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The dam that Bob (nearly) built

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#1
Millions of dollars are due to go to waste and thousands of people and their homes on the verge of being swept away in water as the Tokwe Mukosi Dam wall is inevitably going to collapse.

The Tokwe Mukosi Dam project in Masvingo province was first initiated as an idea by the colonial government but could not immediately take off because of the hotting up of the liberation struggle. At independence the project was high up on government projects. The dam was meant to rescue the drought prone Masvingo Province and provide water for irrigation and consumption by the entire Masvingo province.

On completion the dam should have been the biggest inland dam in the country bigger than lake Mutirikwi also in Masvingo. The dam being built at a cost of US$200 million is expected to carry nearly 2 million cubic litres of water when completed.

Construction of the dam began in the early 1990s and came to a halt in 2002 at the start of Zimbabwe's economic woes. The project resumed in 2009 in the hands of the Government of National Unity. Since its start the project has had several deadline extensions until the heavy rains of this rain season caught up with the project still incomplete.

[Image: Tokwe-River---Zim.jpg]
This little stream was going to become the largest dam in Zim

[Image: Rains-in-the-Tokwe-River-catchment.jpg]
Then a passing shower gave the engineers a kopseer

And the dam wall started to crash like the Zim economy
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[Image: Wall-collapsing-3.jpg]

[Image: Wall-collapsing-4.jpg]
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BWG
#2
Kassie, missed you at the meeting last night.
Besides the downstream residents, those caught stranded in the dam basin are demanding compensation to be moved. Bobville says their engineers predicted the dam would take three years to fill so there was lots of time to relocate people. Now it's happening one shot and Bobville are standing begging again for outside help! Don't you just love this entitlement dilemma that most African countries find themselves in.......

Hope Mteri survives if the wall goes?
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BIG FISH EAT LITTLE FISH....
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#3
<!-- m --><a class="postlink" href="https://www.facebook.com/photo.php?v=10152177603340600" onclick="window.open(this.href);return false;">https://www.facebook.com/photo.php?v=10152177603340600</a><!-- m -->
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#4
Bloody hell!!!!

Check the trucks still driving around the site.
2 at the bottom and one on top!
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#5
By David Coltart
11th February 2014

A top South African based specialist dam engineer has studied the photographs of Tokwe Mukorsi and has made these remarks. They are very technical but do convey the seriousness of the situation: “Tokwe-Mukorsi Dam is a concrete faced rockfill, or “CFRD”. This dam type comprises a rockfill embankment, with a concrete slab on the upstream face to create the impermeable barrier. The concrete face slab is generally constructed after the rockfill embankment is complete, or is at least well in advance, in order to ensure as much settlement as possible occurs before the concrete slab is in place. From the recent photographs of Tokwe-Mukorsi dam, it is clear that the construction river diversion capacity has been exceeded, either as a result of a design for an unusually high risk, which has some precedence in Zimbabwe, or due to the extreme intensity of the flood that recently entered the dam. As a consequence of the upstream concrete face slab not yet having been constructed, the rising reservoir simply flows through the permeable rockfill embankment. Although the rockfill embankment is normally structured to allow flow-through without damage, the expected flow is seepage, rather than a torrent. Furthermore, a subjective observation suggests that the downstream shell rockfill contains excessive fine materials, and consequently might be erodible, while a distinct pattern of the water emerging on horizontal surfaces is a typical sign that some of the fill might be less permeable than it should be. As long as the apparent situation persists, progressive erosion will continue and a real risk exists that the unraveling process could finally lead to the failure of the dam.” In separate comments the same engineer has advised that even if the “progressive erosion” is stopped and the dam is saved the wall will have to be rehabilitated which is going to be a very expensive exercise. What astounds me is how the Herald in particular has studiously ignored this story as if there is not a major crisis. All the engineers I have spoken to have said that whilst it is unlikely that the wall will break, it is seriously damaged now and, as the above statement concludes, if the progressive erosion is not stopped the dam could still fail. What the Zimbabwe public needs are regular reports from Government based on the factual developments at the dam as they evolve. There is far too much at stake for this issue to simply be wished away. - See more at: <!-- m --><a class="postlink" href="http://www.davidcoltart.com/2014/02/blog-zimbabwean-public-right-know-situation-tokwe-mukorsi-dam/#sthash.B8enta6q.dpuf" onclick="window.open(this.href);return false;">http://www.davidcoltart.com/2014/02/blo ... nta6q.dpuf</a><!-- m -->
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#6
Quote:Good news regarding Tokwe Mukosi just received from an engineer on site:

"There is no chance of wall washing away. The emergency spillway has been blasted in case the water level gets higher. The situation may look dire to outsiders but they have it fully in control."

This comes from a person who needs to remain anonymous but who is competent and has given an objective opinion. This is of course a great relief.

Congratulations to all those brave men and women working on the dam site who have been toiling day and night to save this wall and the lives of so many Zimbabweans.
[Image: big_fish_eat_little_fish.jpg]
BIG FISH EAT LITTLE FISH....
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BWG
#7
WATER, Environment and Climate Minister Cde Saviour Kasukuwere yesterday dissolved the Zimbabwe National Water Authority board after expressing displeasure with their response to flooding at Tokwe-Mukosi Dam, which has put the lives of over 60 000 people at risk.Minister Kasukuwere said this while presenting a ministerial statement on the flooding at Tokwe-Mukosi in the National Assembly.
Engineer Daniel Mackenzie Ncube chaired the board, deputised by Mr Andy Mhanga.

Other members were Eng Ian Mutunzi, Mrs Josephine Ncube, Mr Pitiel Mujuru, Mr Elijah Mathe, Dr Beauty Basile, Mrs Francisca Zinyemba, Eng Vavarirai Choga and Eng Albert Muyambo (chief executive).
“I have . . . dissolved the Zinwa board forthwith and a new board will be announced soon.

‘‘I want to assure honourable members here present and the nation at large that all systems have been activated to ensure that our infrastructure (dam wall) is secure,” he said.

In an interview afterwards, Minister Kasukuwere said the Permanent Secretary in the ministry, Mr Prince Mupazviriho, and other officials would run Zinwa’s affairs until a substantive board is appointed in the next two weeks.

“This board has allowed the situation to get to this stage and there was no reason for them to stay in office any day longer. We will be appointing hands-on people with the technical expertise in the new board,” he said.

The minister also said a team of five engineers had been appointed to conduct an independent assessment of the situation at Tokwe-Mukosi Dam, while others from the University of Zimbabwe had volunteered to assist.

In his address to parliamentarians, Minister Kasukuwere said water levels rose dramatically on January 27 resulting in the floods.
“The flood on January 27 and over a 24-hour period, a 17,3m rise in water levels was experienced giving a water depth of 38,28m. By February 5 water levels stood at 672,5m giving a water depth of 56,6m which was already 12,5m above the maximum 44m anticipated depth.

“The total annual flow at the site from the 40-year records is 300 million cubic metres. To date (February 11) the flow through the site has been 800 million cubic metres over a two-week period,” he said.

Minister Kasukuwere said they had adopted a number of measures to safeguard the dam wall.
“Raising the kerb to avoid overtopping of the dam which is now at level 682,4m which is 66,4m in height. Work on raising the kerb to avoid overtopping has been kept ahead of the rising flood waters. To date the kerb is 66,4 m high versus the depth of the flood waters which currently stands at 61,39m giving a 5-metre buffer above the flood waters. The plan is maintain that buffer to avoid overtopping,” he said.

He added that a channel at level 680m which is above the river bed has been excavated to provide an additional water discharge outlet through the right bank spillway.

The dam is being constructed by Italian company Salini Impregilo with Zinwa as the project engineer.

<!-- m --><a class="postlink" href="http://zimbabwe24sevennews.blogspot.com/2014/02/zinwa-board-fired-over-collapsed-tokwe.html" onclick="window.open(this.href);return false;">http://zimbabwe24sevennews.blogspot.com ... tokwe.html</a><!-- m -->
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#8
The Financial Gazette can reveal that while a recent risk assessment ruled out the possibility of the dam wall collapsing, the conundrum dramatically playing out at Tokwe-Mukosi has everything to do with a 1992 decision to change the dam’s design in order to cut costs.

The dam is being constructed by Salini Construttori, an Italian construction company, that has built more than 20 large dams in three continents. With the lake fast filling up due to well above normal rains currently pounding the drought-prone Masvingo province, water is now seeping through the dam wall, heightening concerns that if the seepage persists it could further weaken the massive structure.

Fears are that if the surging waters beat the builders on the race to the spillways, the massive water volume would spill over the wall and wash away the dam wall. Reports are that Salini Construttori is building the dam wall at a rate of one metre per day, the same rate at which the water is rising in the lake.

The Financial Gazette can reveal that the designers of the initial dam wall, Coyne and Bellier, had proposed a concrete arch dam wall with crest overflow which would have cost the country Z$641 million as at October 1992.

“This was considered excessive and so the Designs Division of the Department of Water Development undertook a thorough investigation into the design report from Coyne and Bellier and came up with a cheaper alternative, in the form of a concrete-faced rock fill dam,” reads part of a 1998 report on the dam.

When complete, the dam rock fill wall will stand at 90,3 metres high and 8,5m wide, containing 672 000 tonnes (or 1,9 million cubic metres) of rock. A 0,55m thick concrete face veneer with a volume of 15 270 cubic metres is part of the dam wall.

The colossal stone wall was designed to hold back 1 751 780 megalitres of water from a 7 120 square-kilometre catchment area. This makes the lake 30 percent larger than the country’s current biggest internal lake, Mutirikwe, also in Masvingo. The Tokwe-Mukosi reservoir, at a maximum depth of 82,7m and mean depth of 18,7m, will have a surface area of 96,4 square kilometres, compared to Lake Mutirikwe’s maximum depth of 56m and a mean depth of 14,5m.

The dam has twin drop inlets (16,6 metres in diameter) and tunnel (six metres in diameter) spillways that will each discharge 1 090,0 cubic metres of water per second along each of the approximately two-kilometre long tunnels. The outlets each have a diameter of two metres. Constructors are currently racing against the rising waters which they hope to beat to get to the spillways.

Work at Tokwe-Murkosi, which will have a power plant that is expected to generate 12 mega watts (MW) at peak and 6MW at lowest peak, began in June 1998 at a cost of just under Z$400 million. However, 16 years later, 12 years behind schedule, the dam is still incomplete and shrouded in serious controversy.

Completion of the dam, with four additional saddler dams to compensate for topographical constraints, is now literally five decades behind schedule, having been conceived way back in 1965 when the preliminary report was prepared by the then ministry of water development.

Coyne and Bellier were then commissioned to study the dam design that included a hydroelectricity power station and the company issued their report in September 1967.

However, the project was shelved due to the volatile political situation in the country as the indigenous population began to agitate for majority rule. The project was then revived soon after Zimbabwe gained independence in 1980 with Coyne and Bellier undertaking further studies and reviews of the dam design in 1985.

A detailed report with updated costs was submitted in December 1985. The ministry of energy and water development undertook further design studies in 1989, completing its report in 1990. However, the shape of the arch dam was unsatisfactory, which called for more sophisticated stress analysis that saw Coyne and Bellier, through French government funding, undertaking more extensive feasibility studies whose results were availed in 1993.

The report included studies of the arch dam design, irrigation works, the hydroelectric power plant, the water conveyance system, land preparation costs, proposed crop patterns and the economic analyses.

The completion of Tokwe-Mukosi will result in the development of five irrigation schemes, Tokwane North, Tokwane South, Hippo Valley, Runde South and Matibi II with Matibi II to be located south of Runde River billed to be the largest small-scale irrigation development in Zimbabwe. Financial Gazette

<!-- m --><a class="postlink" href="http://nehandaradio.com/2014/02/15/cheap-design-linked-problems-tokwe-mukosi/" onclick="window.open(this.href);return false;">http://nehandaradio.com/2014/02/15/chea ... we-mukosi/</a><!-- m -->
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#9
If you have got "just a little money" maybe you wish to invest it here............... :eusa_wall:

Chinamasa urges pension funds to invest in Zimbabwe’s largest inland dam

GOVERNMENT has appealed to pension funds to invest in Tokwe-Mukosi Dam, potentially the country’s largest inland dam which finance minister Patrick Chinamasa said is key to agriculture development and power generation in the southern part of the country.

The dam, which has been long in the planning as part of a strategic development to guarantee supply of water to the lowveld sugar and citrus estates, is 90 percent complete but progress has stalled since Italian contractor Salini Impregilio pulled out over non-payment last year.

“For Tokwe-Mukosi we need $30 million to finish the project before the next rains, but I am failing to raise that money,” Chinamasa told the 40th annual congress of the Zimbabwe Association of Pension Funds (ZAPF) in the resort town of Victoria Falls on Thursday.

“I want the money, it’s very little money but I am failing to get it.”

He appealed to pension funds to invest in the dam and other hydro projects saying that would give them guaranteed cash flows.

“If we invest in the dam we can sell water to sugar companies so there is cash flow in that investment. We can even sell hydroelectricity which also generates cash,” the minister added.

In November last year, the Infrastructural Development Bank of Zimbabwe (IDBZ) said it would issue a $50 million bond to fund the dam’s completion.

The dam was initially scheduled to be completed in June this year before the contractor suspended work over Government’s failure to settle an $84 million debt.

At completion, the dam could irrigate up to 25,000 hectares of sugar cane in the lowveld, with citrus plantations and power generation also planned.

Source: <!-- m --><a class="postlink" href="http://www.newzimbabwe.com/business-22407-Chinamasa+appeals+to+pension+funds/business.aspx" onclick="window.open(this.href);return false;">http://www.newzimbabwe.com/business-224 ... iness.aspx</a><!-- m -->
8 May 2015
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#10
"The dam was initially scheduled to be completed in June this year before the contractor suspended work over Government’s failure to settle an $84 million debt." - Good luck getting that back! Wow!
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