When the legislative body determines that an enterprise is necessary and convenient for the preservation of public health, it may adopt a general specification for the enterprise setting forth:
- (a) Definite criteria of capacity and general location of the enterprise.
- (b) General structural requirements.
- (c) Degree of purification and manner of disposal of effluent and sludge.
- (d) The duration of operation under the control, supervision, and responsibility of the contractor after the required performance has been demonstrated.