

What we need from you:

  • Site Address
  • Development Plans
  • Local Planner Contact Details

Extensions

Flood Risk Assessment Single House

Key Benefits:

  • First draft in 48 hours with the final report in 20 days (dependent on ea information)
  • Report in accordance with the environment agency and with national policy planning framework
  • Allows for one set of consolidated comments/amendments following the first issue of the report

What we need from you:

  • Site address
  • Development plans
  • Topographical ground levels