Pre-Construction Drainage Checklist: What You Need to Know

Before any drainage design work can begin, there’s a crucial set of information and documents needed to ensure your project’s success. Let’s break down these requirements into clear, manageable sections.

Essential Documents You Need

First, let’s cover the fundamental documents required for any drainage design project:

A topographical survey is your starting point – this needs to be in DWG format and ideally referenced to OS National Grid. Think of this as your site’s detailed map, showing all existing levels and features that might affect drainage.

Your architectural plans should include:

• Site layout in both DWG and PDF formats
• Proposed ground levels
• Fixed architecture and landscape plans
• Foundation design details and sections

You’ll also need two important ground-related reports:

• A ground investigation report that tells us about soil conditions
• A soakaway testing report to show how well water can drain naturally into your ground

Understanding Surface Water Management

Surface water management is about controlling rainwater that falls on your site. This involves:

• Calculating how much water needs to be managed (based on roof areas and paved surfaces)
• Determining where this water will go
• Planning how to store it during heavy rainfall
• Ensuring it’s clean enough before it leaves your site

Foul Water Considerations

Foul water (from toilets, sinks, etc.) needs its own careful planning:

• We’ll calculate how much wastewater your development will produce
• Plan pipe sizes and routes
• Identify where it will connect to existing sewers
• Check if any special treatments are needed

Important Things to Remember

Some key points that often get overlooked:

• The architectural layout needs to be final – changes later can significantly impact drainage design
• We only provide 2D layout designs
• We don’t cover internal waste pipes
• Additional costs may apply for Local Authority approval fees, Site visits, Design changes after authority comments and External survey costs

Quality Checks

Before submission, we ensure:

• All calculations meet current standards
• Drawings are accurate and complete
• The design complies with local authority requirements
• Construction methods are practical and achievable

This checklist helps ensure your drainage design process runs smoothly from start to finish. Having these elements ready at the beginning helps avoid delays and additional costs later in the project.

Remember, while this checklist covers the essentials, each project is unique and might require additional information depending on its specific requirements and location.

Note: For specific questions about your project’s requirements, you can contact The Drainage Designers during business hours (Monday to Friday, 9 am to 5 pm) at 01256 807116 or email martin.young@thedrainagedesigners.co.uk.