The Corps des ponts, des eaux et des forêts (Corps of Bridges, Waters and Forests) is a technical Grand Corps of the French State (grand corps de l'Etat). It is formed of the State Engineers and doctors with specialized scientific skills useful in the territorial planning, the management of natural resources and the conception and evaluation of environmental policies. Most of them are from École polytechnique where they are chosen on their ranking. these are known as X-Ponts; the rest come from École normale supérieure (Ulm) or the regular curriculum of the École nationale des ponts et chaussées.