Workers in a dam big hurry
C ONSTRU C T I O N teams are working through the nights to finish building KwaZulu-Natal’s newest dam near the town of Mooi River.
Work began on the new Spring Grove Dam about 18 months ago, and engineers hope to finish the dam wall before the target date in February next year.
The dam-building project has been fast-tracked by the government to meet the rapid growth in water demand by industries and almost 5 million people in the Durban and Pietermaritzburg area.
According to an article in the latest edition of the Water Research Commission’s “Water Wheel” magazine, the 37mhigh dam wall will store about 139 million cubic metres of water from the Mooi River, flooding the surrounding river valley and creating a new dam with a surface area of more than 1 000 hectares.
The Spring Grove Dam is the fifth dam to be built on the Mooi-Mgeni River System, which already includes dams at Midmar, Albert Falls, Nagle and Inanda.
Altogether the five dams will produce about 395 million cubic metres of water a year, with Spring Grove providing about 60 million cubic metres of this water – about 15 percent of the total water provided by the system.
Several privately owned properties will also be flooded by the new dam and the owners would have to be compensated for loss of their land west of the villages of Nottingham Road and Rosetta.
Danie Badenhorst, technical director of BKS consulting engineers, told The Mercury that about 180 burial sites would have to be exhumed and relocated, and permission had been obtained from the families involved.
Towards the western end of the future dam, a set of San rock paintings just below the Inchbrakie Falls has been carefully carved out of the rock and taken to the KwaZulu-Natal Museum in Pietermaritzburg.
To compensate for environmental impacts, several rare plant species have been rescued and relocated above the future dam surface level.
A fish barrier will be built above the Inchbrakie Falls, because the falls will be flooded.
Until now the falls have acted as a natural barrier to prevent smallmouth bass in the river from migrating upstream to compete with trout, which have become an important part of the area’s tourism economy.
The new concrete fish barrier will mimic the barrier role of the Inchbrakie Falls to prevent bass from taking over the feeding and breeding habitat of trout further upstream.
Yet even though construction crews and engineers from BKS and Group 5-Pandev are working 24 hours a day to meet the February target date, Spring Grove will not resolve the longterm water demands for the Durban-Pietermaritzburg region. Early last year, eThekwini water and sanitation chief Neil Macleod warned that water use from the Umgeni System already exceeded the assured supply of water by about 18 percent and this could lead to water restrictions.
Although Macleod’s warning to the council came shortly before the decision was made to fast-track the construction of Spring Grove, he cautioned that it would be imprudent to allow any further major development in the region until there was certainty about a “significant” increase in future water supplies.
Macleod noted that there were plans by the government to build another large dam on the Umkomazi River, but he doubted that this proposed dam would be completed before 2023 at the earliest.
As a result, eThekwini would have to consider supplementing the city’s water supplies via a new desalination plant or by recycling sewage effluent.
Members of the public were invited earlier this year to comment on the plan to recycle sewage water into tap water using microfiltration membrane technology, but no final decision on this proposal has been announced yet.