Dry cleaners are a widespread and common source of potential contamination from the use of tetrachloroethene, commonly referred to as perchloroethene (PCE) or perc.  Thousands of these were located in retail buildings and shopping centers from the 1930's to the present although most current dry cleaners have switched to newer "green" chemicals due to the obvious liability associated with PCE.

The California Regional Water Quality Control Board (RWQCB) is actively researching and identifying former dry cleaners and requesting subsurface sampling to identify potential risks to human health and safety and the environment.  Note soil vapor sampling is the standard for subsurface sampling and most subsurface investigations will include soil vapor assessment.  Previous sampling that included only soil sampling will not be sufficient to satisfy the requirements of the RWQCB.  In effect, previous subsurface investigation conducted more than approximately 5 years ago at dry cleaners will likely not be sufficient.