Project outline:
To streamline the drainage system along Worplesdon Road and Holly Lane Junction and simplify future maintenance requirements

Location:
A322 – Worplesdon Road and Holly Lane junction, Surrey

Client:
Surrey County Council Urban and Civic

We provided:
Civil Engineering – Surveys and Principal Design Services.

Key collaborators:
Surrey County Council

Maintenance on the roundabout at the A322 Worplesdon Road and Holly Lane junction in Surrey presented challenges.

The existing drainage included a manhole in the centre of the roundabout,
requiring regular maintenance. Accessing the site for maintenance necessitated traffic management and major road closures, resulting in increased costs and disruption for local residents.

INVVU Construction Consultants was commissioned to conduct both intrusive and non-intrusive investigative surveys, alongside client-provided survey data, to streamline the drainage system and
simplify future maintenance requirements.

The surveys undertaken to support the developing design consisted of a Topographical, Ground Penetrating Radar and CCTV Drainage Survey.

Design Challenges:

• Buried manholes – The site, surrounded by dense woodland, presented challenges in locating buried manholes. Through clearing overgrowth, we identified two previously hidden manholes, allowing us to map the existing drainage infrastructure.
• Pipe conditions – A comprehensive CCTV drainage survey mapped the roundabout’s drainage
  network, highlighting most of the system was in serviceable condition, pipes are manholes in poor condition were selected to be replaced.
• Sustainability – The design considered sustainable drainage solutions, maximising amenity and biodiversity benefits to reduce the impact on the environment, with a detailed maintenance schedule integrated to ensure the long-term performance of the design.
• Traffic Disruption – The design had to consider the impact of road closures and traffic management on road users during construction and for future maintenance.

The Solution:

Surface water flooding was determined to be a maintenance issue, therefore, there was no need for major upgrades to the existing drainage system.

The design focused on replacing the existing gullies
with innovative sumpless road gullies, incorporating 225mm Polypipe RidgiDrain leads that efficiently directed water to a newly positioned catchpit manhole. This catchpit was relocated to the western verge
of the roundabout, ensuring it could be serviced without the need for traffic management. The system was connected to the existing surface water ditch via a bagged headwall. Upstream surface water pipes extending beyond the site area were connected to the new system to ensure flow continuity.

To ensure safe access for maintenance vehicles, a hardstanding area was constructed by removing a small section of an unused footpath, as the crossing was located further up the road. The hardstanding was created using Grasscrete, a permeable surface that facilitates vehicle access, while minimising environmental impact.

Need help with your project?

Contact us to see how taking a joined up approach could benefit you.