Beaumaris, Mill Lane

Installation of an Automatic Trash Screen and associated infrastructure to stop debris build-up in the water course, reducing the flood risk to local properties.

Beaumaris Automatic Trash Screen Installation

The project is located at Mill Lane, Beaumaris, on the Isle of Anglesey. Griffiths are the Term Service Contractor working in partnership with Anglesey County Council.

Storm events over the last 15 years have caused significant flooding and property damage at the site, including demolishing a garage. Debris regularly built up at the existing screen and was difficult to remove safely due to high water flow.

A long-term sustainable solution was required so the Isle of Anglesey County Council secured funding from Welsh Government to install an automatic trash removal screen.

The screen operates like a belt conveyor lifting debris collected at the base, up and over to the top to drop onto the debris collection platform, with the tines returning empty underneath. The material can then be loaded directly into a vehicle for removal. Water level sensors are mounted up and down stream of the screen. Material gathering on the screen results in a dam effect and when there is a differential of 100mm the screen becomes active, shutting off once the levels have equalised.

Access to the Beaumaris site was very restricted, located in a narrow cul-de-sac with private houses nearby, a gas governor kiosk adjacent, a historic low arched stone bridge upstream and a public footpath that was in constant use.

Japanese knotweed was present which influenced the temporary works design and method for working in the river. Dry areas for construction were formed using one tonne sandbags to act as a cofferdam, with potential flood risk monitored at all times. The main structure was formed using precast interlock blocks to speed up the construction process and reduce the environmental risk of using wet concrete.

Design aspects include an overflow channel, a control screen that is hardwired into an adjacent streetlamp and a connection for a generator in the event of a power cut.

The screen has been operating successfully since installation and won the Institution of Civil Engineers Roy Edwards Award for outstanding design and construction.

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