After reading WESTUPLACE's post, I think you should explore this interference/grounding issue with your customer some more and perhaps post them again so WESTUPLACE can give us some additional guidance. I have the feeling that your customer may not be explaining his concerns properly. Though I am not a HAM operator, I'd like to find out what your customers problems might be and what the solution really is.
Supplementary grounding electrodes do not have to be bonded to other electrodes on the premises. The requirements of 250.50, 250.53(C) and 250.56 do not apply to supplementary electrodes.
