present invention the illustrated nozzle assembly includes a plurality of circumferentially spaced apart apertures 41 a formed within a body 41 of the nozzle assembly and a plurality of eccentrically positioned radially extending passageways 41 b that are configured to create an agitation zone directly below the slurry extraction tube inlet 14 a each passageway 41 b is in fluid communication with a respective aperture 41 a and with the first conduit inlet 14 a this configuration is designed to increase the amount of abrasive material in suspension and thereby increase removal of abrasive material fig6 b is a bottom end view of the nozzle assembly of fig6 a illustrating the configuration of passageways 41 a although illustrated as a single nozzle it is anticipated that embodiments of the present invention may utilize multiple inlet nozzles at the inlet 14 a various inlet nozzle sizes and configurations may be utilized without limitation fig1 is a partial cut away view of the nozzle assembly of fig6 a 6b according to embodiments of the present invention and illustrating a slurry extraction tube 14 therein air from the air source and regulator 16 is provided via air supply conduit 30 to nozzle 32 and then via air supply conduit extension 30 a into the slurry extraction tube inlet 14 a a u201c duckbill u201d valve 47 available from a c hoffman engineering inc 5876 republic st riverside calif.