Environment Protection: Henley-on-Thames

The ecological status of Holton Brook (The Holton Brook and tributaries) is currently classified as having ‘Bad’ ecological status overall. This status is driven mainly by a deterioration to invertebrate status from ‘Poor’ to ‘Bad’ in the 2022 classification. The reason for this deterioration is suspected to be the impact from invasive species, particularly North American Signal Crayfish. There are also existing Reasons for Not Achieving Good Status (RANGs) listed against diffuse agricultural pollution, continuous sewage discharge and physical modification to the waterbody. Macrophytes and Phosphate are also at ‘Poor’ status on the Holton Brook and have RANGs associated with continuous sewage discharge and diffuse agricultural pollution. All other ecological elements are at ‘Good’ or ‘High’ status.

For the next water company asset management period (AMP 8), investment period for 2025 – 2030, an improvement scheme at Horton-cum-Studley sewage treatment works has been identified as part of the Environment Act’s Storm Overflow Discharge Reduction Plan. This will ensure the site operates its storm overflow no more than 10 times per year and causes no adverse ecological impact. Forest Hill STW and Stanton St John STW will have schemes in subsequent AMP periods to meet their Environment Act (2021) targets.