Hydro excavation vacuum apparatus having deceleration vessels and methods for hydro excavating a site

1. A hydro excavation vacuum apparatus for excavating earthen material comprising:

a vacuum system for removing cut earthen material and water from an excavation site in an airstream;

a deceleration system for collecting cut earthen material and water from the airstream, the deceleration system comprising:

a deceleration vessel adapted to reduce a velocity of the airstream to allow material to fall from the airstream, the deceleration vessel being adapted such that the airstream is not vortexed within the deceleration vessel, the deceleration vessel having an inlet and a spoil material outlet disposed below the inlet; and

a deflection plate disposed within the deceleration vessel for directing material in the airstream downward toward the spoil material outlet, the deflection plate including a material-engaging face having a longitudinal plane, the longitudinal plane of the material-engaging face forming an angle with a vertical axis of the deceleration vessel, the angle being from 5° to 60°; and

a dewatering system comprising a vibratory screen for separating water from cut earthen material discharged from the spoil material outlet.

2. The hydro excavation vacuum apparatus as set forth in claim 1 wherein the deflection plate comprises a wear plate connected to a support.

3. The hydro excavation vacuum apparatus as set forth in claim 1 further comprising an inlet conduit connected to the deceleration vessel inlet, the inlet conduit having a longitudinal axis, the longitudinal axis of the conduit passing through a central vertical axis of the deceleration vessel.

4. The hydro excavation vacuum apparatus as set forth in claim 1 wherein the deceleration vessel comprises a lower portion that tapers inward toward the spoil material outlet.

5. The hydro excavation vacuum apparatus as set forth in claim 1 wherein the deceleration vessel comprises an air outlet disposed above the inlet.

6. The hydro excavation vacuum apparatus as set forth in claim 5 wherein the deceleration vessel comprises a plurality of air outlets, each outlet being fluidly connected to a cyclone to separate material entrained in an airstream withdrawn from the outlets.

7. The hydro excavation vacuum apparatus as set forth in claim 1 wherein the deceleration vessel has an effective cross-sectional area, the hydro excavation vacuum apparatus comprising a deceleration vessel inlet conduit having an effective cross-sectional area, a ratio of the effective cross-sectional area of the deceleration vessel to the effective cross-sectional area of the inlet conduit being at least 7.5:1 to reduce the velocity of the airstream to allow material to fall from the airstream.

8. A method for hydro excavating a site with an excavation apparatus, the excavation apparatus comprising an excavation fluid pump, a deceleration vessel, a deflection plate disposed within the deceleration vessel and a dewatering system, the deflection plate including a material-engaging face having a longitudinal plane, the longitudinal plane of the material-engaging face forming an angle with a vertical axis of the deceleration vessel, the angle being from 5° to 60°, the method comprising:

operating the excavation fluid pump to direct pressurized water toward an excavation site, the pressurized water cutting earthen material;

removing cut earthen material and water from the excavation site in an airstream and into the deceleration vessel, the airstream not being vortexed within the deceleration vessel, the cut earthen material and water separating from the airstream and falling toward an airlock disposed below the deceleration vessel, the airstream having an average dwell time of less than 5 seconds in the deceleration vessel; and

introducing material discharged from the airlock into the dewatering system, the dewatering system separating water from cut earthen material removed from the excavation site, the dewatering system comprising a vibratory screen.

9. The method as set forth in claim 8 wherein the airstream has a dwell time of less than 3 seconds in the deceleration vessel or less than about 1 second.

10. The method as set forth in claim 8 wherein the apparatus comprises an inlet conduit connected to a deceleration vessel inlet, the inlet conduit having a longitudinal axis, the longitudinal axis of the conduit passing through a central vertical axis of the deceleration vessel.

11. The method as set forth in claim 8 further comprising a vacuum system for removing cut earthen material and water from the excavation site, the vacuum system being capable of generating a vacuum of at least 18″ Hg at 3000 cubic feet per minute.