N.Y. County Law § 299-t

§ 299-t. Extension of the district. A watershed district may be\nextended so as to include territory not previously included within its\nboundaries in the same manner as hereinbefore prescribed for the\noriginal establishment of the watershed district. The cost of the\nextension and of providing the improvements therein shall be assessed,\nlevied and collected as provided in section two hundred seventy-four of\nthis chapter, as now in effect or as hereafter amended.\n