>>1721245On December 17, 1774, an impressive collapse occurred on rue d'Enfer, at the height of the current boulevard Saint-Michel. Paris and its people discovered and were alarmed by the danger that lay beneath their feet.
On September 15, 1776 the King's Council commissioned Professor Dupont to study the state and extent of the voids threatening the stability of public roads. Its conclusions were so alarming that a project aimed at creating an institution intended to draw up an urgent cartography of the underground of Parir was put under study.
This same King's Council having communicated the studies of the architects Guillaumot and Brebion on the underground quarries threatening the substructures of the Arcueil aqueduct decided to create the Inspection des Carrières, by a decree dated April 4, 1777.
By commission of April 27, 1777, Mr. Guillaumot, architect of the King, was appointed to the post of controller and chief inspector general of the Quarries. As a sign of destiny, a new house collapsed the same day in the quarries on rue d'Enfer!
The missions of the I.G. are then to list and consolidate the Parisian careers. To prepare for the most urgent 2 teams are created: a first explores and digs galleries in search of forgotten old voids; a second consolidates those in poor condition. No sooner is a void spotted than it is mapped and consolidated. Consolidation work plans are placed end to end and general maps drawn up. Slowly a veritable underground lining of the city is taking shape, with its streets, its barriers, its property lines.
>So know all the network has been consolidated by the authority known as IGC (the same who're closing down entrances nowadays)Whenever in Paris some people want to build a new building they always check with IGC first if it's safe.
So to answer your question now it almost never happen, as whenever the community see some places which are unstable they can report it to the authority and then they take care of it.
