As previously noted, the need for sidewalks is a municipal policy decision determined by a town planning ordinance. I assume they will be located in a public right-of-way and maintained by the town. If there are no sidewalks on the properties adjacent to yours, then I would not include them...
As mentioned in the previous post, your local zoning code will dictate how far your building must be from the lot line. I would not grade on to neighbors property even if allowed. You should maintain at least 1/2-inch/ft. grade away from your building on the uphill side. Grade away from the...
Defining your template properly in LDD is the solution. The process is a bit cumbersome. I have found that the Autodesk Civil Design "Training-Student Guide" (not the user manual)to be an invaluable resource for this and many other LDD civil routines. I received it when I took a training...
The capacity of a 30-inch circular pipe is roughly equivlent to a 35"x24" corrugated metal pipe arch. This would afford you an extra 6-inches of cover. You can also order the end sections for these.