From Strategy to Design: What are Drainage Engineering Consultants?

When people ask what a Drainage Engineering Consultant does, the answer is often wider than expected. At FPS Environmental Ltd, our drainage engineers handle everything from assessing old drainage systems with CCTV Drainage Surveys to designing new ones, and often the integration of both. This includes connection agreements, build-over agreements, adoption agreements, and more.

Our Civil Engineering team, led by Alex Hanks, specialise in surface water and foul drainage design, supporting developers, homeowners, and businesses through planning, design, and delivery.

Drainage Strategies and Planning Applications

One of the most common reasons clients need a drainage consultant is for planning. A significant part of our work is producing Surface Water Drainage Strategies for planning applications, along with more Detailed Drainage Design once permission is secured.

A Surface Water Drainage Strategy is essentially an overview of the risks at a site and how those risks will be managed. We would advise early stage discussion as this can be the difference between a smooth planning process, or a costly delay.

These strategies can range from large-scale Sustainable Drainage Schemes (SuDS), right down to small-scale measures such as a soakaway on a single property.

SuDS and the Drainage Hierarchy

Our engineers work in line with the Drainage Hierarchy, which promotes a natural approach to managing water and integrating drainage into site design as early as possible.

Since the updated National Planning Policy Framework (NPPF, December 2024), sustainable drainage strategies are now required for all planning applications which could affect drainage on or around a site, not just major developments. That means even minor, or householder applications may need a Surface Water Drainage Strategy (SuDS Strategy), particularly in flood zones, areas of high surface water risk, or where impermeable areas are being increased.

SuDS bring wider benefits too, improving water quality, biodiversity, and amenity, as well as reducing runoff.

From Strategy to Detailed Design

A Surface Water Drainage Strategy is the starting point. Once planning is in place, we often develop this further into Detailed Drainage Designs.

Put simply, the strategy is the overview, identifying how surface water will be managed. The design is the detail, turning that strategy into calculations, drawings, and specifications that can actually be built.

This may involve:

• Percolation testing (BRE365) to assess soakaway viability
• Modelling in InfoDrainage
• Designing alternative SuDS (such as Type C permeable paving) if infiltration isn’t possible
• Pipe sizing, inspection chambers

Detailed Drainage Design can also include Foul Water Drainage Design, which may include:

• Foul drainage design and integration with public sewers
• Section 106 drainage connection consents

For larger sites, we also consider sewer network capacity and whether public sewer upgrades may be required. These issues can have significant programme and cost implications if not identified early.

A sewer adoption on a larger site would fall under a Section 104 adoption agreement.

How We Work

At FPS Environmental Ltd, our engineers provide support from project inception to construction. This can include:

• Pre-planning advice to scope drainage requirements
• Drainage strategy reports for planning applications
• Detailed design drawings and specifications
• Drainage modelling
• Ongoing site support during construction

Our engineers follow best practice and national guidance to ensure drainage systems are not only compliant but practical, cost-effective, and future-proof.

A Drainage Engineering Consultant is the link between policy, planning, permissions, and onto practical delivery.

Contact us to discuss how our engineering team can support your project, or Meet the Team.

Written by Simon Crowther BEng (Hons) C.WEM FCIWEM MIET

Director

15th September 2025