There are many different factors that will play into your design standards, such as soil conditions, environmental conditions, and existing design standards. However as you start looking through different design standards, you'll find that all of them are very similar, yet different. My advice...
Have you checked with the water utility that is providing the water service? They should have a standard specification on what they will accept. Of course if it's a private fire line, they may not be too involved with what you're doing onsite... just a thought.