More frequently, development is occurring at sites having subsurface contamination. When volatile or semi-volatile contaminants are present, the potential for migration of those compounds to interior spaces must be considered and addressed. Two general types of mitigation measures have been utilized extensively in California over the last several years. These include membranes and ventilation systems installed beneath building floor slabs. These two mitigation measures are often combined to provide a higher level of safety and redundancy.

Some of the most common types of membranes used today for solvent or Volatile Organic Compound (VOC) mitigation are spray-applied products, such as CETCO's LIQUID BOOT® spray applied membrane. Spray applied membranes are typically comprised of proprietary mixtures of rubberized asphalt applied to a geotextile substrate. This type of membrane generally has an advantage over sheet products with respect to the ease with which membrane seams, perimeters and penetrations can be sealed. Long-term diffusion tests have been conducted on LIQUID BOOT® membranes at VOC levels in excess of 100,000 μg/m3 without any indication of membrane degradation. ...

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