The City Manager, subject to any regulations which the Council may prescribe, shall contract for and purchase, or issue purchase orders for, all supplies, materials, and equipment for the offices, departments, and agencies of the City government.  Every such contract or purchase exceeding an amount to be established by ordinance shall require the prior approval of the Council.  The City Manager also may transfer to or between offices, departments, and agencies, or sell surplus or obsolete supplies, materials, and equipment subject to such regulations as the Council may prescribe.  Before the purchase of or contract for any supplies, materials, or equipment, or the sale of any surplus or obsolete supplies, materials, or equipment, ample opportunity for competitive bidding under such regulations and with such exceptions as the Council may prescribe shall be given; but the Council shall not except a particular contract, purchase, or sale from the requirement of competitive bidding, provided however, the City Council may by simple majority, waive the bidding and advertising procedure hereinabove set forth and such emergency or unusual contracts can be let immediately upon approval of the City Council; provided that in the motion for waiver of the bidding and advertising procedure the facts or circumstances relied on to waive such procedure shall be included and stated in concise terms. Emergency as used in this section shall be limited to conditions resulting from a sudden, unexpected happening or unforeseen occurrence or condition and situation wherein the public health or safety is endangered or a situation involving injury to persons or injury and damage to public or personal property or immediate financial loss.  Unusual purchase as used in this section shall be limited to purchases for which the taking of bids is not feasible because of practical limitations upon the bidding procedure which are beyond the control of the City of Guthrie.