The owner or operator who is removing, or has removed, any regulated storage tank must demonstrate that no materials stored in, leaked, or spilled from the tank remain within the soils or groundwater. Such a demonstration will consist, at a minimum, of four samples collected from locations with the greatest likelihood of residual materials and analyzed for chemicals that are most likely to identify residual material. The owner or operator must obtain advance approval from the city of a tank removal plan that includes the proposed number of samples to be collected, their anticipated locations, and the chemicals for which the samples will be analyzed.