Notwithstanding any other provision of this code, the chief procurement officer, the head of a purchasing agency, or a designee of either officer may make or authorize others to make emergency procurements only when there exists an immediate threat to public health, welfare, critical economy and efficiency, or safety under emergency conditions as defined in regulations promulgated by the board; and provided, that such emergency procurements shall be made with as much competition as is practicable under the circumstances. A written determination of the basis for the emergency and for the selection of the particular contractor shall be included in the contract file.