Method for detecting and localizing leaks in above ground storage tanks

A method for isolating a longitudinal section of a horizontal bore through the stata under a liquid storage tank for detecting vapor or liquid that is entrapped in the strata after escaping through a leak in the bottom of the storage tank and for localizing the leak along the horizontal bore comprising the steps of:

• (a) positioning a perforated conduit having means positioned on the outside diameter of the conduit at both ends thereof to form a conduit and seal assembly for selectively sealing against the inside diameter of the horizontal bore and the outside diameter of the conduit in the horizontal bore with an elongate member which extends outside the bore and to which the conduit and seal assembly is connected and having a passageway therethrough communicating with the inside of the conduit, the conduit being closed at the end first inserted into the bore;
• (b) activating the sealing means to isolate the longitudinal section of the bore between the sealing means and surrounding the conduit;
• (c) evacuating the isolated longitudinal section of the bore through the passageway in the elongate member to remove any vapor or liquid that is entrapped in the strata surrounding the isolated longitudinal section of the bore;
• (d) measuring any vapor or liquid in the gases evacuated from the strata surrounding the isolated section of the bore with a sensor sensitive to the level of the vapor or liquid that has escaped from the tank that is positioned in the flow of evacuated gases;
• and
• (e) continuing the evacuation of the gases from the strata surrounding the isolated longitudinal section of the bore until the level of any vapor or liquid being measured by the sensor either levels off at a level above background levels, indicating the presence of a leak in the bottom of the tank in the vicinity of the isolated longitudinal section of the bore, or decreases to background level, indicating the absence of a leak in the vicinity of the isolated longitudinal section of the bore.