The City Manager, on or before February 28th of each budget year, shall submit to the Council a budget and explanatory budget message. For such purpose, at such date as he shall determine, he, or an officer designated by him, shall obtain from the head of each office, department or agency estimates of revenue and expenditures of that office, department or agency, detailed by organization units and character and object of expenditure, and such other supporting data as he may request; together with an estimate of all capital projects pending or which such department head believes should be undertaken (a) within the budget year, and (b) within five next succeeding years. In preparing the budget, the City Manager shall review th estimates, shall hold hearings thereon and shall consult with the Finance Committee of Council and may revise the estimate as he may deem advisable.