Storm overflow project investigations to begin in Knaresborough

Yorkshire Water will begin ground investigations in Knaresborough on 2 November as part of its £1.5bn Yorkshire-wide programme to reduce discharges from combined storm overflows (CSOs). 

Five boreholes, approximately 150mm in diameter and 5m deep, will be drilled into the ground on The Parsonage to help understand ground conditions and monitor groundwater levels. The information gathered by contract partners Ward and Burke will help Yorkshire Water decide the most effective and safe way of reducing discharges into the River Nidd from Waterside 49 CSO. 

The utility is currently investigating and planning seven potential CSO discharge reduction projects in Knaresborough, to be completed by 2030.  

CSOs are part of the combined sewer network, which carries both wastewater and rainwater, and act as a relief valve when the sewer is over capacity. During periods of heavy rainfall, CSOs discharge diluted wastewater into watercourses to prevent the system from backing up into homes, gardens, businesses and streets.  

Athif Khan, project manager at Yorkshire Water, said: "Last year, we saw a 24.5% reduction in discharges from CSOs, which reflects the level of investment we have been making in upgrading our network to bring the frequency and duration down. There’s much more to do, and these boreholes are the next step in planning one of seven projects that we’re expecting to complete in Knaresborough. 

“We’ll do everything we can to keep disruption to a minimum and thank everyone for their patience and understanding in advance.”  

Residents have been informed of any localised disruption. Once the investigations are complete – expected to take one week - the boreholes will be backfilled, the area fully reinstated, and the data gathered from the survey will be used to aid the development of the best solution to reduce discharges. Prior to the boreholes being drilled, ecology and arboricultural surveys have been undertaken.  

There will be further ground investigations in Knaresborough as Yorkshire Water furthers planning of the other six projects, and local residents will be informed in advance. 

The £1.5bn CSO discharge reduction programme, being delivered between 2025 and 2030, follows a £180m investment in the couple of years prior. It forms part of Yorkshire Water's wider £8.3bn, largest ever investment into improving services and its impact on the environment. 

There are currently a number of storm overflow projects in delivery across York, Bradford, Leeds, Calderdale, Sheffield, Rotherham and parts of North Yorkshire.