Steve, I think your group 1 price amount is a little steep. Group 2 looks extremely competitive. Here in TX we can get a good amount for work, higher than the rest of the country i think. We get between 45-low 50$ per acre.
If this is municipality, fill out an open records request. by law, they are required to divuldge all information pertaining to previous scope of work, and any contract amounts previously signed. this can help put in perspective what they have spent in the past.
also, ask if they have an "engineers estimate." sometimes the cities can produce their estimated cost. however, try to ask these questions and get this information in private if you can. that way to dont help your competition out on where to start their bid from.
might have it listed. you can also check and see what other companies have viewed the request for propsal / bid.
let me know if this helps at all.