expelling the ultra high pressure water against a surface in a most preferred embodiment the nozzle apertures are between 0 005 and 0 075 inches in diameter and a single spray bar may include nozzles with various diameter apertures a shroud 15 is also secured to a bottom surface of the caster plate preferably in contact with an adapter flange portion 4 of the hydraulic motor assembly 200 to enclose the spray bar assembly 24 for containment of debris and water deflected from the cleaned surface the shroud 15 may also be provided with a vacuum aperture 102 for connection to a vacuum tank for collection of the debris and used water it should be noted that multiple blast heads may be secured to the caster plate to create various arrays of blast heads for cleaning surfaces fig4 illustrates a partial view of the blast head 100 having the shroud 15 and caster plate 14 removed the hydraulic motor assembly 200 of the instant invention includes a thrust assembly portion 108 a motor block portion 110 and a flange adapter portion 112 the thrust assembly portion 108 is constructed and arranged to control the vertical thrust caused by expelling the ultra high pressure water out of the nozzles and against a surface fig2 28 the thrust assembly includes a body portion 118 at least one bearing 18 and at least one thrust washer 28 positioned juxtaposed to the thrust washer is a grease seal 12 threadably connected to the output shaft 8 the grease seal preferably includes at least one o ring 31 or other suitable seal for retaining grease in the.