Dock construction
 

Does anyone know the rules about building a dock and how far it has to be from the neighboring property line? If the water is shallow, are the builders allow to dredge or remove boulders?

dock setbacks +water depth
 

20 foot setback from the imaginary extension of the neighboring property line over the water. Dredging or dock modifications can be permitted if you cannot access a statutory boat slip.

https://www.des.nh.gov/land/waterfro...-stabilization

Permanent? Temporary seasona dock? Crank up? It gets a little confused sometimes depending on what you need especially if you need to extend or dredge for depth. Then it is not only DES but the local Conservation Commission. Your dock builder or contractor is likely very familiar with rules and process. Without detailed info, it is difficult to predict on this web site.
What town?
Size of lot?
Setback?
Depth needed?
Length of dock?
etc?
There's just a lot to know, although not always difficult. Call a contractor for the type of dock you want and get real answers, not just discussion based on what if's?

Dredging
 

You can dredge and you can also remove boulders. If the boulders are natural or man-placed (part of an old wall or cribbing) it doesn't make any difference. It requires getting several agencies involved just to get approval to dredge or remove boulders including the town, state, army corps, neighbors, etc. It can be done, but usually is only granted if there is a good reason for it (navigational hazard, access to home, etc.) not just because the landowner "wants to".

We removed an old crib dock base that was not grandfathered, several years ago to improve the access to our shore, and it took nearly a year to permit and then actually remove.