Civil Designer Showcase


January 2009 signaled Garth Gademan's tenth year at SSI Consulting Engineers. It was exactly a decade ago after completing his degree at the University of Natal funded by a student bursary from the company, that he first became a member of the team. It was also from that day that the allure of a continuous supply of water infrastructure design projects kept him routed. Two of these prized initiatives include the pipeline analysis for the raw water supply to Plettenberg Bay and more recently, the upgrade of the Gansbaai Waste Water Treatment Works.

Garth's fascination with water and sewer reticulation as well as waste water treatment works, started when he was working on various water infrastructure design projects in Port Alfred and Plettenberg Bay. "I was involved in the pipeline analysis for the raw water supply to Plettenberg Bay and came to fully appreciate the exciting nature of water infrastructure design when I first used Civil Designer's water module. The program expertly handled the analysis of the network and could calculate demand levels and identify problem areas with speed and accuracy," he explains.

According to Garth, the pipeline analysis was preceded by a Bitou Water Augmentation study which was requested when the Bitou Municipality experienced difficulty in meeting the water demand over the 2000/2001 summer period. This was largely due to the high peak demand in the summer months from an influx of tourists and holiday-makers, which placed extreme pressure on the existing water supply infrastructure.

"We found that the bulk water pipeline from the Keurbooms River to the central waterworks, which had a limiting capacity of 7.6 mega liters of water per day, was sufficient during the low season. However, this capacity needed to be increased during the peak season to accommodate at least 12 to 13 mega litres of water per day."

"As a result, existing pipes were refurbished in order to reduce the amount of head losses and hence optimize the capacity. During off peak periods the excess flow from the optimized capacity was diverted and stored in the Roodefontein dam and then accessed during the seasonal periods to increase the total bulk water supply capacity to the water works," explains Garth.

According to Garth, the terrain itself presented minor challenges. "In general the pipeline is located on flat terrain but does pass through a steep valley area for the river crossing. We therefore opted for the Plains area because it was much flatter and easier to access.

There were no significant environmentally restrictive areas on the venture as the project addressed bottlenecks on the existing pipeline route. I found the project to be especially interesting because it forced me to consider more efficient methods of increasing water capacity. We've completed the first phase of the pipeline upgrade in 2005," he says.

Another more recent venture was the R25 million upgrade of the Gansbaai Waste Water Treatment Works which was requested by the Overstrand Municipality. "The challenges on this project were numerous. The existing works were unable to accommodate the entire area and the quality of water was deteriorating. It was therefore proposed that the area of Gansbaai receive an immediate two-phase upgrade of their existing waste water treatment system."
  According to Garth, the original intention was that a first phase of a 2 mega litre temporary upgrade of the existing works would be followed by a second phase which would entail the development of a new Waste Water Treatment Works to accommodate the ultimate capacity of 5 mega litres of sewage per day. With the completion of the second phase, the old works will be converted into a pump station.

One of the biggest design challenges on the project entailed the environmental restrictions relating to the huge milkwood forests. "We were not allowed to remove these trees. In the end, I found that the existing milkwood forests created a nice balance around the new Waste Water Treatment Works. The end result has therefore worked out better with more than 5000 permanent residents, many living in informal settlements, benefiting."

In order to avoid the costs and complications of developing a second wastewater treatment works, a small footprint technology in the form of Nereda, a granular sludge treatment developed in the Netherlands, was selected for the upgrade. This site is more aptly located as it is in the vicinity of irrigation areas which can make use of the final effluent, rather than adding load to the potable water system. We are therefore extremely optimistic about the upgrade program as it will benefit the entire community and improve their lives significantly," explains Garth.

The extent to which the community's lives will be transformed can only fully be understood if one considers their current situation. The existing waste water works is able to treat roughly 300 cubic metres per day. In reality, there is around 600 cubic metres per day requiring treatment. This could result in a hydraulic and severe biological overload which would cause a biological hazard.

According to Garth, part of being a civil engineer is not just ticking off the project check box, but thinking laterally and creatively about alternative solutions. Experimenting with various modeling scenarios and adjusting flows to test the best output solution is what drives this talented Associate Engineer.

"SSI Consulting Engineers is an innovative company that likes to invest in new techniques and methodologies. We use forward thinking software like Civil Designer but also learn from our international holding company DHV when it comes to new technology like Nerada. It is when civil engineering introduces new innovative tools and practices like these that I get truly inspired about the future," says Garth in closing.

image Garth Gademan has a Civil Engineering qualification and Masters degree in Waste Water Treatment. After building an extensive track record as an Associate Engineer at SSI Consulting Engineers in water and sewer reticulation, Garth progressed to become a specialist in Waste Water Treatment Works.

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