Draining the sub-base , i.e. subgrade or ground-work

Official title: Draining the sub-base {, i.e. subgrade or ground-work, e.g. embankment} of roads or {of the} ballastway of railways {or draining-off road surface or ballastway drainage} by trenches, culverts, or conduits {or other specially adapted means}({drainage of the ballastway of railways E01B11/00; surface drainage of roads E01C11/224; drainage of soil E02B11/00;} underground drainage E02D; conduits for sewerage E03F)

E01F5/00 (Draining the sub-base , i.e. subgrade or ground-work) appears on 167 US grants and 126 published applications in this corpus.