N.H. Rev. Stat. Ann. § 149-M:19

The selectmen of towns, the county commissioners for each county in which there are located unincorporated towns or unorganized places, the mayor and council of each city and the commissioners of each county are authorized to enter into cooperative agreements with other towns, cities, unincorporated towns, unorganized places, and counties to provide a regional facility for the management of solid waste at mutually agreed upon sites. The selectmen, mayor and council, or commissioners, as the case may be, are authorized to expend funds received from any source to establish and maintain such regional facilities and provide for sharing the costs of establishing and maintaining such facilities in an equitable manner.