Vacuum excavation system

A vacuum excavation system for handling dirt, water or other materials, comprising:

• (a) vacuum generation means for generating sufficient vacuum for vacuum pickup of material from a material site;
• (b) material containment means having a top and a bottom, for receiving and containing materials picked up from a material pickup site at the bottom of said material containment means in response to vacuum drawn thereon by said vacuum generation means;
• (c) first conduit means, comprising a conduit for vacuum, located upstream of said vacuum generation means, connecting said vacuum generation means and the top of said material containment means, for providing sufficient vacuum for material pickup between said vacuum generation means and said material containment means;
• (d) second conduit means, comprising a conduit for vacuum and material, for connecting said material containment means to the material pickup site for providing sufficient vacuum for material pickup between said material containment means and the material pickup site and for delivering material to the bottom of the material containment means;
• (e) valve means located in at least one of said first conduit means and the top of said material containment means;
• said valve means being normally closed to allow vacuum from said vacuum generation means to draw a vacuum in said first conduit means and the top of said material containment means and to draw a vacuum and material in said second conduit and to the bottom of said material containment means;
• said valve means having third conduit means optionally openable to atmosphere;
• with opener means being provided for said valve means for selectively opening said valve means to atmosphere to allow atmospheric air to enter said first conduit and the top of said material containment means, to at least substantially reduce the vacuum draw upstream of said valve means.