I am looking at bidding a pair of walls for either side of a driveway where it passes over a culvert. The walls have to be constructed out of Versa Lok, will be 21 feet long and 3 feet tall (including embedded course). The walls must also be tied together with Geo Grid. I have my materials cost figured at approximately $1400 (crushed limestone base, block for wall, caps, and grid).The project is for a friend of mine that will be helping with the project. I am thinking the project should only take one weekend (we are renting a mini ex to dig for walls and remove the existing stone over the culvert). I am thinking a total bill of approximately $2200. Only because he is helping and is a friend. Any thoughts or criticisms are appreciated.