DEIA Hydro Project Hulu Terengganu (LULUS) MAC 2009
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Tenaga Nasional Berhad (TNB) is planning to construct and operate a 212MW Hulu Terengganu Hydroelectric Project. The proposed Project comprises two storage reservoirs namely the Puah Reservoir (6,000 ha) and Tembat Reservoir (130 ha), two dams (one each at Sg. Terengganu Mati and Sg. Tembat), an underground power house, and an 802 m diversion tunnel between the Tembat and Puah Reservoirs. This hydroelectric development will generate an average of 406 GWh peaking energy per annum to the national grid. Timbers will be extracted from the proposed 6,130 ha of the inundated area (Tembat and Puah Reservoirs) and the Terengganu State Government has further decided to extract timber from the 12,620 ha of the proposed catchment areas around the Tembat and Puah Reservoirs. The proposed project is expected to be completed by the end of 2012.
The proposed Hulu Terengganu Hydroelectric Project and the logging of 18,750 ha of indundated and catchment areas are prescribed activities under the following schedules of the Environmental Quality (Prescribed Activities) (Environmental Impact Assessment) Order, 1987 as follows: 6.
Forestry (b) Logging or conversion of forest land to other land use within the catchment area of reservoirs used for municipal water supply, irrigation or hydro-power generation or in areas adjacent to state and national parks and national marine parks. (c) Logging covering an area of 500 hectares or more.
Power Generation and Transmission (b) Dams and hydroelectric power schemes with either or both of the following: i. Dams over 15 meters high and ancillary structures covering a total area in excess of 40 hectares ii. Reservoirs with a surface area in excess of 400 hectares.
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STATEMENT OF NEED
The needs for the hydroelectric power plants are as follows; •
To meet Peak Power Demand The electricity load profile in Peninsular Malaysia has a large portion of base load, approximately 10,000MW and about 4,000MW of peak demand. To provide for a safe and reliable power system, electricity demand must be met by a combination of base-load and peaking power plants. Base load demand is usually supplied by power plants that operate on long duty cycle providing power output at a constant load. Most of these power plants are either coal-fired steam plants or gas fired combined cycle plants. Peaking plants usually operates on short duty cycle at varying loads. These stations have fast start-up capability that would be able to come into the system in a very short time and would be taken off once the peak periods are over. Currently, the types of power plants that are capable of providing peaking duty, in terms of technology and economics are the open cycle gas turbines (OCGT) and hydroelectric power plants.
Reliable Fuel Source In ensuring effective and reliable power plants, their fuel source should be readily available and not subjected to market volatility and availability. The price of fuel (oil) has increase rapidly in the last few years, and once peaked at USD147 per barrel in July 2008. The limited supply of gas by Petronas for the power sector, capped at 1,350 mmscfd, means that there will be very little spare capacity to meet additional requirement for the power sector. Water, on the other hand is relatively abundant, renewable and cheap. It is therefore the strategy of the Government and TNB to meet the growth in base-load and peak-load power by non-gas fuel sources. Coal-fired thermal plants (Tanjong Bin, Jimah and Manjung) and possibly hydro resources from Sarawak will be expected to meet base-load demand growth in the next 10 years. As for peak-load, the only economic non-gas option will be to harness the remaining hydroelectric resources in Peninsular Malaysia.
Reducing Carbon Emission Another advantage of opting for hydropower instead of OCGT is the potential reduction in carbon emission. The Hulu Terengganu Hydroelectric Project is capable of generating an annual energy of 406 GWh which can be translated to an equivalent carbon reduction of approximately 250,000 tons/year
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NO PROJECT OPTION
Without the Project, TNB’s dependence on fossil fuel, primarily gas and coal for generating energy will continue. Since the cost of fossil fuel has been on the increase for the past ten years and particularly in recent years, the cost of generating energy will increase and ultimately the users will have to pay more for every unit that they use. This Project will also provide the peaking power required to ensure the stability and security of the system.
The proposed Project area is located at the north of existing Kenyir Dam in Kuala Berang, Daerah Hulu Terengganu, Negeri Terengganu Darul Iman. It is about 50km from Bandar Gua Musang – Hulu Terengganu roadway, and about 65km west of Kuala Terengganu. The coordinates of Puah and Tembat dams are N 05o 09’ 6.1”, E 102o 35’ 9.8” and N 05o 13’ 7.0”, E 102o 36’ 6.8” respectively. The project area is located about 20 km away from Saddle Dam A of Tasik Kenyir which is situated to the North-West of Kenyir dam. 5.2
The Hulu Terengganu Hydroelectric Project can be classified into three geographic clusters. These clusters are: (1) (2) (3)
the Puah Dam and its associated Works; the Tembat Water Transfer Scheme; the Power Station and Switchyard Complex.
The salient features of the proposed Project are as follows: • •
• • • • • • •
Two reservoirs known as Puah Reservoir (6,000 ha) and Tembat Reservoir (130 ha); Two dams; one a 78 m high earth-fill dam (Puah) on the upper Sg. Terengganu Mati just downstream of its confluence with the Sg. Puah and the other a 30 m high roller compacted concrete (RCC) dam on Sg. Tembat; An underground powerhouse having 212 MW (2 x 106MW) turbine/generator units. Two intakes, one each at Tembat Reservoir and Puah Reservoir; Two unlined low pressure diversion tunnels to carry flows from the Tembat reservoir to Puah reservoir (802 m) and Puah reservoir (450 m) to the drop shaft; Two surge shafts near the top of the drop shaft; Two high pressure, steel lined penstock tunnels to carry flows from the drop shafts to the powerhouse; A 1.3 km long, concrete lined, free flow tailrace tunnel to carry flows downstream from the powerhouse to the Tasik Kenyir; A 600m long access tunnel to the powerhouse;
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• • •
A switchyard located above ground near the access tunnel portal; Approximately 10 km (estimated based on the existing roads) of new access road to the dam sites, access tunnel and power house; and A 2.2 km long transmission line, which will connect the power station to the existing Kenyir-Tanah Merah line.
EXISTING ENVIRONMENT, MITIGATING MEASURES
The study area has varied landuse types, consisting of primary tropical forest, agriculture, aquaculture, settlements, resort and recreational facilities, water bodies and infrastructures. Forest occupies the largest area, followed by water bodies. Forest occupies the largest area, followed by the lake. Agriculture is confined to a small area, to the north of Pengkalan Gawi. Settlements are located along the main road to Pengkalan Gawi. They are surrounded by rubber and oil palm small holdings and orchards. Project implementation will reduce the forested area as a result of the formation of two new lakes and the construction of dam, power station and access roads. This impact on the landuse is permanent. The formation of the two lakes may lead, at a later stage, to the establishments of resorts, chalets and other tourist facilities. It is suggested that development of tourism facilities take into consideration the area’s carrying capacity.
GEOLOGY AND SOIL
The geomorphological patterns of the study area consist of undulating hilly and mountainous terrain. The highest area is represented by Gunung Lawit to the north at 1518m above sea level. There are other hilly terrains including Gunung Batil (1445 m) and Gunung Susu Dara (1452 m). The elongated terrains at the western part with north-south trend is known as Granit Banjaran Sempadan while moderately high and undulating terrains between mountainous terrains are dominated by metasedimentary rocks. The two main lithologies consist of igneous and metamorphic rocks. In general, an acidic intrusive granitic rock covers approximately 40% of the study area followed by metasedimentary rock (about 30%). Meanwhile, the rest of the area is covered by other rocks such as volcanic, limestone and sedimentary rocks. The metamorphic rocks include phyllites, schists and metasandstone of possibly Carboniferous age while the sedimentary rocks consist of shale/mudstone and small amount of limestone and conglomerate of Permian to Triassic age. The anticipated geomorphology and geological impact of the project are the permanent landscape change, and disturbance on rock stability and seismicity caused by the cut and fill activities, drilling and quarrying of rock and reservoir formation. Seismic activity should be
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monitored and innundation should be carried out slowly to avoid great disturbance to the fault structure underneath the dam. Soils in the area are formed from parent rock of granite, metasedimentary and volcanic rocks. The residual soil from the weathering of granitic rock is characterized by reddish yellow in colour with texture of sand while soil developed from metasedimentary and volcanic rocks give finer texture with yellowish colour. The pH value of soils in the study area is low. The organic content ranges between low and moderately high. Soil at Tembat Dam is more sensitive to erosion compared at Puah Dam which is due to their higher elevation and steeper slope.
The existing average sediment yield for Sg.Tembat and Sg.Terengganu Mati are 84.5 tonnes/ha/year and 37.02 tonnes/ha/year, respectively. However, the rate of soil loss for the worst case scenario (clear felling of trees) is very high at an average of 1,456.8 tonnes/ha/year 1,769.7 tonnes/ha/year for Sg. Tembat and Sg. Terengganu Mati respectively. To reduce the erosion impact, selective logging is proposed for the catchment area and buffer zones should be introduced along rivers of order 3 and 4. This method of logging will reduce the rate of soil erosion by almost 80%. The predicted soil loss when selective logging is adopted is 255.4 tonnes/ha/year for Sg. Tembat and 309.7 tonnes/ha/year for Sg. Terengganu Mati.
The climate is hot and humid with high average annual rainfall, temperature, evaporation and humidity. Humidity, temperature and evaporation show very little variation. The humidity is about 80 % all year round and temperature range from 21 to 32OC. The average annual rainfall depth at the project area is approximately 4138.30 mm ranging from 2517 to 8714 mm over 20-years; the maximum rainfall was recorded in 2001 while the lowest is year 1996 recorded at 2517 mm. The development of future reservoirs will act as a potential evaporating surface that decreases the surface temperature, cools the lower atmosphere, decreasing upward motion, and increasing sinking air mass. This, however may not have a significant impact on local climate as the future Tembat and Puah reservoirs are relatively small compared to Kenyir.
There are two main river catchments in the study area, namely Sg. Terengganu Mati and Sg. Tembat. The Sg. Terengganu Mati catchment comprises more than 13 major tributaries; Sg. Rat, Sg. Lata, Sg. Buluh, Sg. Kura, Sg. Rusa, Sg. Limbang Besar, Sg. Limbang Kecil, Sg. Jalang Kecil, Sg.Ladang, Sg. Rang, Sg. Sireh, Sg. Jalang and Sg. Puah. Meanwhile, Sg. Tembat catchment consists of five major river tributaries: Sg. Lawang, Sg. Anak Tembat, Sg. Ayur, Sg. Tedung and Sg. Ayub. The distance of Sg. Terengganu Mati from their headwater is 55 km long and 30 km long for the Sg. Tembat. Total catchment size for Sg. Terengganu Mati is estimated to be 410 km2 and 101 km2 for the Sg.Tembat Catchment. Average runoff Hulu Terengganu Hydroelectric Project
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for Sg. Terengganu Mati is 2,040 mm and 2,200 mm for Sg. Tembat. The maximum daily flow for Sg. Terengganu Mati is 40.00 m3/s, mean daily flow is 28.00m3/s and the minimum flow is 15.00m3/s. The maximum daily flow for Sg. Tembat is 5.50 m3/s, while the mean and minimum daily flows are 2.50 and 1.00 m3/s respectively. Based on field measurement, daily flow of Sg. Terengganu Mati ranges from 0.146 m3/s to 16.60 m3/s with range of velocity from 0.10m/s to 2.20m/s. Daily flow of Sg. Tembat range from 3.50 m3/s to 5.20 m3/s with range of velocity from 0.18 m/s to 0.915 m/s. During high flow condition, the figures increase 2 to 3 folds, and their range from 32.60 m3/s to 88.87 m3/s for Sg. Terengganu Mati and figures increase 3 to 5 folds for Sg, Tembat, it ranges from 11.84 m3/s to 22.75 m3/s. The minimum flow analysis was performed to determine the magnitude and frequency of low flow for the proposed project site. Analysis of minimum flow was determined based on three methods: 1) Mean Annual Minimum flow (MAM), is 4.520 m3/s for Sg. Terengganu Mati and 0.976 m3/s for Sg. Tembat. 2) 10% of the average annual flow; 4 m3/s for Sg. Terengganu Mati and 0.55 m3/s for Sg. Tembat and 3) Based on the SMEC Engineering study, minimum daily flow was 3.3 m3/s (Sg. Terengganu Mati) and 0.80 m3/s for Sg. Tembat. The hydrological impacts associated with soil investigation, collection of data and lines cutting are expected to be minor or no significant impact during pre-construction. During dam construction, major activities such as earthwork and site clearing, river diversion, construction of access roads and construction of the Puah and Tembat dams are expected to alter the characteristic of the river regime. Increase of surface runoff leads to increase in flow and river banks erosion. The impact can be mitigated by preparing and implementing erosion control plan. The diversion channel should be designed to take into account the maximum capacity of the diverted channel to ensure reduction in water velocity. The alignment of the diversion should be optimized so that the length of dried up river immediately after the dam is minimized Bucking, skidding and hauling, landing and loading of the timbers during logging operation will have the effect of increasing surface runoff as a result of a reduction in the capacity of the area to absorb rainfall and reduction in infiltration. This change in the flow regime will increase river siltation and affect the morphology of the river system such as the reduction in the widths and depths, and increase in the velocity of flows in the rivers that will eventually affect the riparian ecosystems, vegetation, nutrient and food chains for the aquatic fishes and benthos. Selective logging method is recommended for the catchment area that will not be innundated. A 30m river buffer where no logging is allowed must also be maintained to the impact of erosion. During reservoir filling and dam operation, the river stretches downstream of the dam (Sg Tembat-4.14km and Sg Terengganu Mati-4.82km) will be dried up if no water is released during reservoir filling. The river ecology will be completely destroyed. To mitigate the impact a minimum flow of 1.0 m3/s for Sg Terengganu Mati and 0.5 m3/s for Sg Tembat is recommended.
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In this study, 23 stations were selected at Sg Terengganu Mati and Sg Tembat and their tributaries to assess the existing water quality. Samples were taken in July 2008 and analysed based on standard methods suggested by American Public Health association APHA (1995). The laboratory analyses were carried out by accredited laboratory at ALS Technichem (M) Sdn Bhd (MS 120/IEC 17025, SAMM No. 147). The values of water quality parameters recorded at Sg Terengganu Mati are good. Based on the General Rating Scale for the Water Quality Index (WQI), Sg Terengganu Mati is classified as clean (Class I). The result for Sg Tembat indicates that the existing water quality is also good (Class I). Two water quality impact “scenarios” were simulated for this study, namely (i) the impact of logging activity based on clear felling and selective logging methods, and (ii) the impact of Puah-Tembat dam construction with respect to river carrying capacity. In the worst case scenario (clear felling), TSS concentration during high flow along Sg Terengganu Mati is predicted to increase to Class IV and V (INWQS). The river carrying capacity is considered as sensitive with low carrying capacity. For Sg Tembat the TSS concentration along the river falls to Class III at middle stream and Class IV at upstream and downstream stretches during high flow. Again, the river carrying capacity is considered as sensitive with low carrying capacity. For selective logging, the value of TSS at Sg Terengganu Mati during high flow will reduce to Class III at the upstream and middle stream while Class IV is expected in downstream sites. The river carrying capacities at these stages are considered as sensitive (high flow) and moderately sensitive (low flow). At Sg Tembat, TSS concentration during high flow is expected to fall to Class II and Class III (>30 mg/l;