Step-by-Step Planning Stage Considerations and Documentation Needs for Drainage Design

A comprehensive guide to getting your drainage documentation right from the start – saving time, money, and avoiding costly revisions

When it comes to drainage design, proper planning and documentation aren't just helpful – they're essential for project success.

After decades of working with architects, developers, and homeowners across the UK, we have seen how the right documentation at the planning stage can mean the difference between smooth project delivery and costly delays.

At The Drainage Designers, we've developed a systematic approach to planning stage documentation that consistently delivers results.

Projects with complete documentation achieve 75% fewer authority queries and complete 30% faster than those with incomplete information.

Phase 1: Pre-Design Information Gathering

Essential Technical Documentation

Topographical Survey Requirements The foundation of any successful drainage design starts with accurate site information. We require:

• Survey provided in DWG format (preferably to OS National Grid)

• PDF backup format acceptable for initial review

• Detailed contours showing existing ground levels

• Location of existing drainage infrastructure

• Boundary definitions and access points

Why this matters: Inaccurate surveys lead to design revisions in 40% of projects. Getting this right from the start prevents costly redesigns later.

Architectural Plans - The Frozen Design Principle Your architectural layout must be finalised before drainage design begins:

• Fixed architecture and landscape plans in DWG format

• Proposed finished floor levels clearly marked

• External level proposals including paving and landscaping

• Building positions that won't change during the design process

Critical assumption: We work on the basis that architectural layouts are frozen. Major design changes after drainage design begins result in additional fees and project delays.

Ground Investigation Requirements

Soil Analysis Documentation Understanding your ground conditions is crucial for compliant drainage design:

• Ground investigation report with soil classification

• Soakaway testing report (percolation rates)

• Bearing capacity information

• Groundwater level data

• Contamination assessment (if applicable)

Foundation Design Integration Drainage design must work with your structural requirements:

• Foundation design details and sections

• Proposed construction methods

• Basement or undercroft details

• Any structural constraints affecting drainage routes

Phase 2: Regulatory and Compliance Documentation

Planning Permission Requirements

Local Authority Submissions Different authorities have varying requirements, but standard documentation includes:

• Drainage strategy statement

• SuDS proposals with maintenance schedules

• Surface water management calculations

• Foul drainage connection proposals

• Flood risk considerations

Water Company Coordination All projects require liaison with water companies:

• Pre-development enquiries

• Connection applications

• Adoption agreements (Section 104/106)

• Technical approval submissions

Environmental Considerations

Flood Risk Assessment Integration While we outsource flood risk assessments, the documentation must integrate with drainage design:

• Environment Agency requirements

• Local flood risk considerations

• Climate change allowances

• Emergency overflow provisions

Phase 3: Design Development Documentation

Technical Design Standards

Drawing Requirements Professional drainage design requires specific documentation standards:

• Layout plans at 1:200 scale minimum

• Construction details at 1:50 scale

• Longitudinal sections showing gradients

• Manhole schedules and specifications

• Material specifications and standards

Calculation Documentation All designs must be supported by proper calculations:

• Rainfall data analysis

• Runoff calculations using appropriate methods

• Storage volume requirements

• Pipe sizing and gradient calculations

• SuDS component sizing

Quality Assurance Process

Peer Review Requirements Every design undergoes internal quality control:

• Technical review by qualified drainage engineer

• Compliance check against local authority standards

• Hydraulic validation using Causeway Flow software

• Client approval process before submission

Our quality process: We allocate an average of 3 hours per project for peer review, ensuring designs meet all regulatory requirements before submission.

Phase 4: Submission and Approval Documentation

Authority Submission Package

Complete Documentation Set Successful submissions require comprehensive documentation:

• Cover letter explaining the proposal

• Drainage strategy and design philosophy

• Technical drawings and calculations

• Supporting reports and assessments

• Compliance statements and certifications

Submission Timing Strategy Coordinate submissions for maximum efficiency:

• Pre-application discussions (recommended for complex sites)

• Planning condition discharge applications

• Building control submissions

• Water company technical approvals

Post-Submission Management

Response and Revision Process Authority comments require prompt, professional responses:

• Technical clarifications

• Design modifications (if required)

• Additional information requests

• Revised submission packages

Common Documentation Pitfalls to Avoid

Incomplete Initial Information

The Cost of Missing Documentation Projects starting without complete information face predictable problems:

• Design revisions when missing information emerges

• Authority queries causing delays

• Additional survey requirements mid-project

• Increased costs and extended timelines

Assumptions vs. Reality

What We Assume vs. What Often Happens Our standard assumptions include:

• Ground conditions suitable for standard drainage design

• Architectural layouts frozen and unchanging

• 2D layout requirements only

• Standard construction methods

Reality check: When these assumptions prove incorrect, additional fees apply and timelines extend.

Best Practice Recommendations

Front-Load Your Documentation

The 80/20 Rule Invest 80% of your documentation effort upfront to avoid 80% of potential problems:

• Complete surveys before design starts

• Finalise architectural layouts

• Understand ground conditions

• Clarify authority requirements

Communication and Coordination

Stakeholder Alignment Successful projects require clear communication between all parties:

• Regular progress updates

• Clear documentation of decisions

• Prompt response to queries

• Proactive problem-solving

Conclusion

Proper planning stage documentation isn't just about compliance – it's about project success. By following this systematic approach to documentation, you can achieve faster approvals, avoid costly revisions, and deliver better outcomes for your clients.

The key insight from our extensive experience is that time invested in proper documentation at the planning stage pays dividends throughout the project lifecycle. Projects with complete documentation consistently outperform those that try to shortcut the process.

Remember: drainage design is only as good as the information it's based on. Invest in proper documentation from the start, and your projects will run smoother, faster, and more profitably.