Wow.....is that normal where you are?
Gas lines are normally deep also, but one time at an old house we hit one that was 2" deep. Gas company wanted to charge me about 2k for the repair that one guy did, but about 7 other guys one by one rolled up in a truck and left after 5 minutes. They wanted to charge me like 7 guys labor.

I told them to take a hike. They sent a collection company after me after only about 3 weeks. I got on phone with the guy, explained the situation, then explained to him that the gas co. was lucky that I was the one to hit it because i knew what to do...what if the homeowner hit it while planting flowers.. yeah, I played it up a bit...I told him I'd see them in court...he was shocked and said you'd really go all the way to court? I said hell yeah, these charges are ridiculous.....the bill was voided.