Residential properties prone to flooding in Kirk Hallam, Derbyshire prompts sewer network improvements with dB ultrasonic technology and pump control.

Varying factors including population growth and climate change mean that the UK water industry faces increasing pressure to address challenges such as water scarcity and environmental quality, while also improving the resilience of systems and services to customers.

Situations like excessive rainfall causing flooding and unintentional sewage discharge to rivers, as well as long dry periods that cause droughts, are all part of the unpredictable weather conditions we now face. One of the key challenges facing our water companies is the management and improvement of infrastructure in order to cope with the ever-increasing unpredictability of UK weather.

Unintentional discharges can happen following extreme weather events when too much rainwater enters the sewers from surrounding roads, houses and land; or where rivers and watercourses overflow and back up the sewers and surrounding areas.

Water companies across the UK have committed to investing in the improvement of infrastructure to improve our water supplies and to cope with unplanned weather events. Continuously monitoring the flow and levels in pipelines, sewers, reservoirs or treatment facilities is one way in which the water industry is addressing these challenges.

NMCN PLC were tasked with improving the sewer network that runs through the village of Kirk Hallam, Derbyshire to alleviate the risk of flooding to 15 properties located within the village. NMCN work in partnership with their customers to deliver major built environment and critical national infrastructure projects across the UK. Their specialist engineering and construction teams bring multi-sector innovation and technical skill, from building and highways to large scale water networks and treatment plants.

The scheme carried out on behalf of Severn Trent Water included the installation of an offline stormwater shaft tank, which doesn’t receive constant flow to pump away and only comes into operation during long periods of rainfall/storm conditions – a common application seen throughout the UK water industry. The shaft houses 3 submersible pumps including 2 x duty pumps and 1 x ejector/mixer pump, a Pulsar dB10 transducer and 2 float switches.

As well as the Pulsar dB10 Transducer located in the shaft tank, NMCN also installed an additional Pulsar dB10 transducer downstream in the sewer network constantly monitoring the rise and fall of the water level in the main sewer. In times of heavy rainfall/storm conditions, the water levels in the sewer rise meaning that a pre-set weir is breached upstream and the flow cascades down via a section of stainless-steel pipework into the new shaft tank.

The Pulsar dB Transducer Series offer reliable level, volume, open channel flow, pump control and differential measurement within liquid and solids applications. The sensors utilize a low power transducer design with standard interconnecting cables – yet product extremely high acoustic power to give exceptional results in a wide variety of challenging applications.

For pump control, NMCN installed a Pulsar UltraTWIN controller, offering twin channel ultrasonic measurement enabling the constant monitoring of the rise and fall of the level in the downstream sewer and in stormy conditions; the water level of the stormwater shaft tank.

Pre-set levels are built into the Pulsar UltraTWIN controller and once the levels within the main sewer have dropped sufficiently, the Pulsar dB10 Transducer will send a signal back to the controller to start the process of returning fluid back to the main sewer from the stormwater shaft tank. Once the shaft tank is empty, the Pulsar dB10 emits another signal back to the UltraTWIN triggering the stop relay, stopping the duty pump.

As well as a wide range of sophisticated pump control features, the Pulsar UltraTWIN offers the ability to make each channel user-configurable to be able to operate independently, either as a full function open channel flow monitor, a pump control system or as a level and volume monitoring unit for liquids or solids. The controller calculates volumes and provides alarms, aiding the decision-making process about the condition of a network.

Without having the ability to monitor the level downstream, the pumps may be called into operation early causing an unwanted discharge into the trunk sewer which will cause flooding at its lowest point – which had the potential to be residential properties.

Commenting on the project, David Greaves, a Mechanical Project Engineer for NMCN PLC stated, “The Pulsar products are always critical to the operation/installation. Our engineers are experienced with the products and someone is always on hand should we ever encounter any issues.”

Effective flow and level measurement are helping to ensure that our water infrastructure is more resilient and working as effectively as possible, emerging problems are quickly identified and addressed, mitigating the threat of flooding and sewer overruns for the benefit of customers and the environment.