Onn Point Civil Engineering

Onn-Point was recently appointed to design an attenuation pond for a 5x building development with a total impermeable area of 970m² in Coleford, Gloucestershire. 📍

With the main site infrastructure already in place, the scheme required a dedicated attenuation feature to control surface water flows before discharge to the existing watercourse south of the site.

Key elements of the design included:

✔️ A new attenuation pond separating proposed flows from existing drainage features

✔️ Discharge restricted to 1 l/s in line with the agreed LLFA rate

✔️ 1 in 3 pond side slopes with minimum 300mm freeboard

✔️ Hydraulic modelling for the 100-year storm event plus 40% climate change allowance

✔️ Hydro-Brake flow control integrated within the outlet structure

A site-specific attenuation solution designed to manage runoff effectively, protect the wider site, and support long-term drainage performance.

📞 01902 585206 | ✉️ [email protected]

Following the national standards published in 2025 - meant to improve consistency, resilience and long-term performance in surface water design across England - a growing industry trend is that more councils are beginning to apply the new SuDS standards more directly at planning stage. 📍

What that means in practice:

✔ Closer review of drainage submissions

✔ More emphasis on how each standard has been addressed

✔ Stronger focus on maintenance and long-term performance

✔ Less tolerance for vague or generic SuDS statements

The direction is clear: drainage strategies now need to be sharper, better evidenced and more clearly aligned with the standards from the outset.

📞 01902 585206 | ✉️ [email protected]

Percolation testing is a simple process, but it has a major impact on the drainage strategy that follows.

At Onn-Point, the process typically looks like this:

1️⃣ Test the ground - A trial pit is prepared and water is introduced to assess how the soil drains.

2️⃣ Review the results - The infiltration rate is measured to understand whether soakaways are viable.

3️⃣ Shape the drainage route - Those results then inform whether an infiltration-led solution is realistic.

4️⃣ Support the next stage - The data is carried into the wider drainage design and planning submission.

Done properly, percolation testing removes assumptions early and gives the rest of the project a clearer route forward.

📞 01902 585206 | ✉️ [email protected]

Onn-Point provides practical drainage support from the first site questions through to planning-ready design. 🤝

Our service offering includes:

1️⃣ Percolation testing and infiltration-led design

2️⃣ SuDS strategies and drainage statements

3️⃣ Soakaway and attenuation design

4️⃣ Hydraulic modelling and supporting calculations

5️⃣ Drainage layouts, details and maintenance strategies

Everything is built around one objective - giving clients a drainage solution that is clear, compliant and ready to move the project forward.

📞 01902 585206 | ✉️ [email protected]