2.14 LIMITATIONS

        The volatilization formulations given are simplified estimation procedures that yield approximate release rates based on site and contaminant properties. Although these methods do not account for all the factors that can control these volatile release rates, the estimated release-rates should provide the order-of-magnitude estimates of potential rates required for the MEPAS ranking applications. For site-specific applications a more exact release-rate verification of computed release rates by monitoring data is recommended by the EPA (1988).

        The accuracy of the MEPAS volatilization estimate depends directly on how well the problem is characterized. The types, forms, and quantities of chemicals involved need to be defined, along with the physical and chemical properties of the various media.

        Because the MEPAS methodology accounts for contaminant loss at the source if the inventory is known, the potential exposures are limited to the amount of material available. However, in cases where the inventory is unknown, the model can release more material than is really associated with the environmental problem. The total releases for cases with undefined inventories problem.