5.3　Preliminary Investigation

5.3.1　The preliminary investigation shall preliminarily identify the selected site's engineering gedogical and hydrogedogical conditions.

5.3.2　The preliminary investigation report shall include the following contents:

1　Topographical conditions and gedogical phenomena in the site；

2　Lithology（strata），structures，and stratum occurrences in the site as well as the locations，occurrences，sizes，and combination relations of the main faults，fracture zones，and joint/fissure-intensive zones therein.

3　Hydrological parameters of the site，such as ground water table，permeability coefficient，and water chemical composition；

4　Rock mass quality pre-classification and ground stress distribution of the site as well as recommended underground engineering layout，as on cavern axis direction，span，and spacing；

5　Preliminarily determine the elevation of the stable ground water table and propose a cavern tank depth；

6　Physical and mechanical indexes of the rock/soil mass；

7　Water inflow rate estimation，ground water numerical analysis and simulation，and cavern rock mass stability analysis；

8　Unsolved problems and suggestions.