in relation to a grouped hazardous substance, means deposit, discharge. spill. release or cause or permit to be deposited, discharged, spilled or released (whether or not the substance in question is enclosed in a container), in such a place, under such circumstances or for such a period that the person depositing, discharging, spilling. or releasing or causing or permitting it to be deposited, discharged, spilled, or released, may reasonably be assumed to have abandoned it; and "dumping" has a corresponding meaning;