192 Research Journal of Fisheries and Hydrobiology, 6(3): 192-210, 2011 ISSN 1816-9112 ORIGINAL ARTICLES The Probability Of Zagros Mountains Environmental Pollution Due To Seismic Response Of Bakhtiari Dam Zaniar Tokmechi Department of Civil Engineering, Mahabad Branch, Islamic Azad University, Mahabad, Iran. ABSTRACT The Bakhtiari Dam is a planned arch dam on the Bakhtiari River within the Zagros Mountains in Lorestan Province, Iran. At a planned height of 315 meters (1,033 ft), it will be the world's tallest dam once completed and withhold the largest reservoir in Iran. The Zagros Mountains are the largest mountain range in Iran and Iraq. With a total length of 1,500 km (932 mi), from northwestern Iran, and roughly correlating with Iran's western border, the Zagros range spans the whole length of the western and southwestern Iranian plateau and ends at the Straits of Hormuz. In this paper, the probability of environmental pollution due to heavy metals caused by Bakhtiari dam failure is studied. Finite Element and ZENGAR methods are used to analyze the probability of pollution at dam downstream. Different dam cross sections and various loading conditions are considered to study the effects of these factors on the seismic behavior of the dam. Results show that the effect of the highest cross section is not the most significant for heavy metals pollution at the dam down stream. Pollution coefficient due to stress along Y axis (Sy) is always the determinant pollution. While, in all sections Sx and Sy are the determinant parameter affecting downstream heavy metal pollution and normally are bigger than Sz. And, Sz which can never be a determinant. According to results, when the earthquake accelerations are bigger, maximum pollution coefficient due to tensile stress at dam basement is increased. While, the pollution due the maximum compressive stress at dam basement depends on both earthquake acceleration and loading condition. Key words: Environmental pollution, Seismic Response, Bakhtiari dam, ZENGAR, FEM Introduction The main purpose of the Bakhtiari dam is hydroelectric power production and it will support a 1,500 MW power station. By trapping sediment, the dam is also expected to extend the life of the Dez Dam 50 km (31 mi) downstream. The Zagros fold and thrust belt was formed by collision of two tectonic plates — the Eurasian and Arabian Plates. Recent GPS measurements in Iran have shown that this collision is still active and the resulting deformation is distributed non-uniformly in the country, mainly taken up in the major mountain belts like Alborz and Zagros The seismic action on dams is the most important to be considered in dams safety studies and its effects on the environmental pollution (United States Army Corps of Engineers, 1990). In 21st century, hydraulic power exploitation and hydraulic engineering construction have been improved in many countries. Some high dams over 200m, even 300m in height, have been built in many areas of the world (Jianping et al., 2006). Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms (Mohsenifar et al., 2011; Allahyaripur et al., 2011). Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the elements of pollution, can be foreign substances or energies (Arabian and Entezarei, 2011), or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels (Arbabian et al., 2011; Hosseini and Sabouri, 2011). Pollution is often classed as point source or no point source pollution. Pollution has always been with us. According to articles in different journals soot found on ceilings of prehistoric caves provides ample evidence of the high levels of pollution that was associated with inadequate ventilation of open fires. The forging of metals appears to be a key turning point in the creation of significant air pollution levels outside the home. Core samples of glaciers in Greenland indicate increases in pollution associated with Greek, Roman and Chinese metal production. According to the statistics, the construction regions in many areas, are notable for their high environmental pollution (Wang and Li, 2006; Qasim et al., 2010 a; Qasim et al., 2010 b). Therefore, environmental studies affected by the seismic safety of large dams is one of the key problems that need to be solved in the design of Corresponding Author: Zaniar Tokmechi, Department of Civil Engineering, Mahabad Branch, Islamic Azad University, Mahabad, Iran. Tel: +98-918-873-1933, Fax: +98-871-3229437, E-mail: [email protected] 193 Res. J. Fish & Hydrobiol., 6(3): 192-210, 2011 dams. While, difficulties exist in determining the seismic response of dams (United States Army Corps of Engineers, 1995). The most important difficulty is dams complex geometry and forms, motivated by the topography and geotechnical character of the implantation zone and controlling the project pollution effects. According to the previous studies, usually 2D models corresponding to the higher section the dam have been used in the structural seismic analyses of the dams (Fenves and Chopra, 1984). While, normally there is a lot of variation in the dam foundation geometry which can be extremely make the study of the dam downstream pollution difficult. In this paper, the probability of environmental pollution caused by Bakhtiari dam failure is studied. Finite Element and ZENGAR methods are used to analyze the probability of pollution at dam downstream. Different dam cross sections and various loading conditions are considered to study the effects of these factors on the probability of environmental pollution due to seismic behavior of the dam. Materials And Methods Bakhtiari Dam: The Bakhtiari Dam is a planned arch dam on the Bakhtiari River within the Zagros Mountains in Lorestan Province, Iran. At a planned height of 315 meters (1,033 ft), it will be the world's tallest dam once completed and withhold the largest reservoir in Iran. Background: Preliminary studies for the dam began in 1996 and were carried out by Mahab Qods Consulting Engineers. The studies were carried out over a period of 33 months and in March 2000, the results were given to Iran Water & Power Resources Development Co (IWPCO). In May of 2005, IWPCO awarded consultation services for the project to Moshanir Consulting Engineers, Dezab Consulting Engineers, Econo-Electrowatt/Boyri and Stucky Pars Consulting Engineers. On April 30, 2007 the construction contract was awarded to China's Sinohydro Corporation who is also working with Farab Co. of Iran. The contract is worth $2 billion and is being funded with direct investment from China. Sinohydro signed the 118 month contract on March 15, 2011 and will be working with Iran's Farab. Construction: During construction, a total of six bridges will be built to support workers, vehicles and equipment in addition to various access roads. To divert the river, two tunnels, 1,151 m (3,776 ft) and 1,180 m (3,871 ft) in length will be constructed at the dam's left abutment. They will have discharge capacities of 2,090 m (6,857 ft) and 1,680 m (5,512 ft) respectively. To divert the water, two roller-compacted concrete cofferdams will be constructed. The upstream cofferdam will be 51 m (167 ft) high and the downstream 25 m (82 ft). Material to construct the dam including aggregate will come from the actual excavation of the dam site along with three quarries in the area. Design: The Bakhtiari will be a 315 m (1,033 ft) tall and 434 m (1,424 ft) long variable-radius arch dam. It will be 10 m (33 ft) wide at its crest and 30 m (98 ft) wide at its base while being composed of 3,100,000 m3 (109,475,467 cu ft) of concrete. The dam's reservoir will have a normal capacity of 4,845,000,000 m3 (3,927,905 acre·ft) and an active or "useful" capacity of 3,070,000,000 m3 (2,488,890 acre·ft). At a normal elevation of 830 m (2,723 ft) above sea level, the reservoir will have a surface area of 58.7 km2 (23 sq mi), maximum width of 1 km (1 mi) and length of 59 km (37 mi). Its catchment area will be 6,288 km2 (2,428 sq mi). The dam will contain two spillways. The main service spillway will be an 11 m (36 ft) diameter tunnel in the right abutment with two flood gates. The discharge capacity of this spillway will be 5,830 m3/s (205,885 cu ft/s). The second spillway will be two radial gates on the dam's orifice with a discharge capacity of 1,510 m3/s (53,325 cu ft/s). The dam's powerhouse will be located underground at the left abutment. It will be 161 m (528 ft) long, 64 m (210 ft) high and 24 m (79 ft) wide; containing 6 x 250 MW vertical Francis turbine- generators. Before reaching the power station, water will be transferred by six 51 m (167 ft) long penstocks. Feeding water to the penstocks is a 504 m (1,654 ft) long headrace tunnel with a three gate intake structure. Figure 1 shows the dam place. 194 Res. J. Fish & Hydrobiol., 6(3): 192-210, 2011 Fig. 1: Bakhtiari dam place Zagros Mountains: The Zagros Mountains are the largest mountain range in Iran and Iraq. With a total length of 1,500 km (932 mi), from northwestern Iran, and roughly correlating with Iran's western border, the Zagros range spans the whole length of the western and southwestern Iranian plateau and ends at the Straits of Hormuz.