I'd look to my friends in earthworks contracting. I have found that most of these engineers are very willing to help on such things, probably because it might give them a leg up on doing the job some day. It should include specifications also detailed for the specifics of the job.

Edit add: Not seeing much added help I'd also see what is to be built so that proper materials, equipment and testing is covered. Sometimes certain stone, soil gradations are needed and sources may be rare. Knowing local gravel sources, etc can help in specs as to what might be best for the job. Unfortunately sometimes the best sources of paving materials, etc. are tied up and prices also are up. Alternatives might cost plenty also. Local geotech engineers may help on this problem, if present. Job testing sometimes needs clarification in who pays, etc.