Ok this was bothering me so I looked through my notes this morning and I think I found my mistake. The 4″ is called for as a minimum (5-6 is recommended) in what they call a “full-depth” asphalt which is apparently from the soil subgrade up. They figure 1″ equals 3 inches of aggregate base.
I’m not sure how deep our base is. They did the prep work over an exisiting old gravel drive a couple of weeks ago. The blacktop will be going down in August. I know that is not the norm but there were some things we needed to get done first. I see from our bid that he is using 1100 asphalt. Is that just something used in our area or is that a standard label that you guys might know what size the aggregate is? I really appreciate everybody’s help!