Dwr Cymru Welsh Water
Mermaid Quay Sewer Upgrade

Mermaid Quay

Welsh Water invested over £2 million to upgrade the sewer system in the Mermaid Quay area of Cardiff Bay. This work was 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 that was done in the area.

Work was needed following reports of local internal flooding caused mainly by the illegal discharge of fat, oil and grease (FOG) down the drains and other items such as wet wipes and cotton buds being flushed down the toilet that build up in the sewer and cause blockages. Frequent cleaning to clear the blockages damaged the sewer in Mermaid Quay which needed to be replaced.

Work carried out in the area was done in a phased way to minimise the impact on the local area. The first phase of the scheme involved the removal of the temporary footbridge on Stuart Street, repairing the original Victorian brick sewer, removing FOG blockages along Stuart Street and Bute Street and installing a new sewer pipe on Stuart Street was completed in December 2018.

Due to the number of collapses found in the area, a second phase to the scheme was delivered to fix the collapsed areas and install a new long term sustainable sewer within the existing sewer on Bute Street in Mermaid Quay was started in January 2019. This was completed in July 2019.

Here is a timeline of what we have done in Mermaid Quay since September 2017:

September 2017 - We installed a temporary bridge over Stuart Street once collapsed sewer was identified which was partly due to the heavy build-up of FOG in the area.

September 2018 – We started work onsite by removing temporary bridge and carried out some initial repairs on the collapsed sewer on Stuart Street.

October and November 2018 – We used specialist equipment to excavate hole and extracted FOG from Sewer. Identified further collapses under the bridge canopy which was excavated.

December 2018 and January 2019 - We continued to work on all collapses, making them safe and extracted FOG from the sewer along Bute Street and Stuart Street. We also installed new pipework within the existing brick egg sewer on Stuart Street, creating a new sewer.

February and March 2019 – We excavated two new manhole areas on Bute Street – one next to Fabulous Welshcakes shop and the other next to La Cha Cha’s and Bupa Dental Care and inserted new pipework into the existing sewer.

April and May 2019 - We modified and completed the manhole outside Fabulous Welshcakes shop and between La Cha Cha’s and Bupa Dental Care on Bute Street and relaid the paving in both areas, completing the sewer replacement work on Bute Street.

June and July 2019 – The work was completed on building the manhole on Stuart Street. Once this was completed, the area was tarmacked and the fencing was removed. This completed all work on the Mermaid Quay Sewer Replacement Scheme.

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