3.3　Engineering Geology of Reservoirs

3.3.1　The investigation of reservoir seepage shall include:

1　Existence of thin drainage divides and low adjacent valleys around the reservoir，permeable bed，fractured fault zone，or ancient river course that lead outwards from reservoir；and assessment of probability and extent of seepage.

2　Pattern of karst development in soluble rock zones of reservoir，distribution elevation of springs and groundwater watersheds，distribution and sealing condition of relative confining beds，replenishment and discharge relationship between groundwater and river，and assessment of probability of seepage，seepage routes，seepage features（conduits，solution cracks）and their impact on reservoir construction.

3.3.2　The investigation of reservoir bank stability shall include:

1　Features and structural composition of rock（soil）mass on bank slopes，distribution of soft soil strata，incision condition of fault tectonics，and attitude，extension and combination relationship of various controlling structural planes that are unfavorable for bank slope stability.

2　Weathering of rocks，unloading status and deformation features of reservoir rock slopes，and identification of the type，nature，scope and formation conditions of any deformation.

3　Distribution，scale and stability of landslides，slide mass and dangerous rocks at near-dam reservoir slopes，and assessment of impact of debris flow in the vicinity of dam.

4　Distribution elevation and stable slope angle of various soil strata at the areas with potential of bank caving，stable slope angle of wave zone，and prediction of scope of bank caving.

3.3.3　The immersion survey shall include:

1　Structure，thickness and composition of soil strata at potentially immersed area，and the buried depth of underlying bedrock or opposite confining beds.

2　Permeability of soil stratum，bury of groundwater table，replenishment and discharge conditions of groundwater，rising height of capillary water in soil stratum，critical depth of groundwater that causes immersion，prediction of the scope of potential immersion and analysis of the causes of potential swamping and salinization.

3.3.4　Reservoir construction conditions and environmental and geological issues that may possibly occur after impoundment shall be assessed by investigation，and suggestions on treatment measures shall be proposed for unfavorable geological issues.