A device and method for venting a tank comprising an intermediate shutoff valve as part of a cover that closes a tank opening. The intermediate shutoff valve is placed between an existing valve and a vent port in a liquid storage tank. The shutoff valve is operable to substantially fluidly seal the vent port when the vent valve is displaced greater than a predetermined amount. The intermediate shutoff valve facilitates complete removal of the existing vent valve during an impact wherein a wall of the storage tank impacts the existing valve. Upon impact, the intermediate shutoff valve is operable to close and seal a tank opening created by the displacement and removal of the existing vent valve.