Beach formation and restoration via the introduction of sand requires a permit filed with the state. Both formation and restoration are regulated by both the NH Wetlands Bureau and the Department of Environment Services Water Quality Engineering Section. The regulation can be found at the following site:
Both formation and replenishment, if for a single family private property, with no fill below the water line, and with less than 10 cu ft of sand are considered minimum impact projects, which means they still require a permit but approval can be expedited. The important thing is that the sand can only be replenished once every 6 years and has to be controlled in a prescribed way (like washed sand and no sand below the waterline). Both the frequency and protections can be monitored and controlled by the permit approval. Larger projects obviously require an application but the review may take longer.
Though regulated by both the NH Wetlands Bureau and the Department of Environment Services Water Quality Engineering Section, a single permit can be used to get both approvals. Approval from both organizations is required. The application can be found at:
A fact sheet describing the rational can be found at:
It states that sand can contribute to filling in of the lake and it can have chemical and biological impacts as well.