The paper describes the geological and geotechnical investigations and engineering design and execution for the construction of an LPG underground storage in an impermeabilized rock cavern in silicified chalk above the watertable. It explains the ecological, technical, economical and safety reasons which are the basis for this novel approach for hydrocarbon underground operational storage.


A small operational storage in the vicinity of a suitable pipe network is under construction to supply the Jerusalem district and surrounding areas with LPG. Techno-economical, safety, security and ecological reasons made a novel approach for this task necessary. Terms of reference were to find a site for the excavation of cavern in suitable geological and hydrological conditions for the storage of 7,500 tons of LPG. The investigation of rock formations and hydrological conditions of Mesilat Zion area was made to find a suitable location for the excavation of a cavern in suitable rock. The area of study is located at the foothills of the Judean Mountains, 20 km west of Jerusalem, between two highways leading from Tel Aviv to the Capital. (Fig. 1). The landscape is built of rounded, nari encrusted, chalky hills of about 300–380 m height, covered with planted woods. Many dirt roads cross the area and accessibility is very good. Westwards, the hills become lower and gradually disappear into the Coastal Plain. Eastwards, there is a steepening of the slope into a prominent escarpment, building the west flank of the Judean Mountains. The area of study is part of Hashephela, which means in Hebrew, low land.


The rock formation required should have the following features:

Thickness of Layer

Thickness of relevant layer should be about 60 m, including a cover of 50 m over the hanging wall.

Rock Strength

The rock formation should be in the range of at least 100 kg/cm unconfined compressive strength, in order to achieve an economically viable profile without support. The rock quality should be suitable for mechanical mining without blasting.

Hydrological Conditions

The cavern should be located above any existing aquifers and above any clay layers with excessive swell factors.

General Geological Setting

The area of study is located in the centre of Hashephela Syncline flanked to the east by the prominent Judean Anticline and to the west by the Kefar Uriyya undulation (Fig. 2). The strata in the area are horizontal to subhorizontal (3°- 4°). Upper Cretaceous rock (Cenomanian, Turonian, Senonian and Maastrichtian) crop out at both highs, east and west of the area, whereas Tertiary rocks (Paleocene and Eocene) comprise the selected site. The upper Cretaceous rocks are of no direct interest for building the storage, nevertheless, they are of interest while discussing water levels, aquifers and the question of preventing active aquifer pollution. The area is considered to be stable tectonically and seismically, only few faults are observed in the margins of the area (2–3 km southwards).

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