1 /

    Vyrnwy Dam Monitoring: Overcoming Extreme Environmental Challenges

    Vyrnwy Dam Monitoring: Overcoming Extreme Environmental Challenges

    Contact us

    Challenge

    Located in mid-Wales, the historic Vyrnwy Dam, the first gravity dam built in Britain from mass-cut stone in the 1880s, presented unique monitoring challenges as part of meeting safety legislation.

    With a dam over 140 years old, it is vitally important regular maintenance work should be carried out, to protect against catastrophic failure.

    On this occasion, two critical monitoring systems had become compromised at the dam:

    1. The pendulum monitoring device measuring dam displacement had failed due to a build-up of ochre blocking its optical sensors
    2. The uplift pressure drain monitoring device stopped working due to ochre blocking pipe-work

    Additionally, there was interest in monitoring over 80 uplift pressure well flows in the dam's adit - a narrow, wet, and difficult-to-access tunnel running through the dam's foundation.

    Traditional monitoring methods would be prohibitively expensive, with the following extreme challenges presented to SOCOTEC’s Monitoring team:

    • Confined space requiring specialist access equipment and rescue teams
    • A 200m long tunnel: narrow, low, wet, and covered with slippery ochre deposits
    • Equipment rapidly becoming covered with ochre when exposed to air
    • Optical-based monitoring equipment failing quickly in these conditions

    Our Solution

    The SOCOTEC Monitoring team developed and implemented multiple innovative solutions to be implemented at Vyrnwy Dam, starting with:

    • Developed a novel pendulum wire position monitoring system using 4-20mA ultrasonic distance sensors
    • Eliminated vulnerability to the disruptive ochre by avoiding optical components
    • Created a significantly smaller, easier-to-protect solution
    • Delivered comparable accuracy to established commercial devices at substantial cost savings

    Rather than installing individual monitors on 80+ drainage wells, the SOCOTEC Monitoring team engineered an elegant solution by:

    • Identifying an existing horizontal steel threshold to function as a weir plate
    • Blocking a drain beneath to force all leakage water over the plate
    • Installing a high-precision pressure sensor (±0.5mm accuracy)
    • Connecting to an existing analogue radio node

    Connected all instruments to radio nodes that wirelessly transmit readings to a GSM Gateway:

    • Relayed data to monitoring software for remote access
    • Provided real-time insight into asset behaviour
    • Eliminated manual reading requirements

    We built an experimental model with two sensors monitoring the X and Y movement axes, refined it in the workshop to test its abilities and then installed it in another of our client’s dams, Clywedog, where an established commercial automated pendulum device from China had been monitoring.

    We then compare side by side to ensure our device matched the established device’s readings – which it did. Our device doesn’t use optics, it is much smaller to house and therefore easier to protect against the ochre problem. A further benefit is that it is much cheaper to build than the commercial devices available from other suppliers.

    We therefore decided to remove it from its trial at Clywedog and install it in the adit at Vyrnwy Dam.

    Rob King-Mason, Project Delivery Manager at SOCOTEC UK

    Want to find out more about our Monitoring services?