El Morado (Santiago de Chile)

I was planning on going hiking and camping at El Morado tomorrow (Cajon de Maipo), and someone told me that an energy company is building a dam, and that it is almost impossible to get there without a 4x4. They also said that I would need special permission to enter the park and get to the hiking areas (it was all very vague).. Has anyone hiked El Morado in the last few weeks? Is this true? And also, in general, does anyone know how long it take to drive there from Santiago? How long it takes to hike? Or just general recommendations for me?