English to Russian Tech/Engineering

The topic is digging out a tunnel. And the sentence where I’m at a loss is as follows:
“In principle, the arrangement and distribution of boreholes will be as follows: on the arch generator and two further generators, one located 30 degrees to either side of the arch crown generator, based approximately 5 m intervals”.
I wonder what GENERATOR means in this context. It doesn’t look like a real generator. And mind you, it’s been written not by a native speaker. So don’t be too freaked out. Thanks for help. Good luck.