N.H. Rev. Stat. § 155-B:13
If in any city or town, an excavation for building purposes is left open for more than 6 months without proceeding with the erection of a building thereon, whether or not completed, or if any excavation or basement is not filled to grade or otherwise protected after a building is destroyed, demolished or removed, the governing body may order such excavation to be filled or protected or in the alternative that erection of a building begin forthwith if the excavation is for building purposes. The order shall be served upon the owner or his agent in the manner provided by RSA 155-B:4. If the owner of the land fails to comply with the order within 15 days after the order is served upon him, the governing body shall cause the excavation to be filled to grade or protected and the cost shall be charged against the real estate as provided in RSA 155-B:9.
RSA 155-B:13
1967, 334:1, eff. Sept. 1, 1967.