Project brief

The proposed works involved the installation of a combined sewer outflow (CSO), an APRNV chamber, new manholes and associated pipework as part of Scottish Water’s £3m improvement to its waste water infrastructure in Paisley to help improve the water quality and natural environment in local rivers.

The installation of better screening and new pipework will improve the environment on local water courses, and in turn the River Clyde, benefiting aquatic life, flora and fauna.

Marshalls Solution

To meet the strict quality requirements of the project, contractor Amey Black & Veatch specified a Marshalls Civils and Drainage precast concrete CSO chamber to reduce excessive flows into the sewer during periods of high rainfall, following talks between the contractor, Keyline BM and Marshalls Civils and Drainage.

Marshalls Civils and Drainage can custom design a combined sewer chamber to suit specific wastewater treatment and sewer needs. Depending upon the size of the sewer and flow specifications, there are a number of options available from one-piece chambers to larger flat-pack arrangements.

For this project, Marshalls supplied a flat pack CSO comprising eight separate components. These were the four external walls, a two-piece split base, a centre weir wall and a single cover slab.

The components were supplied by specialist distributor Keyline with whom Marshalls Civils and Drainage has an ongoing framework agreement. They were delivered to site and installed by specialist sub-contractor Clean Tech. Assembly comprised installation of the base slabs on a prepared surface founded at formation level of 3.24m below ground, followed by the four walls, bolted together at the corners, and weir wall. Joints were sealed with rubber seals and grouted. The finished CSO chamber measured 3.6m x 2.05m x 2.59m deep.

Compared with conventional CSOs built using either in-situ concrete or traditional brick, the modular pre-cast concrete option is much quicker, safer and easier to install and, because the components are manufacturer off-site in controlled factory conditions, finished quality is very high.

Marshalls offer a range of SuDS solutions, as part of their water management precast systems, to combat the effects of surface and flood water.

Client comments

“The precast units used offered a quality finish, the installation was simple and the ease of installation assisted in delivering the CSO according to the programme,” says Amey Black & Veatch project manager John Townshend.

“We have used Marshalls Civils and Drainage precast products many times in the past and always found them easier and faster to install than alternative methods. We now specify precast in preference to other options for structures such as CSOs,” adds Mr Townshend.