Mermaid Quay Sewer Upgrade | Dwr Cymru Welsh Water
Dwr Cymru Welsh Water
Mermaid Quay Sewer Upgrade

Mermaid Quay

Welsh Water is investing £2million to upgrade the sewer system in the Mermaid Quay area of Cardiff Bay. The work is essential to make sure we continue to provide customers in the area with a first-class wastewater system they can rely on. This page provides an overview of the work and information on progress on site.

The work is being carried out in phases, firstly along Stuart Street and then Bute Street. The work will involve carrying out repairs to a Victorian brick sewer which runs under Bute Street. During the work, the team will also be laying a new sewer pipe in the area.

The work needs to be done following reports of local internal flooding caused by people putting fat, oil and grease (FOG) down the sink that has now built up in the sewer. More frequent cleaning to clear the FOG can wear out old sewers quicker than we would like and that is what has happened here in Mermaid Quay.

Our designers have been developing plans for the most cost effective, best engineering solution to repair the sewer while causing the least disruption possible to local businesses and residents.

In planning the work, we have liaised closely with businesses and residents in the area to ensure the work is carried out with the least disruption possible. To minimise the impact of the work, we will stop work over the autumn half term week and also throughout December to avoid the busy Christmas period.

Phased Approach

The work will be carried out in a phased way to minimise the impact on the local area. Below is information on what we will do at each stage.

Phase 1 - September 10th 2018 for a period of 4 - 5 weeks
Work will begin to remove the temporary footbridge located near Salt and carry out some repairs to the current wastewater pipe. This will involve a deep excavation in the currently pedestrianised area of Mermaid Quay between Salt Bar and The Dock

Stuart Street bridge Mermaid Quay

Removal of temporary footbridge along Stuart Street - Sept 2018

Welsh Water work Mermaid Quay

Creating a safe working area to repair the sewer - Oct 2018

Collapsed Victorian egg sewer - Sept 2018

Update – 18th December 2018

Since September 2018, we have been working hard onsite and have now removed all of the fat, oil and grease (FOG) blockages from the sewer. This has taken longer than we expected due to the volume of FOG which had built up in the sewer. To date, we have removed an estimated 800 tons of sewerage and FOG (the equivalent of 133 African Bull Elephants) from the sewer. We also found further collapses between Bute Street and Stuart Street which are now being repaired.

We will continue to work on these collapses until the 21st December 2018 when we break for Christmas. We will return on the 8th January 2019 to continue the work. During this period, there will be full pedestrian access to both sides of Stuart Street onto Bute Street and Tacoma Square.

Pedestrian access and access to all businesses will be maintained while we carry out this work.

Collapsed sewer with FOG - Nov 2018

Collapsed sewer with FOG cleared - Nov 2018

Phase 2A - Will follow on from phase 1
As soon as phase 1 is complete, work will begin on phase 2A which involves laying a new higher level sewer along Stuart Street between The Dock and Subway.

Phase 2B - Will follow on from phase 2A
As soon as phase 2A is complete, we will start work to install a new section of sewer along Bute Street, between Gourmet Burger and the lane near next to the Welsh Water site office. This will affect some of the businesses and residents along Bute Street. We will provide more information on this phase as we get nearer the time.

In November 2018, we will be working on site working 5 days a week (Monday to Friday) between 7 am and 7pm.

Click here to view our latest newsletter.

Want to know more?

We will also keep you informed of any changes to the works and provide you with regular updates throughout the scheme. You are also welcome to visit on site office at 19A Bute Street for more information. The site office is open 5 days a week, Monday to Friday between 9am and 5pm.

Please don’t hesitate to call in and speak to our Customer Engagement Officer, Tomos Davies. You can also reach Tomos on 07866818183 or You can also give us a call on 0800 085 3968 and we’ll be happy to answer any questions about the work. Just ask to speak with Sheena Thomas.