Yorkshire Water drills five boreholes on The Parsonage from 2 November to plan cuts at Waterside 49, which spilled 16 times in 2025. All 10 town overflows ranked.
Yorkshire Water will start drilling five boreholes on The Parsonage in Knaresborough on Monday 2 November. The work is the first step towards cutting sewage discharges into the River Nidd from an overflow called Waterside 49.
The company announced the work in a release on 27 October. It expects the investigation to take one week.
What is happening on The Parsonage
According to Yorkshire Water:
- five boreholes will be drilled, each about 150mm across and 5m deep
- they will show what the ground is like and track groundwater levels
- the drilling is done by its contract partners, Ward and Burke
- ecology and tree surveys have already been carried out
- afterwards the holes will be backfilled and the area fully reinstated
The Parsonage is a short lane off Waterside, close to where the Waterside 49 overflow discharges into the Nidd, according to OpenStreetMap.
The company said residents had been told about any localised disruption.
One of seven Knaresborough projects
Yorkshire Water says it is investigating and planning seven possible overflow reduction projects in the town, all due to be finished by 2030. It has not yet said which overflows the other six cover. It said further ground investigations will follow, with residents told in advance.
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.”
The Knaresborough work is part of a £1.5bn programme across Yorkshire running from 2025 to 2030. That sits inside the company’s £8.3bn investment plan, it said.
How often Knaresborough’s overflows spilled in 2025
A combined storm overflow is a relief valve on a sewer that carries both wastewater and rainwater. When heavy rain overloads the pipe, the overflow releases diluted wastewater into a river rather than letting it back up into homes and streets.
Every overflow is fitted with a monitor, and the companies report the results each year. We pulled the 2025 figures for every Yorkshire Water overflow in Knaresborough from the Environment Agency’s Event Duration Monitoring return for 2025. The agency counts spills using its standard rule, which bundles a burst of activity into blocks of 12 and 24 hours, so one count can cover several shorter releases.
| Overflow | Discharges into | Counted spills, 2025 | Hours spilling, 2025 | Monitor working |
|---|---|---|---|---|
| Manse Lane 57 | River Nidd | 59 | 199.5 | 99.0% |
| Knaresborough sewage works (storm tank) | River Nidd | 38 | 379.5 | 99.6% |
| Waterside 47 | Mill Stream | 28 | 59.75 | 92.1% |
| Waterside 48 | Mill Stream | 24 | 42.75 | 88.6% |
| Spital Croft | River Nidd | 21 | 42 | 99.4% |
| Abbey Road No 2 | River Nidd | 19 | 48.75 | 80.6% |
| Waterside 49 | River Nidd | 16 | 14.25 | 98.3% |
| Cragg Top | River Nidd | 11 | 106 | 95.7% |
| Boroughbridge Road | Frogmire Dyke | 5 | 2.5 | 98.3% |
| Abbey Mill | River Nidd | 0 | 0 | 74.6% |
Between them the ten recorded 221 counted spills and 895 hours of spilling in 2025. The storm tank at the sewage works spilled for the longest, 379.5 hours. Manse Lane 57 spilled the most often.
Waterside 49 sits in the lower half of the list, with 16 counted spills lasting 14.25 hours in total. Its long-term average, as recorded in the same return, is 13.67 spills a year.
Some monitors were not working for part of the year. Abbey Mill’s recorded for 74.6% of the time and Abbey Road No 2’s for 80.6%, so their real totals could be higher than shown.
What it means for you
- If you live on or use The Parsonage or Waterside: expect drilling rigs and some localised disruption for about a week from 2 November. Yorkshire Water says the ground will be put back as it was.
- If you use the river: this is planning work, not a fix. Nothing changes at the overflow itself this winter, and the projects are due by 2030.
- To report a problem with the works: contact Yorkshire Water through its get in touch page.
The town’s flood protection bid for 130 homes in Harrogate and Knaresborough is covered in our earlier report. Road closures across the district are on our roadworks and travel page.
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