Site Optimization and Saving You Money on Your Drainage Installation

Drainage design is a fundamental requirement for almost every new development project in England, Scotland, and Wales. With stringent planning conditions and local authority requirements, it’s crucial to ensure your surface water drainage systems are compliant, cost-effective, and designed to meet Greenfield runoff rates (pre-development conditions). However, in the race to secure planning permission, many developers end up with standardized, over-engineered drainage solutions that inflate construction costs.

At Cornerstone, we believe in optimizing drainage systems from the start to save our clients money—without compromising on compliance or design integrity. In this blog, we’ll explore:

1. Why drainage optimization is often overlooked

2. How understanding design events can reduce costs

3. Our unique “no fee, no saving” arrangement

   
   

1. Why Is Drainage Optimization So Often Overlooked?

1.1. Early-Stage Pressure and Limited Budgets

When projects are at their initial planning stages, developers are under intense financial pressure. They often have:

• High upfront costs and fees

• Uncertainty about final planning approval

• A desire to keep spending low until risk is minimized

As a result, drainage consultants are typically engaged to deliver a viable design as quickly and inexpensively as possible—rather than a fully optimized scheme. The goal at this stage is simply to pass planning, not necessarily to minimize construction costs.

1.2. Passing Planning vs. Minimizing Construction Costs

Most local authorities mandate that surface water runoff must be controlled to pre-development (Greenfield) rates. To satisfy this, designers often propose standard attenuation solutions, such as oversized below-ground tanks or large stormwater attenuation crates. These solutions are easy to justify at planning—but may be costly to install.

Key insight: Once planning is secured, many developers either sell the site or move into the next phase without revisiting the drainage design. Hence, significant savings that could have been achieved through an optimized approach are left on the table.

2. Understanding Design Events and Their Cost Implications

When designing a surface water drainage system in the UK, two principal rainfall events must be considered:

1. 1 in 30-year event (plus climate change)

   • System must be designed so that no flooding occurs; runoff is stored or conveyed effectively.

2. 1 in 100-year event (plus climate change)

   • Minor flooding is permitted on-site, as long as floodwaters do not leave the site boundary or pose a risk to property or people.

2.1. The Hidden Saving: Allowing On-Site Flooding for Larger Events

To meet the 1 in 100-year standard, a drainage system does not have to keep water entirely below ground. Instead, you can design ground levels and create shallow landscaped areas (e.g., car parks or low-lying basins) to temporarily store water during extreme storm events.

• Example: Lowering a section of car park is much cheaper than installing an extra 50–100 cubic metres of below-ground storage.

• Result: You can significantly reduce the size (and cost) of pipes, tanks, and other hard infrastructure.

However, in most early-stage planning designs, consultants may default to larger underground tanks because it’s a quick and straightforward way to satisfy local authority criteria.

3. Overcoming Early-Stage Barriers to Optimization

3.1. The Developer’s Dilemma

Many developers are reluctant to invest in optimization at the early planning stage because:

• They may sell the site once planning is granted.

• They have no guarantee of planning approval and want to limit upfront spending.

3.2. Our “No Saving, No Fee” Arrangement

To address these concerns, Cornerstone offers a unique engagement model:

1. We undertake an optimization review of your existing or proposed drainage scheme.

2. If we identify ways to reduce your below-ground storage (and overall construction costs), we propose design changes.

3. We only charge a 20% share of the actual savings realized from our optimizations.

Example: If your current design would cost £100,000 to implement and we find a way to reduce this to £50,000, you keep £40,000 of the savings. We receive a £10,000 fee (20%), and there are no fees if we don’t reduce your costs.

This approach removes the financial risk for developers and encourages us, as consultants, to push for maximum savings.

4. Key Benefits of Optimized Drainage Designs

1. Lower Construction Costs

   • By minimizing tank sizes and pipe diameters, you directly reduce materials, excavation, and installation costs.

2. Enhanced Sustainability

   • Integrating surface-level flood areas can also improve biodiversity and amenity value if properly landscaped.

3. Better Use of Space

   • Freed-up space from smaller below-ground systems can be used for parking, green spaces, or additional development.

4. Regulatory Compliance

   • Well-designed solutions still meet strict planning conditions and SUDS requirements while maximizing cost savings.

     
     

5. How to Get Started with Drainage Optimization

1. Review Your Existing Designs

   • If you already have a planning-stage design, let us evaluate it for optimization potential.

2. Engage Early

   • The best time to optimize is as early as possible—ideally before finalizing your site layout.

3. Consider Future Development

   • Even if you plan to sell the site post-planning, an optimized drainage design can increase the site’s value and attractiveness to potential buyers.

4. Ask the Right Questions

   • Encourage your designers to consider using topography for storage rather than defaulting to larger underground structures.

     
     

6. Secure Real Savings with Zero Upfront Risk

At Cornerstone, we understand the pressures and financial risks inherent in development. Our goal is to streamline your drainage system, ensure regulatory compliance, and save you money on construction.

• No Upfront Costs

• Transparent, Results-Driven Fees

• Proven Track Record in delivering significant savings

Ready to Explore an Optimized Drainage Strategy?

Contact our team today. We’ll help you determine the best way to reduce construction costs, improve sustainability, and take your project forward with full planning approval.

Conclusion

Drainage systems in the UK, Scotland, and Wales must meet strict requirements to control and attenuate runoff to pre-development levels. However, the traditional approach of oversizing below-ground infrastructure can be unnecessarily expensive. By allowing controlled flooding on-site during extreme events and carefully designing ground levels, you can drastically reduce tank volumes—and construction costs.

If you’re a developer seeking to optimize your drainage solution with no financial risk, reach out to Cornerstone. Together, let’s challenge the industry norm and create high-quality, cost-effective drainage systems that work for you and the environment.

Get in Touch Today