15 K would make sense, it is enough for the miner to flee if they are quick enough and for the pie-rat to catch him ...
Back on the OP , the only reason I could think of of having a POB in the middle of the mining fields, ( apart from the usual let's-put-tons O' weapon platforms out kind of thibng would be if POBs could deploy "automated miners" .. as long as you feed it, it mines ore into the POBs hold