Section 299-U. Joint construction and operation of projects

Where two or
  more adjoining counties  have  established  agencies  and  have  created
  watershed districts for the purposes of this act in the watershed common
  to  the  counties,  the agencies and the administrative heads or bodies,
  subject to the approval of their respective boards of  supervisors,  may
  enter  into  agreements  for  the  planning, installation, construction,
  operation, maintenance, assessments of costs and repair of a joint small
  watershed project. Any agency or agencies within this state, established
  by a county or counties for the purposes of this  act  with  respect  to
  small watersheds, may, subject to the approval of the board or boards of
  supervisors  of the county or counties, enter into agreements respecting
  joint projects with one or more "local organizations" in other states as
  defined in section ten hundred two of title sixteen of the United States
  code. The provisions of all sections  of  this  article  concerning  the
  planning,    installation,    construction,    operation,   maintenance,
  assessments of costs and repair of, and the  approvals  required  for  a
  project within a single county of this state, shall apply with equal and
  full  force  and  effect to a joint project, but nothing herein shall be
  deemed to prevent or restrict the additional  applicability  thereto  of
  any requirements of another state in any matter relating to its interest
  or the interests of its subdivisions therein.