Thank you for your question regarding the calculation of step and touch voltages in a substation, it is our pleasure to help.
Properly calculating step and touch voltages is quite difficult. Here are a few links you should review:
It sounds like your substation is in real need of a properly designed ground safety grid. We recommend the CDEGS grounding software package for design, however it is quite expensive and is rarely worth your time to purchase the software and then learn how to use it. We would be glad to help you with the design for only a fraction of the cost.
Please email us over a site plan so that we may quote you the work. Once the paperwork is taken care of, we will only need some soil resistivity data from you and we can handle the entire process via email.
We look forward to working with you.
The Engineering Team at E&S Grounding Solutions
Photo credit: http://www.flickr.com/photos/vax-o-matic/3808126381/sizes/o/in/photostream/