Rehabilitation of Lower Sundays Canal delayed after recent floods

Image: SANews.gov.za

The department said the postponement of the project is due to the recent heavy rainfall that resulted in flooding in various areas of Nelson Mandela Bay Municipality (NMBM), which may have compromised infrastructure, including water supply systems.

“This is to afford the municipality time to complete its disaster assessment and response, as well as the resumption of the state of readiness for the project,” the department said in a statement.

The Lower Sundays River Canal forms part of the Lower Sunday’s Government Water Scheme (LSGWS).

The LSGWS canal system supplies two main users with bulk water, including agricultural users, the Sundays River citrus producing area, and domestic users, Kirkwood, Uitenhage, Enon, and the Nelson Mandela Bay Metro amongst others.

The LSGWS forms part of the greater Orange-Fish-Sundays Inter Basin Transfer Scheme and it transfers 740 million kilolitres of water annually from the Gariep Dam to the Eastern Cape through the 80km Orange-Fish Tunnel.

The repair of the canal is a result of a May 2017 incident, where a section of the canal embarkment slipped, about 4.4km south of Enon.

The department then had to construct a temporary embarkment using a plastic membrane to ensure the continuous supply of water to users. However, a secondary embankment failure has occurred, with 200m downstream of the initial embankment and canal failure.

The work on the canal includes demolishing the existing canal at the upstream and downstream tie-in sections, surface preparations, and the placement of a High-Density Polyethylene (HDPE) liner over the upstream and downstream tie-ins.

The department emphasised that during the tie-ins construction, the canal will not be completely shut down, but there will be intervals at which, upon completion of certain segments that are being repaired, water will be allowed to flow through to the dams for end users.

“During this period, on average, the canal will be closed for seven to ten days for construction and be opened for seven days for the flow of water to fill up dams for the areas to be impacted by the temporary shutdowns. The major domestic users to be impacted by the canal supply interruptions will be the towns of Addo, Paterson and the Nelson Mandela Bay Metro.

“However, measures are being put in place to ensure less interruptions to these areas. Kirkwood, which is located upstream of the shutdown point will continue to be supplied from the main canal. Addo and Paterson which are supplied from the Caesar’s Balancing Dam, downstream, which will be filled prior to canal shutdown, and continuously recharged during the seven days open flows,” the department said.

The department also noted that balancing dams are designed to act as multipurpose reservoirs and are commonly used to serve as distribution points from where water is diverted into pipelines, canals, or to serve as pumping stations or store water for short period and immediate usage.

It said the seven days closure and opening interval of the canal was determined based on the storage capacity of these dams.

Considering the developments, the department said it will continue with its consultations on the new start date of the canal tie-in to bring all stakeholders on board to enable them to plan for this period and inform their customers.

“The department continues to hold meetings with these stakeholders to discuss action plans to mitigate any possible challenges and bottlenecks when the planned dry period gets implemented. It is important to note that the emergency rehabilitation to be carried out is critical for the reliability and sustainability of supply to the users. If the damaged canal remains not repaired, the scheme stands a total collapse,” the department said.