One question per week, 2015.11.4 (EIA discussion); a reward of 3 Wealth points for participation (certain scores are given to the top 40 participants)

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This post was last edited by Zhang Xiaopeng on 2015-11-4 at 15:55. The proposed hydroelectric power plant is the second unit in the cascade development plan for the A River’s hydropower resources; it is of the dam-type design, intended primarily for power generation, with additional functions related to urban water supply and flood control. Its total installed capacity is 3,000 MW. The average annual flow at the dam site is 1,850 m3/s. The designed height of the dam is 159 m, the designed normal water level is 1,134 m, and the storage capacity for regulation is 555 million m3, granting it the ability to provide cyclic regulation; it can also carry out daily peak-shaving tasks when required by the power system. The method used for flood discharge and energy dissipation is splash discharge. The project construction area is equipped with a sand and gravel processing system, concrete mixing and cooling systems, mechanical repair facilities, vehicle repair and maintenance shops, as well as owner’s camp and contractor’s camp. The peak number of workers during construction is 9,000, and the total construction period is 92 months. The project requires the expropriation of a total area of 59 km2 for construction, and 3,000 people need to be relocated; 3 centralized settlement sites for the immigrants have been established. The area upstream of the dam site features a high-mountain canyon landscape, and the water environment quality in the reservoir section is classified as Class III, with the current water quality meeting the standards. At the normal water storage level, the length of the backwater area is 96 km. The flooded area of the reservoir contains spawning grounds for fish species unique to River A, whose spawning period is from March to April. It is predicted that after the reservoir is filled with water, a weak seasonal stratification of water temperature will occur; the water temperature exiting the reservoir in March and April will be 1.8°C and 0.4°C lower, respectively, than the natural water temperature at the dam site. City B is located about 27 km downstream of the power plant, built along the river. The intake points for the two existing water treatment plants, as well as those for 7 industrial enterprises, are all situated on River A. Urban domestic wastewater and industrial wastewater are discharged into River A after being treated. After the power plant was completed, the water intake points of the two existing water treatment plants in City B were moved upward to the reservoir area. Question: 1. Identify the main environmental protection objectives of this project. [Reference Answer] (1) Endemic fish species of River A and their spawning grounds. (2) Current status: River sections in the A River reservoir area and the completed reservoir area (with water supply functions) where there are three types of water bodies. (3) The two existing water intakes in City B downstream of the power plant, as well as the water intakes of 7 industrial enterprises. (4) Residential areas to be relocated and their resettlement sites. Scoring criteria: One point is awarded for each correct answer. 2. The main factors affecting aquatic organisms during the operation period of this project. 【Reference Answer】 (1) The barrier of the dam. After the dam was built, it prevented the exchange of aquatic species between the areas above and below the dam, particularly hindering the movement of fish species unique to River A as well as other migratory fish. (2) Changes in hydrological conditions. Due to the reduced flow velocity in the reservoir area, the fish population structure there may change: fish adapted to flowing water may decrease or disappear, while those adapted to still water will increase ； The prey organisms in the reservoir area also change, with some of them showing a tendency to increase further. (3) Reservoir area inundation. It destroyed the spawning grounds for the unique fish species of River A. (5) Low-temperature water. It has an adverse effect on the aquatic life in the reservoir area and above the dam. (6) Gas supersaturation. If effective measures are not taken, the gas supersaturation resulting from high dams, large reservoirs, and stream diversion for energy dissipation has an adverse effect on fish. Scoring criteria: 1 point can be earned for answering any one of the above questions correctly. 3. Are supporting engineering measures required for this project to ensure the minimum ecological water demand downstream of the reservoir? Explain the reason. 【Reference Answer 1】 (1) Not required. (2) Since it is a dam-type hydropower station, the water discharged during normal power generation is sufficient to meet the ecological water needs of the downstream area; even when no power is generated, water can still be released through the spillway to ensure ecological water supply for the downstream area. 【Reference Answer 2】 (1) Necessary. (2) Considering the possibility that environmental management may not be carried out strictly in accordance with the plan, ecological discharge bottom holes and ecological discharge surface holes should be installed to ensure that the required amount of water for ecological purposes can be released. Scoring criteria: 5 points if the reasons are sufficient. 4. Identify the water quality protection measures to be taken during the construction period. Answer 1: (1) Collect construction wastewater centrally, treat it uniformly, and then reuse it. (2) The domestic wastewater from construction workers (including that from the owner’s camp and the contractor’s camp) is biologically treated before being reused for site landscaping or dust suppression by watering. (3) Construction wastewater and domestic sewage must be discharged into the A River or other surface water bodies without any treatment ； If discharged, it must meet the standards and comply with total quantity control requirements. (4) The construction site should be kept as far away from rivers as possible. (5) Solid waste generated during construction shall be disposed of promptly; no soil, debris, or household waste shall be dumped into rivers. (6) Strengthen soil and water conservation during construction. (There are many measures to consider, including carrying out cleanup work in the reservoir area before water is stored there during construction and preventing the drainage of water from farmlands; however, it is crucial to strengthen the management of construction wastewater, utilize it after treatment, and ensure that it is not discharged into water bodies unless it meets the required standards. ) Answer 2: (1) The wastewater from the sand and gravel processing system is treated by sedimentation before being reused. (2) The wastewater from the concrete mixing plant is treated by neutralization and sedimentation before being reused. (3) The wastewater from mechanical repair shops, automobile repair and maintenance facilities should first undergo oil separation, followed by sedimentation and biochemical treatment before being reused. (4) Reuse of domestic wastewater after biochemical treatment. Scoring criteria: One point is awarded for answering any one of the above questions correctly