DCWW advise they are hoping to start repairs on the sewer chamber sited in the river below Ynys-Afan Bridge in June 24. This is following a number of years of AVACC pressing home the fact that this asset is becoming a real risk of catastrophic failure. This is the main trunk sewer which runs down the valley. At present there is a hole in one side which allows the river water to enter the trunk sewer network and cause problems lower down the catchment. Previously this had been planned as a future project but due to climate change with obvious increases in rainfall and frequency, decisions have been made to start this project immediately. AVACC welcome the decision but this will impact on fishing to some extent. NRW have been consulted and we hope therefore this will ensure control measures for silt migration will be kept to a minimum whilst maintaining fish passage. We are advised that the bridge will be open throughout but there may be some restrictions during crane operations. it is expected that the project will take approximately 6 weeks depending on weather conditions.
You will note the 3 yellow pump units are in position as a precautionary measure. These pumps, if needed will pump effluent from the upstream chamber to the downstream chamber and bypass the damaged chamber site to avoid discharge into the river.
We first reported this problem to DCWW in early April 2021. We highlighted then our concerns with regards to the foundations being eroded by the river to an extent that the chamber structure could possibly fail which would result in the whole of the valley trunk sewer being discharged into the Afan. During the repairs recently undertaken, divers were employed to assess the condition below the chamber. Our initial concerns and fears were confirmed. The foundations of the chamber had parted company from the upper structure allowing sewage to leak into the river undetected for a period which we will never know. The repairs required the trunk sewer to be bypassed before the external repairs were undertaken by the divers (please see pics). Provision for the bypass were already in place to allow this work to be completed by placing bagged material around and under the chamber. This material sets when in contact with water, we are advised that the bags are biodegradable. Concrete was then poured into the cavity between the bags and old chamber. The hight of the chamber has been slightly reduced and they intend to cap the whole chamber once internal repairs are completed.
We were advised that all in water work would be completed by week ending 19/07/24. However following a final inspection by DCWW, they decided to insert a liner into the section that crosses the river. It is estimated this will take a further week. We have however been advised that there has been a delay in manufacturing the liner. The crane is due back on site on 19/08/24. Unfortunately the trunk sewer will need to be bypassed to fit this liner, and will require flexi pipes to be placed across the river, below the bridge. Hopefully this will not disrupt fish migration and members too much.
