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Donegan Civil Engineering

Detention Tank and CSO Screening – Witton Park, Blackburn

A 20m internal diameter, 4,500m³ detention tank with self-cleansing vac-flush system, resolving an unsatisfactory intermittent discharge to the River Blakewater

By: Valentine Donegan

Published: August 6, 2026

Detention Tank and CSO Screening - Witton Park, Blackburn

Client: United Utilities

Project Description / Main Operations

V J Donegan & Co Ltd completed this project direct for United Utilities as part of the larger Blackburn UIDs scheme. The purpose of the project was to resolve the unsatisfactory intermittent discharge (UID) from the combined sewer network to the River Blakewater.

The solution ensures that spill flows up to and including a 1 in 5 year return period are screened to a 6mm standard in two dimensions, and contributes to the River Quality Objective (RQO) for the River Blakewater.

Scope and method:

Design and construction of a 20m internal diameter detention tank, stored volume 4,500m³, complete with vac-flush central column to be self cleansing.
Reinforced concrete discharge chamber and reinforced concrete static screen chamber.
300mm diameter outfall sewer.
Modifications to an existing CSO chamber in Preston Old Road.
110m of 700mm diameter auger-bore, with a 4.00m diameter drive shaft for its installation.
750mm diameter pipework from the detention tank to the River Blakewater via the new CSO chamber, and a reinforced concrete outfall structure.

MEICA scope

Design and installation of 1 no. isolation penstock and 1 no. 750mm diameter flap valve.
2 no. submersible storm return pumps and 1 no. submersible scavenger pump.
1 no. tank flushing system, complete with vacuum pump, actuated valves, pressure and vacuum pipe, and flushing column diaphragm valve assembly.

For More Information, contact us at http://www.donegan.co.uk

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