N.Y. County Law § 253-B
When the board of supervisors or county legislature shall have established a district pursuant to this article and adopted a plan of a service or improvement for such district, such plan shall not be modified by the board of supervisors or any officer of the county nor by the administrative head or body of such district except as provided in this section. The administrative head or body shall submit a report in writing to the board of supervisors specifying the particulars in which it is proposed to modify such plan. Upon receipt of such report the board of supervisors shall adopt a resolution calling a public hearing thereon. Notice of such public hearing shall be given in the manner provided by section two hundred fifty-four of the county law. Such notice shall specify in terms sufficient for identification the particulars in which it is proposed to modify the plan of the service or improvement, and the time and place when the board of supervisors will meet to hear and consider any objections which may be made thereto, which time and place shall be not less than ten nor more than twenty days after the first publication of such notice. When any change shall be made in the plan proposed and once adopted, a revised or additional map and profile shall be made showing the change, and all such maps and profiles shall be carefully preserved in the office of the county clerk, or if the county district shall have an office, in the office of such county district, and shall be open to inspection by all persons interested. However, in the case of water quality treatment districts, amendments or modifications of plans must have the written approval of the department of health prior to adoption. At the request of an owner of a parcel of property within the county, if the private well water on such property is contaminated, a water quality treatment district plan may be amended, from time to time, to include said parcel of property. If an owner of a parcel of property within the county requests exclusion from the district, such request shall be granted without the state department of health approval and without the procedure set forth in section two hundred fifty-six of this article. The removal of a parcel of property from a district shall in no way affect the owner's liability for charges which have accrued against the owner's property, prior to said exclusion, for the procurement, installation, modification, replacement and removal of a water quality treatment unit or device or for expenses of operation and maintenance including monitoring, testing, regenerating and treating. Should a public or private water system, supplier or authority commence supplying water to any parcel of property within a water quality treatment district, such parcel of property shall no longer be considered part of the water quality treatment district, and all services to such parcels shall be terminated. Termination of services shall include, the removal of all water quality treatment units or devices and a charge for the cost of doing so to the benefited property, except when such unit or device was acquired and owned by the property owner or when the district determines that such unit or device is obsolete and no longer useful for any district purpose.
N.Y. CountyLaw § 253-B