Natural Risk Forecast Plan (NRPP) Regulated Area — Underground Cavities R111-3

For natural PPRs, the Environmental Code defines two categories of zones (L562-1): risk-exposed areas and areas that are not directly exposed to risks but where measures can be foreseen to avoid exacerbating the risk.Depending on the hazard level, each area is subject to an enforceable settlement. The regulations generally distinguish three types of areas:1- ‘Building prohibited areas’, so-called ‘red areas’, where the hazard level is high and the general rule is the construction ban;2- ‘prescription areas’, known as ‘blue zones’, where the hazard level is medium and projects are subject to requirements adapted to the type of issue; 3- areas not directly exposed to risks but where constructions, works, developments or farms, agricultural, forestry, crafts, commercial or industrial could aggravate risks or cause new ones, subject to prohibitions or requirements (cf. Article L562-1 of the Environmental Code). The latter category applies only to natural RPPs. Many municipalities in Yvelino have been the subject of local underground mining activities for the extraction of various materials (calcareous, chalk, gypsum, marl). These sub-mined territories are studied by the Versailles General Quarry Inspectorate (IGC), which capitalises knowledge of voids by drawing up maps and lays down preventive measures to reduce risks.Some zonings are regulated by the Prefectural Decree of 5 August 1986 which delimits risk areas linked to former underground quarries in the Yvelines. This order, made under former article R111.3 of the Urban Planning Code (Article repealed by the Barnier Law in 1995), is a plan for the prevention of natural hazards (PPRN). This layer, published by the IGC, covers all the submined areas known in the department of Yvelines and regulated by the prefectural decree. For each zoning, it is specified the type of material (calcareous, chalk, gypsum, marnière or other). Within these areas, land tenure and land use permits may be subject to special conditions such as to ensure the stability of the buildings.