Umgeni Water’s Mhlabatshane Bulk Water Supply Scheme in the Ugu District Municipality will eventually supply 100 000 people with potable water.
The vision of providing potable water to over 100 000 people in scattered rural and peri-urban communities on the lower south coast of KwaZulu-Natal is close to becoming a reality. After many years of careful planning and consultation with communities in the uMzumbe and Hibiscus Coast local municipalities, Umgeni Water is implementing a bulk water supply scheme. One of the key elements is the Mhlabatshane Dam on the Mhlabatshane River, situated approximately 25 km inland from Highflats.
The R200 million multi-disciplinary project includes all aspects of Bosch Stemele’s engineering capability and will be completed through five separate contracts.
“The project will bring this sparsely populated, deep rural community, a new dam and ultimately 60 ℓ of clean drinking water per person per day,” explains project director, Raj Ramchuran.
The community currently has access to 12 to 15 ℓ per day which is normally drawn from informal sources. The project includes the construction of the new dam, access roads, a pump house, water supply pipelines, a water treatment works and reservoirs. Mechanical, electrical and instrumentation works will also be carried out.
The planning phase ran from 2007 to 2009 with construction beginning early last year.
“The project is well under way and scheduled for completion and commissioning by December 2012,” points out Ramchuran.
The biggest challenge facing the project was the steep, single-lane access gravel road to the remote site, which made delivery of all construction materials extremely difficult and ruled out the use of a conventional concrete batch plant. The solution was provided by Lafarge Readymix. Their proposal to position a semi-mobile batch plant on site won Lafarge the concrete supply contract from the main contractor, Cyclone Construction.
“We had the right equipment and experience to tackle the job,” explains Lafarge’s project leader, Marco Sebastiano.
“Using one of our semi-mobile batch plants, we were on site and ready to produce in no time at all. This versatile unit can supply an average of 450 m³/day, with a peak output of over 50 m³/hour, which is coping readily with the current average project usage of around 200 m³/day. To date, we have supplied 27 000 m³ of concrete against the estimated total requirement of 30 000 m³.”
Sebastiano handled the contract negotiations with the contractors and is continually in communication with Cyclone Construction to ensure the smooth operation of the concrete supply contract. All raw materials are being sourced locally: pre-blended CEM III cement comes from NPC’s Durban plant and the independently owned Port Shepstone Quarry is supplying 19 mm stone. Contingency planning for the access road becoming impassable during periods of heavy rain included installing a 180 t capacity cement silo.
The main product supplied by NPC Cimpor is PRO-TEC (Cem III A 32.5 N).
PRO-TEC is specifically manufactured for the readymix concrete industry providing the benefit of a product that has a constant blend ratio of 55% Slagmore. This consistency offers the client greater control in their quality processes with the added benefit of reduced Heat of Hydration due to the high Slagmore content.
The greatest challenge NPC Cimpor faced in supplying cement to this project was to ensure safe delivery. The access road to site was complicated by a steep decline with a long radius bend at the top and a short radius bend at the bottom of the decline. Risk factors considered were the total weight of a fully loaded tanker including the vehicle equating to approximately fifty tonnes, this factor in its self poses a risk of the load pushing the vehicle out of control due to the steep decline. The other risk factors were the gradient of the road surface, the deterioration of the road surface due to constant use affecting the traction and causing excess gravel on the surface and peak demand required three to four deliveries a day. Consideration had to be given to minimise risk in the event of a run-away vehicle as the entire site was bellow this access road. After various meetings and adjustments to site, NPC Cimpor supplied all the cement without any fatalities or incidents.
Construction work on the dam started at the end of August 2010 and is approaching 90% completion.
“After our initial reservations about the production rate and quality from the mobile concrete plant, the supply has been good. We have also been getting good support in general from the Lafarge team to address any queries and help maintain the rate of construction,” comments Ramchuran.
“The associated raw water pipeline, which was a separate contract, was completed at the end of June. Tenders for the other main elements of the bulk water supply scheme include bulk storage reservoirs and a pump house building, which are currently being constructed and a new 8 Ml/day water treatment works and MEI works, which are in the process of being awarded. At this stage everything is on track for commissioning by the end of 2012.”
Pietermaritzburg based, Cyclone Construction, specialise in all types of civil concrete work and have extensive experience of working in remote areas. “The location of this dam is certainly challenging,” says site agent, Dave Roux. “Lafarge’s mobile batch plant is giving us much more flexibility and the best possible service under difficult circumstances. Once completed, the dam and the water reticulation network it is supplying will be an enormous benefit to thousands of people who previously had to draw their water from the Mhlabatsane River.”
Key facts of the project
The dam has a composite earth embankment dam with a central labyrinth type concrete spillway.
Classification: Category 2 medium significant
Crest length: 179 m
Maximum height above foundation: 24.8 m
Spillway width: 35 m
Effective length of labyrinth: 57.3m