What the public should know about the Amaila Falls Project August 8, 2013 | By KNews | Filed Under Letters Dear Editor, The handling of the access road to the controversial Amaila Hydro Project has already caused much concern and dismay amongst a wide cross section of Guyanese. Now the main project is in jeopardy because of a number of factors including financial, construction, civil and post-construction uncertainties. Harza Engineering and Synergy along with Kaehne Consulting Limited of Canada were the entities that designed the civil works of the project. Sithe Global group of the United States is an international energy company. The company’s presence in Guyana is for the sole purpose of developing, owning and operating the Amaila Hydro Project. The company has already spent millions on the project and intends to spend more during the construction period. Sithe Global will supervise and manage the construction. The construction would be done by China Railway, a world famous infrastructure builder. Northwest Hydro Consulting Engineers (NHCE) of Xian, China would work along with China Railway. The project’s working drawings come in the English language, so NHCE’s task would be to interpret and translate the language to Chinese. Both companies have many workers. They plan to bring them along to do the work. There would not be any need for locals to be employed. On completion of the Project the Chinese would have completed a rock-filled dam of 60 feet high, 120 feet wide at the base and 24 feet wide at the top. Vehicular traffic would be possible on the dam. The dam begins from the hill on the right bank at the mouth of the Amaila River crosses the Amaila Falls and continues its course half a mile to the Kuribrong River.The dam crosses the Kuribrong to end at the foot of the hill on the left bank of the Kuribrong. The side of the dam facing the reservoir would be lined with cement 8 inches thick to prevent leaks. So the two rivers would be dammed between two hills and a reservoir of 23 square kilometres formed. An airstrip would be made on the left side of the Kuribrong and vehicles could cross the dam to reach the power house or the access road. An underground tunnel of 33 feet wide, 24 feet high and three-quarter of a mile long would be built. It resembles the tunnel across the English Channel. The purpose of the tunnel is to convey water from the reservoir to the turbines in the power house which would be located at the bottom side of the Amaila Falls. The reservoir–tunnel construction resembles a wash sink with the drain pipe at the bottom. The tunnel will begin at the bottom of the reservoir then proceed in a horizontal direction until it comes out at the slope of the Amaila Falls. One-inch thick steel plates would line the inside of the tunnel. Four smaller branched tunnels, called penstocks, would be connected to the main tunnel at the side of the slope of the Amaila. Each of the small tunnels would be connected – one to each of the four 25 MW turbines. But before this task is completed, the Chinese will have to blast away thousands of tons of rocks. Most of these rocks are the size of two-storey houses. An apparatus called a surge tank would be mounted about halfway on the topside of the tunnel. The main purpose of this system is to smooth out the violent pulsation and water shocking in the tunnel. It comprises a large bottle-shaped concrete structure mounted on the top side of the tunnel and protrudes above ground to about 90 metres high. The mouth of this huge bottle-shaped structure, which measures about nine feet in diameter, would be connected to the top of tunnel. The section that protrudes above ground measures 38 feet in diameter. It would be a reinforced steel/concrete structure and 18 inches thick. One-inch steel plates would be used to line the inside. It would be well sealed and filled halfway with water and trapped air. On the intake side of the tunnel, known as the headrace, an elaborate filtering system would be constructed. This is to prevent fallen trees, pieces of floating wood, and sediment from entering the tunnel. Around three shut-down valves would be incorporated there too. They would be automated. They serve the purpose of stopping the entire hydro at any given moment. The catchment area, referred to as the area where rain gathers before streaming down to the reservoir, is about 90 square miles. In case of heavy rainfall in the catchment area, a spillway is provided to prevent the reservoir from exceeding its storage capacity. Spillways are usually installed with hydraulically-operated steel sluice doors. But this one would be a natural spillway. The dam across the Amaila River would be constructed a little lower to allow the process to happen. The rivers, Kuribrong and Amaila, continue beyond the hydro site to about fifty miles until they reach the foot of the Ayanganna mountain where they were born. Both rivers beyond the site have no creeks or swamps emptying into them. They depend entirely on the natural springs at the base of Raleigh and Ayanganna mountains as sources of water in the absence of rainfall. The reservoirs would contain 30 days of reserved water. If there is no rain in the catchment area for a little over one month, electricity could be produced for about 26 days on reserved water. Should the dry weather continue beyond this time, the reservoir becomes dried out and the turbines starve. The project is located only about 52 miles from where the two rivers were born at the foot of the Ayangana Mountain, and so only 9% of all the water contained in the whole of the Kuribrong River would be dispensable to it. The bulk of the water of the Kuribrong would run off to merge with the waters of the full length of the Potaro River to form real rugged rapids at the Tumatumari, where indeed the project should have happened in the first place. Weight for weight, the civil works when completed on the Amaila Hydro Project would equal to nearly half the size of the civil works done on the Guri Hydro Dam in Venezuela. The Guri Hydro Dam, the third largest in the world, produces 10,500MW from 20 large Frances turbines with just about double the size of civil works to be done at Amaila. The Amaila would produce only 100MW from four 25MW Frances mini-turbines. Much too low compared to the size of civil works to be done. The power weight ratio of the Amaila project is daunting, since the annual tariff paid by GPL for the capacity provided by the project increases as the capital cost increases with dam length and dam height/reserve size and installed turbine capacity.The contractor needs to be cautious, because the general idea of hydro dam installations is to locate a site where there is less demand for too big and costly civil works and an abundance of water. The power/weight ratio must always be 80% to 90% ratings so that in the end the general public could enjoy cheap and reliable electricity. The high cost of electricity would also chase away investors. The engineering world today tends to produce products much smaller but with more performance and capacity. It’s a trend. The question is why the only possible site for a hydro dam installation in the Potaro area has been more than once neglected – the Tumatumari Falls. British Consolidated Gold mining company installed two small Kaplan turbines at the Tumatumari Falls. The facility produced more than enough to power the company’s two giant bucket dredges plus provided energy for the camp sites at Tumatumari and Konawaruk, nine miles away. With only servicing those two turbines, folks at Mahdia, just 9 miles away could have enjoyed 24-hour electricity supply. Instead, two fuel-guzzling diesels were installed to provide electricity only at nights. A reverse process indeed. It would be very inaccurate to say that the Tumatumari Falls was not chosen for the project because of fear of flooding the area. The Tumatumari Falls has a catchment area of nearly 680 square miles, compared to the meagre 90 square miles of the Amaila Falls. It is sufficient to erect a 40-feet high dam to maintain a reservoir of only 35 feet deep. All the water flow of the entire length of the Amaila River plus the water flow of the entire length of the Potaro River merge into one powerful flow before reaching the Tumatumari Falls. A regular and steady supply of water is guaranteed to maintain the level of the reservoir even through the dry period. So there is no necessity to have an oversized reservoir. The hydraulic potential of the Tumatumari Falls make it possible to install 5 Kaplan or Frances turbines each of 78MW summing a total of 390MW. That’s power enough to energize 150 large-size alumina smelting pots, similar to those used in Alcasa of Venezuela – enough to lure investors over a 30-year period or more. Investors go where there is plentiful, cheap and reliable electricity. An experienced engineer, with more than 15 years in the field of estimating cost of hydro dams, estimated that a hydro project at Tumatumari would cost no more than US$498,000 give or take a few thousand. He estimated the Amaila project to cost nearly US$1.2 billion plus or minus, on completion, because of its oversized civil works. It would not be capable of meeting the demands of development over the next 25 years. Delgado5 (Name and address provided)
Posted on: Mon, 12 Aug 2013 01:19:03 +0000
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