When a corrosion hole penetrates a pipe, tank, or pressure vessel where the leak is in contact with the ground and not visible or evident, the natural question arises as to how much fluid has or can escape into the environment. We propose a simple model that assumes a hemispherical pit grows from the process side surface to the external surface and as soon as it breeches the steel wall liquid flow occurs. We assume that the hemispherical pit is growing at a constant rate which provides a function that yields the diameter of the hole with time. A simplified application of Bernoulli flow is used to model the flow rate. Because of the uncertainties in the actual geometric shape as a function of time we consider that the assumption of an inviscid fluid is adequately conservative for most petroleum liquids. The application of this kind of model has significant utility in cases where a spill has already occurred, and where an estimate is need to determine the expected loss or in a predictive manner, when a risk assessment is being conducted to determine the scale of contamination that might occur as a result of a breeched tank wall in contact with the soil.