Many of us know or have heard of drillers and/or helpers that have been killed. Some of the more dangerous conditions that can be encountered during drilling include underground fuel tanks, high pressure gas lines, high voltage electrical lines, and lost circulation zones which can catastrophically collapse and consume a whole drill rig (and crew) in minutes.
Don't assume your client has marked all utilities before drilling commences. It is true there are companies that will mark utilities, however this is usually only along the right-of-way and not on private property. Engineering drawings are usually not accurate or up-to-date on older properties, especially when ownership has changed. I have personally drilled into buried bulldozers and 10,000-gallon tanks no one knew were there. Once we knocked out power for half of a small town and melted the tires of the rig. Fortunately, no one was hurt.
No one getting hurt is great, however other mishaps can be financially devastating. I once over-drilled an existing 2" monitoring well and damaged a 12-inch PVC sanitary sewer line. The next morning, I found out why the 35 bags of portland cement didn't come back to land surface. When I showed up at 8 am, 12 city trucks with yellow lights flashing were trying to roto-rooter my hardened cement out of their line from a large shopping mall. Three weeks later, we finished repairing the damage.
That is not nearly as bad as drilling into an optic fiber main line. Many of these telecommunication lines carry thousands of dollars per minute through their underground lines. Most of us would be frightened to know how close we have come to these lines. Do your contracts indemnify your company for boring locations selected by your driller? If in doubt, hand auger at least the first five feet or so to help minimize potential for encountering unknown utilities and tanks.
It would behoove many of us to take a little extra time and care to check the shallow subsurface more thoroughly. There should always be time allotted to work safely.