If you can talk the county into a swaled or ditch block style driveway, over a culvert, that will save some $$$$. I think a 40 ft 18" CMP with 4:1 cut miters is around $1800 for just the pipe. If you do have to do the culvert; go with 40 ft over 32 ft; you won't regret it down the road (unless they spec the length in the permit).
Swaled drive basically goes down to the flow line, following the existing grades/slopes; and allows free flow of water. If that creates a slope of greater then 10% down and then 10% back up; you'll drag trailer jacks or corvette noses. Only good with a hard surface drive (asphalt or concrete)
A ditch block drive has a minor low point at the center for water to flow after it stages up; but doesn't follow the contour of the ditch. This works well where there is very little flow, and good percolating soils. Only good with asphalt or concrete.
This all assumes there is somewhat of a swale on their road side; a typical paved road cross section. should be about 2-3% 'crown'; 4-10% grassed shoulder; 4:1 front slope; flow line/ditch invert; then 3:1 or less back slope to the ROW line. Dirt or gravel roads; might have more cross slope or none at all; and may or may not have a grassed shoulder at all; or even a shoulder that is higher then the edge of travel; from a lack of maintenance...