The grants made under § 22a-339b shall be subject to the following conditions: (1) No grant shall be made for any study, report, plan or restoration measure except if such study, report, plan or restoration measure is in accordance with a priority system established by the Commissioner of Energy and Environmental Protection in accordance with the provisions of the federal Clean Water Act (33 USC 1251 et seq.), (2) no grant shall be made until a municipality or lake association has agreed to pay that part of the total cost that is in excess of the applicable state grant, and (3) the grant to each municipality or lake association shall equal seventy-five per cent of the cost of a diagnostic feasibility study and fifty per cent of the cost of implementation measures. Notwithstanding the provisions of this section, (A) if federal funds are available in the amount of seventy per cent of the cost of a diagnostic study, the state grant shall not exceed thirty per cent of the cost of the study, and (B) if federal funds are available in the amount of fifty per cent of the cost of implementation measures, the state grant shall not exceed twenty-five per cent of the cost of the measures. The commissioner may require the recipient of a grant implementing restoration measures to establish watershed management practices to prevent the reoccurrence of a water quality problem.