No officer of such town shall expend or enter into any contract by which the town shall become liable for any sum which, with any contract then in force, shall exceed the appropriation for the department, except in cases of necessity connected with the repair of highways, bridges, sidewalks and water and sewer systems and the care of the town poor, and then not more than one thousand dollars. If any occasion arises whereby more money is needed for any department of the town than has been appropriated as provided for in this chapter, the selectmen shall notify the board of finance of such fact, and the chairman of such board shall forthwith call a meeting thereof to consider the appropriation for such department and the board may make the necessary appropriation therefor, after inquiry, but, if, in towns where the grand list is not more than twenty million dollars, the amount required or the amount required, together with the sum of any additional appropriations made by the board for such department within the same fiscal year, exceeds ten thousand dollars, or, in towns where the grand list exceeds twenty million dollars, if the amount required or the amount required, together with the sum of any such additional appropriations, exceeds twenty thousand dollars, such appropriation shall not be made until, upon the recommendation of the board, the same has been voted by the town at a meeting called for such purpose, provided no more than one such additional appropriation for any one department shall be made in one year without town meeting approval, and provided the board may make additional appropriations for the care of town poor without town meeting approval not exceeding, in the aggregate, two thousand dollars in towns where the grand list does not exceed twenty million dollars or four thousand dollars in towns where the grand list exceeds twenty million dollars. The board may call a public hearing prior to the town meeting at which parties in interest and citizens shall have an opportunity to be heard so that the board may obtain information to assist in making its recommendations. The amount required for such appropriation may be drawn either from any cash surplus available or from any contingent fund established as hereinafter provided. If no cash surplus exists and no funds are available in the contingent fund, such appropriation may be financed by borrowing, and the amount of such borrowing shall be included in and made a part of the next tax levied. The estimate of expenditures submitted by the board of finance to the annual town meeting or annual budget meeting may include a recommended appropriation for a contingent fund in an amount not to exceed three per cent of the total estimated expenditures for the current fiscal year. No expenditure or transfer shall be made from the contingent fund until such expenditure or transfer has been approved by the board of finance. The provisions of this chapter shall not be a limitation upon the town in issuing bonds under the provisions of law or expending the proceeds thereof in accordance with the vote of such town nor shall such provisions be a limitation upon the settlement of claims or judgments against the town under the provisions of law.