Abstract: A double secondary seal for a floating roof type of liquid storage tank is disclosed. The secondary seal includes generally a weather shield of edge overlapping steel panels which extends upwardly and outwardly from the peripheral edge of the floating roof. The panels terminate upwardly in flexible wipers which are normally biased into sealing contact with the tank sidewall. A flexible vapor barrier underlies the steel panels to prevent the escape of vapors therethrough and defines a peripheral log space below the panels. A resilient foam log is positioned within the log space to provide a reserve seal. The dimensions of the foam log are designed to maintain the foam log away from contact with the tank sidewall when the wipers are in contact with the sidewall and assure sealing engagement of the foam log and the sidewall whenever the tank is filled sufficiently to raise the wipers above the top of the sidewalls.