5　Layout of Project and Hydraulic Structures

5.1　General Requirements

5.1.1　The scales of projects and the grades of structures shall meet the following requirements:

1　Scales of hydropower stations shall be classified as Scale IV and Scale V depending on their sizes.The classification shall be defined according to the provisions as shown in Table 5.1.1-1.

2　The grades of hydraulic structures shall be defined according to the scales of projects as shown in Table 5.1.1-2.

3　If the dam heights exceed those as stated in Table 5.1.1-3，their grades may be raised by one grade，but the standards for flood control may keep unchanged.

5.1.2　The flood control standard for hydraulic structures shall be in compliance with the following requirements:

1　The flood control standards for hydraulic structures of reservoir projects shall be determined according to the specifications in Table 5.1.2.

2　If the water retaining height of permanent structures of a hydropower project in mountainous or hilly areas is less than 15m and the difference between upstream and downstream water heads is less than 10m，the flood control standard should be set up as that stipulated for plain and coastal regions.If the water retaining height of the permanent structures of a hydropower project on plains or in coastal regions is above 15m and the difference between upstream and downstream water heads is more than 10m，the flood control standard should be set up as same as that stipulated for mountainous and hilly area.

3　If a failure of an earth-rock fill dam would result in fatal disaster to the downstream area，the check flood standard for Grade 4 structures may be raised by one grade.

4　For water retaining and releasing structures with lower water head or their failures would not result in big losses，their check flood standards may be lowered by one grade after being deliberately assessed and submitted for approval of competent authorities.

5.1.3　The flood control standard for non-retaining powerhouse in mountainous or hilly areas shall be determined according to the grades as shown in Table 5.1.3.For the powerhouse of a hydropower station in river channel，the flood control standard for its water retaining parts shall be consistent with that for the main water retaining structures，and the flood control standards for auxiliary rooms，main transformer yard，switchyard and access to powerhouse shall be set up according to Table 5.1.3.The flood control standard for powerhouse on plains or in coastal region shall be determined in accordance with Table 5.1.2.

5.1.4　The types of hydropower stations may be categorized into dam type，diversion type and composite type according to their development patterns.

5.1.5　For areas where the seismic intensity reaches 7 degree or above，the anti-seismic design shall be carried out for the hydraulic structures.

5.1.6　For general layout of a project and the design of hydraulic structures，the following basic data should be made available according to the specific situation of the project:

1　Items and scales of topographical mapping that may be selected according to the provisions are given in Table 5.1.6.

2　Engineering geological investigation report and drawings.

3　Meteorological and hydrological data，calculation result of hydraulic and waterpower energy.

4　Data for river basin planning and comprehensive utilization of water resources.

5　Data for environmental protection，soil and water conservation.

6　Data for hydraulic machinery，electrical system and hydromechanical structures.

7　Data for construction conditions.

8　Relevant approval documents from superior competent authorities.