An underground historical quarry in the Hanbury Botanical Gardens of Ventimiglia (Italy)
F. Faccini1, M. Corvi2, L. Perasso2, E. Raso1 & M.G. Mariotti1
1 University of Genova, Department of Earth, Environment and Life Sciences
2 Ligurian Speleological Agency
This paper concerns with the original survey of an ancient underground quarry located in the internationally known Hanbury botanical gardens.
The Hanbury gardens are included in a protected regional area managed by the University of Genoa and located on the Mortola promontory, 4 km west of Ventimiglia on the western Ligurian coastline and a 2 kilometers far from the Italy – France boundary.
The whole area occupies a surface of 19,94 hectares between the sea level and the upper zones 200 mt high.
The gardens were established by Sir Thomas Hanbury who purchased the extant Palazzo Orengo property in 1867 after his comeback from a business trip in China, and over decades created the garden with the aim of acclimatizing several rare botanical species and of pharmacological interest coming from all the temperate climate regions of the world.
Many restoration works have been executed, among which the realization of pedestrian walks, the restoration of several buildings and the architectural arrangement of the gardens.
To this end an extended sandy layer located on the upper portion of the property was used as building material: it was extracted from weakly cemented yellow siltstones and sandstones belonging to the top of the pliocenic Ortovero clay formation; the other geological formations outcropping inside the Villa Hanbury area are the Capo Mortola calcarenites, the Olivetta S. Michele marls and the shallow debris covers.
The quarry opens up to about 90 mt a.s.l. and has a total length of 133 mt and a maximum difference in level of 8 mt; the total volume extracted is of the order of 1,500 m3 and the internal stability seems guaranteed by some stone pillars.
The northeastern portion of the underground quarry hasn’t been surveyed yet because of the dangerousness of the cavity: some testimonies from inhabitants report a possible prosecution under the on top village of Mortola Inferiore.
The sand quarry of the Hanbury Botanical Gardens is therefore a cultural heritage with a high tourist potential, even if the site requires further analyses about the geotechnical features of the material aiming to assess the stability of the underground volumes