Yorkshire Water Intermittent Discharges Project

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This was an extensive project, conducted as part of a team headed by Titan Environmental Surveys over three years, to assess the impacts of Combined Storm Overflow (CSO) outfalls and storm overflow outfalls at Waste Water Treatment Works (WWTW) across Yorkshire Water’s extensive holdings as part of the client’s AMP 3 and AMP 4 planning and responsibilities.

Many of the locations of the CSO outfalls were unknown to the water company and had not been visited for many years, hence the first task was to locate and document them using available sewer maps and data. Once located surveys of both the aquatic invertebrate communities of the watercourses into which the outfalls discharged, as well as their aesthetic impact (using the 466 survey method) were conducted upstream and downstream of each outfall to assess their environmental impact.

Receiving watercourses varied greatly across the study area, from small first order headwater streams to major rivers, within a varied landscape from remote and rural, to intensively urban, each of which brought its own challenges. A huge number of sites was sampled and invertebrate samples analysed, with sampling methods varying from kick sampling to deployment of a boat for air-lift sampling on the deeper rivers. The analysis of the samples was audited both internally and externally by CEH.