Is it legal to cut a utility ground rod sticking out of my yard?

You are looking in the wrong book. The National Electrical Code (NEC) generally stops at the service point. For utility-owned equipment like that fiber vault, they follow the NESC (National Electrical Safety Code). Section 097G is the standard there, and having a rod sticking out like a spear in a public right-of-way is definitely a violation. It is supposed to be driven flush or below grade to avoid exactly what you are describing. I woud not take an angle grinder to it. If you cut it, you are technically damaging utility property, and you will leave a sharp, jagged edge that is arguably more dangerous than the blunt end. Plus, if they haven't finished the bonding, you might be cutting off where the wire is supposed to attach. If you cannot wait for them, get a five-pound sledgehammer and just drive the thing the rest of the way down. It is alot less obvious than a clean cut and solves the trip hazard immediately. To get them to actualy move, skip the standard customer service line. Ask for the outside plant or construction department. Tell them there is a protruding **grounding electrode** in a high-traffic area where kids wait for the bus. Use the words safety hazard and liability. If they do not have a crew there in 48 hours, file a formal complaint with your state Public Utility Commission. They usally have a consumer complaint division that lights a fire under these companies faster than anything else.

The mud and straw mess is typical for these fiber rollouts. Usually, the crew that installs the vault is not the same crew that does the final grading and seeding. But the ground rod being left up is just lazy work by a subcontractor. Most of these guys are paid by the vault or by the foot, so they skip the extra five minutes of hammering if the ground is hard or if they hit a rock.

I had no idea the NESC was even a thing, I thought the NEC covered everthing electrical. If I go out there with a sledgehammer like you suggested, is there any chance I’d hit something buried right under the rod? I'm always paranoid about hitting a gas line or an old pipe when I'm pounding stuff into the yard. Also, if I do hammer it down and the utility crew finally shows up, will they be able to tell I messed with it? I just don't want to get stuck with a bill for tampering if they realize the rod is deeper than they left it.

Hitting a gas line is pretty unlikely if you're just finishing what they started. Those rods are usally 8 or 10 feet deep, so any damage whould've happened when the sub first drove it in. Just check for the 811 paint marks or flags first. If there's no yellow or orange line right on top of that spot, you’re safe to sink it. The crew won't even blink when they see it flush. They're usually just looking to slap the clamp on and move to the next site. Just try not to mushroom the top too much with the sledge, or they'll have a hard time getting the bonding connector to slide on.

If you go the sledgehammer route, watch your swing. Those rods can mushroom at the top if you whale on them, which makes it a total pain to slide a ground clamp over later. I've seen guys have to file the edges down just to get the hardware on.

Honestly, just throw a five-gallon bucket or a bright orange cone over it for now. It makes the hazard visible to the kids and the mower guy without you potentially messing up thier bonding point. If the rod is actually outside the vault, the sub probably just missed the mark when they dropped the pre-cast box in.