Eric Wright Water

Sockbridge and Tirril Better Rivers

Introduction

Sockbridge Wastewater Treatment Works (WwTW) in Cumbria serves the villages of Sockbridge and Tirril, with a catchment that is primarily residential and projected to grow from 459 to 620 people by 2050.

The site has historically struggled with high levels of combined sewer overflow (CSO) spills, averaging over 50 events per year since 2018.

Client

Eric Wright Water

Sector/ Project Type

Water Companies - CSO Spill Reduction, Better Rivers

Date

September 2025

Location

Cumbria

Our Approach

A comprehensive hydraulic model was developed and updated using recent surveys, rainfall data, and population projections. This model was used to assess baseline performance, identify discrepancies in spill frequency (partly due to monitoring calibration issues), and evaluate the impact of future developments.

The project was guided by regulatory targets set by Ofwat’s PR24, prioritizing a reduction in storm overflows to no more than 10 events per year and the installation of effective screening.

The Solutions

The proposed solution includes several key interventions:

Replacing the existing macerator with a 6mm bi-directional powered screen.
Constructing a new 90m³ storm tank within a redundant filter bed.
Upsizing the storm overflow pipework and installing duty/standby pumps for stormwater return.
Ensuring all new infrastructure is integrated with existing works to maintain operational continuity.

These measures are designed to significantly reduce the frequency and volume of storm spills, while also improving screening and resilience.

Project Outcome

The solution is predicted to reduce annual spill frequency from 49 to just over 5 events, with substantial reductions in spill duration and volume. The interventions ensure compliance with flooding and surcharge standards, do not increase upstream.

Our Work